A NEW SPECIES OF AKGULUS. WITH A MORE COMPLETEACCOUNT OF TWO SPECIES ALKEADV DESCRIBED.
By Charles Branch Wilson,Depurtment of Bloloff;/, Stale XomixJ SrJionl. Wcufjield, Mas.-<,
In u paper already published in these Proceedings" four new speciesof Argulus were described. But the diagnosis of each was necessarih'very lirief and only specific differences could be noted. Such accountsanswer very well for preserved material, and may be allowed to standuntil further information is obtained from a study of living specimens.But as soon as such information is olitained it becomes expedient togi^e a more detailed description together with as much of the habitsand mode of life as may be of vakie.Such an attempt has been made in the present paper upon two ofthe species previously described, A. ain<nlv(iint.s and ^1. rcrsicolor^ theonly ones which have been obtained alive. In addition a diagnosis isgiven of a third species which proves to be new.ARGULUS AMERICANUS Wilson.
Arfjulus nmericaniis Wilsox, Proi-. U. S. Xat. Mus., XXV, p. 718.Much of the anatomy of this interesting species has already beengiven in the paper referred to, but it was disconnected and min-gled with that of many other species. It is here gathered togetherand completed and suppl'.mented by an account of the development.The species was obtained b}' Prof. Jacob Reighard at Ann Arbor,Michigan, from some Amia calva kept in aquaria and was sent to theauthor in the winter of 1901-2. It was diagnosed as a new speciesand described supposedly for the first time.But shortly- afterwards a manuscript upon The Yermine and Crus-tacean Parasites of Fresh-Water Fishes, by Dr. R. R. Curley. wassent to the author from the U. S. Fish Commission. This manuscriptwas evidently prepared with considerable care and labor about ten3'ears ago, but has never been published.In it are included two new species of Argulus, one of which is evi-dently the same as A. americamts, since it corresponds in every detail.
?Proc. V. S. Nat. Mus., XXV, pp. 635-742.Proceedings U. S. National Museum, Vol. XXVII?No. 1368. tiL'7
628 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvii.The account also includes a partial description of the eggs and larva\and it is unfortunate that the manuscript name could not have beengiven to the species, since this description so far iuitedates that of theauthor.In the present account acknowledgment has been made of such factsas have been taken from Dr. Gurley's manuscript.At present this species has been found only upon the dog-fish. Am lacalva. Professor Reighard writes that it is found over the outside ofthe fish generally, the larger number on the anterior part of the bodyand the head. Init some on the tins. The}^ are most numerous on theventral side of the body in front of the pelvic fins. They are neverfound on the gills or anywhere else internally. They are not notice-able until the fish have been for some time in the aquarium.This is one of the largest of the American fresh-water species andis the best of any the author has seen for purposes of study, since it isparticularly transparent when alive and also when cleared in clove oil.There is no difficulty in making out all the details of the internalanatomy even to the nervous system and its connections.It is pale brownish white in color, sparsely covered on the dorsaland A'entral surfaces with small pigment spots of a reddish hue. Inall the living specimens seen by the author there were eight faint red-dish bars running transA^ersely across the dorsal surface. Gurley,however, sa3\s:The ground color is faint grayish or grayisli green. The nio.st conspicuous mark-ings are the rose to purphsh red bars, which are most distinct marginally where theyform well-defined spots.Probably the color as well as the distinctness of the bars varies con-siderably in difierent lots of individuals.The dorsal surface of the ovary and semen receptacles in the femaleand the abdomen of the male in the vicinit}- of the testes are heavil}'^pigmented with circular spots of a rich dark brown. The structuraldetails are as follows:General form.?Dorsal surfaci\?The carapace is obovate andfully as wide as and often wider than long; the antero-lateral sinusesare distinct, leaving a well-defined frontal lobe which, however, doesnot project yqvj far, since it is flattened anteriorly. The posteriorsinus is narrow and about one-third the entire length of the carapace,and is squarely truncated at its base. Its sides converge rapidly inpassing backward so that the broadly rounded lobes of the carapaceoverlap considerably at their tips (fig. 1).The sutures dividing the carapace into its respective areas are char-acteristicalh^ arranged. The two central longitudinal ribs {r) are fairlyclose togethei" for such a broad carapace and are almost parallel exceptat their anterior ends. The horseshoe suture {hs.) separating thecephalic from the other areas is comparatively short and narrow.
DESCRIPTIONS OF AUG ULID.Ii^ 1VILSON. 629This makes the lateral areas wide anteriorly ai)d lea\es a thoi'acicarea (/) posterior to the sutuiv wiiich is actually longer than it iswide, a condition rareh' found among- the Argulidje. From the sidesof the horseshoe suture near its anterior ends a well-detined secondarysuture (.v.y) extends backward on either side in a liroad outward sweepthrough the center of the lateral area nearly parallel with the marginof the carapace. These sutures divide each lateral area into an outerand an iimer portion, the former of which can lie flexed on the latter,
12 4 m ?'.Fig. 1.?DoKSAi, vikw of jiai.e ARot'i.rs america.nts.thereby greatl\' increasing the mobility of the carapace. The freethorax is entirely concealed beneath the overlapping lobes of the cara-pace which also cover the anterior third of the abdomen, giving thisargulid a ver^' compact appearance in dorsal view. The abdomen isbroadly triangular, one-half wider than long, with all its angles wellrounded. The lateral margins project forward slightly, suggesting aheart shape. The anal sinus is triangular, cut less than a third thelength of the abdomen and carries the anal papilhe upon its lateralmargins close to the tips of the lobes. The papilUe are st)mewhatclub-shaped, rather short and l)lunt, and each is tipped with threesette of medium lenoth.
