Epicepon japonicum Nierstrasz & Brender

Barahona-Segovia, Rodrigo M., Guzmán, Vicente Valdés & Pañinao-Monsálvez, Laura, 2021, Holops pullomen Barahona-Segovia & Guzmán & Pañinao-Monsálvez 2021, sp. nov., Zoological Studies 60 (4), pp. 1-10 : 2-4

publication ID	https://doi.org/ 10.6620/ZS.2021.60-04
persistent identifier	https://treatment.plazi.org/id/03E987A8-FFA5-FF9F-FCA9-4F15F4645DC2
treatment provided by	Felipe
scientific name	Epicepon japonicum Nierstrasz & Brender
status

Treatment

Epicepon japonicum Nierstrasz & Brender View in CoL à Brandis, 1931 ( Fig. 1 View Fig )

Epicepon japonicum Nierstrasz & Brender View in CoL à Brandis, 1931: 188–189, figs. 71–73; Dollfus et al. 1933: 76 [list]; Shiino, 1936: 168–170, fig. 3; Danforth, 1963: 8 [list].

? ”a bopyrid” — Takeda et al. 2005: 108.

Material examined: Mature female syntype (5.0 mm TL), mature male syntype (2.2 mm TL) parasitizing Tymolus sp. (see Remarks), Misaki, Osaka, Japan, 21.9–146.3 m, coll. T. Mortensen, 10 Jun 1914 ( ZMUC CR- 6930). Ovigerous female (7.2 mm TL), mature male (1.8 mm TL), parasitizing right branchial chamber of male Tymolus uncifer ( Ortmann, 1892) (11.6 mm CL × 13.4 mm CW), Shizuoka, Suruga Bay, Japan, from aquarium trade, imported into Singapore, obtained by P. Y. C. Ng, 2016 ( ZRC 2016.0452).

Redescription: Female ( Fig. 1A–I View Fig ) length 5.0 mm; maximum width (across pereomere 3) 3.0 mm; head length 0.8 mm; head width 1.4 mm; pleon length 1.8 mm. Body slightly dextral; all segments of body distinct ( Fig. 1A View Fig ).

Head ovate, wider than long, frontal margin slightly bilobate. Frontal lamina large and extending beyond sides and frontal margin of head ( Fig. 1A View Fig ). Eyes lacking. Antennules and antennae with three and four articles each, respectively, distalmost two articles of antennule and distalmost article of antenna terminally setose ( Fig. 1B View Fig ). Barbula with two slender short, distally rounded lateral projections on each side, outer projections longer and thinner than inner ones, middle region smooth with lateral low lobe near inner projection ( Fig. 1G View Fig ). Maxilliped with prominent anterior segment, palp as low non-articulated projection lacking setae, plectron triangular, short and thin ( Fig. 1F View Fig ).

Pereon broadest across pereomere 3. Irregularly shaped tergal projections prominent on both sides of pereomeres 1–4 and right pereomere 5, dorsolateral bosses on both sides of pereomeres 1–5 (crescent-shaped on pereomeres 1–3, triangular on pereomeres 4–5), thin coxal plates on both sides of pereomeres 1-3 and right pereomere 4 ( Fig. 1A View Fig ). No mid-dorsal projections on any pereomeres. Oostegites enclosing brood pouch, oostegite 1 ( Fig. 1E View Fig ) with ovate anterior article, longer than posterior article, internal ridge smooth, posterior article rounded distally, triangular proximally. Pereopods subequal in structure, first four shorter than others ( Fig. 1A View Fig ). All pereopods with short, blunt dactyli, cylindrical propodi, carpi and meri fused in posterior pereopods ( Fig. 1C, D View Fig ).

Pleon with six segments, first five pleomeres each bearing five pairs of biramous pleopods and longer uniramous lateral plates, all margins with slight undulation but not digitate, surfaces smooth ( Fig. 1A, H View Fig ). Stub-like endopods of pleopods no more than 1/4 length of slender, distally tapering exopods ( Fig. 1H, I View Fig ); exopods greater than 1/2 length of lateral plates ( Fig. 1H, I View Fig ). Terminal pleomere ending in uniramous uropods, similar to but slightly longer than fifth pleopodal exopods, surfaces smooth, margins with slight undulation but not digitate ( Fig. 1A, H, I View Fig ).

Male ( Fig. 1J–M View Fig ) length 2.2 mm; maximum width (across pereomere 3) 0.6 mm; head length 0.25 mm; head width 0.4 mm. All body regions and segments distinct ( Fig. 1K View Fig ).

Head broadly rounded distally, extending posteriorly to rounded point overlapping approximately 1/3 length of pereomere 1, distinctly separated from first pereomere ( Fig. 1K View Fig ). Thin, slit-like dark eyes near posterolateral margin of head. Antennules and antennae not visible beyond margins of head in dorsal view, of three and four articles, respectively; both bearing setae on all articles ( Fig. 1L View Fig ).

Pereomeres 3 and 4 subequal in width, other pereomeres only slightly narrower ( Fig. 1J, K View Fig ). All pereomeres tapered laterally, lacking mid-ventral tubercles. First pereopod larger than second, both larger than other five ( Fig. 1J View Fig ); all carpi with setae on distoventral ventral surface. Dactyli of pereopods 1 and 2 elongate, overreaching distal margins of carpi ( Fig. 1J, L View Fig ), dactyli of pereopods 3–7 short, inserted into cup-like indentations at distoventral margin of propodi ( Fig. 1J, M View Fig ).

Pleon with six pleomeres, rounded laterally, each slightly narrower than preceding one ( Fig. 1J, K View Fig ). Mid-ventral tubercles lacking, pleopods as low ventrolateral swellings on pleomeres 1–5. Pleomere 6 without uropods, posterolaterally extended into two slender rami, each as long as rest of pleotelson, both tipped with short setae; minute anal cone present distomedially ( Fig. 1J, K View Fig ).

Range: Known from the Pacific coast of Japan, Suruga Bay to Osaka, 21.9–146.3 m depth.

Remarks: The figure of the female syntype in dorsal view was labeled incorrectly by Nierstrasz & Brender à Brandis (1931: fig. 71): “C II” (Coxalplatten II) is actually the coxal plate on pereomere 1 and “HS III” (Hintere Seitenteile) is actually the tergal projection on pereomere 2. Shiino (1936) reported on a pair of specimens found parasitizing Tymolus japonicus Stimpson, 1858 from Shimoda, Japan; the male and female greatly resemble the syntypes but were likewise incompletely described and figured. The identity of the host of Shiino’s (1936) specimens may be incorrect as at that time T. dromioides ( Ortmann, 1892) (see below) was considered a synonym of T. japonicus ( Tavares, 1992) .

The identity of the type host is uncertain as it was not retained with the parasites, but it is likely T. dromioides based on identification of a pair of male specimens collected from the type locality, Misaki, on 30 June 1914 ( ZMUC NHMD- 226207). The identity of the bopyrid reported by Takeda et al. (2005) on a female T. uncifer from west of Amami-Oshima Island (28°33.25'N, 126°58.11'E – 28°22.09'N, 126°57.03'E, 334–348 m) is also unknown but is likely E. japonicum based on host choice and the known distribution of the parasite. The type specimens likely came from the right branchial chamber of the host, as the female is slightly dextral (dextral females are found in the right branchial chamber, sinistral ones in the left in all known host species; see Markham 1985).