THE LIFE HISTORY OF THE SEA-HORSES (HIPPOCAMPIDS). By Theodore (Jill,Hotioniry Associate hi Zoology. In the ordinary works on tishes or natural history very little is saidabout the inttn-esting- little fishes popularly known as sea-horses.Many details, however, have been published in isolated notes or Ijuriedin general articles, which only one familiar with ichthyological litera-ture would be likely to know about or even to find by using thecurrent bil)liographies. For the benefit of those interested in thegroup the notes here presented, l^rought together for a general workon tishes, are published. I.The sea-horses (Hippocampids) vary in form, but all are compressedand incapable of flexing the body sideways to any very considerableextent, the plates having extensions which are buttressed against cor-Ta,. ?9'^ JSSn. 4^Fiu. 1.?Bkoad-nosed Pipe-fish (Siphonostoma typhle). Skull frum side showing elongationOF FACIAL BONES, small MOUTH AND JAW BONES, AND ABSENCE OF PREOPERCLE. (AFTER SCHAFF. ) B. 0., Basioccipital; Ect., Ectethmoid; Kt/i., Ethmoid; E.t: O., Exoccipital; Fi:. Frontal: Hw.,Hyomandibilak: ./. ()., Infraorbital; Mil., Mandibular; M.c, Maxillary; Op., Operculum;Pa.. Parietal; PL, Palatine; Pin.r., Premaxillary; PL, Pterotic; Qh., Quadrate; ,S'. 0., Supra-occipital; Sjih.. SpiiENOTic; Si/m.. Symplectic.responding ones of the preceding and succeeding plates, thus prohibit-ing any decided laN'ral movements. The tail is more or less curveddownward, and in typical forms highly prehensile; it is quadrangularin section.The head in front of the eyes, or snout, is prolonged in a tubiformmanner as in the pipe-lishes (Syngnathida?), and the mouth and jawsare small and at the end of the tube; the preopercle is absent and theoperculum greatly enlarged. Proceedings U. S. National Museum, Vol. XXVIII-No. 1408. 805 806 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVIII. \7i 1' v\ LIFE inSTORY OF SEA-HORSES?(ULL. 807lor faculty, but a new function?prehension?results from its powerto curl inward, and, to some extent, sideways.The species are numerous, and one or more may he found in ahnostevery tropical and temperate sea. Somewhere near three dozen spe-cies have heen described, and of these one {///'p/Hx-a/iipu.s /u'jjpoca/npusor aiitujuoruni) is a common European tish, and half a dozen are inhab-itants of north oi' middle American seas. One of them {Hippocain-pi/s hudsonim) extends northward in the Atlantic as far as Cape Cod,and another {Hippocampus liKfrus)^ one of tbe laro-est of the oeuus, inthe Pacilic to San Diej^o.Strongly marked and ))izurre as is the form, the fishes neverthelessare not conspicuous in themidst of their natural sur-roundings, and indeed the lit-tle animals appear to be ableto readily adapt themselvesto their environment. Kent(1883) tells that "some veryextraordinary colored speci-mens" of the coimnon Medi-terranean species {Uippocam-pus hippocmnpuH) were givento him; some were '"brightred, others pale pink, brightor light yellow, and evenalmost pure white, with manyother interblending shades.Such colors had apparentlybeen assumed b}' the fish inkeei)ing with and as a meansof concealment among thebrilliant vegetation and zoo-phytic growth indigenous tothe locality from whence theywere derived. These tints in confinement gradually disappeared, untilthe tish had assumed the normal light-brown orsp(H-kled hue l)y whichthev are generallv characterized." Br- "-JT Fig. 4.?Sea-hokse (Hu'i'ocAMPr.. r.AMii.osus). TwoMIDDLE SIDE-SHIELDS SHOWING MANNER OF INTER-LOCKING BUTTRESSES ( A'. R.). (AFTER SCHAFF.) II.The attitudes and movements of the sea horses are eminently char-acteristic. The most frequent is a state of rest, with the tail woundaround the stem of a plant or some other substance and the body isthen carried nearly or quite erect. Such is the most frequent position,but notwithstanding the apparent rigidity of the cuirass, almost everyother attitude consistent with such a form mav be assumed. The 808 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvni.body may be thrown outward at v^arious angles and even downwardand the tail wound around a plant in a double coil. Once in a whileone eye may roll toward you, while another ma}^ be passive or lookbackward or in an op[)()sitc diivction. It ])ecomes obvious that thelittle tish can move its eyes independently of each other and in entirelydi tierent ways.A comical effect is pi'oduced by the way in which the little fishespeer at some object, reminding one of the actions of a very near-sighted person.Releasing itself at length from its support, one may slowly progress,still