630 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVII.Yentral sirrface {f[g. 2).?The frontal lobe is plainly divided into ananterior and posterior portion V)y a line parallel with the edge of thecarapace except at either end where it curves around abruptl}" to thebase of the anteunre. From the center of this line there projectsbackward into the posterior portion a triangular area (the post-frontaltriangle) whose ventral surface is on the same level as the rest of thecarapace. But the remainder of the posterior portion on either sideof the triangle is hollowed out for the antenntt^. The ventral surfaceof the triangle, the anterior rim, and the anterior half of the lateral
Fig. -VEXTRAL view of female ARGIUS AMERICAXl'S.areas are thickly covered with sharp triangular spines of considerablesize, which must hold the creature ^ery firmly on its host.Antennm (fig. 3).?These are small ))ut well armed with stout hooksand spines.The proximal portion of the basal joint of the first pair carries twostout spines on its inner ])order, the posterior of which is stronglycurved backward. The distal portion of this joint has the usual hookson the outer and anterior margins and two spines upon its posteriormargin, one of which is long and stout, while the other is very slender.The terminal portion of this antenna is two-jointed and projects con-siderably beyond the basal portion. The second antenna are four-jointed, and each carries two large triangular spines on its inner
NO. 1368. DESCRIPTIONS OF ARGULID.E?WILSOX. 631
marofin and a smaller and sharper one on the posterior marg-in of itsbasal joint. Thv latter is reenforeed by si-veral s(?tie. All these hooksand spines are of a rich yellow eolor.J'Jyei'i.?These are small, made u]) ofnumerous facets, and quite widely sepa-rated.
Fig. 3.
?
.Vntenx.k of ke.malk ARorn'SAMERIC.\XrS.
Fig. 4
?
Mouth parts of argulus americanus. I.LOWER lip; /;;, LABIAL PALP; md, mandibles;iiu, maxill.e; r, chitix ribs.
Mouth (tio-. 4).?This organhas a peculiar, almost trape-zoidal, form, and its lateralmargins are strongly serrated.The lower lip (/) has a sharpercurve than in A. foliaceus andthe labial palps (7/y) are rela-tiveh' smaller. But the great-est difference is in the mandi-bles {md): instead of beingbroadh' sickle-shaped, withteeth along the inner marginonly, the^' are widened into a spatula form, with long and sliarp teethon both the inner and outer margins and around the end, twelve orfifteen of them in all. The maxilla {in;i) are also much stouter thanin foliaceus, but the single tooth at the tip is shorter and ])lunter. Asa whole the proboscis is onlyslightly club-shaped and israther smaller than would beexpected on so large an Argu-lus. The chitin framework,while agreeing in its generalmake-up with that oifoliactus^differs in several details. Thelongitudinal ril)s (/') are notforked at their distal ends, andthe transverse ribs are lesscomplicated.
^4;^ ta'ior iuaxilliped^.?Theseare small, not more than one-sixth the width of the carapace, and closetogether. The shape of the chitinous rods which support the mem-branous edge and the arrangement of the fringe are peculiar. Tliere
-B<)i;nK,K OK SICKING DISK in ARoru-sAMERICAN IS.
632 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVII.
Fig. 6.
?
Posterior maxillipeds argulis americanus.
are two concentric rows of the rods, the inner about twice the length ofthe outer, while outside of the latter is a wide free marg-in (fig. 5).The rods in })oth rows are shaped like the letter J when viewed fromthe inside, the bases ofthose in the outer rowarticulating with the tipsof those in the inner row.Around the edge of themembrane is a fringe ofelongated linger-like pa-pilla^, each terminated b}^three or four slender hairs.Posterior niaxillipeds (tig. G).?These are small but well armed. Ofthe tire joints, the three terminal ones are much smaller than the twobasal ones. The basal plate has an elongated triangular form andcarries upon its posterior margin threeteeth so wide and so squarely truncatedas to be plates rather than teeth, as isalso the case in A. catostomi. The platesare reenforced by a pair of stout, bluntspines near the median line just behindthe mouth. The papillated area is small,but has a bunch of long and sharp setseon its posterior margin; the remainderof its surface and the entire ventral sur-face of the four terminal joints are cov-ered Avith short, stiff hairs, each with aswollen base.The terminal joint ends in three small,rather blunt claws of about the same size,arranged in a broken row anteriorly,while opposed to them posteriorly is ashort, rounded papilla or thumb.Sioimnnng legs.?These are long andslender, projecting well beyond the edgeof the carapace, the two anterior pairs withrecurved tlagella. The basal lobes on theposterior pair are large and boot-shaped,with a distinct heel. The}^ are fringedalong the posterior margin with a row ofplumose setfB, and the toe of the boot car-ries two much longer setjs, also plumose.Tactile fapillae.?These, for ovipositing, are large, long, and quitewidely flaring in the female, but reduced to mere stumps in the male.Circulation.?This, while agreeing with that in other species, differsmarkedly in the structure and working of the heart (fig. 7). This is
Fk;. 7.
?
Dorsal view of the heartof argulus americanl's (diagram-matic), o, paired lateral open-i.N'(;s; h. ANTERIOR opening of aorta;C, ANTERIOR: d, POSTERIOR VENTRALOPENING.
NO. 1368. DESaUPTIOXS OF AUG I'LIDJ:? WILSON. 633of the usual shape, but has only five openings instead of six. theventral one consistino- of a single lonoitudinal slit.
All the blood enters through the lateral valved openings {(i)\ a partof it passes out of the aorta {h) anteriorly and another part out of the
Y-[r,. 9.
?
Thk nervot'p system of AKnri.rs amf.ruaxvs.posterior median aperture {d)\ each of these streams follows the usualcourse (fig. 8), but the greater bulk turns downward and passes out ofthe ventral median slit {c).
634 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVII.This stream pour.s around the intestine and separates naturally intotwo side streams running forward past the bases of the swimming legsand sending out lateral streams into each of them, tinally joining theanterior streams from the aorta under the l)rain. On its return theblood percolates through the lateral sinuses of the carapace and, join-ing the streams from the borders of the abdomen, enters the openingsat the sides of the triangular base of the heart.JS^ervous system (fig. 9).?This consists of a dorsal brain and a ventralchain of six ganglia. The brain is rather small, but well pigmented.
