Occurrence of Podocotyle Dujardin, 1845 (Opecoelidae, Podocotylinae) in three species of deep-sea macrourids from the Gulf of Mexico and Caribbean Sea with an updated key to species and host-parasite checklist

Abstract

Podocotyle pearsei Manter, 1934 is documented from the intestine of Vaillant’s grenadier, Bathygadus melanobranchus Vaillant (Macrouridae: Bathygadinae), collected from the northeastern and western Gulf of Mexico from 783–841 m depth. The finding of P. pearsei in B. melanobranchus represents the first originally published report of this genus from this host and the fifth documented host species for P. pearsei. We report three unidentified species of Podocotyle, represented by one individual each, from the intestine of the western Atlantic grenadier, Nezumia atlantica (Parr) (Macrouridae: Macrourinae), and from Bathygadus favosus Goode & Bean (Macrouridae: Bathygadinae) found at 637 m, 710 m and 1,143 m depths in the northeastern Gulf of Mexico off Florida and from the Caribbean Sea off Colombia. We provide a checklist of the parasites known from the three macrourid species relevant to this study, comment on the biogeography of the five species of Podocotyle now known from the deep sea and discuss the low host specificity observed across this genus. The high number of fish hosts for Podocotyle (i.e. type hosts include at least 22 piscine families) encompassing a wide phylogenetic diversity and diet makes it unlikely that members of a single genus could evolve such a broad array of life histories (i.e. utilize dissimilar intermediate hosts), and we predict in the future that Podocotyle will be taxonomically divided up. Morphological and especially molecular work is needed for Podocotyle as well as for other digenean genera known to inhabit the deep sea. Podocotyle sp. 1 & 2 represent the first originally published reports of this genus from N. atlantica while Podocotyle sp. 3 represents the first report of this genus from B. favosus. Podocotyle koshari Nagaty, 1973 is declared a species inquirenda, and a dichotomous key to the 27 species of Podocotyle we recognize is provided.

Molecular and morphological screening of Podocotyle spp. (Trematoda: Opecoelidae) sheds light on their diversity in Northwest Pacific and eastern European Arctic

“…The presented specimens of trematodes are fully consistent with modern concepts of P. reflexa , namely: the body is elongated and relatively narrow, the cirrus-sac is elongated claviform and extends posteriorly from the ventral sucker, the seminal vesicle is coiled, the fields of vitelline follicles are interrupted at the testicular level and not penetrated into the forebody and the ventral sucker is twice as wide as the oral sucker (Blend et al 2019 with addition by Edmiston 1971). The type locality of P. reflexa is the Baltic Sea (Northern Atlantic) (Creplin 1825).…”

“…The most significant morphological differences between P. angulata and P. atomon are the relative sizes of testes (width of each testis >½ width body at their level versus <½), a ratio of body length and width (5–6 : 1 versus 4 : 1), the cirrus-sac length (extends noticeably posterior to ventral sucker versus short distance from sucker) and a sucker ratio (1 : 2 versus 1 : < 2 ) (Gibson and Bray 1982; MacKenzie and Gibson 1970). According to Blend et al (2019), P. angulata differs from P. atomon in testes separated by a distinct distance filled with vitelline follicles. This finding is consistent with the description of P. angulata sensu stricto but contradicts that of P. staffordi because this nominal species has an intertesticular space filled with vitelline follicles (compare with Dollfus (1968); Miller (1941)).…”

“…This finding is consistent with the description of P. angulata sensu stricto but contradicts that of P. staffordi because this nominal species has an intertesticular space filled with vitelline follicles (compare with Dollfus (1968); Miller (1941)). However, Blend et al (2019), following Gibson and Bray (1982), consider P. staffordi to be a junior synonym of P. angulata. It is possible that P. angulata sensu stricto and P. staffordi are actually different species, but we prefer to consider them conspecific for the present.…”

“…The presented specimens of trematodes are characterized by both features corresponding to the description of P. atomon , namely a not very elongated body, a cirrus-sac slightly protruding into the hindbody, relatively small testes occupying ≤½ of the body cross section, and by features that have an intermediate manifestation between P. atomon and P. angulata (sucker ratio 1 : 1.87–2.05). According to Blend et al (2019), P. atomon is characterized by separated testes. However, this thesis at least contradicts the description of Podocotyle odhneri Issaitschikov, 1928, the conspecificity of which with P. atomon is recognized by this author.…”

“…A recent revision of Podocotyle recognizes 27 valid species of the genus (Blend et al 2019). This view, in turn, builds on a number of previously published sources on Podocotyle taxonomy (e.g., Blend and Dronen 2015; Blend et al 2016; Bray and Campbell 1996; Gibson 1986; Gibson and Bray 1982; Martin et al 2017; Park 1937; Pritchard 1966).…”