Hatschekia hemicyclium, 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 : 3-6

Hatschekia hemicyclium n. sp.

( Figs 1–15 )

Type material. Holotype, female ( NSMT –Cr 20898), ex Rhinecanthus rectangulus (Bloch & Schneider) ( Tetraodontiformes : Balistidae ), off Cape Maeda (26°26’N, 127°46’E), Okinawa-jima Island, the Ryukyu Islands, East China Sea, Japan, 2 September 2005. Paratypes, 4 females ( RUMF –ZC–00921), ex R. rectangulus , off Cape Maeda (26°26’N, 127°46’E), Okinawa-jima Island, the Ryukyu Islands, East China Sea, Japan, 2 September 2005.

Other material examined. 3 females ( NSMT –Cr 20899), ex R. aculeatus (L.), off Odo (26°5’N, 127°42’E), Okinawa-jima Island, the Ryukyu Islands, North Pacific Ocean, Japan, 1 September 2005; 2 females ( NSMT –Cr 20900), ex R. verrucosus (L.), off Sunabe (26°19’N, 127°44’E), Okinawa-jima Island, the Ryukyu Islands, East China Sea, Japan, 18 August 2006.

Description of female. Body ( Figs 1–2 ) 1105–1344 (1242 ± 88) long, excluding caudal rami (n = 5). Cephalothorax semicircular, wider posteriorly, shorter than wide [232–294 (272 ± 25) × 301–356 (328 ± 20)], widest near posterior end, bearing dorsal, M-shaped chitinous frame. Trunk elongated, elliptical, longer than wide [874–1080 (976 ± 76) × 270–316 (290 ± 19)], widest slightly anterior to middle. Urosome ( Fig. 3 ) excluding caudal ramus rounded, shorter than wide [49–71 (56 ± 9) × 104–117 (111 ± 5)]. Genital complex fused to abdomen without border. Caudal ramus ( Fig. 3 ) oval, length 25–31 (27 ± 3), width 17–20 (19 ± 1), bearing 5 naked setae.

Rostrum with 1 round process on posterolateral corners ( Fig. 4 ). Antennule ( Fig. 4 ) indistinctly 5- segmented, 166–202 (183 ± 15) long; armature formula: 9, 5, 4, 1, 13 + 1 aesthetasc. Antenna ( Fig. 5 ) 3- segmented; proximal segment (coxa) unarmed; middle segment (basis) ornamented with surface pits; terminal claw bearing 1 basal seta and shallow groove near base; proximal segment length 58–89 (74 ± 13); middle segment length 141–184 (159 ± 20); terminal claw length 41–52 (46 ± 4); total length 241–316 (279 ± 33). Parabasal papilla ( Fig. 6 ) aggregated, wrinkled, carrying apical process. Oral cone robust. Mandible ( Fig. 7 ) slender, with 4 sharp apical teeth. Maxillule ( Fig. 8 ) bilobate; both lobes armed with 2 tapering elements. Maxilla ( Fig. 9 ) 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 10–11 ) biramous, with exopods composed of 2 indistinct segments and 2–segmented endopods; leg armature formula as follows:

Leg 1 ( Fig. 10 ) 104–112 (110 ± 3) long; protopod length 61–68 (64 ± 3); exopod length [43–48 (45 ± 2)] exceeding endopod length [21–28 (26 ± 3)]. Leg 2 ( Fig. 11 ) length 103–107 (106 ± 2); protopod length 62–76 (70 ± 5); exopod length 31–42 (36 ± 4); endopod length 22–26 (25 ± 2). Protopods and rami of legs 1 and 2 ornamented with rows of blunt spinules on anterior surface.

Intercoxal sclerites of legs 1 and 2 ( Figs 12–13 ) bearing 4 processes.

Leg 3 ( Fig. 14 ) represented by 2 simple setae on small papilla at anterior mid-lateral surface of trunk. Leg 4 ( Fig. 15 ) represented by 1 simple lateral seta on posterior ¾ of trunk.