Fig. 10.?Sexual organs op female aegultjs amekicanus. o, ovary; n. v., oviduct; s. p., semenpapill.e: .s. v., semen receptacle; t. p.. tactile papillae at the openings of the oviduct.SO as to be prominent l)y contrast with the light-colored carapace. Itsventral portion extends quite a distance in front of the pigmenteddorsal portion and is nearly three times as wide. From the anteriorborder of this ventral portion a pair of nerves extend forward to theanterior antennae. Another pair arise from about the center of thelateral borders and lead to the posterior antennt^?. These two pairsare the only cranial nerves. The ventral ganglia diminish in sizerapidl}-; they are distinctly lobed along the sides, but fused through
NO. 1368. DESCRIPTIONS OF AEG VLIDJ'J? WILSON. fi85the center. Each of the five anterior ones gives off a single pair ofnerves, while the sixth and last one gives off two pairs. The nervesfrom the first ganglion, which is consideral)ly the hii'gest of the six,go to the sucking disks; a ])ranch arises from this nerve very soonafter it leaves the ganglion and passes forward to the moutli ])arts.The nerves from the second ganglion are a little larger than any ofthe others, which is fully accounted for when it is found that theyijuickly divide, one large branch going to the second maxillipeds andthe other innervating the lateral areas of the carapace.The nerves from the third, fourth, and lifth ganglia and the hrstpair from the sixth ganglion supply the swimming legs in order oneither side. The last pair of nerves which are given off from the pos-terior border of the sixth ganglion innervate the reproductive organs.Reproductive organs (fig. 10).?These are beautifully typical and can
Fig. 11.?Semen receptacles and papill.e of argulus americanus female under greaterenlargement. 6. i., basal lobes of posterior legs; s. rf., dvcts leading from the recep-tacles to the papill.e; s. p. semen papilla; .?. r., semen receptacles: t. )).. tactile papill.e.be plainly seen through the outer covering, even in preserved andmounted specimens. In the female the semen receptacles {s. /., fig. 11)are large and close together; the semen papilhv (s.p.) are also large andthe hardened chitinous tip of the duct which leads to them fi'om thereceptacles projects forward rather than inward toward its fellow onthe other side. In the figure the tactile papilhv (f.p.) used for ovi-positing are much smaller than the average, and the specimen wasselected for this reason, since these papilhe would conceal the under-lying organs as little as possible.The r(>lative size shown in the full-length figure of the femaliHtig. -2)is nearer the average.In the male the essential organs (fig. 12) are ([uite typical. I)ut theaccessor}" organs surpass those of any species so far examined. In
636 PROCEEDINGS OF THE XA TIONAL MUSEUM. VOL. XXVII.addition to the regular peg and semen receptacle on the fourth andthird legs, respectively, we find on the anterior surface of the thirdleg a long cluh-.sliaped projection, which arises from the outer end ofthe basal joint and projects diagonall}^ forward and outward past thedistal basipod joint and far out on the exopod (tig. 13). Its surface issmooth and even and it seems to be tactile in function. There isanother conical projection, a trifle smaller, on the posterior surface
Fig. 12.
?
Sexi'al ()Rgan.s of male ARGrLrs americaxus. h. c. blind fAPsuLE: r. d., EjAcrLATORVduct; ?. ('., SEMEN VISICLE; t., TESTES; V. d., VAS DEFERENS; I', i ., VAS EFFERENS.of the preceding pair of legs, exactly opposite the one just described.This also has a smooth surface and a probable tactile function. Toincrease this probability both projections are well innervated and theirsurfaces are plentifully covered with short setw. There are also smallprojections, varj'ing considerably in diflerent individuals, upon theopposite surfaces of the same joints as bear the large ones.
DESCRIPTIONS OF ARGULID.E? WILSON. (337Eggs and deveIop7ne}it.?Gur\ey, in the manuscript already referredto, has given an outline of devolopniont, with a description of the larva.But, again, the present author had obtained ripe females from ProfessorReighard at Ann Arbor, Michigan, and had successfully reared thelarva' before Ourlev's manuscript wasplaced in his hands. It is a pleasureto find that these two accounts agree inevery detail.The eggs are laid in single rows (tig.14). exacth' as those of A. inegalops^and not at all resembling either A.folUlceus or A. catostonii. But theeggs themselves are more like those ofA. eatostom! than of any other specieswhose eggs are known.The}^ are arranged end to end, theheads all pointing in one direction, butwith every third or fourth one re-versed. The jelly in which they areenveloped, on hardening in the water,assumes an appearance verv similar tothat on the ^gg^ of ^4. catostoin'i?that is, it is raised into ridges run-ning lengthwise of the ^gg^ each ridge composed of a row of club-shaped papilla? standing out at right angles to the surface of the ^gg(tig. 15). There are about six of these rows on the free surface of theeggs, including those along the sides where the eggs are attached to
Fig. 1h.?Posterior legs and abdomeniif argulus americanus.
'n
Fig. 14.?Mk'ro-photograph of egg string of argulus americanus, showing the .IELI.Y PRO-tiberances and the larv.e partially developed.the surface on whic4i they are laid. The rows coalesce at tlie ends andare most widely separated at the center.In addition to these crenated ridges there are also a few large scat-tered masses of jelly, some of whicli are nearly two-tiiirds as large as
638 PROCEEDINGS OF THE NATIONAL MUSEUM.the entire egg. They also stand out nearly at right angles to the sur-face of the egg, and while thej^ are really attached at random, yetthere is an average of about one on either side of each egg in the row,so that, viewed as a whole, the}' are at fairly regular intervals. Thisfeature is sufficient to distinguish the eggs at once from any othersthat are known.The eggs are small, measuring 0.375 by 0.275 mm. exclusive of thejelly, light yellow in color and quite clear when first laid. But theyspeedily turn darker in color and become opaque within the first two
?7,5 /ii m
Fig. 15.
?
