Flagellotrema convolutum Ozaki, 1936

Hall, Kathryn A. & Cribb, Thomas H., 2008, Revision of Flagellotrema Ozaki, 1936 (Digenea, Gyliauchenidae Fukui, 1929), including the description of two species from acanthuroid fishes from the Great Barrier Reef, Queensland, Australia, Zootaxa 1718, pp. 1-35 : 6-9

Flagellotrema convolutum Ozaki, 1936

( Figs 1–2 )

Type-host: Prionurus scalprum Valenciennes, 1835 (as Xesurus scalprum ), Acanthuridae ; scalpel sawtail.

Site: intestine; as “rectum” in the records of Meguro Parasite Museum (MPM).

Type locality: Ozaki (1936) provided no locality data. This species, however, is described from the intestine of the same host, Prionurus scalprum (Acanthuridae) , as Telotrema caudatum , which is also presumably from Japan (see Hall & Cribb 2005b). This species description was published in Zoological Magazine ( Japan), and Ozaki stated that his address was the “Literature and Science College of Hiroshima”, further suggesting that this material was collected from Japanese waters. The physical type material we have examined does not provide detailed information on the provenance of the specimens, although the information card from MPM lists the location as Hiroshima.

Records: 1. Ozaki (1936).

Hosts: Prionurus scalprum , Acanthuridae (1).

Locations: presumably Hiroshima, Japan (1).

Material examined: Holotype MPM Lot 30063, Box E–0555–0591, Specimen 11 (coll. Y. Ozaki); paratypes MPM Lot 30063, Box E–0555–0591, 19 whole mounts and 20 serially-sectioned specimens; vouchers MPM Lot 14703a (coll. T. Shimazu), 3 slides, B1440, C1163 and C1831, as “ Flagellotrema sp.”.

Redescription. Based on holotype, 2 sectioned worms and Ozaki (1936). Measurements in Table 2 . Body elongate, fusiform, distinctly curved dorsoventrally; pale orange in life. Tegument smooth. Ventral sucker round, posterior, not ventrosubterminal. Pharynx barrel-shaped, ventrosubterminal; fleshy pre-oral lip prominent. Oesophagus long, with 1 complete dextral loop which crosses midline, lacking posterior thick-walled chamber, invested with glands along entire length. Oesophageal bulb well-developed, spheroid, smaller than pharynx. Intestinal bifurcation immediately posterior to oesophageal bulb; caeca 2, blind, occupy approximately 1/4 of body length; gastrodermis very thick.

Testes 2, entire, ovoid, diagonal, in posterior third of body, not contiguous. Cirrus-sac present, encased in muscular capsule. Seminal vesicle partially external to cirrus-sac, bipartite; anterior portion globular, internal to cirrus-sac, connected to posterior portion via short, narrow duct, surrounded by muscular capsule contiguous with cirrus-sac; posterior portion elongate, external to cirrus-sac. Pars prostatica large, cylindrical; prostate gland cells external to cirrus-sac, very dense. Cirrus-sac prominent, median, posterior to caeca, globular; ejaculatory duct long, convoluted within cirrus-sac, with distal expansion, eversible. Genital atrium large, irregular, with cilia-like lining. Genital pore not clearly discerned, at level of termination of caeca.

Ovary entire, intertesticular, dextral, not contiguous with testes. Seminal receptacle prominent, canalicular, saccular, posterodorsal to ovary. Mehlis’ gland anterodorsal to ovary. Laurer’s canal opens anterodorsal to ovary. Uterus entirely pre-ovarian, coiled in median field. Opening of uterus unspecialised, enters genital atrium sinistral to cirrus-sac. Vitellarium follicular; follicles extend from level of oesophagus to immediately anterior to testes, form distinctive X-shaped distribution in ventral field, dorsal field not clearly observed. Vitelline reservoir ventral to ovary. Eggs large, tanned, operculate, apparently unembryonated in utero.

Excretory vesicle elongate, saccular. Excretory pore subterminal, opens on prominent, but small, papilla. Primary collecting ducts arise anterolaterally. Lymph system described by Ozaki (1936) as similar to that of Telotrema caudatum Ozaki, 1933 , consists of 9 pairs of longitudinal canals, 4 pairs ventral to caeca and 5 pairs dorsal and lateral to caeca.

