Chelonocytherois omutai, Tanaka & Hayashi, 2019

Tanaka, Hayato & Hayashi, Ryota, 2019, Chelonocytherois omutai gen. et sp. nov. (Crustacea: Ostracoda) from the back of loggerhead sea turtles, Zootaxa 4624 (4), pp. 507-522 : 511-518

publication ID	https://doi.org/ 10.11646/zootaxa.4624.4.4
publication LSID	lsid:zoobank.org:pub:8B01E009-7FC4-4141-85C5-2C82186F1DF5
persistent identifier	https://treatment.plazi.org/id/974187C2-B90F-FFA0-13C8-FE8DFB0EF857
treatment provided by	Plazi
scientific name	Chelonocytherois omutai
status	sp. nov.

Treatment

Chelonocytherois omutai View in CoL sp. nov.

( Figs. 2–9 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 )

http://zoobank.org/9ff1897d-9482-4cd1-9eb1-3bd363e3bcd5

Material examined. Holotype: adult male (UMUT RA 33122), right valve length 0.44 mm, height 0.22 mm, left valve length 0.45 mm, height 0.21 mm, soft parts mounted on a glass slide and valves preserved on a cardboard slide . Paratypes: 5 adult males (UMUT RA 33123–33125, UMUT RA 33130, UMUT RA 33132) and 5 adult fe- males (UMUT RA 33126–33129, UMUT RA 33131) . Type specimens (holotype and paratypes) were collected from epizoic algae on the carapace of a female loggerhead sea turtle, Caretta caretta (Fig. 2A; Table 1), landing on the Yotsuse Beach (30.4156 N, 130.4394 E) of Yakushima Island, Kagoshima Prefecture, Japan, June 15, 2016, col- lected by Ryota Hayashi . Additionally, three non-type specimens collected by Chihiro Kinoshita from epizoic algae on the carapace of two loggerhead sea turtles were examined (see Table 1): two adult females (UMUT RA 33133 and UMUT RA 33134) and one juvenile (UMUT RA 33135).

Description. Adult male

Carapace (Figs 2B, 3, 4A–E; 5, 6): Left valve slightly larger than right in length and smaller than right in height (Table 2). Carapace subovate, moderately compressed. In lateral view, anterior margin narrowly protruded; dorsal margin arched; posterior margin broadly convex. In dorsal view, carapace narrowly oblong. Carapace surface with numerous shallow horizontal striations (Figs 4A, B; 6). Pore system consisting of pores with one sensory seta and a large sieve structure (Figs 2B, 3; 4C, D; 5). Fused zone moderate. Marginal infold broad. Marginal pore canals developing a distinctive pattern (Fig. 3). Four adductor muscle scars form a vertical row (Figs 3; 4C, D; 5G). Hinge- ment of lophodont type (Fig. 5A–F). Antennula ( Fig. 7A View FIGURE 7 ): Six articulated podomeres, slender. First podomere bare. Second podomere twice as long as first podomere, with tufts of setulae on anterior and posterior margins. Third podomere two-thirds as long as first podomere, with one short setulous antero-distal seta and setulae on anterior margin. Fourth to sixth podomeres same length as third podomere. Fourth podomere with two medium antero-distal setae and one medium postero-distal seta. Fifth podomere with two medium antero-distal setae. Sixth podomere with two medium setae and one blunt tipped seta (aestetasc) on distal end.

Antenna ( Fig. 7B View FIGURE 7 , B’): Six articulated podomeres. First podomere (basis) slightly trapezoidal, with one long four-segmented exopodite (spinneret seta). Second (first endopodal) podomere with one long stout setulous and one medium setulous postero-distal setae. Third podomere as long as second podomere, with one short setulous and one short simple postero-distal setae and setulae on anterior margin. Fourth podomere two-thirds as long as third podomere, with one stout setulous medium postero-distal seta and one slender setulous medium seta on anterior margin. Fifth podomere bare, as long as fourth podomere. Sixth podomere as long as fifth podomere, with one short simple postero-medium seta, one stout comb-like seta ( Fig. 7 View FIGURE 7 B’), and one large stout distal claw with sharpened tip and several spines on posterior margin Mandibula ( Fig. 8A View FIGURE 8 , A’): Coxa with one short setulous dorsal seta and a row of triangle-shaped processes on dorsal margin. Coxal endite consisting of four small and one large teeth. Palp consisting of five podomeres. First podomere (basis) with one very long setulous seta (exopodite) near proximal end. Second and third podomeres bare. Fourth podomere with two setulous setae on medio-dorsal margin and four dorsal setae near distal end ( Fig. 8 View FIGURE 8 A’). Fifth podomere with four setae ( Fig. 8 View FIGURE 8 A’).