An egg of ARGULrs americants approachixg mati'rity. The fully formed larvaCAN BE SEEN THROUGH THE JELLY ENVELOPE.days. Toward the middle of the .second week, about the tenth day,the eyes appear as two jet black large-sized spots near one end of theegg. These spots are elliptical in shape, with their longer diametersinclined toward the central axis of the egg, which is also that of theembryo.The egg now begins to clear and becomes more and more trans-parent up to the time of hatching. Through the membranes and thejelly can be seen the outline of the embryo's body and appendages.These can not be distinguished as plainly as in rnegalojps, for manyreasons. The jelly covering the egg is not as transparent as inviegalojpfi and the papillte render it still more opaque. Again, thepartial development of the appendages renders it possible to pack the
NO. 1368. DESCRIPTIONS OF ARGULIJJJ:? WILSON. 639
em])rvo in a mnch smaller space, with a resultant confusion of theparts.Such close packing explains, furthermore, the small size of the egg,and ^ye are forced again to the conclusion that the size of a copepod'seoo- has very little to do with the size of the adult female. It is,
PlO. It;.?NKWI.Y IIATCIIKII I.AUVA OF AROrlTS AMKKirANVS.
rather, dependent upon the length of time the em))ryo is to roniainwithin the eg^ and the degree of development it is to attain beforeliatching. An adult amerkana.s is much larger than a nn<iiih>ps^ andyet the eggs of the two are about the same size. This is explained l\vthe fact that the megalojys larva spends sixty days or more inside theProc. N. M. vol. xxvii?03 45
640 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVIL
egg", and comes forth a miniature adult, while the anieriea/ni!^ larvaspends onh' sixteen or seventeen daj^s in the egg and comes forth in atypical Cyclops stage to undergo many subsequent transformationsbefore reaching the adult form.The temperature of the aquarium was about 72? F., or a fewdegrees warmer than our fresh-water ponds during the summerseason. The eggs which were laid June 8 began to hatch the 25th, aperiod of onl}^ seventeen days, about half the length of time requiredby the eggs of ^1. foUacenx and catostomi and only one-fifth of thatrequired by -i. stizostethii and mtgaJojM.The newly hatched larvae (tig. 16) are not as lively as those ofinegalopti^ which woidd be ex-pected from the fact that theyare not proxided with as goodorgans of locomotion, but theyare also more sluggish than thevatoxtomi larva% which have ex-actly the same structure. Fur-thermore, when first hatchedthey stick to the bottom of thedish and do not swim up andtoward the light until the thirdor fourth day. And when theydo get up to the surface theyprove to be negatively helio-tropic, in sharp contrast with allthe other Argulus larvje thus farstudied, which are positivelyheliotropic to a very markeddegree.Owing both to the position andincomplete development of thetemporary locomotor organs, themotion of these nauplii is jerkyand cyclops-like. They are notas transparent as the other larva^ and do not furnish as favorableobjects for study, owing to the presence of a large area of rust-coloredpigment over the stomach and anterior intestine which hides much ofthe internal anatomy.In general shape they are short and broad, the carapace being wellrounded anteriorly, with a broad and shallow posterior sinus, while thefree thorax and abdomen form a broad triangle, relatively shorterthan that oifoliaceus and catostomi . Around the anterior margin ofthe carapace can be seen large tactile hairs similar to those foundupon other species. But they are much fewer in number and morescattered than in megaJojJs, and the intervening cilia are very minute
17.
?
Free thorax axd abdomen of argulx'samericanus larva.
NO. 1368. DESCRIPTIONS OF AL'OILIDJJ?WILSOX. 041and situated not at the very margin, but a little way back on theventral surface.The first free sog-nient of the thorax (rig. 17) is about half the widthof th(; carapace, while the succeeding- segments diminish rapidl3' insize. The abdomen is about the same width as the last thorax segment,is well rounded at the sides, and terminates posteriorly in a pair of analpapillie which are large, almost spherical in shape, and tipped with threelong, sharp spines.The first antennse (fig. IS) are three jointed, as in other species, Vmtthe basal joint is relativel}^ nuu-h smaller; in fact, it is but a tritie largerthan the two sphericalterminal joints, but isarmed with the usual stoutsickle-shaped hook. Thebristles and spines onthese terminal joints arerather more numerousthan in other species.The second antenna? aremodified into locomotor organs, and ])oth in the segments and in thenumber and arrangement of the long plumose rowing sette they areexactly like those of follaceuH and catostornl nauplii. The temporar}'mandibular palps are also like those of the species just named, but areattached somewhat farther forward relative to the other mouth parts.
Fig. 18.
?
First antenna ok the kewly uai
?. ARGUI.rs AMERICANVS. II KD I.ARVA OF
Fig. 19.?.\NTF.RI0R MAXII.I.IPF.n of the newly hatched ARrJULI'S AMERICANrS.The anterior maxillipeds (fig. li?) are stout, four jointed, and tenni-nate in the usual pair of sickle-shaped hooks, the ventral one of whichis barbed. The basal joint of these appendages is very stout, and inits interior can ])e seen the group of large cells Avhich are to form thesucking disks in later development.The posterior maxillipeds (fig. 20) are much smaller, five jointed,and very rough on their ventral surface, while the outer biuder ofevery joint is arnjed with one and often two or more sharp spines.These appendages terminate in two small but stout claws capable ofindependent motion and a conical papilla tipped with two short spines.The ])asal joint has no spine upon its posterior border.
642 PROCEEDINGS OF THE NATIONAL MUSEUM.The swimming legs are the same as in foUaceus and catostomi.^ thefirst pair only being developed, while the rest are immovable stumps.This first pair (fig. 21) consists of two basal joints well roughened andarmed with numerous spines upon their ventral surface, a two-jointedendopod tipped with two short spines, and a one-jointed exopod tippedwith two long rowing sette.The only difference here from other larvae already described is thatthe endopod has only two instead of three joints.The leg stumps attached to the other thoracic segments all showthe endopods and exopodsclearly, the former beingtipped with a single spine, thelatter with two.In their internal structurethe most noticeable differ-ence from other larvte is thealmost complete absence ofskin glands.Fig. 20.?Second maxilliped of the xewly hatchedlarva of argvlrs americaxus. The megalops larva, withits sixty days of inculcation, came forth with a wonderfully well devel-oped system of skin glands; the foUaceus and catostomi larva?, withabout half as long an incubation, showed a little more than lialf asmany glands.And now these americanus larvte, with an inculmtion of onlv seven-teen days, show almost no glands at all. We can not escape theconviction that these glands are developed quite slowly and that theydo not appear until comparatively late in larval life. It would seemalso that they must be de-veloped independently ofthe incubation period, sothat while the latter ischanged greatly, beingdoubled in some species andhalved in others, the glandsapparently alwa3^s requireabout the same time for de-velopment. In these americanus larva? we find but a single small groupof glands, six or seven in number, on either side near the posterioredge of the carapace lobes. They are much smaller than in megalops^and the ducts are not at all distinct. There are also a few scatteredglands along the dorsal surface of the carapace, thorax, and abdomen,but they are all very small, and none of them show the structure givenfor foliaceus and megalops. They have rather the appearance of beingin an immature and partiall}" developed condition.The paired shell glands are invisible, due to the opacity of the
Fig. 21.
