Podocotyle nimoyi Blend, Dronen & Armstrong, 2016, n. sp.

Podocotyle nimoyi n. sp.

(Figs. 1–3)

Synonyms: Podocotyle (Podocotyle) sp. n. #3 of Armstrong (1974); Podocotyle (Neopodocotyle) sp. n. of Armstrong (1974); Genus novum B, sp. n. of Blend (1996); Opecoelidae indet. of Klimpel et al. (2001, 2009).

Type-host. Pugnose grenadier, Sphagemacrurus grenadae (Parr, 1946) (Gadiformes: Macrouridae: Macrourinae).

Other host. Common Atlantic grenadier, Nezumia aequalis (Günther, 1878) (Gadiformes: Macrouridae: Macrourinae).

Type-locality. S. grenadae: Northeastern Gulf of Mexico off Florida, 28°12’N, 87°06’W, depth = 995 m, 11/ July/1966.

Other localities. N. aequalis: Northeastern Gulf of Mexico off Florida, 28°02’N, 85°37’W, depth = 583 m, 24/ June/1971; 28°11’N, 85°51’W, depth = 546 m, 25/June/1971; 28°31’N, 86°33’W, depth = 534 m, 27/June/1971.

Site of infection. Intestine.

Prevalence. S. grenadae: 1 of 1 fish infected (100%); N. aequalis: 4 of 89 (4.49%).

Intensity. S. grenadae: only 1 worm; N. aequalis: 1–2.

Mean intensity. S. grenadae: 1.00 (1/1); N. aequalis: 1.25 (5/4).

Relative density/abundance. S. grenadae: 1.00 (1/1); N. aequalis: 0.06 (5/89).

Deposited Specimens. Holotype NHMUK 2016.4.28.1, paratypes NHMUK 2016.4.28.2–5 (4 slides), voucher NHMUK 2016.4.28.6 (1 slide).

Records. 1. Armstrong (1974); 2. Bray (1995); 3. Blend (1996); 4. Klimpel et al. (2001, 2009); 5. Blend et al. (2012); 6. Present study.

Descriptions. 1, 3, 6.

Etymology. The species designation is named in honor of the passing of Leonard Nimoy, an actor in the Star Trek television series and movies. His fictional character, Mr. Spock, and his career strongly influenced one of us (CKB) in childhood to pursue a career in science.

Description. [Based on 1 holotype and 4 paratypes. Measurements and proportions given in Table 2.] With characteristics of genus. Body triangular to longitudinally elongate; in triangular specimens, body widest in posterior third of body, anterior end attenuated to bluntly-rounded extremity, posterior end truncated with small invagination at extremity; in more elongate specimens body widest in posterior third of body. Forebody about 1/4 length of body, attenuate. Hindbody widens posteriorly toward midbody and beyond, truncates at posterior end of body. Tegument aspinose. Pre-oral lobe absent. Oral sucker subterminal, spherical to subspherical, unspecialized. Ventral sucker large, muscular, subspherical to transversely oval, unspecialized, sessile, conspicuous border around perimeter, aperture in mid- to anterior half of sucker, wider than long and almost as wide as entire worm at that level, larger than oral sucker, pre-equatorial at junction of first and second 1/4 of body. Prepharynx not observed. Pharynx muscular, subspherical to oval to dolioform in shape, anterior end ventrally-overlapped by oral sucker. Esophagus thin-walled anteriorly, more thick-walled posteriorly, short, straight (one specimen with slightly sinuous esophagus), longer than pharynx. Intestinal bifurcation anterior to ventral sucker in posterior half of forebody. Ceca thick-walled, parallel, variable in width being narrow anteriorly then gradually wider posteriorly with maximum width near posterior end of worm, terminates blindly near posterior extremity.

