Pseudosarcotretes omorii, Yumura & Nishikawa & Ohtsuka, 2024

Yumura, Nanami, Nishikawa, Jun & Ohtsuka, Susumu, 2024, A New Species and a New Genus of the Family Pennellidae (Copepoda: Siphonostomatoida) Parasitic on North Pacific Lightfish Maurolicus japonicus (Actinopterygii: Stomiiformes: Sternoptychidae) Collected from Suruga Bay, Japan, Species Diversity 29 (1), pp. 81-90 : 83-88

publication ID	https://doi.org/ 10.12782/specdiv.29.81
publication LSID	lsid:zoobank.org:pub:C1C34CBC-A3B0-4A3D-B4AA-D872848EFA31
persistent identifier	https://treatment.plazi.org/id/0395D714-FFE9-FF9F-FC68-FA71C2A6A84D
treatment provided by	Felipe
scientific name	Pseudosarcotretes omorii
status	sp. nov.

Treatment

Pseudosarcotretes omorii sp. nov.

( Figs 2–4 View Fig View Fig View Fig )

Type-material. Holotype (NSMT-Cr 31576), one ovigerous female infecting Maurolicus japonicus (standard length 38 mm) collected from the eastern beach of Miho Peninsula in Suruga Bay (34.9899ºN, 138.5214ºE) on 9 February 2019, cephalothorax partly dissected and mounted on a glass slide, body in a vial GoogleMaps . Paratype 1 (NSMT-Cr 31577), from the same host fish as in the holotype; paratype 2 (NSMT-Cr 31578) from another individual host (standard length 38 mm) collected from the eastern beach of Miho Peninsula in Suruga Bay (34.9899ºN, 138.5214ºE) on 3 February 2019; paratypes 3 and 4 (NSMT-Cr 31579, 31580), two copepodids from egg string of paratype 2; paratype 5 (NSMT-Cr 31581), from another individual host (standard length 46 mm) collected from the eastern beach of Miho Peninsula in Suruga Bay (34.9846ºN, 138.5165ºE) on 11 February 2019.

Type locality. The east coast of Miho Peninsula (34.9847ºN, 138.5164ºE), Japan GoogleMaps .

Host. Maurolicus japonicus Ishikawa, 1915.

Attachment site. The cephalothorax, neck, and anterior part of the trunk of the parasite were embedded in the host’s musculature from posterior to right pectoral fin.

Description. Ovigerous female. Body ( Fig. 2B View Fig ) comprising laterally expanded cephalothorax, relatively slim neck, and trunk with anterior part constricted and posterior cylindrical. Total length ca. 5.5–7.1mm from anterior tip of cephalothorax to posterior end of caudal ramus. Anterior part of trunk embedded into host tissue. Cephalothorax produced lateral paired semicircle holdfasts ( Fig. 2B View Fig ). First pedigerous somite incorporated into cephalosome ( Fig. 2C View Fig ). Oral cone ( Fig. 2E View Fig ) in the form of elongated proboscis; pair of semicircular processes on constricted area between proboscis and cephalothorax ( Fig. 2A View Fig ). Neck ( Fig. 2C View Fig ) consisting of pedigers 2 and 3, and anterior part of trunk, 0.2–0.3 mm in length. Trunk ( Fig. 2B View Fig ) 3.4–4.4mm in length, about 1.8 times as long as the cephalothorax and neck; abdomen moderately reduced ( Fig. 2D View Fig ); caudal ramus ( Fig. 3F View Fig ) bilobate; setae missing, probably due to stranding damages. Egg string ( Fig. 2D View Fig ) straight and uniseriate. Number of eggs per string ranging from 298 to 324.

Antennule ( Fig. 3A View Fig ) incompletely two segmented, bearing middle seta; some elements possibly lost during dissection. Antenna subchelate ( Fig. 3B View Fig ), relatively wide, 3-segmented; second segment produced into robust process near anterior edge; third segment curved inward acting as subchela against preceding segment. Mandible ( Fig. 3E View Fig ) short, spatular, with three teeth. Maxillule ( Fig. 3C, D View Fig ) simple, inner lobe with one terminal seta; outer lobe absent. Maxilla not observed.

Legs 1 and 2 biramous ( Fig. 3G, H View Fig ); rami 2-segmented; leg 3 ( Fig. 3I View Fig ) uniramous; armature elements are shown in Table 2.

Male. Unknown.

Copepodid dissected from pre-hatching egg. Body comprising cephalosome with incorporated first pedigerous somite, second and third free somites, 2-segmented urosomes, and caudal rami. Cephalothorax ( Fig. 4A View Fig ) ellipsoid, the tip of anterior slightly hollow, oral cone ( Fig. 4B View Fig ) weakly developed. Naupliar eyes conspicuously present. Second pedigerous somite about two-thirds length of third pedigerous somite; urosomite separated vaguely from caudal rami ( Fig. 4G View Fig ).

Antennule ( Fig. 4D View Fig ) 2-segmented. Antenna ( Fig. 4C View Fig ) 3-segmented, proximal segment large, having blunt process at mid length, middle segment short, terminal segment curved inward to form subchela with serrate notch. Oral cone ( Fig. 4B View Fig ) short, slightly conical. Oral appendages rudimentary, invisible.

Legs 1 and 2 ( Fig. 4E, F View Fig ) biramous, rami unsegmented; armature elements shown in Table 2; leg 3 ( Fig. 4H View Fig ) represented by single spine on posterior tip of third pedigerous somite.

Variation. The number and shape of knobs on the anterior parts of body of adult females vary among specimens. While the holotype has a pair of wing-shaped knobs on the anterior end of trunk, paratype 1 bears two pairs of spherical knobs in addition to one hump near the constricted part ( Fig. 2F, G View Fig ).

Etymology. The specific name is named in honor of the late Dr Makoto Omori, who deceased on 4 June 2022, and had been making a great contribution to copepodology of Japan and keen to study the taxonomy and ecology of the pelagic shrimp Lucensosergia lucens (Hansen, 1922) in Suruga Bay.