?
First swimminc* leg of the newly hatchedLARVA OF ARGULUS AMERICANUS.
NO. 1368. DESCRIPTIONS OF AKULLW.E?WILSOX. 643surface pij^ment. which is so dense just in front of tlic side linincliesof the stomach where tlu^se olands are situated, and also in nianvoth(n- places, as to conceal all details of internal structure". The eir-culation is similar to that ch'seribed in other larva' except for theabsence of a well-detined peripheral sinus in both the abdomen andthe cephalo-thorax.Th(> internal cellular lacuna> appear about the same, but the currentsare not as well detined, espin-ially those of th(" abdomen. This larvalcirculation is carried on chiefly by means of certain muscles in thecephalo-thorax and abdomen, similar in both position and function tothose already descrilied for niegalopx. The heart lias not yet appeared,and hence those differences which make the adult circulation peculiarcan not yet be detected. The transverse dorso-ventral band or curtainat the place occupied later by the posterior wall of the heart is notas well developed as in megalops larvjB, another natural result of thedifferences in the period of development.Furthermore, in view of the immature condition of all the swim-iiiinjj" legs except the first pair, the muscles in the basipods of thoseappendages can not aid circidation to an}' appreciable extent. In fact,the undeveloped condition of most of the larval organs may wellexplain the feeble circulation.As soon as the heart acquires deffnite form after the lirst moult weshould ex))ect to tind the circulation showing the same peculiaritiesas in the adult.The nervous and reprodiactive S3'stems present no peculiaritiesworthy of special note, but are similar to those already descril)ed inthe adult. ARGULUS VERSICOLOR Wilson.
Arffuhis versicolor Wii.sox, Proc. U. S. Nat. Mu8., XXV, ]>. 71(i.This is a ver}' clean-looking Argulus and by far the most beautifulof any American species. It can be distinguished from all others at aglance by its brilliant coloration, which is as variegated as that of anold-fashioned patch-work quilt or the traditional Jos(>])h's coat. Theground color is a soft yellow-green, which forms a wide border aroundthe edge of the carapace and extends inward in a series of bands andirregular spots, the former being a deeper green than the margin,while the latter have somewhat of a rusty tinge. One of these bandsruns from the marginal border on either side just behind the suckingdisks diagonally backward to the base of the central longitudinal ribs.From the center of each diagonal band another narrower one extcMidsbackward parallel with the edge nearly to the posterior margin of thecarapace. These longitudinal bands are joined with the marginal l>or-der at about their center by a short radial l)and. which shows the samerusty tinge as the spots. These latter are found just outside the mi.1<-
644 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvii.ino- disks and also opposite the base of the tirst swimming legs in thelateral lobes.The rest of the surface is filled in with orange-j'ellow of varyingintensity, the posterior portion of the carapace lobes ))eing tingedwith brown, while the side branches of the stomach give more or lessof a reddish hue to the parts overlying them.Through this variegated groundwork the ribs, the digestive tube,and the reproductive organs stand out prominently. The ribs are abright golden orange, the two central longitudinal ones being bor-dered with yellow green.The digestive tube, when the parasite has taken a full meal, is deepwine red in the carapace and thorax, but fades to a green-yellow in theabdomen. It has a dark-green border on either side which occupiesall the thoracic segments outside the intestine itself and extends forwardanteriorly to the frontal border and posteriorly to the extreme tip ofthe abdomen lobes.The testes and semen receptacles are a rich purj^le-red, so deep as tobe almost opaque.The e3'es and brain are large and of a ))rilliaut black.With such a rich variety of color it would be natural to suppose thatthese copepods would fade quickly in preservatives, but such is not thecase. After being hardened in chrome-acetic, corrosive-acetic, andPeren^'i's, they have been kept nearlj^ three years in alcohol with solittle change as hardly to be distinguished from fresh specimens.The}' can also be run up through the alcohols, cleared inxjiol or cloveoil, and mounted in balsam without change of color. Indeed, eau-de-javelle is the only agent yet tried which will bleach the color. Thisremoves it entirely and leaves the Arguhis perfectly transparent.Thus far the species has been found only upon the common pickerel{Lucius reticulatus Le Sueur), but is likely to be found upon other iishalso at the breeding season.Actual experiment has proved that they are capable of living on red-fin shiners, bream, etc., for a long time."This single host is, however, very widely distributed throughout theUnited States, and in all probability the parasite has an equal distribu-tion. Not more than two or three specimens are found upon a singlefish, and these are always in the gill cavity. Often also it is necessar}'to examine fifteen or twenty fish before finding a single parasite, sothat they could be easilj^ overlooked and a good summer catch of fishmight not reveal their presence. For this reason winter is the besttime to secure them upon fish caught through the ice, and as theyremain alive for some time after the fish is dead an entire da^-'s catchcan ])e looked over. In this manner as many as thirty have beenobtained in a single afternoon from three adjacent ponds. Thus far
?Proc. U. S. Nat. Mus., XXY, 1902, p. 647.
yn.v.m. DESCniPTlnXS OF AEGULID.IJ?WILSOX. (J45the}' have not been sought in a single locality without success. Whenkept in aquaria they are lively, moving about and changing from onetish to another more often than other spocios. Tlie long plumose setieupon the swimming legs make powerful oars atid enable them to dartal)Out with great rapidity. One of their favorite movements is toleave the side of the aquarium and, turning back downward, scuttleswiftly along the under side of the surface ti.lm of the water after themanner of the very much slower aquatic snails.(rENKRAL FORM
?