in a vertical position, its tail curved inward, its dorsal tin rapidlyundulating and reminding one of a screw propeller, its pectoralsvibrating in harmony. The I'apidity of the undulatory or vibratorymovements of the dorsal and pectorals is especially noteworthy.Incased as it is in an almost inflexible coat of mail, progression cannot be effected by lateral flexion of the body as in ordinary fishes, andflexion in a vertical direction is limited.With such limited powers of progression, a nice adjustment of organsis called for, and Dufosse has explained one method. The air bladderis comparatively large and always distended by a quantity of gas soexactly in harmony with the specific gravity of the bod}' that thisentire body is a hydrostatic appai'atus of extreme sensibility. A proofof this is that if a single ))ul)l)le of gas no larger than the head of avery small pin be extracted, the hsh inuuediately loses its equilibriumand falls to the ground, on which it must crawl till its wound has beencicatrized and a new supply of gas secreted by the internal membraneof the l)ladder. III.Another noteworthy peculiarity is a faint sound which is sometimesevoked. Kent, while making '"some colored sketches'' of the fishes,had two "isolated in separate glass receptacles some few yards apart,when unexpectedly a sharp little snapping noise was heard at shortand regular intervals to proceed from one of the vases placed on a sidetable, and to which a response in a like maimer was almost immedi-diately made from the vase close at hand. On seeking for the cause,the sound was found to proceed from the mouths of the little Ilippo-camp!., which were thus conversing with, or signaling to, one another.The noise observed was produced by the muscular closing and suddenexpansion of the lower jaw. and much resembled in strength and tonethe snapping sound produced for a similar purpose, but in thisinstance with its claw, ])v the little scarlet prawn {Alpheus riihei')^''''relatives of which occur along the southern coast of the United States.The mechanism which produced the sounds emitted by the sea horsewas explained at length hy Dufosse in 1874 to whose memoir refer-ence may be made by those who wish to learn details. Suffice it here LIFE insroRY OF SEA-HORSES?GILL. 809to note that Dufosse found that the fishes had the powei- of makinglong series of movements so slight and so rapid that they evade tliesight, but are appreciable to touch, and consequently are simple quiver-ings or vibrations (fremissements), and that these quivering move-ments are accompanied ))y sounds which, however, are I'arely distinctlyaudible (commensurablcs). The soiuids are produced by females aswell as males; notably in the spawning season, when they are bothmore frequent and more intense. IV.The natural food of the sea-horses consists mainly of small crusta-ceans, such as copepods, sand-fleas {Gfuitm((r!dH)^ and the opossumshrimps {^[yxidx) as well as the young of higher forms. Such beingnot readily obtainable by aquarium keepers,Kent improvised for his acjuaria "a suc-cessful substitute in the form of the larvaeof the common gnaf or mosquito {Ciilexpij>!en.s) and '?"other water insects.""The mode of feeding is curious. A sup-ply of amphipodous crustaceans may besupplied to them and a fish will slowlymove toward one, peering at it, approach-ing the mouth to it, and suddenly the ani-malcule may disappear without an}^ per-ceptible movement of the jaws as thoughthe fish had sucked it in. But the aniphi-pod (or other animal) must be at rest or onthe ground or a plant; for the fish is tooslow to get one moving; nevertheless itmust be alive. The fish may throw itselfon its side or in any other attitude most fitto o'et hold of the coveted "l)uo-." As the season for reproduction approaches fig. 5.?sea-horse (Hippocampus ,1 1 J !? -A fTM HUDSONIUS). Male WITH DILATEDthe sexes become prepared for it. The ^^^^^^ (after kaup.)mature female's cloaca or "genital papilla"is somewhat extended and becomes a kind of intromittent organ for thetransfer of her eggs to the male. The receptive male's pouch becomesthickened and vascular and thus prepared for the reception of theeggs and the nutriment of the embryos. The males, as usual in fishes,are somewhat smaller than the females. ?The many sea-horses in the atjuaria at St. Louis (1904) were fed ahnost entirelyon the larvae of trout and sahuon; the yelk-sac of the latter was broken before thelarva could be swallowed. 