On a New Species of Caligus (Copepoda Parasitica)from the Coast of California

SUEO M. SHIIN01

AMONG THE MATERIAL of parasitic copepod swhich Dr. W. 1. Klawe of the Inter-AmericanTropical Tuna Commission collected fromfishes in the eastern Pacific and sent to theauth or for identification, there was an inter­esting specimen representin g a new species ofthe genus Caligus. The specimen , consistingof a single female, was obtained off the coastof California . It has been preserved togetherwith the host, Engraulis mordax, to whosebody it was firmly clinging. The present notecontains the description of this parasite.

The author wishes to express his thanks toDr. Klawe for providing the present material,and takes a great pleasure in associating thename of the species with the naturalist.

CaligtlS klawei sp. nov.Figs. 1- 3

A female found on a specimen of Engraulismordax 7.9 cm. long, taken off CoronadoHotel , San Diego, California, late in May,1956. It was clinging to the side of the hostabove the pectoral fin. The anterior region ofthe body is lapped by a fleshy fold which isan abnormal outgrowth of host skin causedby the presence of the parasite.

Body flattened, length excludin g rami5.46 mm ., carapace excluding marginal rim2.39 mm . X 1.71 mm. , fourth thoracic seg­ment 0.21 mm. X 0.61 mm ., length of ex­posed region of same 0.07 mm. , genitalsegment 2.47 mm . long on midline, 2.89 mm .long in lateral region, 2.25 mm. wide, abdo ­men 0.56 mm . X 0.61 mm . Color whitish informalin, without pigment.

Carapace elongate oval, about three quar­ters as wide as long, somewhat more strongly

1 Faculty of Fisheries, Prefectu ral Un iversity of Mi e,Tsu -City, J apan.

convex above than in ordinary case, withlateral regions turning downward. Two sidesvery widely curved and fringed by relativelynarrow rim. Frontal plates two thirds thewidth of carapace, only slightly arched onmargin and provided with a lunule close toeach lateral end . Median lobe half as wide asthe carapace at its base, and about as long asit is wide. It is rough ly trapezoid in shape,with well-rounded corners, and extend s con­siderably beyond the lateral lobes . Sinusesbetween adjoining lobes are shallow and nar­row, opening backward. The transverse dorsalrib is placed at about the center of the cara­pace, and arches forward to make, togetherwith the incurved posterior halves of thelongitu dinal ribs, a continuous semicircle.Anterior halves of the latter extend diagonallyoutward, separating narrower lateral areasfrom the broader central area, in the center ofwhich the eyes are located . Fourth thoracicsegment is covered by carapace in front andby genital segment in the rear, showingmerely a very short central region in dorsalaspect. Genital segment is a huge quadrangu­lar segment which is produced backward oneither side of abdomen into a pair of ovallobes . Anterio r end is contracted into a shortneck, but expanded just behind this abruptlyto form gracefully roun d shoulders whichcontinu e back to slightly arched lateral mar­gins. Segment as long as carapace on the mid­line, but one fifth longer on the lateralregion ; width across middle of segment isone and one thi rd that of carapace. Abdomenis about a quarter of preceding segment inlength , beyond whose lateral lobes it extendsonly a little. It is one-segmented, as long aswide, and has slightly undulated sides andV -shaped caudal margin .

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352 PACIFIC SCIENCE, Vol. XIII, October, 1959

FIG. 1. Engraulis mordax infected by Caligus klawei sp. nov. X 2.5.

First antennae two-jointed as usual. Apicaljoint ends in several delicate hairs and twothicker spines , and bears a solitary hair atabout the center of its side. Basal joint tri­angular and fringed by three or four rows ofstout pinnate spines on frontal margin .Lunules semicircular, truncate on front side.Second antennae three-jointed. Terminal jointsharp, strongly curved and carrying two tinyspinules, one at the base and the other a shortdistance distally . Basal joint armed with apointed, spurlike posterior process. Mouthtube has broad apex, enclosing slender man­dibles well dentate on their curved apicalblade . First maxillae small in size, apex hook­like, base oblong and furnished on the sur­face with two delicate hairs, each arising froma papilla. A similar hair present on the ster­num behind the maxilla . Second maxillaebroad at base, slender toward tip and directedstraight backward ; exopodite made up of onelonger and two shorter spines . First maxilli­peds slender; terminal joint longer than basaljoint, ending in two unequal claws withfinely pectinate, narrow rims and carrying anarrowly triangular accessory lamina a shortdistance behind. Second maxillipeds cheli­form , moderately stout. Their palm fusiform,about thrice as long as wide and with a veryslight bulge at about the center of inner mar­gin. Finger straight in its basal half, but termi­nating in a strongly curved , sharp claw which

acts against the bulge of the palm. Claw bearstwo short spines at its base. Sternal furcaV -shaped , branches uniform in breadth, bluntat tip and without marginal rim.