DorHttlHurface (fig. 22).?Carapace almost perfectlyorbicular, the antero-lateral sinuses shallow, but leaving a well-roundedfrontal lobe; the posterior sinus is one-third the length of the cara-pace and only one-sixth its width, so that the lateral lobes are broad
Fig. 22.?DoRs.\r. vikw of fkm.\i.k. .\RGrLi\s versicolok.and well rounded. In the female they just reach the alxlomen; in themale they overlap it somewhat. The free thoracic segments aretwice as wide as long and are half concealed beneath the carapacelobes on either side. The abdomen has a very graceful oval out-line in the female and is about three-sevenths the length of thecarapace. In the male it is more nearly triangular, but narrowsconsiderably anterior to the testes, and the lateral margins projectforward in a well-detined and rounded lobe on either side. The analsinus is very short and slit-like, with the papilhv subterminal.^The arrangement of the grooves dividing the carapace into its areasis very symmetrical. The longitudinal ri])s are close together, andthe joints in them just behind the brain can be clearly seen. The
646 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvii.horseshoe suture is longer and narrower than in mnericanus^ and fromnear its base two sutures radiate outward into the lateral area. Thethoracic area is separated into an anterior crescent-shaped and a pos-
FiG. 23.
?
Ventral view of female argulus versicolor.terior rectangular portion, the tormer of which is much wider thanthe latter and follows closely the posterior curve o^ the horseshoe.
Fig. 24.
?
Detail of antenx.e of argulus versicolor.Ventral m/i'face (tig. 23).?The frontal lobe is simple and, togetherwith the anterior half of the lateral areas, is covered with inconspicu-ous triangular spines. The antenna are of good size and well armed;
NO. 1368. DESCRIPTIONS OF ARGULIDJi>- WILSON. 647the hooks upon the basal joint of the first pair are lar^-e and powerful,while the spines are ver}' long- and sharp. The two tcrniiiiul jointscarry numerous setaj, but do not project much beyond the lateralhook (fig-. 24:). The second antenna' are -l-jointed. the ba.sal jointhaving- a long- spine on its posterior margin, while each of theremaining- joints has a tuft of stout setee at its distal end. The eyesare large, somewhat lunate, and inclined toward the longitudinal ribs;the facets are small and numerous and crowded closely together.On the median line between the eyesand posterior to the large spines w^hicharm the base of the second antennasthere is a groove for the reception ofthe stylet (fig. 25). It extends back asfar as the base of the proboscis, andis lined on either side with a heavilycorrugated layer of chitin.The mouth difl'ers considerably fromthat of other described species, andpresents a peculiar appearance )w rea-son of the arrangement of its chitinframework. The mouth opening isnarrowed antero-posteriorly and elon-gated sidewise so as to appear like anarrow transverse slit, broken at thecenter by the protruding under lip(fig. 2H). On examining- the chitinskeleton, we find the same four longi-tudinal ribs connected at the latitudeof the mouth by a transverse frame-work. But the structure and arrange-ment of this latter is very differentfrom anything yet described, as canbe readily seen in fig. 26. The mostnoticeable differences are the ellipticalloops on either side of the mouth anda trapezoidal projection which extendsdown into the center of the upper lipto the very edge of the mouth opening.The transver.se rib also, which is situated at the junction of the upperand under lips on either side, turns outward at the joint nearest themouth and protrudes like a knob through the side of th(> probo.scis.The rudimentary palp along-side this joint is very small. Inside thelips may be seen a part of the long, sickle-shaped mandibK>s. edged withsharp saw teeth. The maxilhe have not yet been seen.The anterior maxillipeds are large, well separated, and i)lace<l farforward close to the maroin of the antero-lateral siinises. The nuMU-
e.in.
c h.r.
Ho. 25.
?
Sting and poison gland ok argu-LUS VERSICOLOR, ch.r., CHITIN RIB OF PRO-BOSCIS; (/., DrCTS OF POISON GLAND; <7.,POISON gland; m.m., mandible mvscles;oe.m., lEsoPHAGUS mvscle; 01:111.', sidemuscle of cesophagus; r.jM., retractormuscle; X.. STING.
648 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVII.
Fig. 26.
?
Chitin skeleton of the proboscis inargulrs versicolor.
branous edge is quite wide, and is supported b}^ chitin ribs whoseconstruction is peculiar. The stiffened circle which serves as anattachment for the powerfulnuiscles of these niaxillipeds, aswell as the membranous edge,is raised into knobs at equal in-tervals around its circumfer-ence (fig. 27). From each knoba chain of four slightly oblongchitin plates extends outwardto the edge of the membrane.These are placed end to end anddiminish regularly in size, thedistal one being less than half aslarge as the proximal. Each isconvex at the proximal and con-cave at the distal end, the con-vexity of one plate fitting intothe concavity of the one nextinside it. In the first and secondplates the concavity is eccen-trically situated, but in the twoouter ones it is approximately symmetrical. The plates are arrangedend to end and do not quite touch oneanother, but leave narrow open spacesof membrane. Thus, while strengthen-ing the membrane they still leave it veryflexible.Posterior maxillipeds {^g. 28).?Theseare also large and well armed. Thejoints diminish in size much more regu-larly than those of americanus; the plateon the basal joint is triangular, withlong, stout, and not very sharp teeth;the papillated area is comparatively large and armed with strong setae.The anterior half of thesecond joint and the entireventral surface of the re-maining three joints arecovered with good-sizedpapillae, each carrying atoothed scale. These pap-illated scales are similar tothose on mnericanus, andconsist of a hemispherical or hemiellipsoidal papilla, upon whose sum-mit is borne the toothed scale. The latter is inclined at an angle of 10
Fig. 27.^Chitix ribs ix the margin ofthe sucking disks of argull's versi-COLOR.
0.5;;/ ;;;.Fig. 28.?Posterior .maxilliped of argulus versicolor.
NO. 1368. DESCRIPTION.^ OF xiRd ULIDA-^WILSON. 649
a
Fig. 29.
?
