Megaperinae Manter, 1934

Blend, Charles K., Karar, Yasser F. M. & Dronen, Norman O., 2017, Revision of the Megaperidae Manter, 1934 n. comb. (Syn. Apocreadiidae Skrjabin, 1942) including a reorganization of the Schistorchiinae Yamaguti, 1942, Zootaxa 4358 (1), pp. 1-44 : 8-9

Subfamily Megaperinae Manter, 1934

Diagnosis. (Based on Bray 2005b; Pulis et al. 2014) Body small, rounded, oval or elongate. Tegument spinous at anterior extremity; posterior extent of spines variable. Eye-spot pigment present. Oral sucker subterminal, oval, globular or infundibuliform, larger than ventral sucker. Ventral sucker round, equatorial or pre-equatorial. Prepharynx present. Pharynx weakly muscular, cup-shaped, with lobed anterior margin. Esophagus present or absent. Intestinal bifurcation in mid-forebody. Caeca broad to narrow, with or without anterior extensions to oral sucker, open via ani at posterior extremity. Testes two, large, tandem or opposite, pre-ovarian or post-ovarian, in forebody or hindbody. Cirrus pouch absent. Seminal vesicle saccate to elongate, near ventral sucker. Pars prostatica globular, well-developed; prostatic cells present. Genital atrium short, muscular or shallow. Genital pore median, in posterior region of forebody. Ovary subspherical or lobed, at level of ventral sucker or anterior hindbody, median or submedian, pre- or post-testicular. Canalicular seminal receptacle and Mehlis’ gland present. Laurer’s canal present or absent. Vitellarium follicular; follicles lateral, in hindbody only or in both hindbody and forebody. Uterus short, extends posteriorly to level of ovary. Eggs few to many, medium to large, thin-shelled. Excretory vesicle I-shaped in adults, Y-shaped in cercariae; excretory pore terminal. Eggs unembryonated when laid, embryonate to produce miracidia which infect marine calyptraeid snails wherein polyembryony produces rediae that develop oculate cercariae that are shed out into open environment, encyst, and develop metacercariae infective to definitive host. Adults in intestine of marine teleosts ( Tetraodontiformes ); NW Atlantic Ocean.

Type genus. Megapera Manter, 1934 .

Remarks. Members of the Megaperinae are unique within the Megaperidae n. comb. in possessing a genital pore anterior to the ventral sucker, an oral sucker lacking a partial U-shaped sphincter encircling the aperture of the sucker, and caeca that open via ani. The main features used to distinguish the three recognized genera of megaperines include the morphology of the intestine (H-shaped vs caeca posteriorly-directed only), the presence or absence of an esophagus, the presence or absence of radiating alternating muscular and cellular bands within the oral sucker, and whether or not the oral sucker is enclosed in a fold of the body wall ( Bray 2005b; Cribb 2005; Pulis et al. 2014).

As detailed earlier, Megapera (Syn. Eurypera Manter, 1933 nec Pascoe, 1870) was established by Manter (1933, 1934), who described the type species, Megapera pseudura ( Manter, 1933) Manter, 1934 (Syn. Eurypera pseudura Manter, 1933 ), from the intestine of the scrawled cowfish, A. quadricornis , from off Dry Tortugas, Florida. In that same publication, Manter (1933) erected Thysanopharynx with the description of T. elongatus from the same host species and locality. Pulis et al. (2014) erected Haintestinum and described H. amplum obtained from A. quadricornis off Florida in the eastern Gulf of Mexico. The single species of Haintestinum known to date is unique in that it possesses an intestine composed of paired caeca directed anteriorly and posteriorly (H-shaped) and has an esophagus; members of the other two genera of megaperines have neither of these features. Members of Megapera and Thysanopharynx can be differentiated by the former having an oral sucker that is much larger than the ventral sucker with radiating alternating muscle and cellular bands and an oral sucker not enclosed in a fold of the body wall; whereas, species of the latter genus have an oral sucker only slightly larger than the ventral sucker, lack distinct radiating muscle bands and the oral sucker is almost wholly enclosed in a fold of the body wall ( Bray 2005b; Pulis et al. 2014). Given this information, we consider the Megaperinae to be a distinct, well-defined taxon.

Key to genera of Megaperinae Manter, 1934 (based on Bray 2005b; Pulis et al. 2014)

1a. Intestine composed of paired caeca directed anteriorly and posteriorly (H-shaped); esophagus present............................................................................ Haintestinum Pulis, Curran, Andres & Overstreet, 2014 .

1b. Intestine composed of paired caeca directed only posterior; esophagus absent..................................... 2.

2a. Oral sucker much larger than ventral sucker with radiating alternating muscle and cellular bands; sucker not enclosed in fold of body wall................................ Megapera Manter, 1934 (Syn. Eurypera Manter, 1933 nec Pascoe, 1870).

2b. Oral sucker only slightly larger than ventral sucker and lacking distinct radiating muscle bands; sucker almost wholly enclosed in fold of body wall........................................................... Thysanopharynx Manter, 1933 .