Comments: Ozaki (1936) observed morphological parallels between F. convolutum and Gyliauchen papillatus (Goto & Matsudaira, 1918); both species possess a convoluted pharynx, diagonal testes, prominent excretory papilla and a restricted vitellarium, which forms an X-shaped distribution in the ventral field. Ozaki distinguished F. convolutum from G. papillatus, and other gyliauchenids known at the time, by the intertesticular, rather than pretesticular, position of the ovary in F. convolutum . We have observed the intertesticular position of the ovary, however, we further distinguish F. convolutum from species of Gyliauchen by the relatively posterior position of the genital pore. In species of Gyliauchen the genital pore is immediately posteroventral to the intestinal bifurcation, whereas in F. convolutum it is well posterior of the bifurcation and is ventral to the extremities of the caeca. The position of the ventral sucker, which is distinctly posterior, but never ventrosubterminal, in F. convolutum further distinguishes this species from species of Gyliauchen, in which the ventral sucker is definitely ventrosubterminal.

We have examined the holotype specimen and additional paratypes (wholemounts and sections) deposited by Ozaki. Unfortunately, the wholemount specimens were not in good condition and examination of many of the internal structures of the worms was very difficult. The holotype itself is distorted; the anterior of the worm lies dorsoventrally, the posterior is mounted laterally, and the specimen seems to have been flattened ( Fig. 1 ). Many of the other specimens are similarly distorted. Some of the specimens have not been fixed well and are curled and lying askew. Further, the specimens are not well-cleared and the dense pigment in the parenchyma makes it difficult to discern the structure of the terminal genitalia. The voucher material is in a similar condition, and the internal morphology of the worms was difficult to observe. The voucher specimens were collected from the type host and locality, and although distorted and broken, appear to be authentic vouchers of F. convolutum . A distinctly pyriform, rather than barrel-shaped, pharynx was observed in a single specimen (MPM Lot 14703a, slide B1440). We have chosen not to measure any of these specimens and the types because of the distortion and lack of clarity. The serial sections deposited by Ozaki are, however, in excellent condition, and we have found these specimens very useful in our examination of the male terminal genitalia. In the sections, and the holotype, a cilia-like lining of the genital atrium can be clearly seen ( Figs 2 ). This lining is like that observed in specimens of Ptychogyliauchen Hall & Cribb, 2004 .

Dyer et al. (1988) reported F. convolutum from Centropyge ferrugata Randall & Burgess, 1972 (as C. ferrugatus ) ( Pomacanthidae ; rusty angelfish) caught in Okinawa, Japan. We have examined the voucher specimen for this record (USNM 79978) and do not believe that specimen agrees with the holotype and paratype material of F. convolutum . The specimen USNM 79978 is immature and distorted, however, we find that it bears close resemblance to another gyliauchenid species, Paragyliauchen chaetodontis Yamaguti, 1934 . We can not confirm the identity of this specimen because it is immature, but we assign it as Paragyliauchen sp., and do not consider that USNM 79978 is a valid voucher specimen for F. convolutum .

Figures

FIGURE 1. Flagellotrema convolutum Ozaki, 1936 from Prionurus scalprum, presumably from Japan. Holotype. Scale bar = 500 µm.

FIGURE 2. Flagellotrema convolutum Ozaki, 1936 from Prionurus scalprum, presumably from Japan. Detail of male terminal genitalia; composite sketch based on paratypes (sections). Scale bar = 250 µm.

Tables

TABLE 2. Measurements of Flagellotrema convolutum Ozaki, 1936 in micrometres (µm) (from Ozaki, 1936). Unavailable measurements are indicated by a dash (-).

Variable	Min	Max
body length	-	4800
body width	-	1000
pharynx length	-	350
pharynx width	-	300
oesophageal bulb length	-	350
oesophageal bulb width	-	300
ventral sucker diameter	-	480
average testis diameter	-	380
ovary diameter	-	150
cirrus diameter	-	450
egg length	67	73
egg width	37	41