Scale.s ox ventral .surface ftpTHE POSTERIOR MAXII.I.IPEDS OF ARun.rsVERSICOLOR.
or 15 degrees to the body and is an elongated ellipse in outline (.see a infig. 29). Its ))asal half, whicli is fused with the sunnnit of the i)apina.is solid, but the free half is cut into from two to six long and acumi-nate teeth. In general the scales nearer the anterior margin of tlicmaxilliped have the larger luimber ofteeth. Often one of the outer teeth isshort and stands out at an angle fromthe others like a thumb. Evidentlysuch an arrangement forms a surfacewhich nuist give the copepod a firmhold even through the slimy coat ofthe fish's body.The terminal joint of the.se maxilli-peds ends in three hooks of unequalsize; the anterior one is much thelargest, with a thick, blunt tip armedwith a single short, sharp seta. Theother two are more slender and strongh- curved (tig. 3(?).Swlmin'nig ZtY/*-.?The.se are long and slender and reach far In-yoiidthe edge of the carapace. The}' arefringed with stout plumose setae andenable this argulus to swim with greatpower and rapidity. The tlagella uponthe first two pairs have a double curve,as can be seen in fig. 81, which is adorsal xiew looking through the cara-pace in a bleached specimen. Thel)a.sal lobes upon the- posterior legs arever}' long and their tips extend beyondthe edge of the abdomen. Thej^ have the usual boot shape, with asingle seta on the toe of the boot much longer than the rest. Thechitin rings in the laterallobes of the carapaceextend farther forwardthan those in americanuH^and the concavity inthe posterior one intowhich the smaller ringfits is on the inner mar-gin a short distance backfrom the anterior end in-stead of at the end itself.Tactile papilhi'.^TheHii are long and slender in the female and curvein toward each other at the tips, while in the male they are so rudi-mentary as to be almo.st invisil)le.Clrcidation.?T\\m is the same as that given for A. f.Jni,; us.
Fig. 30.
?
Terminal joint of posteriorMAXILLIPED of ARGULrs VER.SICOLOR.
Fio. 31.?Dorsal surface of the anterior leg on the rightSIDE OF ARGULUS VEPSICOLOR. SHOWING SIZE AND ATTACHMENTof normal FLAC.ELLUM.
650 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVII.
Fig. 32.
?
Three posterior pair.s of leg;IX the male ARGULtS VER.SICOLOR.
Reproductive organs.?These are similar in position and arrangementto those of americanus, but the unpaired seminal vesicle in the male isquite different in shape, being- nearly spherical, with an emarginate ante-rior border. Another difference was the fact that, after removing thepigment from several males, no trace ofany accessor}" blind capsules could beseen. The second legs of the male havea large conical projection on their pos-terior surface at the outer end of thebasal joint (fig. 32). There is a similarmuch smaller one in a corresponding-position on the third legs, and theselegs also have a rounded knob on theanterior surface of the second joint atthe end next the body.But the chief interest, both iri thisspecies and americanus^ lies in the factthat it was possible to ascertain in themfrom actual observation the structureand exact function of the semen recep-tacle and peg upon the bases of thethird and fourth legs, respective!}'.The peg consists of two parts, basal and terminal; the basal portionis a blunt papilla whose walls are stiff' and covered with rough tuber-cles (fig. 33). It does not appear to be hollow, but readily permits ofthe withdrawal of the terminalpart inside itself. This termi-nal portion is a slightly curvedconical tube, with walls as ff^xi-ble as rubber and so thin asto be perfectly transparent andcolorless. The tip of the tubeis somewhat enlarged and sur-rounded by a row of minutehairs. Inside both tube andpapilla can be seen a musclestrand which extends from thetip of the tube diagonally back-ward to the posterior margin ofthe leg. By means of thismuscle, together with the circular muscles in its own walls, the tubecan be withdrawn inside the papilla or protruded at pleasure.The semen receptacle is a cavity in the posterior part of the distalend of the basal portion of the third legs; the opening into this cavityis on the ventral surface, near the posterior margin. This opening is
Fig. 33.
?
Basal joints of the two posterior legsOF male ABGULUS VErSICOLOR, SEEX FROM THEventral SURFACE.
guarded by a strong sphincter muscle.
DESCRIPTIONS OF AUG ULID.E?WILSON. <*) 5 1Just in front of the opening, upon the anterior part of the ventralsurface, are two rounded papilliB, covered with rough tubercles. Thisreceptacle is tilled with semen from the testes, probablv through theagency of the peg. though this was not actually observed. Once fiUed,however, it operates as follows: The sphincter muscle around the open-ing relaxes enough to allow the entrance of the peg on the fourth leg.Being protruded as far as possible and the sides of the basal pai)illabeing compressed b}" internal muscles, the peg tube acts like a pipetteand becomes tilled with semen from the receptacle. It is then with-drawn and inserted in the opening of the duct leading to the semenreceptacle in the abdomen of the female. The sides of the basal papillaare again compressed, the internal muscles being aided by the roughpapilhv on the ventral surface of the fourth leg, which bend over andseize the base of the peg securely, one on either side. By this meansthe peg is emptied of its contents again ver}^ similarly to a pipette.ARGULUS TRILINEATA, new species.The U. 8. Fish Commission recently received from Messrs. Kingand Oliphant, pharmacists, of Macon, Georgia, a single specimen of afemale Argulus taken from one of their goldfish. This was forwardedto the author for identification, and proves to be a new species, withcharacters as follows:Carapace elliptical, reaching well beyond the base of the abdomen,with the longitudinal and transverse diameters in the i)roportion of14:12.5 (fig. 34). The posterior sinus is three-sevenths the length ofthe carapace and a little more than twice as long as wide. The antero-lateral sinuses are so shallow as to l)e scarcely perceptible, so that thecephalic area does not project appreciably. The central longitudinalribs are close together and nearly parallel; the joints in them behindthe brain are indistinct and easily overlooked. The horseshoe sutureis long and narrow and comparatively pointed at the posterior end,leaving the lateral areas very symmetrical and about the same sizeanteriorly and posteriorly. The thoracic area of the carapace, behindthis suture, is a short strip one-fourth as long as wid(> and only halfthe length of the first free thoracic segment.These thoracic segments increase in lejigth from in front backward,the posterior one being more than twice as long as the anterior. Theyalso increase somewhat in breadth, and since the posterior sinus of thecarapace is about the same width, the free thorax is almost eiitiivlyexposed.The abdomen is very small and spindle shaped, one-quarter thelength of the rest of the l)ody and two-thirds as wide at the center asit is long. The anal sinus is cut just to the center, and is narrow butof uniform width, leaving stout, bluntly conical lot)es: the anal inipillivare small and ])asal.