Testes 2, tandem, median, irregularly indented to lobed, transversely elongate, contiguous, intercecal, postequatorial in posterior 1/3 of body. Post-testicular region confined to posterior fifth of body. Cirrus pouch distinct, thin-walled, clavate, slender, extends to posterior margin of ventral sucker or slightly posterior to it. Seminal vesicle internal, bi-partite; proximal portion small, saccate, in posterior or posterosinistral portion of cirrus pouch; distal portion narrow and extensively coiled, winds throughout posterior 1/2 to 3/5 of cirrus pouch. Pars prostatica indistinct, long, thick-walled; ejaculatory duct thick-walled with numerous dark-stained cells lining duct, 16 [n = 1] long; cirrus short; prostatic gland cells well-developed, distributed throughout cirrus pouch, most numerous in posterior half and at very distal portion of cirrus pouch. Genital pore submedian (sinistral), pre-acetabular, bifurcal to just pre-bifurcal at level of lower esophagus. Genital atrium distinct, oval.

Ovary large, 3- to 4-lobed (some lobes inconspicuous), submedian to markedly dextral, anterior to but not contiguous with anterior testis, separated from latter by loops of uterus, equatorial to just post-equatorial in middle third of body. Seminal receptacle canalicular, large, median to submedian (dextral), postero-dorsal to and overlaps posterior margin of ovary, anterior to anterior testis. Laurer’s canal present; entire course of canal not observed but it passes dorsal to ovary; distal end expected to open dorsally to exterior. Vitelline reservoir conspicuous, median, sinistral at mid-ovarian level to posterosinistral to ovary, directly anterior to anterior testis and dorsal to uterus. Vitelline ducts at mid-ovarian level, pass medially anterior to anterior testis, bifurcate to left and right of vitelline reservoir along midline of worm to form longitudinal ducts; right vitelline duct passes dorsally over posterior half of ovary before it bifurcates. Oviduct inconspicuous, originates from medial side of lobe of ovary and runs short course to oötype, itself surrounded by conspicuous, dark-stained Mehlis’ gland cells, directly to left and at level of ovary, immediately anterior to or dorsally overlapped by vitelline reservoir, ventrally overlapped by uterine loops posteriorly. Uterus extensive, intercecal, wider posteriorly; uterine loops pass directly to left of ovary then extend down posteriorly over anterior testis as far as inter-testicular area before they turn and proceed anteriorly, loops narrow as they pass dorsally over ventral sucker then turn slightly anterosinistral to pass directly dorsal to and alongside distal portion of cirrus pouch prior to entering genital atrium. Metraterm conspicuous, thick-walled, occasionally dilated, extends from genital pore to near anterior margin of ventral sucker, 160–324 (242) [n =2] long × 36–40 (38) [n =2] wide. Vitellarium large (observed occasionally to be smaller-sized directly lateral to anterior testis), follicular, numerous, subglobular to globular to elongate in shape, circumcecal in uninterrupted lateral bands, extends from posterior extremity anteriorly up to level of posterior margin of ventral sucker (3 individuals each with left lateral band and 1 individual with right lateral band of vitelline follicles that failed to extend to ventral sucker [see Table 2]; 1 specimen with right lateral band of follicles that extend to mid-level of ventral sucker), encroaches over lateral margins of gonads, not confluent in pre-ovarian region, in space between ovary and anterior testis and in inter-testicular region, confluent in post-testicular region. Eggs collapsed and/or crenulated, relatively small, operculate, amber, non-filamented, numerous, densely packed in uterus, with nib on one pole.

Excretory vesicle tubular, observed to extend at least to posterior testis; excretory pore terminal.

Remarks. Based on its possession of a canalicular seminal receptacle and a well-developed cirrus pouch enclosing an internal seminal vesicle, P. nimoyi n. sp. is assigned to the Plagioporinae within the Opecoelidae (Cribb 2005). The new species keys to the genus Podocotyle based on its possession of the following diagnostic combination of morphological characters: an egg lacking a unipolar filament and having a length> 40–50 µm; blindly-ending ceca; a round to transversely oval, non-pedunculate and unspecialized ventral sucker; vitellarium that are restricted to the hindbody, post-testicular and extend to the posterior end of the body; two tandem testes; an oral sucker that is not funnel-shaped; an excretory vesicle that is neither diverticulate nor enters the forebody; a clearly submedian genital pore; a pre-testicular uterus (while a few loops of the uterus extend into the intertesticular region in P. n i m oy i n. sp., the majority of the uterus is pre-testicular); and an ovary that is deeply lobed (Cribb 2005).

