Sarcotretes umitakae, Uyeno, Daisuke, Wakabayashi, Kaori & Nagasawa, Kazuya, 2012

Uyeno, Daisuke, Wakabayashi, Kaori & Nagasawa, Kazuya, 2012, A new species of parasitic copepod, Sarcotretes umitakae sp. n. (Siphonostomatoida, Pennellidae), on the rattail (Actinopterygii, Macrouridae) from the East China Sea, Japan, ZooKeys 246, pp. 1-10 : 2-4

Sarcotretes umitakae sp. n. Figures 14

Type material.

Holotype female ( NSMT–Cr 22253) and 2 paratypic females ( NSMT–Cr 22254), ex Coelorinchus jordani Smith and Pope ( Gadiformes : Macrouridae ), taken off the Tokara Islands (29°58.02'N, 127°43.79'E to 29°59.57'N, 127°44.28'E), Kagoshima, East China Sea, Japan, 308.5-309.3 m depth, 8 October 2011, reg. K. Wakabayashi and Y. Tanaka.

Type locality.

off the Tokara Islands (29°58.02'N, 127°43.79'E to 29°59.57'N, 127°44.28'E), Kagoshima, East China Sea, Japan.

Description of postmetamorphic adult female.

Body (Fig. 2A) elongate, comprising head, neck, and trunk. Total length 43.42 (from tip of cephalothorax to end of abdomen). Head (holdfast) composed of cephalosome to third pediger (Fig. 2A, B), bearing elongate oral area projecting forward as cylindrical proboscis with multiple constrictions and mouth tube at its tip, with paired lateral processes (Fig. 2A, B) consisting of bulbous base drawn out into highly sclerotized horn-like process. Vestige of dorsal shield of cephalothorax and tergites of first to third visible on dorsal surface of head (Fig. 2D). Two paired small sclerites on ventral surface of basal region of oral cone (Fig. 2E). Neck (Fig. 2A) slender, longer than trunk, twisting and bearing bulge and constriction at posterior portion. Cylindrical trunk (Fig. 2A) 12.23 long (from enlarged end of neck to abdomen), 3.08 wide at widest part bearing paired hemispherical protrusions and reduced abdomen (Fig. 2F, G). Caudal rami absent.

Rostral area (Fig. 2H) triangular. Antennule (Fig. 3A) not segmented, located on sclerotized protrusion, bearing 10 blunt, long elements, and at least 17 short elements; 1 long distal seta with bifurcated tip. Antenna (Fig. 3B) subchelate, 3-segmented; proximal segment, unarmed; middle segment stout with a pointed process on innerdistal corner, hollowed out to receive terminal claw; terminal segment representing terminal claw with single basal seta. Mandible (Fig. 3C) located on lateral side of base of oral cone (Fig. 2E), represented by sclerotized process with unequal processes tip. Maxillule (Fig. 3D) bilobate; large inner lobe tipped with two naked setae; small outer lobe bearing one naked seta. Maxilla (Fig. 3E) 2-segmented; proximal segment rod-like, bearing round protrusion with pointed process in middle portion; terminal segment rod-like, tipped with curved spinulose process, small pointed process, and setulous lobe (Fig. 3F). Maxilliped absent.

Legs 1 to 4 occurring tightly together and located between paired lateral processes of holdfast. Legs 1 and 2 (Figs. 3G, 4A) biramous, composed of inter coxal sclerites, protopods, and 2-segmented rami. Leg 3 (Fig. 4B) uniramous, without endopod; leg armature formula as follows:

Leg 4 (Fig. 4C) represented by vestigial intercoxal sclerite. Legs 5 and 6 absent.

Variability of female. The necks of all paratypes twist and turn in complex fashion (Fig. 4D). Measurements of the body parts of the specimens from the type series (n = 3) are as follows: body length (anterior margin of the head to distal end of the posterior processes on the trunk) 30.26-50.12 (41.27 ± 10.10); trunk length 11.27-13.48 (12.33 ± 1.11); trunk width 2.84-3.17 (3.03 ± 0.17).

Male. Unknown.

Site.

The copepod attaches to various parts of the body surface of the host fishes (Fig. 1A). The head to the neck of the copepod was embedded in the host’s musculature, and the trunk was protruded into the water (Fig. 1B)

Etymology.

The specific name “umitakae” refers to the Umitaka-maru, a training and research vessel of TUMSAT.

Remarks.

Currently, three species of Sacotretes : Sacotretes eristaliformis , Sacotretes longirostris , and Sarcotretes scopeli , are considered to be valid ( Ho et al. 2007). Sarcotretes umitakae sp. n. differs from Sarcotretes eristaliformis and Sarcotretes scopoli by having the holdfast with paired bulbous swellings drawn out into an elongate, horn-like process (vs. bulbous with or without a blunt tip) and the neck approximately 3 times as long as the trunk (vs. nearly as long as the trunk in Sarcotretes eristaliformis and less than 3/4 of the trunk length in Sarcotretes scopeli ) ( Brian 1912; Hogans 1988; Boxshall 1989; Cherel and Boxshall 2004; Ho et al. 2007). The two specimens described as Sarcotretes eristaliformis by Kabata and Gusev (1966) were judged to be Sarcotretes scopeli on the basis of a body length of 15.8-21.2 mm, the neck being shorter than the trunk, and relative length of the proboscis ( Hogans 1988; Ho et al. 2007). In addition, Sarcotretes scopeli differs from the new species by the absence of the vestige of leg 4 (vs. presence) ( Boxshall 1989; Cherel and Boxshall 2004). Sarcotretes longirostris has the neck longer than the trunk like Sarcotretes umitakae sp. n. and only these 2 species possess an extremely long proboscis among their congeners. Sarcotretes longirostris is, however, easily distinguishable from the new species by having the following characters: slender lateral head processes without swollen basal portions (vs. a bulbous swelling with a slender process); a not defined rostral area (vs. triangular); and a large and conical reduced abdomen, protruding to posterior (vs. small and non-conical and slightly protruded to posterodorsal) ( Ho et al. 2007). In addition, the trunk has an anterior constriction in Sarcotretes umitakae sp. n. not shared with any of the three known species (Figs. 2A, 4D).