810 PllOCEEDINdli OF THE NATIONAL MUSEUM. VOL. XXVIII.Curiosity is naturally excited as to the manner in which the eggs aretransferred into the narrow-mouthed ovigerous sack of the male.Many have watched, l)ut. so far as known, the only one who has caughtthe female and male in the act of transfer was Dr. Filipo Fanzago. InMay, 1S74, the doctor observed the approach of the two in an aqua-rium at Naples. The approach was not once for all, but oft repeatedand very short each time. The male remained passive and the ^gg-l)urden(Kl female advanced toward him and pressedthe apei'ture for the extrusion of the eggs against themouth of the male's pouch. At the most a few eggs ? perhaps not more than a single one?were passedfrom the female to the male and then she retreated.After a not very long interval?it varied?she againapproached and another transfer was made. Fivetimes Fanzago ol)served this strange kind of copula-FiG. (1.?SKA-HORSK tion in a short space of time (in breve spazio di(Hippocampus tcuipo), but exactly how long is not stated. HeHUDSoNius). Very , i j. i l i j. ' i .? iu i ^- i i.YOUNG WITH YELK- '^opccl to bc ablc to uiakc further observations, butSAC. (After Lock- has left no other rccords. The eggs are doubtlessfertilized during the act of transfer.The ovigerous pouch is especially adapted not only for the receptionof the eggs l)ut for the sustenance of the newly hatched offspring.Dufosse (1,S74) found thatthere was a lining nuicousmembrane which had the fac-ulty of secreting an arM'Iformfluid. Further, this functionis liable to pathologic devia-tion, in which case the bladdermay become stopped up andthe tish be unabh^ to controlitself and carried to the surfaceof the water, where it remainshelpless till death follows.Lockwood (ISIJS), before theinvestigations of Dufosse,found out for himstdf that thepouch may actually COntril)Ute Fig. -.?Sea-horse (Hippocampus hudsonrs). Male ? ' 4- 4^1 ' i- DLSCHARGING YOUNG FROM POUCH. (AFTER LOCK-ni som(? way to the sustenance wood)of the brood. '^At the timeof receiving the spawn the Avall of the pouch is not less than 8 linesthick and well stored internally with fat. At the time of expulsion ofthe developed fry tiie same sack is not half a line thick and hangstlaccid on the animal, a mei'e thin meml)rane.''If the male would relieve itself of its burden it uses its tail. Lock-wood has described the operation as he saw it. "Bending this ap- NO. 140S. LTFE HISTORY OF SEA-HORSES?GILL. 811pendage upward like an inverted crook, thus imparting to it muscularrioidity, the animal pressed it against the bottom of the embryonalpouc-h, which occupied thelower part of the abdomen,thus pushing its contentsupward, and forcing themout of the opening on thetop of the sack, the creatureall this time sustaining itsnormal, erect position in thewater." Another may takeadxantage of the presence ofsome object on which it canget a purchase?a winkleshell, for instance. A '' win-kle afforded real help inthe lal)or of extruding theyoung" to another male ob-served by Lockwood. Thisoperation 'Ms in no sense aparturient process, Init onthe contrary is entirely me-chanical, and in the presentcase was effected in the fol-lowing manner: With itsalxlomen turned toward theshell, its tail attached to theunder part of it, the l)odyerecttHJ to its full height,the animal, by a contractileexertion of the proper mus-cles, would draw itself down-ward and against the shell,thus rubbing the pouch up-ward, and in this simpk',yet effective wav, expelledthe fry at the opening ontop of tii(^ sack," This isnot a contiiuious operation,but each effort was '"fol-lowed ))v a few minutesof rest," and the extru- Fi(i. 8.?Sea-horse (Hippocampus hudsonius). Yoitng,VIEWED FROM SIDE AS A TRANSPARENT OBJECT. (RE-DUCED FROM Ryder.) ah, air bladder; af. anal fin;((/, I'RINARY VESICLE OR BLADDER; (it, VENOUS SINUS;an, AUDITORY CAPSULE; h' , h", h'", h" ", FIRST, SECOND,THIRD, AND FOURTH BRANCHIAL ARCHES OF THE RIGHTSIDE; ha, BULBOUS AORTA: hl\ KASIRADIAL CARTILAGES;/)/", BREAST OR PECTORAL FIN; C, CEREBELLUM; Ce, CERE-BRUM; Ch, CHORDA DORSALIS OR NOTOCHORD; CS, CORACO-SCAPULAR ARCH, C?/, CERATOHYAL CARTILAGE; df, DORSALFIN; C, INTERNASAL CARTILAGE; llhy, HYPOHYAL CAR-TILAGE; hm, HYOMANDIBULAR CARTILAGE; (V. INTER-KADIAL CARTILAGES OR BASALIA OF FIN RAYS; Iv, IN-TESTINAL VALVE; /(', LIVER; m, MEDULLA SPINALIS ORSPINAL ('(jrd; m, mouth; mh, mid-brain; mk, Meckel'.sCARTILAGE; mo, MEDULLA OBLONGATA; nit, METAPTERY-GOID CARTILAGE; 1)a, NASAL PIT; OC, OESOPHAGUS; p,PARACHORDAL CARTILAGE; pll, PINEAL GLAND; pij, PITU-ITARY BODY, q, ROD-LIKE QUADRATE CARTILAGE; )T,ROSTRAL CARTILAGE OR PROLONGATION OF THE TRA-BECITLAR CORNU: ri.. RECTAL PORTION OF INTESTINE; .V, SPIRACULAR OUTLET OF THE GILL-CHAMBER: SC,DERMAL SCUTES OR PLATE-i; SIJ . ELONGATED SYMPLECTIC;/, TRABECUL.E CRANII SEEN FROM THE SIDE; tc, TEGMENCRANII; i', VENT OR anus; Ve, VENTRICLE OF HEART: W.WOLFFIAN OR SEGMENTAL DUCT; X, SUPRA-ANGULARCARTILAGINOUS ELEMENT, THE RUDIMENT OF THE SUPRA-MAXILLARY.sion of the 3^oung ''lastedfor nearly six hours, from three to six individuals being set freeat a time." The young then are fully developed. 