Podocotyle bathyhelminthos, Podocotyle harrisae Bray & Campbell, 1996, P. pearsei, Podocotyle schistotesticulata Bray & Campbell, 1996, and P. n i m oy i n. sp. are the only species of Podocotyle known from the NW Atlantic Ocean (Blend & Dronen 2015). Podocotyle bathyhelminthos differs from P. ni m o yi n. sp. in possessing a larger body (3,420–4,200 long vs 2,620–2,640 long), an invaginated posterior terminus that produces a deep cleft, a small transverse ridge on the ventral surface immediately anterior to the ventral sucker, a smaller sucker width ratio (1:1.40–1.94 vs 1:1.64–2.47) and the ventral sucker appears smaller in relation to the entire body, a smaller ratio of pharynx width to oral sucker width (1:1.25–1.90 vs 1:2.14–2.58), a moderately longer and more sinuous esophagus (11.4%–17.8% vs 6.1%–6.4% of body length), an intestinal bifurcation overlapped by the ventral sucker, deeply lobed testes, a pre-bifurcal genital pore located at the mid-esophageal level vs a bifurcal to just pre-bifurcal genital pore located at the level of the lower esophagus, an ovary that is median, contiguous to and immediately anterior to the anterior testis vs an ovary that is submedian to markedly dextral and not contiguous with the anterior testis, an entirely pre-testicular uterus vs a uterus with post-ovarian loops that extend down posteriorly over the anterior testis extending into the inter-testicular space, a larger post-uterine region (40.5%– 47.8% vs 25.3% of body length), a dorsally subterminal excretory pore located at the anteriormost point of a deep cleft at the posterior end of the worm vs a terminal excretory pore, and P. bathyhelminthos has a larger egg (76–86 long × 34–44 wide) that lacks a nib at one pole vs P. ni m o yi n. sp. with a smaller egg (44–56 long × 24–34 wide) and a nib at one pole (Blend & Dronen 2015). Podocotyle harrisae differs from the new species in having a distinct pyriform body shape vs a triangular to longitudinally elongate body, a smaller sucker ratio (1:1.33–1.88), a distinct prepharnyx, a smaller ratio of pharynx width to oral sucker width (1:1.25–1.67), irregularly oval testes, a larger post-testicular region (21%–27% vs 11.8%–13.4% of body length), a seminal vesicle that is not bi-partite, a prebifurcal genital pore located at the level of the pharynx or anterior esophagus, an ovary that is median, contiguous to and immediately anterior to the anterior testis, an entirely pre-ovarian uterus, a dorsally subterminal excretory pore, and the egg of P. harrisae lacks a nib at one pole (Bray & Campbell 1996). Podocotyle pearsei differs from the new species in having a smaller body (1,460–1,840 long), a smaller ratio of pharynx width to oral sucker width (1:1.50), an intestinal bifurcation overlapped by the anterior margin of the ventral sucker, smooth to slightly lobed testes, a cirrus pouch that extends to the middle of the ventral sucker or slightly beyond vs one that extends to the posterior margin of the ventral sucker or slightly posterior to it, an ovary that is median, contiguous to and immediately anterior to the anterior testis, an entirely pre-ovarian uterus, and P. pearsei has a larger egg (96–105 long × 39–45 wide) that lacks a nib at one pole (Manter 1934). Podocotyle schistotesticulata differs in possessing a considerably larger body (5,525–8,809 long), a usually distinct prepharnyx, a smaller ratio of pharynx width to oral sucker width (1:1.48–2.07), deeply lobate testes with a distinct indentation in the median line in both anterior and posterior margins—at times almost dividing each testis into two parts longitudinally, a cirrus pouch that just overlaps the anterior edge of the ventral sucker, an ovary that is median, contiguous to and immediately anterior to the anterior testis, an entirely pre-ovarian uterus, and P. schistotesticulata has a larger egg (68–81 long × 38–48 wide) that lacks a nib at one pole (Bray & Campbell 1996).

