Ichthyotrema Caballero & Bravo-Hollis, 1952

Hall, Kathryn A. & Cribb, Thomas H., 2007, Rediagnosis of Ichthyotrema Caballero & Bravo-Hollis, 1952 (Digenea: Gyliauchenidae Fukui, 1929), including the redescription of I. vogelsangi Caballero & Bravo-Hollis, 1952, Zootaxa 1549, pp. 63-68 : 64-66

Genus Ichthyotrema Caballero & Bravo-Hollis, 1952

Emended diagnosis: Body large, elongate, fusiform. Tegument smooth, with few posterior annulations. Ventral sucker elongate, posterior, close to posterior extremity. Pharynx barrel-shaped, ventrosubterminal, surrounds mouth, smaller than ventral sucker; pre-oral lip reduced. Oesophagus long, sigmoid, lining developed, invested with glands along entire length. Oesophageal bulb well-developed, spheroid, distinct, smaller than pharynx. Intestinal bifurcation immediately posterior to oesophageal bulb; caeca 2, blind, extend to midpoint of body length. Testes 2, entire, ovoid, diagonal, in posterior third of body. Cirrus-sac prominent, entirely posterior to caeca, globular; ejaculatory duct short, eversible. Seminal vesicle partially external to cirrus-sac. Pars prostatica large, cylindrical, surrounded by dense prostate gland cells which partially penetrate cirrussac. Genital atrium regular. Genital pore posterior to caeca, equatorial, median, strongly muscular, laterally elongate. Ovary entire, post-testicular, median. Seminal receptacle prominent, canalicular. Vitellarium follicular; follicles dense, extend from level of pharynx to immediately anterior to testes; dorsal, ventral and lateral fields confluent. Uterus entirely pre-ovarian, coiled between testes, enters genital atrium sinistral to cirrus-sac. Eggs large, tanned, apparently unembryonated in utero. Excretory pore subterminal; papilla virtually absent. Excretory vesicle saccular, short. Primary collecting ducts arise anterolaterally. Parasites of intestine of herbivorous East Pacific marine teleosts ( Acanthuridae , Prionurus only). Type species Ichthyotrema vogelsangi Caballero & Bravo-Hollis, 1952 .

Ichthyotrema vogelsangi Caballero & Bravo-Hollis, 1952 ( Fig. 1 ) Type-host: Prionurus punctatus Gill, 1862 (as Xesurus punctatus ), Acanthuridae . Site: Intestine.

Type locality: Puerto Vallarta, Mexico.

Records: 1. Caballero & Bravo-Hollis (1952). 2. Winter (1960).

Hosts: Prionurus punctatus , Acanthuridae (1, 2).

Localities: Mexico, Pacific Coast (1, 2).

Redescription: Based on the examination of 3 paratype specimens (UNAM 0 0 1051.03, 0 0 1051.06, 001051.09). Measurements in Table 1 . Body large, elongate, slender, fusiform; width equal along length of body. Tegument smooth, with few posterior annulations. Ventral sucker elongate, posterior, ventrosubterminal. Pharynx barrel-shaped, ventrosubterminal, surrounds mouth, smaller than ventral sucker; pre-oral lip reduced. Oesophagus long, sigmoid, lining developed, invested with glands along entire length. Oesophageal bulb well-developed, spheroid, distinct, smaller than pharynx. Intestinal bifurcation immediately posterior to oesophageal bulb; caeca 2, blind, extend to midpoint of body length; gastrodermis thick.

Testes 2, entire, ovoid, diagonal, in posterior third of body ( Fig. 1 a). Cirrus-sac prominent, entirely posterior to caeca, globular, encased in muscular capsule ( Fig. 1 b); ejaculatory duct short, eversible; everted cirrus not observed. Seminal vesicle partially external to cirrus-sac, bipartite; proximal and distal portions globular, separated by narrow constriction; proximal portion internal and encased in muscular capsule contiguous with cirrus-sac, distal portion external. Pars prostatica large, cylindrical, surrounded by dense prostate gland cells which partially penetrate cirrus-sac. Genital atrium regular, muscular. Genital pore posterior to caeca, equatorial, median, strongly muscular, laterally elongate.

Ovary entire, post-testicular, median; oviduct with insemination chamber immediately proximal to ovary ( Fig. 1 a). Seminal receptacle prominent, canalicular, posterodorsal to ovary. Mehlis’ gland not observed. Laurer’s canal not observed. Oötype anterior to insemination chamber and seminal receptacle. Uterus entirely preovarian, coiled between testes, proceeds sinistral to male terminal genitalia. Opening of uterus unspecialised, enters genital atrium sinistral to cirrus-sac. Vitellarium follicular; follicles dense, extend from level of pharynx to immediately anterior to testes; dorsal, ventral and lateral fields confluent; vitelline ducts pass posterolateral to testes, unite to form globular vitelline reservoir dorsal to ovary. Eggs large, tanned, apparently unembryonated in utero, opercula not observed.

Excretory pore subterminal; papilla virtually absent. Excretory vesicle saccular, short. Primary collecting ducts arise anterolaterally. Lymph system not observed.

Comments. Specimens of I. vogelsangi are massive, reaching lengths greater than 7.5 mm. There have been 2 records of this species ( Caballero & Bravo-Hollis 1952; Winter 1960), both from Prionurus punctatus from Mexico (East Pacific). The measurements and illustrations of both records are broadly congruent. We are confident, from our examination of the paratype material deposited by Caballero & Bravo-Hollis and reviews of the literature, that the specimens obtained by Winter (1960) represent a second record of this species. The paratypes are in fair condition, although the caeca were difficult to observe because of the density of the vitelline follicles, and the specimens have been mounted somewhat askew, with the anterior end of the body presented dorsoventrally and the posterior extremity mounted laterally. The curved morphology of gyliauchenids makes them often difficult to mount, and despite the differences in presentation anteriorly and posteriorly, the internal structures of these specimens is clear. In particular, the morphology of the female reproductive system is able to be well observed; we were able to discern the forked junction of the seminal receptacle, insemination chamber and oötype. The ventral sucker of paratype specimen UNAM 0 0 1051.06 (see Figure 52.1 in Hall & Cribb 2005a) was retracted deep within the body and was contiguous with the seminal receptacle; powerful retractor muscles were observed associated with the ventral sucker of this specimen.

Figures

FIGURE 1. Ichthyotrema vogelsangi Caballero & Bravo-Hollis, 1952 from the intestine of Prionurus punctatus. Paratype (UNAM 001051.09). A. View of entire worm. Note that the path of the caeca is obscured by the extensive vitellarium and that the specimen is distorted; the anterior of the body is presented dorsoventrally, whereas the posterior extremity is mounted laterally. Scale bar = 500 µm. Legend: gp, genital pore; ob, oesophageal bulb; oes, oesophagus; ph, pharynx; t, testes. B. Detail of cirrus-sac. Note that the muscular capsule surrounding the globular proximal portion of the cirrus-sac, which contains the ejaculatory duct, is contiguous with the capsule surrounding the pars prostatica and the proximal portion of the seminal vesicle. In addition, the prostate glands are external to the cirrus-sac wall, and the tails of these glands penetrate the wall laterally. Scale bar = 250 µm. Legend: pg, prostate glands; pp, pars prostatica; sv, seminal vesicle.