[Jpn. J. Parasitol., Vol. 39, No. 4, 384-396, August, 1990] Trematodes of a New Genus, Neoplagioporus gen. n. (Digenea: Opecoelidae: Plagioporinae), and an Unidentified Opecoelid from Freshwater Fishes of Japan Takeshi SHIMAZU (Accepted for publication; July 2, 1990) Abstract A new genus, Neoplagioporus gen. n., is proposed in the subfamily Plagioporinae Manter, 1947 (Opecoelidae). It is morphologically characterized chiefly by the distinctly bipartite, short and straight seminal vesicle, the sinistrally submedian genital pore, the usually trilobate or rarely smooth to bilobate ovary, and the vitelline follicles usually entering the forebody or rarely being confined to the hindbody. Neoplagioporus zacconis (Yamaguti, 1934), comb. n. (= Caudotestis zacconis Yamaguti, 1934, type species), TV. ayu (Takahashi, 1928), comb. n. ( = Podocotyle ayu Takahashi, 1928), N. elongatus (Goto et Ozaki, 1930), comb. n. ( = Lebouria elongata Goto et Ozaki, 1930 = C. orientalis Yamaguti, 1934, syn. n. = C. gnathopogonis Yamaguti, 1934, syn. n.), and an unidentified opecoelid are described and figured from Japanese freshwater fishes. Data on their hosts, geographical distribution and life cycles are given. Key words: digeneans, Neoplagioporus gen. n., Opecoelidae, freshwater fishes, Japan This paper, the fifth in a series on the digenetic absent. Genital pore ventral, median or sinistrally trematodes of the Japanese freshwater fishes, submedian, prebifurcal. Ovary pretesticular or covers three species of a new genus in the sub opposite anterior testis. Seminal receptacle family Plagioporinae Manter, 1947, and an present, canalicular. Uterus usually pretesticular, unidentified trematode, all in the family sometimes extending into testicular region. Eggs Opecoelidae Ozaki, 1925. filamented or not, nonembryonated when laid. The materials and methods and the diagnosis Vitelline follicles distributed along ceca, entering of the Opecoelidae have appeared in the first and forebody or confined to hindbody. Intestinal third papers (Shimazu, 1988a, b). parasites of marine and freshwater fishes and amphibians. Subfamily Plagioporinae Manter, 1947 Miracidia nonoculate, with one pair of flame cells; epidermal cell formula reportedly 6, 7, 4, Plagioporinae Manter, 1947, p. 286 (type genus, 2. Cotylomicrocercous cercariae produced in Plagioporus Stafford, 1904). daughter sporocysts in prosobranch snails; flame cell formula 2 [(2 + 2) + (2 + 2)] = 16. Metacer- Diagnosis. Opecoelidae. Intestinal ceca ending cariae encysting in aquatic arthropods and blindly, forming a cyclocecum or opening octopuses, rarely attaining sexual maturity to separately at or near posterior extremity of body. bear eggs while still in their cysts. Ventral sucker sessile or pedunculate, with no Discussion. This diagnosis has been based appendages. Testes two or three to ten. Cirrus mainly on Manter (1947), Yamaguti (1971, 1975), pouch entire, containing seminal vesicle, prostatic Gibson and Bray (1982, 1984) and the present complex and cirrus. External seminal vesicle study. Nagano Prefectural College, 49-7Miwa 8-chome, Nagano Although it is beyond the scope of this paper, 380, Japan it would be worth mentioning the cirrus pouch mm & ( 385 in the Opecoelidae. The cirrus pouch may fall Genus Neoplagioporus gen. n. roughly into two types: type 1, in which the cirrus pouch is entire and encloses the whole of the Diagnosis. Opecoelidae: Plagioporinae. Body seminal vesicle, the prostatic complex and the elongate to ovate, nonspinose, not oculate. Oral cirrus as seen in the Plagioporinae (see this sucker ventroterminal. Prepharynx very short. paper); and type 2, in which it is not entire and Pharynx well developed. Esophagus fairly long, encloses only the anteriormost or distal portion bifurcating in front of ventral sucker; intestinal of the seminal vesicle, the prostatic complex and ceca ending blindly near posterior extremity of the cirrus, or may be weakly developed or almost body or slightly more anteriorly. Ventral sucker lacking as seen in the subfamily Opecoelinae sessile, in anterior half of body. Testes two, Ozaki, 1925 (Shimazu, 1988b), except in a few smooth or indented, tandem or slightly diagonal, genera or species with an entire cirrus pouch in posterior half of body. Cirrus pouch entire, (Holton, 1984). Opecoelus variabilis Cribb, 1985 in front of ventral sucker or overlapping it (Opecoelinae), has the cirrus pouch of type 2 in posteriorly; seminal vesicle distinctly bipartite, the adult stage (Cribb, 1985; my unpublished short, straight; pars prostatica small, accom reexamination of his specimens). I was able to panied by prostatic cells; cirrus short. Genital observe the formation and change in structure of atrium small. Genital pore ventral, sinistrally the cirrus pouch in the metacercarial stage of this submedian, prebifurcal. Ovary usually trilobed trematode. Living metacercariae were obtained or rarely globular to bilobed, usually submedian, from Caridina nilotica and Macrobrachium pretesticular. Seminal receptacle canalicular, australiense caught in the Brisbane River, postovarian. Laurer's canal present. Ootype com Queensland, Australia, from 1988 to 1989. My plex preovarian. Uterus usually pretesticular, observations suggest that the cirrus pouch of type rarely extending into testicular region, intercecal. 