First swimming legs provided with triangu­lar rudiment of endopodite. Protopodite ofsecond legs indistinctly divided into twojoints . Two rami of third legs widely sepa­rated from each other by a crescentic dilata­tion of basal apron; exopodite two-jointed,whereas endopodite is practically one-jointed,owing to almost complete reduction of basaljoint. Fourth legs uniramous, having proto­podite longer than two-jointed exopodite.Arrangement of spines and setae present ineach of four pairs of legs is shown in Table l.

Of the apical spines on the first legs, themiddle two are deeply forked into parallel,unequal branches ; the external branch isshorter and has fine pectination on the sides .The outermost of them is bifid to a veryslight extent, and the innermost is simple andmore than once the length of the others.Plumose spines borne on the third joint offirst legs, on the exopodite of second legs,and on the first endopodite joint of the latterare rimmed on one side for some distancefrom the base by hairs which are shorter butstiffer than those fringing the opposite sideand other regions . The similar spine on theprotopodite of second legs is dilated at thebase into a semicircle, where it bears stiff hairs

New Species of Caligus - SHIINO

G

353

FIG. 2. Caiigas klawei sp . nov. A, female, dorsal aspect ; B, first antenna with lu nule ; C, second antenna, mouthtube and first and second maxillae in situ; D , first maxilliped ; E, seco nd maxilliped ; F, sternal fur ca; G , urop od .A X 19, B-G X 100.

354 PACIFIC SCIENCE, Vol. XIII , October, 1959

F

FIG. 3. Caligus klawei sp . nov. A, first swimm ing leg ; B, apex of same ; C, second leg ; D , one of the spines onthe exopodite of same; E, third leg ; F, fo urth leg . A, C, E, F X 100; B X 340; D X 170.

New Species of Caligus - SHIINO

TABLE 1A RMATURE P RESENT ON SWIMMING LEGS

355

STERNAL PROTOPODITE EXOPODITE ENDOPODITELEG BORDER PLATE

I II I II III I II III

I o uter I s , l p Irh 3H, 1Hin ner Ip c 3P

II o u ter f f, Is f,IH IH 2H, I Q c CC cInner IS,IP f, Is c,IP c, IP 5P I P c, IP 6 P

III o u rerf

f, l p IH ' , C c, 3h Cinner I P , f, 25, C C, IP 4 P I P 6P

I

---IV ourer IH 3H

inner

Abbreviations : c, row of hairs; CC, area covered with spin ules: f, mernbraneous /lange; H , stouter simple spine; h , feeblersimple spine; H '. hooklike spine; P, stouter plumose spine; ph. feebler plumose spine; Q. spine rimmed with hairs on one side,with membrane on the other; rh, tiny spine; s, solitary hair. Roman numerals represent the ordinals of legs or of joints andArabic numerals denote the number of spines, or of other armature present on each of them.

the same as those on the spines just named.External spine on the first two exopoditejoints of the same legs acuminares toward thetip and has pectinate rims along two oppositeborders ; that of the first joint accompanies abasal lamina with parallel striat ion on itssurface. The basalmost of external spines onthe third joint of the same exopodite is muchreduced in size, without rim; the middle spinehas a broad striated membrane on the innerside, and the terminal one bears an inner rowof hairs besides the outer membrane. Basalhook on the exopodite of third legs ends ina straight apex which is narrowed to a pointresembling an arrowhead. Termina l spines onthe fourt h legs are equal in length except theoutermost, which is sligh tly shorter; all ofthem are doubly edged with a narrow rim andassociated at the base with a fusiform lamina,circumscribed with pectination. Spine on thesecond joint is simple and devoid of basallamina. Genital segment lacks any trace offifth legs. Caudal rami are small in size andtermin ate in three plumose spines , which areattended outside with two similar, but muchshorter, spines and inside with another shortone. Inner margin of the rami is fringed by ashort row of hairs. Egg strings are longer than

the body and packed with uniserial, Bat­tened eggs .

REMARKS

The new species is characterized , above all,by the enormous size of its genital segment,which surpasses the carapace in length andwidth . In the genus Caligus, there are a num ­ber of species which present certain resem­blances to the new species in the outline ofthis segment, in its size relative to tha t of thecarapace, and in the possession of a smallone -segmented abdomen. To facilitate dis­tinction of k/awei from such species some ofthe characters are summed up in Tab le 2.

As may be seen from this table, no specieshas a genital segment so strongly expanded asthat of k/awei. It is, however, close to po/y­canthi, g/andifer, fistu/ariae, and maearovi inthe outline of this segment. The first of thesehas . the second maxillipeds stouter than ink/awei, the second has the same limbs feebler,and the others are longer in the abdomen,which in them extends considerab ly beyondthe foregoing segment.

