Hatschekia mihkagan, Uyeno, Daisuke & Nagasawa, Kazuya, 2010

Uyeno, Daisuke & Nagasawa, Kazuya, 2010, The copepod genus Hatschekia Poche, 1902 (Siphonostomatoida: Hatschekiidae) from triggerfishes (Pisces: Tetraodontiformes: Balistidae) from off the Ryukyu Islands, Japan, with descriptions of eleven new species, Zootaxa 2478, pp. 1-40 : 31-33

Hatschekia mihkagan n. sp.

( Figs 133–147 )

Type material. Holotype, female ( NSMT –Cr 20916), ex Odonus niger (Rüppell) ( Tetraodontiformes : Balistidae ), off Sesoko-jima Island (26°37’N, 127°52’E), the Ryukyu Islands, East China Sea, Japan, 16 August 2006. Paratypes: 8 females ( NSMT –Cr 20917), ex O. niger , off Sesoko-jima Island (26°37’N, 127°52’E), the Ryukyu Islands, East China Sea, Japan, 16 August 2006; 3 females ( RUMF –ZC–00930), ex O. niger , off Sesoko-jima Island (26°37’N, 127°52’E), the Ryukyu Islands, East China Sea, Japan, 16 August 2006

Description of female. Body ( Figs 133–134 ) 966–1261 (1113 ± 90) long, excluding caudal rami (n = 12). Cephalothorax ovoid with 2 lobes on frontal margin, indistinctly separated from trunk, shorter than wide [187–222 (200 ± 10) × 232–300 (257 ± 16)], with dorsal, double ring shaped, chitinous frame. Trunk fusiform, longer than wide [780–1064 (919 ± 88) × 235–336 (284 ± 28)] with posterior knobs. Urosome ( Fig. 135 ) excluding caudal ramus shorter than wide [18–42 (33 ± 7) × 45–68 (59 ± 7)]. Genital complex fused to abdomen without border. Caudal ramus ( Fig. 135 ) slightly longer than wide [12–21 (18 ± 2) × 8–12 (9 ± 1)], bearing 6 naked setae.

Rostrum with 1 round process at each posterolateral corner ( Fig. 136 ). Antennule ( Fig. 136 ) indistinctly 5- segmented, 87–104 (94 ± 6) long; armature formula: 8, 5, 4, 1, 13 + 1 aesthetasc. Antenna ( Fig. 137 ) 3- segmented; proximal segment (coxa) unarmed; middle segment (basis) ornamented with surface pits; terminal claw with basal accessory element; proximal segment length 22–29 (26 ± 2); middle segment length 55–71 (64 ± 6); terminal claw length 18–25 (22 ± 2); total length 97–120 (112 ± 7). Parabasal papilla ( Fig. 138 ) rodlike, as long as middle segment of antenna. Oral cone robust. Mandible ( Fig. 139 ) slender, with 4 sharp apical teeth. Maxillule ( Fig. 140 ) bilobate; both lobes armed with 2 tapering elements; elements on inner lobe shorter than on outer lobe. Maxilla ( Fig. 141 ) 4-segmented; proximal segment unarmed; second segment rod-like, with 1 basal seta; third segment elongate, with 1 distal seta; terminal segment small, with 1 small seta and bifid claw. Maxilliped absent.

Legs 1 and 2 ( Figs 142–143 ) biramous; both legs with exopod composed of 2 indistinct segments and 2- segmented endopod; leg armature formula as follows:

Leg 1 ( Fig. 142 ) 58–64 (61 ± 2) long; protopod length 33–40 (36 ± 2); exopod length 18–29 (25 ± 3); endopod length 15–22 (20 ± 2). Leg 2 ( Fig. 143 ) length 67–78 (72 ± 3); protopod length 36–46 (42 ± 3); exopod length 25–33 (30 ± 2); endopod length 24–31 (28 ± 2). Protopods of legs 1 and 2 ornamented with rows of blunt spinules on anterior surface. Both rami of legs 1 and 2 ornamented with semicircular membranes and fine rows of spinules.

Intercoxal sclerites of legs 1 and 2 ( Figs 144–145 ) bearing 4 similar processes.

Leg 3 ( Fig. 146 ) represented by 2 simple setae originating on mid-lateral line of surface of trunk. Leg 4 ( Fig. 147 ) represented by 1 simple lateral seta on posterior of trunk.

Attachment site. Gill filaments.

Remarks. Hatschekia mihkagan n. sp. share the possession of 4 processes on the intercoxal sclerites of legs 1 and 2 with 10 species (see remarks of H. hemicyclium ) and 8 new species (i. e. H. churaumi n. sp., H. hemicyclium n. sp., H. izenaensis n. sp., H. jonesi n. sp., H. kabatai n. sp., H. mongarah n. sp., H. nakamurai n. sp. and H. zanpa n. sp.). Of these 18 species H. cylindrus and H. izenaensis n. sp. share a single seta on the endopod of leg 2 and the caudal ramus with 6 setae with the new species. Even though H. cylindrus resembles the new species, H. mihkagan n. sp. it differs from it in having a fusiform trunk (rather than a sausage-shaped trunk) with posterior knobs although the knobs are often very small and indistinct. Additionally, the new species has and a higher cephalothorax/body length ratio [0.18 ± 0.01 vs. 0.15 ± 0.01 (U-test; p <0.001), Table 1, see also table 1 in Uyeno & Nagasawa 2009b]. Hatschekia izenaensis n. sp. is easily distinguishable from the new species by having a trichotomous chitinous frame on the dorsal surface of the cephalothorax (instead of a double ring shaped frame), by the trunk having a constriction and by the presence of additional processes on the intercoxal sclerites of legs 1 and 2. It is uncertain in the original description of H. balistae (Nuñes- Ruivo 1954), whether a single seta is present on the first segment of the endopod of leg 2 as in the new species, but H. balistae differs from the new species by having a distinct apex on the cephalothorax.

Etymology. The new species name, mihkagan , refers to the similarity between the traditional swimming glasses in Okinawa and the chitinous frame on the cephalothorax of the new species.

Figures

FIGURES 133 – 141. Hatschekia mihkagan n. sp., female, holotype NSMT – Cr 20916. 133, habitus dorsal; 134, habitus lateral; 135, posterior part of trunk, dorsal; 136, antennule, ventral, rp = rostrum process; 137, antenna, ventral; 138, antenna with parabasal papilla (drawn from a paratype, NSMT – Cr 20917); 139, mandible; 140, maxillule; 141, maxilla. Scale bars: 133 – 134, 200 μm; 135 – 138, 141, 20 μm; 139 – 140, 10 μm.

FIGURES 142 – 147. Hatschekia mihkagan n. sp., female, holotype NSMT – Cr 20916. 142, leg 1, anterior view; 143, leg 2, anterior view; 144, intercoxal sclerite of leg 1, anterior view; 145, intercoxal sclerite of leg 2, anterior view; 146, leg 3; 147, leg 4. Scale bars: 142 – 145, 20 μm; 146 – 147, 10 μm.