THE PAEASITIC ISOPOD LEIDYA DISTORTA (LETDY)FOUND ON A NEW HOST.
By Harriet Richardson,CoUdhnrdtor. Diri.sioii of Mnrinc fiircrtcbratcs. F. S. \(itioii(il Muaeum.
Prof. A. E. Verrill has recently sent me specimens from the Ber-mnda Ishinds of Pach(/(/t'apsi(,s transvcrsus (Gibbes), infested withan Isopod parasite. The parasite is located in the branchial cavityof the host. On examination the Isopod was fonnd to be Leidya (h's-torta (Leidy), heretofore recorded as parasitic on Uca pugilato/-(Bosc). This genus and species is therefore not confined to onegenus and species of host.The species found by Fritz Mueller in the branchial cavity of aCxrapsoid Pachygrapsus transversus (Gibbes), from the coast ofBrazil, is probably this species and genus, and not GrapsiceponfrltziL the nominal species of Giarcl and Bonnier."Because GrapHieejjon edwardsi was found on a Grapsoid, PlanentnimttKS, according to the theory advanced by these authors the para-site of another Grapsoid of the same family, Pacliygrapsus tn/ns-versus, would naturally be a Grapsicepon. The facts prove, however,that this is not always the case, in this instance as in other parasiticIsopod genera before cited.Leidya is found parasitic on both Uca and Pachygrapsus, twowidely separated genera of hosts belonging to different families.As no descriptions or figures of this form have been given sincethose published by Leidy, the following descriptions and figures maybe of interest, in that the young female is also described and figuredfor the first time
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"Trav. du Labor, de Wimereux, V, 1887, p. 70, and VIII, 1900, p. 226.Proceedings U. S. National Museum, V6l. XXXIV?No. 1593. 23
24 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV.LEIDYA DISTORTA (Leidy).Cepon difttortus Leidy, Jour. Acad. Nat, Sci. Phila., (2), III, 1S55, p. 150,pi. XI, figs. 26-32,?Harger, Report U. S. Fish Commission, Pt, 6, 1880,p, 311.?KossMANN, Zool, Ergeb, einer Reise in die Kiist. des RothenMeeres, III, Malacostraca, 1880, p. 122; Mittheil. aus der Zool, Stationzu Neapel, III, 1881, first half, p, 182.?Richardson, Am. Nat, XXXIV,1900, p, 309,Lridija di^iorta Cornai.ia and Panceri, Mem. II. Acad. Sci, Torino, (2),XIX, 1858-1861, J). 114.
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Giard and Bonnier, Trav. dn I^abor. de Wime-reux, \, 18S7, p. 68, fig, 12.?Richardson, Proc. U. S. Nat. Mus.. XXIII,1901, 1). 579: Bull, U. S, Nat, Mus., No, 54, 1905, pp, 511-512.Localities.?Atlantic City, New Jersey, on Uca pugilatoi' (Bosc) ;Bernuidas on Pachygrapsus transversus (Gibbes).It is interesting to note that although Leidya distorta was firstfound at Atlantic City, New Jersey, its liost, Ilea pugilator, extendsas far south as the coast of Florida, andthe new host, Pachygrapsus transversi/s^extends as far north as the Florida coast,so that the continental ranges of the twohosts overlap,Descriptio7i of female.?Body rather ir-regular in outline, oblong-oval. Coloryellow. (See figs. 1-2.)Head large, bilobed, and with the frontproduced in a wiiU* border or margin,p]yes wanting.First two segments of thorax short. Thethree following segments are the largest,and are subecjual in length, about twnce as long as the first; sixth alittle shorter than fifth; seventh about halfas long as sixth. The second, third, fourth,and fifth segments have in the middle ofthe dorsal part of the segment a squarishplate, which in the fifth segment has theouter edges considerably elevated, so as toform a longitudinal carina on either side,which extends posteriori}^ over the sixthsegment. Coxal plates or epimera are pres-ent on the anterior portion of the lateralmargin of all the segments, but are almostcompletely hidden by the large ovarianboss which projects upward in a large,prominent lobe. There are five pairs of incubatory j^lates, which
Fl?. 1".
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LEIDYA DISTORTA. AlU'LTFEMALE (DORSA I, VIEW).
Fig. 2.?Leidya distorta. Adultfemale (ventral view).
? Figs. 1, 2, and 5 are from photographs taken in the IT. S. National Museum.In the specimens photographed the pleural lamellse and the iileojioda werebent, so that they do not apiiear as long as in Leidy's figures.
NO. 1593. ON LEIDYA DISTORTA?RICHARDSON. 25()\'orlaj) each other on the ventral side, completely inclosin<2^ theiiiiirsiipiiil cavity. The seven pairs of legs are siiinll and feeble, thepropodus and dactylus forming a prehensile hand." (See fig. 3.)The six segments of the abdomen are more or less coalesced in themiddle of the dorsal surface. The lateral parts ofeach of the first five segments are j)rodiiced into anelongate double-branched jiinnate appendage oneither side, so that altogether there are five pairs orten i)innate appendages to the first five segments.The n])per branches probably represent the pleural p,G 3 _j,k,uya i.is-lamelhe and the lower branches the pleopods, so that, torta. lw; okin this interpretation, there are five pairs of single- ^^^^^"^ ikmale.branched |)leo))oda and five pairs of single-branchedpleural lamelhe. The sixth or terminal segment is furnished witha single paii' of elongated ])innate appendages, the nropoda.Dcscr'tptioii of yoKiKj fcriijilc.?The young female differs from theadult in its narrower and elongated form, in not having the thoi-ax so
a bFig. 4.?Lkiuya uihtc^kta. You.nv; fkmaj.k. n, dorsal vikw; h, vkntrai, view.greatly distended, in the more equal length of the segments of thethorax, which do not have the median dorsal plate as in the adult, inhaving the segments of the abdomen more distinctly separated andthe lateral appendages more elongated.
" Leidy mistook the prebeiii^ile band for the " recurved, abortive boolvlet." Insome jtositions tbe band bas tbe appearance of a blunt booli; and the dactylusis difficult to see. Leidy's figure is inaccurate and misleading. The articleimmediately preceding tbe " boolilet," in I.ieidy's figure, is probably tbe carpusand the merus combined. Tbe line of sei)aration between tbe two articles issomewhat difficult to see. Another interi)retation might be given to I.eidy'sfigure, the "booklet" being tlie dactylus, tbe article jtreceding it, the proi)odus,and tbe one preceding that, the combined carpus, merus, and ischium.
26 PROCEEDINGS OF THE NATIONAL MVSEVM. VOL. XXXIV.The incubatory plates are much smaller than in the adult, and themarsupial pouch greatly reduced in size. The pouch is never filledwith eggs at this stage. ( See fig. 4.
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Description of rnale.?Body narrow, elongate.Color yellow. (See fig. 5.)Head but little wider than long; frontal marginstraight, with antero-lateral angles rounded. Pos-terior portion somewhat wider than anterior. Eyeswanting. First pair of antennje composed of threejoints, second pair composed of seven, the last twobeing minute and tipped with hairs.The seven thoracic segments are separated fromeach other by lateral incisions, so that the lateralmargins are not continuous. There are seven pairsof prehensile legs.The six abdominal segments are perfectly dis-tinct, are separated from each other by lateralincisions, and decrease gradually in width, fromthe first to the sixth, which carries a pair ofelongated, tapering appendages, the uropoda. The pleopoda are?Leidya dis-Male. " X 23.rudimentary.
? Some allowiiiice must Ite miul<' for Leidy's tijiures, winch nre somewhat(liaKramniatic.