The specimen will be preserved in the mu­seum of the Prefectura l University of Mie.

356 PACIFIC SCIENCE, Vol. XIII, October, 1959

TABLE 2COMPARISON OF Ca/igus k/awei WITH ALLIED SPECIES

C.L _ length of carapa ce, C.W - width of same, G .L - length of genital segmen t, G .W _ width of same.Proportion of genital segment and carapace is taken from the drawings given by the original authors unless otherwise ind icated.Numerals show n in the rightmost column represent from the le ft to the right the number of spines on each of joints from basalto apical in due order. They denote, when put in parentheses. the spine borne on the oute r border of joint, otherwise the terminalspines. Presence or absence of spine on the protopodite is indicared. by 1 ) or 0) .

lK irtisinghe's alalongae does not seem conspecific with Krover 's,:!C. !ttlvip1Jrpllreus Shiino is a synonym of maca rovi.

FOURTH LEG

G .L/C.L G .W / C.W Number of Numberjoints of of

exopodite spin es

a/a/ongae Kroyer (afrer K irtis inghe)! . ........... . 1.00 0.66 3 6), 1, 1, 3

a/a/us Heegaard . . . . . . . . . ... . . . . . .. . . . . .. . . .. . . 0.70 0.77 2 0) , 1, 3

bicycle/us Heegaard . . . . . . . . . . . . .... . . .. . . . . . . .. . 0.92 1.00 3 0) , 1, 1, 3

fistulariae Yam aguti . .. ... . .... . . .. .. ... . .. ... . . 0.86 0.82 2 0) , 1, 3

g/andife r Shiino . . . . . . .. . .. . . .. . .. . .. . .. . . . ... . 0.81 0.68 2 1) , 1, (1) 3

maearovi Gus sev". . ... . . . . .. . . . . . . .. . . . . . . . . .. . 0.77 0.87 2 1) , 1, 3

minimus Otto (after Bria n) ... . . . . . . . . . . . .. . ... .. 1.00 0.73 2 1), 1, 3

polycantbi Gnanamuthu ... .. . .... . .. . . .. . . . . . . .. 0.66 , 0.77 2 0), 1, 3

zei Norman an d Sco tt. . . . ... . . . . . . . . . . . . . . . . . . . 0.71 0.76 2 1) , 1, (1) 3

k/awei sp . no v.. . . . . . . . . .. . ... . . . . . . . . .. ... ... . 1.21 1.31 2 0), 1, 3- - - -

REFEREN CES

BRIAN, A. 1935. I Caligus parassiti di Pescidel M edi terraneo (Copepodi) . Ann. M us.Stor. Nat . Genova 57: 152-211.

GNANAMUTHU, C. P. 1950. Sex differences inthe chalimus and adult forms of CaNguspolycanthi , sp. nov. parasi tic on Balistesmaculatus from M adras. Rec. Indian M us.47 (1) : 159-170.

G USSEV, A. V. 1951. Paraziticheskie Cope­poda s nekotorykh M orskikh Ryb. Para­zitol. Sborn. Zoolog. Inst. A kad. N auk SSSR13: 394-403.

H EEGAARD, P. E. 1943. Parasitic cop epodsmainly from tropical and An tarctic seas.Ark . Zool. 34 A (18) : 1-37.

- -- 1945. Some parasitic copepods fromfishes in the Uppsala University Collection s.Ark. Zool . 35 A (18): 1-27 .

K IRTISINGHE, P. 1937. Parasitic copepods of

fish from Ceylon II. Parasitology 29: 435:­452.

KROYER, H . 1863. Bidrag til K undskab omSnyltekrebsene . N aturh. Tidsskrijt, 3 Raek­ke, Vol. 2: 75- 426, pls . 1-18.

SCOTT, T. , and A. SCOTT. 1913. The B ritishParasitic Copepoda. 2 vols ., pp. ix + 252,pls. A, B + 72.

SHIINO, S. M . 1954. A new fish louse foundon the mackerel pike. Annot . Zool. J ap .27 : 150-153 .

--- 1954. A new fish lou se found onZenopsis nebulosa (T. & S.) . Annot. Zool. Jap .27: 154-156.

--- 1956. Copepods parasi tic on Japanesefishes , 10 . The redescription of three spe­cies of CaNgus. Rep. Fac. Fish. Pre! Univ.M ie 2: 223- 241.

YAMAGUTI , S. 1936. Parasitic Copepods fromFishes ofJ apan. Pt . 2, Caligoida I. Pp . 1-22,pis. 1-12.