Some Polyclad Flatworms from the Hawaiian Islands

LIBBIE H. HYMANl

ONE MAY SUPPOSE that a rich polyclad faunaexists along the shores of the Hawaiian Is­lands, but our knowledge of Hawaiian poly­clads is, in fact., very limited. As far as I canascertain, only the follo.wing species are re­corded from the Hawaiian Islands in theliterature: Planocera hawaiiensis Heath, 1907;Taenioplana teredini Hyman, 1944; and 5ty­lochoplana inquilina Hyman, 1950. The firstmerits further examination, but the specimenscannot be located. Three further species fromHawaii have been received for identification,from the United States National Museum,and furnish the material for the present article,which thus adds something to our smallknowledge of the polyclad fauna of theseislands. All three species belong to the Aco­tylea and to the section Schematommata. Asthe taxonomic categories that concern thesethree species have been carefully defined ina recent publication (Hyman, 1953a), thereappears no need for repetition of these def­initions here.

Family LEPTOPLANIDAE

Euplana trapicalis n. sp.Fig. 1

The species is based on one specimen thatwas collected near Kapoho, Hawaii, Septem-

1 American Museum of Natural History. Manuscriptreceived June 19, 1953..

ber 25, 1929. The species is rather large, ofelongated oval form, 38 millimeters long by17 millimeters wide (Fig. 1a), but, as it isevidently contracted, it presumably reachesa much greater length. The specimen hadacquired the usual dark-brown color typicalof museum specimens but in life was prob­ably tan with dark-brown spots. The tenta­cular eyes form small but conspicuous clustersof about 10 eyes on one side and 15 on theother, but the cerebral eyes could not be madeout satisfactorily. They appeared to be veryfew in number and were seen chiefly on oneside. The form of the pharynx as far as seenand the locations of mouth and gonoporesappear in Figure 1a.

The posterior half was removed and theregion of the copulatory complexes sectionedsagittally. The histological condition is poor,but the parts of the complexes were followedsatisfactorily and are represented in schematicsagittal view in Figure lb. Both complexesappear unusually sinuous, much more so thanas represented in the figure, but whether thisis natural or the result of the contraction ofthe specimen is uncertain. The complexesoccur shortly behind the pharynx as is usualin the Leptoplanidae. The gonopores arewidely separated. The male gonopore leadsinto a somewhat expanded male antrum linedwith a sinuous epithelium and bearing at itsinner end a small penis sheath. From this along penis pocket proceeds anteriorly, sur-

331

332 PACIFIC SCIENCE, Vol. VIII, July, 1954

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FIG. 1. Euplana tropicalis, a, Entire specimen; b, sagittal view of rhe copulatory complexes from sections.1, Cerebral eyes; 2, tentacular eyes; 3, pharynx; 4, mouth; 5, male gonopore; 6, female gonopore; 7, male antrum;8, penis sheath; 9, penis pocket; 10, penis papilla; 11, ejaculatory duct; 12, seminal vesicle; 13, horns of seminalvesicle or spermiducal bulbs; 14, sperm duct; 15, female antrum; 16, vagina; 17, uteri; 18, entrance of oviductinto vagina; 19, Lang's vesicle.

Hawaiian Polyclads - HYMAN

rounded by dense mesenchyme, and afterbending dorsally terminates in a slightly ex­panded chamber housing the elongated, con­ical penis papilla. The central duct of thepapilla, or ejaculatory duct, proceeds forwardand downward very sinuously and becomescontinuous with the central part of a tripartiteseminal vesicle. This has pronounced muscu­lar walls of chiefly circular fibers. It is verypeculiar in that one horn of this tripartitestructure descends ventrally, receiving onesperm duct, and the other ascends dorsally,receiving the other sperm duct. This lack ofbilateral symmetry in the entry of the spermducts into the seminal vesicle is certainly veryunusual. Possibly the two horns of the tripar­tite seminal vesicle should be regarded asspermiducal bulbs, that is, as thickened term­inations of the sperm ducts.

The female gonopore leads into a short,expanded antrum from which the vagina pro­ceeds forward and then dorsally in a verysinuous manner, not indicated in the figure.Shortly after bending from a vertical to ahorizontal position, the vagina receives thecommon oviduct and then continues as anoval Lang's vesicle. The female tract through­out has a well-developed muscular coat ofmainly circular fibers. The same peculiar asym­metry seen in the entry of the sperm ductsinto the male apparatus also obtains in theentry of the oviducts into the vagina. Asshown in Figure 1b, one oviduct is situatedventrally, the other dorsally. Cement glandswere not evident, no doubt because of thepoor histological condition. The uteri alsocould not be traced anteriorly.