652 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVII.Ventral surface (fig. 35).?Both pairs of antennae are relativeh' smalland weak, but are fairly well armed with hooks and spines. Theanterior and lateral hooks on the basal joint of the first pair are slender,but the spine on the posterior border is above the average size.The terminal portion of these first antenna' is slender and does notproject beyond the lateral hook (fig. 36).The basal joint of the second antennje is as long as, and much thickerthan, the two terminal joints, and the latter are attached obliquely to
/ ^ C il 111 111.
-Dorsal surface of a female argulus trilineata.one of its distal corners, so that the two portions of the antenna? standnearly at right angles to each other.The basal joint carries a stout spine on its posterior margin justwhere it joins" the head, and two long, slender spines on the ventralsurface at the distal end. The second joint has a single long spine onits anterior border at the distal end, while the terminal joint carriesfive or six large and stout spines. The spines along either side of themid line of the body opposite the bases of the antennae, those on the
I>ESCRI1>T1(>XS OF AliGlLJIU:? UJLSOX. 653posterior border of the basal joints of the antennae, and the lateralhooks on the first antennse are deep yellow in color and opaque; allthe others are traiispar(Mit and colorless.The eyet^ are small, lunate, and more or less inclined to the centralaxis; they are situated well forward and widely separated.The sucking- disks are small, not more than one-eig-hth the width ofthe carapace; they are situated far forward and are widely separated.
Fig. 35.?Ventral .surface of a female ARorLCS trilineata.The chitin ribs, which support the membranous border, are made oftrough-like scales overlapping one another, very similar to those inA. megalops.Posterior m.axillipeds.?These are large and very fidly armed, tooffset the slender antenna? (tig. 37). The basal joint has an oval pai)il-lated area, which is placed obliquely, is elevated consideral)ly above
654 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. XXVII.
Fig. 36.?First .\ND SECOND ANTENNA OFTRILINEATA.
the surroundino- surface, and entirely covered with short conical spines.The three teeth on the posterior l)order of this joint are very long,stout, and acute. The second joint carries on its distal end a papillatedarea even larger than that on the basal joint. The third and fourthjoints are enlarged at their distal ends, and their whole ventral surfaceis covered with spines and papillse. The terminal joint is tipped withtwo curved claws and a flesh}""thumb."Swimviing legs. ? Thesereach well beyond the edge ofthe carapace, and the two an-terior pairs have recurvedflagella. The distal joints ofall four pairs carr}^ a row of
j \ /y^ Nv ^:=- plumose setie along their pos-ly^ 1 / v^^^^ terior border. The lobes onthe basal joints of the last pairare small and well rounded.The tactile papillae at theopening of the oviduct are broad and pretty thoroughly fused withthe ventral surface of the abdomen.Of the chitiu rings in the lateral lobes of the carapace the anteriorone is small and egg shaped, and is situated very close to the base ofthe sucking disks, while the posterior one is large and so broad thatits inner border reaches to thebases of the swimming legs.The contrast in the size of thesetwo rings is greater than that ofany other species so far exam-ined. The ventral surface ofthe anterior portion of the cara-pace is covered with triangularspines as large and as numerousas those in am erlean us.Nothing could be definitelyascertained with reference tothe nervous and reproductivesystems without danger of spoil-ing the specimen for a type, andtherefore the}^ are allowed to pass for the present. Of course thesemen receptacles were visible. They prove to be large, spherical,and situated rather far forward. The papillw connected with themare close together on the median line, well concealed beneath the tactilepapillae.Total length, 4.5 mm.: length of carapace, 8.7 mm.; breadth ofcarapace, 3.3 mm.; length of abdomen, 1 mm.; breadth, 0.6 mm.
-Posterior maxii.ijpeds op ARGin.ufiTRILINEATA.
DESCRIPTIOXS OF ARGULID^E? WILSON. 655
DORSAL SURFACE OF THE FREE THORAX OFARGULUS TRILISEATA.
Color a uniform pale 3'ellow, deeper along the central axis andlighter toward the niaroins. The dorsal surface of the thorax isornamented with three well-detined rows of dark ])rown y)igment spotswhich stand out prominenth' against the yellow background and catchthe eye at once when the creature isviewed under a low power. Themiddle row is made up of a dozenlarge spots in single line along thecentral axis; the lateral rows aremade up of numerous smaller spotsarranged altei'natel}' in two brokenlines. Under strong magniticationthese spots are seen to be transverselyol)long and very irregular, the edgesbeing cut repeatedl}' more than halfthe distance to the center (fig. 38).The large semen receptacles are also fig. 38.?one of the pigment sdots on thedark brown and show through theabdomen very prominently-Locating this species in the artificial key already published ? weshould have:A. Carapace lobes overlapping the base of the abdomen.B. Anterior swimming legs with a flagelluin.C. Carapace elliptical, considerably longer than wide.7, a. Sucking disks only 0.12, far forward and widely separated; abdomen small,spindle shaped, cut to the center. Color light yellow, with three rowsof dark pigment spots on the dorsal surface of the thorax trilineatn.{ti'es ? three, lineatus ? arranged in lines.)The author also desires to record the occurrence of Arguhis alosse atCasco Bay on the coast of Maine.Several fine males were obtained from the common cunner {Otenola-hrus adsjMrsus Walbaum), and they seemed fairlj' numerous. This isthe first instance where this species has been positively identified northof Woods Hole since its original discover}^ b}^ Dr. Gould. And itwill increase the probabilit}' that the habitat may extend to the (Tulfof St. Lawrence as doubtfully recorded by Mr. J. F. Whiteaves.Incidentally also it is the first species of this family to be obtainedfrom the cunner, but as no females were found it may be inferredthat this was only a temporary host used during the breeding season.
?Proc. IT. S. Nat. Mus., XXV, 1902, p. 701.Proc. N. M. vol. xxvii? 03 46