When compared to the remaining 22 species of Podocotyle (see Table I of Blend & Dronen 2015), we noticed numerous differences with P. nim oyi n. sp. described herein. A noticeably protuberant to pedunculate and/or specialized ventral sucker is present in Podocotyle caithnessi Manter, 1954, Podocotyle californica Park, 1937, Podocotyle congeri (Yamaguti, 1970) Bartoli, Bray & Gibson, 2003, Podocotyle reflexa (Creplin, 1825) Odhner, 1905, Podocotyle sinusacca Ching, 1960 and Podocotyle temensis Fischthal & Thomas, 1970 (Park 1937; Miller 1941; Manter 1954a; Ching 1960; Fischthal & Thomas 1970; Yamaguti 1970). Sucker width ratio differs in Podocotyle apodichthysi Park, 1937, Podocotyle ayu Takahashi, 1928, Podocotyle enophrysi Park, 1937, Podocotyle novella (Maillard & Lambert, 1978) Bartoli, Bray & Gibson, 2003, P. sinusacca, Podocotyle syngnathi Nicoll, 1913, and Podocotyle tohei (Yamaguti, 1970) Bartoli, Bray & Gibson, 2003 (Nicoll 1913; Takahashi 1928; Park 1937; Ching 1960; Yamaguti 1970; Maillard & Lambert 1978; Bray & Campbell 1996). The testes position (tandem vs oblique/diagonal) differs in Podocotyle atherinae Nicoll, 1914, Podocotyle breviformis Manter, 1940, P. temensis and in P. t oh e i (Nicoll 1914; Manter 1940; Fischthal & Thomas 1970; Yamaguti 1970). The testes texture (irregularly indented to lobed vs entire/smooth) differs in Podocotyle araii Gibson, 1986, P. atherinae, P. ayu, P. breviformis, P. caithnessi, P. congeri, Podocotyle longiformis Wang, Wang & Zhang, 1992, P. novella, Podocotyle radifistuli (Acena, 1941) Gibson & Bray, 1984, Podocotyle scorpaenae (Rudolphi, 1819) Bartoli & Gibson, 1991, P. syngnathi, P. temensis, Podocotyle. theragrae (Lloyd, 1938) Gibson & Bray, 1984, and in P. tohei (Nicoll 1913, 1914; Takahashi 1928; Lloyd 1938; Manter 1940, 1954a; Acena 1941; Fischthal & Thomas 1970; Yamaguti 1970; Maillard & Lambert 1978; Gibson 1986; Bartoli & Gibson 1991; Wang et al. 1992). The shape of the testes differs in P. ar a i i, P. atherinae, P. ayu, P. breviformis, P. caithnessi, P. congeri, P. enophrysi, P. longiformis, P. novella, P. radifistuli, P. scorpaenae, P. sinusacca, P. syngnathi, P. temensis, P. theragrae and in P. tohei (Nicoll 1913, 1914; Takahashi 1928; Park 1937; Lloyd 1938; Manter 1940, 1954a; Acena 1941; Ching 1960; Fischthal & Thomas 1970; Yamaguti 1970; Maillard & Lambert 1978; Gibson 1986; Bartoli & Gibson 1991; Wang et al. 1992). The testes are not contiguous in P. apodichthysi, P. a r ai i, Podocotyle atomon (Rudolphi, 1802) Odhner, 1905, P. caithnessi, P. californica, Podocotyle gibbonsia Johnson, 1949, P. longiformis, P. novella, P. radifistuli, P. refl exa, P. scorpaenae, P. sinusacca, P. syngnathi, P. temensis and in P. t h e r ag r a e (Nicoll 1913; Manter 1926, 1954a; Park 1937; Lloyd 1938; Linton 1940; Acena 1941; Miller 1941; Johnson 1949; Ching 1960; Fischthal & Thomas 1970; Maillard & Lambert 1978; Gibson 1986; Bartoli & Gibson 1991; Wang et al. 1992). The extent of the cirrus pouch relative to the ventral sucker differs in Podocotyle angulata Dujardin, 1845, P. atherinae, P. enophrysi, P. longiformis, P. radifistuli, P. reflexa, P. scorpaenae, P. sinusacca, P. temensis, P. theragrae and in P. tohei (Nicoll 1914; Park 1937; Lloyd 1938; Acena 1941; Miller 1941; Ching 1960; Fischthal & Thomas 1970; MacKenzie & Gibson 1970; Yamaguti 1970; Bartoli & Gibson 1991; Wang et al. 1992). The position of the genital pore differs in P. ay u, P. caithnessi, P. californica, P. gibbonsia, P. radifistuli, P. scorpaenae, P. temensis, P. t h e r ag r a e and in P. t ohei (Takahashi 1928; Park 1937; Lloyd 1938; Manter 1954a; Acena 1941; Johnson 1949; Fischthal & Thomas 1970; Yamaguti 1970; Bartoli & Gibson 1991). The anterior extent of the vitellarium relative to the ventral sucker differs in P. atherinae, P. atomon, P. caithnessi, P. californica, P. congeri, P. enophrysi, P. longiformis P. novella, P. radifistuli, P. reflexa, P. sinusacca, P. syngnathi, P. temensis, P. t h e r a gr ae and in P. t o he i. The distribution of the vitelline follicles (i.e. gaps and/or confluency) differs in P. apodichthysi, P.