A penis papilla at the inner end of a longmale antrum guarded distally by a penissheath also characterizes two other species ofEuplana-concolor Meixner, 1907, and clipper­toni Hyman, 1939. However, a penis stylet ispresent in the latter, and the Lang's vesicle isvery small in the former. Further, no otherspecies of Euplana has the peculiar asym­metry of the sperm ducts and the oviductsthat distinguishes E. tropicalis.

333

The holotype has been deposited in theUnited States National Museum in the formof slides bearing the· anterior half mountedwhole and the copulatory complexes as sagit­tal serial sections.

Family PLANOCERIDAE

Paraplanocera oligoglena(Schmarda) 1859

One specimen of this species, collected byH. W. Henshaw at Hilo, Hawaii (no date),was sent as a whole mount. The specimenwas much ruffled, measuring 33 millimetersin length by 28 millimeters in breadth. Thefeatures of the copulatory apparatuses, in­cluding the two large teeth at right angles toeach other in the cirrus sac, were readily seenin the whole mount and considered to es­tablish the identification without the necessityof sections: This species is cosmopolitan intropical and subtropical waters and has beenrecorded from a number of localities in theIndo-Pacific region, further from the GulfofCalifornia (Hyman, 1953a: 353-357). Thewhole mount has been returned to the U. S.National Museum.

Planocera pacifica n. sp.Figs. 2, 3

A fine, perfect specimen was taken in theHawaiian Islands by P. S. Galtsoff, July 27,1930, in the evening, hence presumably swim­ming at the surface. The specimen (Fig. 2)is of broadly oval form, with ruffled margins,40 millimeters long by 25 millimeters wide.The color is indeterminable, but the wormappears thin and transparent. There is a pairof conspicuous conical tentacles near thebrain, far back from the anterior margin. Aring of tentacular eyes occurs at the base ofeach tentacle. The fairly numerous, small cere­bral eyes (Fig. 3a) are more abundant anteriorto than behind the brain level. The broad,ruffled pharynx with about six main lateralfolds on each side occupies approximately thecentral region of the worm (Fig. 2), and di-

334

FIG. 2. Planocera pacifica, entire specimen. 1, Cerebraleyes; 2, tentacular eyes; 3, pharynx; 4, mouth; 5, malegonopore; 6, female gonopote; 20, btain; 21, tentacles; .22, prostatic vesicle; 23, cirrus sac; 24, large teeth ofcirrus sac; 25, uterine sac; 26, bulbous antrum; 27,cement glands.

rectly behind it is seen the male copulatoryapparatus, armed nhr the male gonopore withthree large teeth. Behind this is seen the bulb­ous terminatio~ of the female copulatory ap­paratus. To either side of the male apparatus.there occurs a sacciform enlargement of theuterus, presumably for the purpose of storingeggs. Such sacs are unusual in acotylean poly­clads. The details of the copulatory appara­tuses, insofar as they could be seen in thecleared whole specimen, are shown in Figure3b.

For species discrimination, it was consid­ered necessary to remove the copulatory re­gion of the worm and section it sagittally.A view of the copulatory complexes as con-

PACIFIC SCIENCE, VoL VIII, July, 1954

structed from the series of sagittal sections isgiven in Figure 3c. At the anterior end of themale apparatus is seen the elongated, curvedseminal vesicle closely applied to the ventralwall of the prostatic vesicle. The commonsperm duct enters the ventral surface of theseminal vesicle, passes slantingly and upwardin the muscular wall of this vesicle, then turnsback and becomes the lumen of the vesicle. Itenters the proximal end of the cirrus sac incontact with the prostatic d~ct. The prostaticvesicle is a slightly oval sac situated at theanterior end of the cirrus sac but not boundwith the latter in its muscular sheath. Theprostatic vesicle has a thin muscular wall, andthe interior is filled as usual with a much­folded, glandular eosinophilous lining. Theshort prostatic duct and the duct of the sem­inal vesicle enter the anterior end of the cirrussac in contact with each other and terminatein the beginning of the ejaculatory duct. Thecirrus sac is a large oval body with a thickmuscular wall distally, a thinner wall prox­imally. This proximal half of the cirrus sacis filled with a loose tissue traversed by diag­onal muscle fibers and contains the slightlysinuous ejaculatory duct. This opens on aprojection into what is presumably the lumenof the cirrus sac. This is widened anteriorlyaround the projection in question, then nar­rows to a tube running to the male gonopore.The lumen of the cirrus sac is lined by smallteeth that increase in size distally. At the distalend of the cirrus lumen, where it opens intothe male gonopore, are the three large teethalready mentioned. One of these and part ofanother appear in Figure 3c.

