Abyssopedunculus, Martin & Huston & Cutmore & Cribb, 2019

ABYSSOPEDUNCULUS View in CoL GEN. NOV.

Diagnosis: Body elongate, subcylindrical. Forebody short, about one-sixth body length. Tegument smooth, thin. Oral sucker unspecialized, terminal. Ventral sucker, unspecialized, larger than oral sucker, pedunculate. Prepharynx short. Pharynx unspecialized, smaller than oral sucker. Oesophagus relatively long. Intestine bifurcates in forebody or dorsal to ventral sucker. Caeca blind, extending well beyond testes near to posterior extremity.Testes two, smooth, ellipsoidal, medial, separate; post-tesicular zone occupies about one-quarter total body length. Cirrus-sac well developed, short, broad oval, mostly dorsal to ventral sucker, may protrude slightly beyond ventral sucker into hindbody. Seminal vesicle internal, occupying most of cirrus-sac, broad proximally, becoming looped distally. Pars prostatica indistinct. Ejaculatory duct short. Common genital atrium short, simple. Genital pore pre-bifurcal, sinistro-submedial. Ovary smooth, medial, anterior to and separated from anterior testis, situated aboutone-halfbodylengthfromanteriorextremity.Seminal receptacle canalicular, smaller than and antero-dorsal to ovary. Laurer’s canal present, short, opens dorsal to ovary. Mehlis’ gland present. Uterus preovarian, intercaecal, approaches genital atrium ventral to cirrus-sac. Vitelline follicles dense, restricted to hindbody, extending from near to posterior extremity to well beyond ovary anteriorly but not reaching level of ventral sucker, distributed dorsally, laterally and ventrally, becoming confluent ventrally in post-testicular zone and preovarian zone. Eggs oval, operculate, unembryonated in utero. Excretory vesicle tubular, extends to level of ovary. Excretory pore terminal. In mesopelagic north-west Atlantic fishes, known only from Congridae ( Anguilliformes ).

Type and only species: Abyssopedunculus brevis (A n d r e s & O v e r s t r e e t, 2 0 1 3) c o m b. n o v. (s y n. Podocotyloides brevis ).

ZooBank registration LSID: http://www.zoobank. org/ urn:lsid:zoobank.org:act:8337048F-1E99-4C54-8C02-D651BC00A341

Etymology: The generic name is composed from Latin abyss, the deep, and pedunculus, a peduncle or stem. The name is chosen because the concept is distinguishable among plagioporine (s.l.) type taxa in deep-sea fishes by a pedunculate ventral sucker. The genus is to be treated as feminine.

Remarks: Podocotyloides Yamaguti, 1934 was recently revised by Martin et al. (2018c). Genuine species are known mostly from Indo-West Pacific shallow-water fishes of the Haemulidae ( Perciformes ) and resolve to clade B in the major marine Plagioporinae (s.l.) clade. Abyssopedunculus brevis resolves among the deep-sea taxa and was described based on material from Conger esculentus ( Anguilliformes : Congridae ) collected at a depth of 200 m off Puerto Rico ( Andres & Overstreet, 2013). Thus, it cannot be considered to belong in Podocotyloides . Morphologically, it differs most obviously from genuine Podocotyloides species in that its excretory vesicle reaches only to the level of the ovary vs. the level of the ventral sucker, its cirrus-sac is short and oval vs. long, tubular and sigmoid, its ejaculatory duct is short and simple vs. long and provided with petalloid appendages, and its metraterm is indistinct vs. well developed and provided with a prominent sphincter. Among the taxa represented in the deep-sea + freshwater clade, A. brevis is distinct in that it has both a pedunculate ventral sucker and a canalicular seminal receptacle.