Doridicola similis Ho and Kim, 2001

Kudoh, Fumitaka & Nagasawa, Kazuya, 2017, Doridicola similis (Copepoda: Poecilostomatoida: Rhynchomolgidae) Associated with Sepioteuthis sp. (Cephalopoda: Myopsida: Loliginidae), New to Japan, Species Diversity 22, pp. 161-166 : 161-164

publication ID	https://doi.org/ 10.12782/sd.22_161
persistent identifier	https://treatment.plazi.org/id/C67487C5-7703-A866-FC1C-F8FAFB4169D5
treatment provided by	Felipe
scientific name	Doridicola similis Ho and Kim, 2001
status

Treatment

( Figs 1–3 View Fig View Fig View Fig )

Doridicola similis Ho and Kim, 2001: 80–84 , figs 1–3 (type locality: Gulf of Thailand).

Description of female. Body ( Fig. 1A View Fig ) cyclopiform, 1.45–1.65 (1.54) mm long (excluding setae on caudal rami) and 0.55–0.63 (0.59) mm wide (greatest width of cephalothorax) (measurements based on 5 specimens). Prosome ( Fig. 1A View Fig ) comprising cephalosome and four pedigerous somites. Anterior margin of cephalothorax smoothly rounded. Cephalosome separated by dorsal furrow from first pedigerous somite, with protrusions at posterolateral corners of latter. First to fourth pedigerous somites progressively decreasing in size. Urosome ( Fig. 1B View Fig ) 5-segmented. Fifth pedigerous somite wider than long. Genital double somite ( Figs 1B View Fig , 3C View Fig ) wider than long, respectively 200–250 (235)×190–235 (210) µm, with anterodorsal bulge and posterolateral eggsac attachment areas. Three free abdominal somites ( Fig. 1B View Fig ) 85–150 (110)×105–123 (116), 75–103 (92)×95–105 (102), and 128–138 (133)×98–113 (107) µm long and wide, respectively. Caudal rami ( Fig. 1C View Fig ) 3.80–4.12 (4.00) times longer than wide, 165–185 (177)×40–45 (44) µm, and bearing 4 plumose setae at posterior extremity and 2 additional short setae (1 on outer lateral margin and other near posterior extremity). Egg sac ( Fig. 1D View Fig ) elliptical and slightly curved, 540×240 µm (n =1).

Antennule ( Fig. 1E View Fig ) 7-segmented, with armature formula: 4, 13, 6, 3, 4+1 aesthetasc, 2+1 aesthetasc, and 7+1 aesthetasc. Antenna ( Fig. 1F View Fig ) 4-segmented, with armature formula: 1, 1, 2+1 small claw, and 5+2 large, unequal claws. Labrum ( Fig. 1G View Fig ) with pair of large posteroventral lobes. Mandible ( Fig. 2A View Fig ) with shallow proximal notch; inner margin linear with row of short, thick spinules; convex margin with 3 outer scales followed by row of short, thick spinules; terminal lash long, tapering, bilaterally spinulose. Maxillule ( Fig. 2B View Fig ) with 2 terminal and 2 subterminal setae, one of former with spinules. Maxilla ( Fig. 2C View Fig ) 2-segmented; syncoxa unarmed; basis with large seta (seta I) bearing long spinules on both margins, simple seta (seta II) on posteri- or surface, and simple small seta (seta III) on outer margin of base; terminal lash armed along one side with large spinules. Maxilliped ( Fig. 2D View Fig ) 3-segmented; syncoxa largest, unarmed; basis carrying small simple seta and longer uniserlally spinulate seta; free endopodal segment terminating in barbed spiniform process with long spinulate spine and short simple seta at base.

Legs 1–4 ( Figs 2E–G View Fig , 3A View Fig ) biramous with 3-segmented rami, except for 2-segmented endopod of leg 4. Armature formula of legs 1–4 shown in Table 1.

Leg 5 ( Fig. 3B View Fig ) consisting of elongate free segment with 2 unequal simple setae at tip. Leg 6 ( Fig. 3C View Fig ) represented by 2 small naked setae in posterodorsal area of genital double somite.