812 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxviii.After the (exclusion of the young", eonnectioii ])etween them and theparent ceases, so far at least as recourse to the pouch is concerned.Unlike the open-pouched pipe-tishes the sea-horses apparently cannot readmit the young to the shelter of its small-mouthed sack-likepouch. It was Lockwood's " belief that with the sea-horse the termina-tion of development is the end of their solicitude for the young,""The newly born young, 5 to <> lines in length, are quite luilike theparent tish in some respects, while in others they resemble him. Thescales are undeveloped, and instead of the pipe-like mouth the snout isshort and broad; nevertheless the general form is similar to that ofthe adult, and the tail, though shorter and rounded, is incurv^ed inward.The tail is immediately utilized, we are told by Lockwood,VI,The species of UippociivipuK are numerous (})etween 30 and ?10), butthe many connnon characters are so much more prominent and strikingthan the specific ones that the latter are apt to be lost sight of andovershadow^ed by the former. The distinctions between the speciesare chiefly based on the length and number of rays of the dorsal tin,the luuuber of rings encircling the body, the comparative lengths ofthe body and tail behind the anus, the depth of the body or distanceacross from the dorsal I'idge to the ventral, and the relative length ofthe head and snout in front of the eyes. These are supplemented bythe comparative development of the tul)ercles or spines, of the coronetat the crown of the hea rays, about 45 (10+32-35) rings, thetail longer than head and truidv combined, the snout short but appre-ciably hmger than rest of head (1.3?1.4:1), and the depth of the))ody ai)pr<^ximately equals the length of the head. The coronet islittle developed, the tubercles and spines weak, and the filamentsrather few, short, and mostly simple. The color is dusky and spotless(but ])l()tched) and the dorsal has a submarginal dark band.The sea-wrack sea horse {Hippoeainpus zosterse) of Florida contrastswith the connnon species of the north in most of its characters. Ithas a short dorsal (covering only 3 rings) with about 12 rays, about 41(11+ 30) rings, the tail rather shorter than the rest of the body, thesnout extremely short and not more than half the rest of the head, andthe depth of the body great and almost equal to length from snout tomargin of pectoral fins. The coronet is high, the spines are welldeveloped, and the hhnnents moderate and often branched. The coloris olive green, more or less mottled, and the dorsal has no distinct NO. I-IOS. LIFE HISTORY OF SEA-IIORSES?GILL. 813submarginal band. It is, according to Jordan and Evermann, " thesmallest known species of sea-horse, abundant in shallow water in thelagoons, always found clinging by its tail to the sea-wrack {ZosteraWith these two species, two from Japan first described not long ago(11)01) by Jordan and Snyder may be compared. The descriptions Fig. 9.?Sea-horse (Hippocampus hudso-Mus). Female. (After Jordan andEvermann.) ^^^-^s^'Mr Fig. 10.?Sea-horse (Hippocampvs zostek-e).Female. (After Jordan and Evermann.) here given will furnish hints enough to discriminate between themand others and indicate the range of variation.VII.Certain Hippocampines of southern seas, especially the Phf/IIoj?ter(/:ffoliatus: and Phycoduras e/jues^ develop exaggerated characteristics,which are more or less manifest in the ordinary sea-horses. TheProc. N. M. vol. xxviii?04 52 814 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXVIII.cutaneous appendages, wliich are merely: tags of skin in most species,l)econie greatly developed, especially about the tail, and simulate in aremarkable degree the appearance of the seaweeds in which they arewont to lurk. Fig. n.?Sea-horse (HippocampusATERRiiMus). Male. Fig. 12.?Sea-horse (HiPPOCAMPrs sin-DONis). Male.The Solegnathines have the upper ridge of the caudal region deflectedand continuous into the lateral ridge, while the lower caudal ridge iscontinuous with the ventro-lateral ridge of the trunk; the nuchal plateis not elevated and not connate with the head. Nothing is knownrespecting tlieir liabits,