The female gonopore occurs some distancebehind the male pore and leads into an an­trum with excessively thick muscular walls,composed of circular and radiating fibers in­termingled. This muscular antrum, or bulbousvagina as it is termed by some, extends an­teriorly, gradually narrowing until it reachesnearly the level of the male gonopore. It thennarrows abruptly into the vagina which turnsfirst backward and then forward again, run-

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Hawaiian· Polydads - HYMAN 335

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FIG. 3. Planocera pacifica. a, Enlarged view of eyes and tentacles; b, copulatory complexes seen from above incleared entire· specimen; c, sagittal view of the copulatory complexes from secrions. 1, Cerebral eyes; 2, tentaculareyes; 5, male gonopore; 6, female gonopore; 11, ejaculatory duct; 12, seminal vesicle; 14, sperm duct; 16, vagina;18, entrance of oviduct into vagina; 19, Lang's vesicle; 20, brain; 21, tentacles; 22, prostatic vesicle; 23, cirrussac; 24, large teeth of cirrus sac; 26, bulbous antrum; 27, cement glands; 28, granule masses of brain; 29, prostaticduct; 30, small teethdining lumen of cirrus sac; 31, cement glands entering vagina.

336

ning just above the distal part of the cirrussac. Along much of this course it is heavilysupplied with cement glands. It then turnsbackward, narrowing as it receives the com­mon oviduct; beyond this it continues for ashort distance as a narrow, tubular, somewhatsinuous Lang's vesicle.

Until recently but one species of Planocerawith three large teeth in the distal end of thecirrus sac was known, namely, P. crosslandiLaidlaw (1903: 100), from the coast of BritishEast Africa. Laidlaw gave a good descriptionof this but did not furnish any figures. Re­cently Prudhoe (1952: 175) assigned a spec­imen from the Gulf of Aqaba, Red Sea, toP. crosslandi on the basis of the presence ofthree large cirrus spines but did not sectionthe worm. I recently studied a Planocera fromthe Galapagos Islands with three large teethin the distal end of the cirrus sac and decidedit was not identical with P. crosslandi, namingit tridentata (Hyman, 1953b: 188). Both triden­tata and pacifica differ from crosslandi in thatthe prostatic vesicle is not bound in commonwith the cirrus sac in the same muscularsheath. Further, tridentata lacks a Lang's vesi­cle, having instead a very long and narrowvagina recurved on itself, whereas crosslandiis described as having a long, thread-likeLang's vesicle, and in pacifica Lang's vesicleis short and tubular. It may be concluded thatthere are several species of Planocera armedwith three large teeth at the exit of the cirrussac and that the presence of these teeth is nota sufficient basis for species identification.

The holotype, preserved in alcohol, hasbeen deposited in the U. S. National Museum,accompanied by the slides of sections of theremoved copulatory region.

REFERENCES

HEATH, HAROLD. 1907. A new turbellarianfrom Hawaii. Acad. Nat. Sci. Phila., Proc.59: 145-149, 1 pI.

PACIFIC SCIENCE, Vol. VIII, July, 1954

HYMAN, LIBBIE H. 1939. Polyclad worms col­lected on the Presidential Cruise of 1938.Smithsn. Inst., Misc. Collect. 98(17): 1-13,15 figs.

--- 1944. A new Hawaiian polyclad asso­ciated with Teredo. Bernice P. Bishop Mus.,Occas. Papers 18 (4): 73-75, 1 fig. .

--- 1950. A new Hawaiian polyclad, Sty­lochoplana inquilina, with commensal hab­its. Bernice P. Bishop Mus., Occas. Papers 20

(4): 55-58.

--- 1953a. The polyclad flatworms of thePacific coast of North America. Amer. Mus.Nat. Hist., Bul. 100 (art. 2): 269-392, 161figs.

---1953b. Some polyclad flatworms fromthe Galapagos Islands. Allan Hancock Pac­ific Exped. 15(12): 183-210, 14 figs.

LAIDLAW, FRANK F. 1903. On the marinefauna of Zanzibar and British East Africa,from collections made by Cyril Crosslandin the years 1901 and 1902. TurbellariaPolycladida. Part I. The Acotylea. Zoo!' Soc.London, Proc. 1903: 99-113, 7 text figs.,1 pI.

MEIXNER, A. 1907. Polycladen von der Soma­likiiste, nebst einer Revision der Stylochi­nen. Ztschr. f. Wiss.Zool. 88: 385-498, 2 textfigs., 5 pIs.

PRUDHOE, STEPHEN. 1952. Manihine Expedi­tion to the Gulf of Aqaba, 1948-1949. IV.Turbellaria: Polycladida. Brit. Mus. (Nat.Hist.), Bu!., Zoo!' 1 (8): 175-179, 2 figs.

SCHMARDA, LUDWIG. 1859. Neue wirbelloseThiere beobachtet und gesammelt auf einerReise um die Erde 1853 bis 1857. Erster Band.Turbellarien, Rotatorien und Anneliden.Erste Hiilfte. xviii+66 pp., 15 pIs. WilhelmEngelman, Leipzig.