Description of male. Body ( Fig. 3D View Fig ) cyclopiform, 1.29–1.49 (1.38) mm long (excluding setae on caudal rami) and 0.39–0.46 (0.42) mm wide (measurements based on 10 specimens). Prosome 5-segmented and urosome 6-segment- ed. Genital somite wider than long, 235–295 (267)×210– 235 (227) µm. Caudal rami 3.25–3.63 (3.41) times longer than wide. Antenna ( Fig. 3E View Fig ) similar to that of female but proximal half of inner margin of second segment ornament- ed with small spinules.

Maxilliped ( Fig. 3F View Fig ) 4-segmented, subchelate; syncoxa unarmed; basis with row of spinules and 2 inner setae; free endopodal segment smallest, unarmed; terminal claw bearing lamellae near tip and 2 unequal setae near base. Leg 5 ( Fig. 3G View Fig ) tipped with 2 unequal simple setae. Leg 6 ( Fig. 3H View Fig ) represented by small lobe bearing 2 ventral naked setae at posterolateral corner of genital somite.

Host. Sepioteuthis sp. 2 (called shiro-ika, see Imai and Aoki 2012) ( Cephalopoda: Myopsida : Loliginidae )

Locality. Western North Pacific Ocean, Owase Bay off the coast of Hiki-Motoura, Kihoku, Mie Prefecture, Honshu, central Japan.

Site. Gills.

Number of copepods per squid. Forty-one and 91 individuals each on the two squids examined (220 and 205 mm DML).

Remarks. As indicated by Ho and Kim (2001), the three species of Doridicola reported from cephalopods, viz., Doridicola longicauda (Claus, 1860) from Sepia officinalis Linnaeus, 1758 in Europe ( Ho 1983), Doridicola similis Ho and Kim, 2001 from Sepioteuthis lessoniana Férussac in Lesson, 1831 in Thailand ( Ho and Kim 2001), and D. sepiae from Sepia esculenta in Japan and Korea ( Izawa 1976; Kim 1998), are morphologically very similar, but they are distinguished from each other by the length-to-width ratio of the female caudal rami: 2.2, 4.22, and 3.18 times longer than wide, respectively (see also the next paragraph). In the female specimens examined in this study, this value ranges from 3.80 to 4.12 (mean: 4.00) and is almost identical to that in D. similis . Our specimens are also separated from D. longicauda and D. sepiae by the absence of a protrusion on the anterior margin of the cephalothorax. It is thus reasonable to identify our specimens as D. similis , although the following slight differences are found between Japanese and Thai specimens: (1) scales are present on the convex margin of the mandible in the Japanese female specimens but absent in the Thai females, and (2) a seta on the basis of the leg 4 is naked in the Japanese female specimens but barbed in the Thai females.

Ho and Kim (2001) reported, based on Izawa (1976), that the length-to-width ratio of the female caudal rami of D. sepiae was 3.18: 1, which, however, differs from the value (“nearly 3.5 times”) reported by the latter author (p. 92). One possible explanation for this difference is that Ho and Kim (2001) did not notice Izawa’s (1976) printed data, and they measured the caudal ramus using Izawa’s fig. 1. We obtained a similar ratio (3.13: 1 as the average for the left and right caudal rami) from this figure. Using material of D. sepiae from Korea, Kim (1998) reported a ratio of 3.22: 1.

In the original description of D. similis, Ho and Kim (2001) misidentified maxillary seta III and seta I as “seta I” and “seta III”, respectively, both having been originally defined by Humes and Boxshall (1996: 178, fig. 1). Ho and Kim (2001) also misreported the female’s leg 4 (fig. 3A), free segment of leg 5 (fig. 3B), and genital area (fig. 3c) as those of the male in their figure caption.

Kingdom	Animalia
Phylum	Arthropoda
Class	Hexanauplia
Order	Cyclopoida
Family	Rhynchomolgidae
Genus	Doridicola