Maxillula ( Fig. 8B View FIGURE 8 , B’): Branchial plate (exopodite) with 14 plumose setae and two reflexed setae (directed towards atrium). Basal podomere with one palp (endopodite) and three endites. Palp consisting of two indistinct podomeres: first podomere with four distal setae; second podomere very small, with two distal setae. Endites ( Fig. 8 View FIGURE 8 B’): dorsal one with six setae; middle one with seven setae; ventral one with five setae.

Fifth limb ( Fig. 9A View FIGURE 9 ): Four articulated podomeres; first podomere with one antero-lateral setulous seta and one antero-distal setulous seta; second podomere half as long as first podomere, with one broad, short antero-distal seta; length of third podomere two-thirds of second podomere, bare; fourth podomere as long as third podomere, with one sharp spine on antero-medial margin, one stout sclerotized distal hook with antero-proximal sharpened protrusion and several spines on ventral margin.

Sixth limb ( Fig. 9B View FIGURE 9 ): Four articulated podomeres; first podomere with one antero-lateral setulous seta and one antero-distal setulous seta; second podomere half as long as first podomere, with one medium antero-distal seta; length of third podomere two-thirds of second podomere, bare; fourth podomere as long as third podomere, with one sharp spine on antero-medial margin, one stout sclerotized distal hook with antero-proximal sharpened protrusion and several spines on ventral margin.

Seventh limb ( Fig. 9C View FIGURE 9 ): Four articulated podomeres; first podomere with two tiny spines on anterior margin and one antero-distal setulous seta; length of second podomere two-thirds of first podomere, with one long antero-distal seta; length of third podomere two-thirds of second podomere, bare; fourth podomere as long as third podomere, with one stout sharp spine on antero-medial margin, one stout sclerotized distal hook with antero-proximal sharpened protrusion and several spines on ventral margin.

Oral cone ( Fig. 8C View FIGURE 8 ): triangular in lateral view, with imperfect small suctorial disc with fine long setae on apex.

Brush-shaped organ: absent

Copulatory organ and posterior body ( Fig. 10A, B View FIGURE 10 ): Asymmetrical. Right hemipenis ( Fig. 10A View FIGURE 10 ): Basal capsule (bc) rounded. Copulatory duct absent. Dorso-distal prehensile process (ddp), sclerotized, elongate, curved ventrally. Dorso-distal lobe (ddl) elongate, spine-shaped. Ventro-distal lobe (vdl) broad, lamelliform. Left hemipenis ( Fig. 10B View FIGURE 10 ): Basal capsule (bc) rounded-square shaped. Copulatory duct (cd) sclerotized, narrowly curved ventrally. Dorso-distal prehensile process (ddp) a small, rectangular-shaped lamella. Dorso-distal lobe (ddl) elongate triangular plate with blunt tip. Ventro-distal lobe (vdl) broad, lamelliform bending ventrally. Posterior body left and right sides bearing two setulous setae and one tiny spine on ventral margin. Abdomen with one seta (caudal ramus and rows of setulae.

Adult female. Carapace ( Fig. 4 View FIGURE 4 F–J): Both, left and right valves of female slightly smaller than valves of male ( Table 2 View TABLE 2 ).

Distal part of antenna ( Fig. 7C View FIGURE 7 , C’): Sixth podomere, with one short simple postero-medium seta, one stout short comb-like seta, and one medium stout distal claw with sharpened tip and several spines on posterior margin.

Copulatory organ and posterior body ( Fig. 10C View FIGURE 10 ): Female genital opening (fgo) unpaired. Sclerotized framework of right genital opening elongate ovate. Spermathecal duct (sd) long connecting with genital opening and large receptaculum seminis (rs). Numerous sperms are closely packed in spermathecal duct and receptaculum seminis (sperms are not shown in the figure). Genital lobe paired with two setulous setae and one short seta, respectively. Abdomen with one setulous seta (caudal ramus and rows of setulae.

Etymology. The new species is named in honor of Mr. Kazuyoshi Omuta in his long-time sea turtle research in Yakushima Island, Kagoshima, Japan.

Distribution. This species was found within epibiotic algae taken from the carapaces of loggerhead sea turtles caught in the type locality (Yakushima Island, Kagoshima Prefecture, Japan) and in Funakoshi Bay (39.4133N, 142.0231E; Yamada Town, Iwate Prefecture, Japan).

DNA sequence. The 18S rDNA sequence of paratype (UMUT RA 33132) was obtained. Accession number is LC380021 View Materials (1728 bp). A homology search with BLAST showed highest identity scores (95% identity, 1644/1735 bp) against Xiphichilus sp. (accession no. AB076624 View Materials ) that belongs to the family Paradoxostomatidae .