araii, P. atherinae, P. atomon, P. californica, P. enophrysi, P. gibbonsia, P. radifistuli, P. re f l e xa, P. scorpaenae, P. sinusacca, P. syngnathi, P. temensis, P. theragrae and in P. t o he i (Nicoll 1913, 1914; Manter 1926, 1954a; Takahashi 1928; Park 1937; Lloyd 1938; Linton 1940; Acena 1941; Miller 1941; Johnson 1949; Ching 1960; Fischthal & Thomas 1970; Yamaguti 1970; Maillard & Lambert 1978; Gibson 1986; Bartoli & Gibson 1991; Wang et al. 1992). Egg size differs in P. angulata (syn. Plagioporus [Caudotestis] angulatus [Dujardin, 1845] Szidat, 1944), P. apodichthysi, P. a r ai i, P. atherinae, P. atomon, P. a y u, P. breviformis, P. caithnessi, P. californica, P. congeri, P. enophrysi, P. gibbonsia, P. longiformis, P. novella, P. radifistuli, P. reflexa, P. scorpaenae, P. sinusacca, P. syngnathi, P. temensis, P. t h e r ag r a e and in P. t o he i (Odhner 1905; Nicoll 1913, 1914; Takahashi 1928; Park 1937; Lloyd 1938; Linton 1940; Manter 1940, 1954a; Acena 1941; Johnson 1949; Ching 1960; Fischthal & Thomas 1970; Yamaguti 1970, 1971; Maillard & Lambert 1978; Gibson 1986; Bartoli & Gibson 1991; Wang et al. 1992). Finally, P. novella possesses a distinct fusiform shape (Maillard & Lambert 1978, fig. 1), P. enophrysi has a seminal vesicle divided into one main part and three smaller parts (tripartite?) within the posterior part of the cirrus pouch and an esophagus “sometimes with an enlargement of its anterior end” (Park 1937, figs. 8 & 9), P. araii and P. scorpaenae lack a distinct metraterm (Gibson 1986; Bartoli & Gibson 1991) while P. congeri has a very long metraterm commencing halfway between the ovary and the ventral sucker (Yamaguti 1970), and P. ni m o y i n. sp. has the unique combination of a markedly dextral ovary and a post-ovarian uterus that extends posteriorly over the anterior testis into the inter-testicular area.