1 is fully formed by earlier stages of development Eggs not filamented, not embryonated when laid. of the metacercaria and that later in more ad Vitelline follicles distributed along ceca, usually vanced stages it changes its structure from type extending into forebody or rarely limited to hind- 1 to type 2 when its proximal or posterior part body, separate or confluent anteriorly, ending disappears (possibly degenerates or ruptures) posteriorly at posterior extremity of body or some while leaving the remainder enclosing the distal distance in front of it. Excretory vesicle I-shaped, portion of the seminal vesicle, the prostatic com reaching to level of testes; flame cell formula plex and the cirrus. A similar change in structure 2[(2 + 2) + (2 + 2)] = 16. Known from intestine of the cirrus pouch during ontogeny might also of freshwater fishes. occur in some other species of an opecoeline Type species: Caudotestis zacconis Yamaguti, genus, Coitocaecum Nicoll, 1915 (Shimazu, 1934. 1988b), though C. anaspidis Hickman, 1934, Life cycle: Unknown. keeps an entire cirrus pouch of type 1 even in the Discussion. Major morphological characters adult stage (Holton, 1984). The entire cirrus of this new genus, Neoplagioporus gen. n., are: pouch of type 1 is considered primitive, and the the seminal vesicle being distinctly bipartite, short partial or not entire cirrus pouch of type 2, and straight; the genital pore being ventral, derived. This supports, in part, Gibson and sinistrally submedian and prebifurcal; the ovary Bray's (1984) speculation on evolutionary rela being usually trilobate or rarely globular to tionships among opecoelid subfamilies. bilobate; and the vitelline follicles usually ex There have been reported three plagioporines tending into the forebody or rarely being limited from Japanese freshwater fishes. Since they to the hindbody. In morphology the genus cannot be adequately allocated to any of the appears to be more closely related to Podocotyle known genera in the subfamily, a new genus is Dujardin, 1845, Plagioporus Stafford, 1904, erected for them as follows. Neolebouria Gibson, 1976, and Macvicaria 386 Gibson et Bray, 1982, out of many genera pro Montreal in 1904. They were indeed similar to posed in the subfamily, but it can be readily the syntypes in morphology, but in one of them distinguished from them by a combination of the the ovarian complex was located between the two above-mentioned characters. The genus Podo- testes. Many species were described in the genus cotyle (probably brackishwater and marine Plagioporus from not only freshwater fishes but forms) has a trilobed ovary and the vitellaria also amphibians and marine fishes. Gibson and usually confined to the hindbody (Gibson and Bray (1982) restricted the genus to freshwater Bray, 1982). Fasciola atomon Rudolphi, 1802, or forms with a short excretory vesicle which reaches P. atomon (Rudolphi, 1802) Odhner, 1905, which forward at the most to the level of the posterior has been generally accepted as the type species, testis and created a new genus, Macvicaria, for possesses a long, looped or convoluted tubular marine forms with a longer excretory vesicle seminal vesicle (Odhner, 1905; MacKenzie and which extends at least to the level of the anterior Gibson, 1970; Gibson and Bray, 1982). Accord testis. The type species, Distomum alacre Looss, ing to Gibson and Bray (1982), the type species 1901, or M. alacris (Looss, 1901) Gibson et Bray, is Distoma angulatum Dujardin, 1845, or P. 1982, has a rounded ovary, a long and looped angulata (Dujardin, 1845) Stiles et Hassall, 1898 or convoluted seminal vesicle and the vitellaria (= P. staffordi Miller, 1941 = P. atomon var. commencing about the level of the genital pore dispar Nicoll, 1909 = Podocotyle sp. of (Gibson and Bray, 1982). The genus Neolebouria MacKenzie and Gibson, 1970), in which a tubular (marine forms) has a trilobed ovary, a long, cirrus pouch is long and looped as well (Nicoll, looped (or convoluted) seminal vesicle and the 1909; Dollfus, 1968; MacKenzie and Gibson, vitelline follicles entering the forebody (Gibson, 1970). Stafford (1904) and Miller (1940, 1941) 1976; Gibson and Bray, 1982). The present new gave brief descriptions