Variability of measurement. The ”other material” specimens shares all important morphological characters with the type series. Measurement of their body parts and appendages was as follows: body length 1261–1383 (1309 ± 47), cephalothorax length 282–319 (304 ± 14), cephalothorax width 356–393 (369 ± 15), trunk length 969–1080 (1028 ± 40), trunk width 288–337 (305 ± 21), abdomen length 55–74 (59 ± 8), abdomen width 110–132 (121 ± 8), caudal ramus length 25–28 (25 ± 1), caudal ramus width 15–21 (18 ± 2), antennule length 193–215 (202 ± 9), antenna proximal segment length 72–98 (81 ± 10),antenna middle segment length 195–213 (204 ± 8), antenna terminal segment length 43–52 (47 ± 4), antenna total length 314– 350 (332 ± 15), leg 1 length 109–130 (118 ± 8),leg 1 protopod length 66–78 (71 ± 5), leg 1 exopod length 43– 52 (47 ± 4), leg 1 endopod length 25–33 (28 ± 3), leg 2 length 112–124 (117 ± 5), leg 2 protopod length 75– 84 (79 ± 4), leg 2 exopod length 35–40 (38 ± 2), leg 2 endopod length 25–34 (29 ± 3).

Attachment site. Gill filaments.

Remarks. Hatschekia hemicyclium n. sp. shares 4 processes on the intercoxal sclerites of legs 1 and 2 with 10 species, namely H. balistae Nuñes-Ruivo, 1954 ; H. bibullae Uyeno & Nagasawa, 2009 ; H. cylindrus Uyeno & Nagasawa, 2009 ; H. khahajya Uyeno & Nagasawa, 2009 ; H. kuroshioensis Uyeno & Nagasawa, 2009 ; H. lima Uyeno & Nagasawa, 2009 ; H. monacanthi Yamaguti, 1939 ; H. ostracii Yamaguti, 1953 ; H. pseudostracii Uyeno & Nagasawa, 2009 and H. sunaoi Uyeno & Nagasawa, 2009 . Of these species, 6 (i.e. H. bibullae , H. cylindrus , H. khahajya , H. kuroshioensis , H. lima and H. monacanthi ) are differentiated from this new species by the number of leg elements. Hatschekia pseudostracii differs from the new species by having 10 setae on the proximal segment of the antennule. The setal elements of the antennule and legs 1-2 were inadequately described for H. balistae by Nuñes-Ruivo (1954) and it is thus difficult to compare the numbers of elements of these appendages between H. balistae and the new species. Nonetheless, H. balistae differs from the new species by having a distinct apex on the cephalothorax. Hatschekia ostracii is also distinguishable from the new species in bearing distinct posterior processes on the trunk while H. sunaoi differs from the new species by the following characteristics: the lack of a distinct parabasal papilla and the swollen base of leg 3.

Etymology. The specific name of the new species, hemicyclium , refers to its semicircle cephalothorax.

Figures

FIGURES 1 – 9. Hatschekia hemicyclium n. sp., female, holotype NSMT – Cr 20898. 1, habitus dorsal; 2, habitus dorsal with egg sacs; 3, posterior part of trunk, dorsal; 4, antennule, ventral, rp = rostrum process; 5, antenna, ventral; 6, antenna with parabasal papilla; 7, mandible; 8, maxillule; 9, maxilla. Scale bars: 1, 200 μm; 2, 500 μm; 3, 6, 70 μm; 4 – 5, 9, 50 μm; 7 – 8, 20 μm.

FIGURES 10 – 15. Hatschekia hemicyclium n. sp., female, holotype NSMT – Cr 20898. 10, leg 1, anterior view; 11, leg 2, anterior view; 12, intercoxal sclerite of leg 1, anterior view; 13, intercoxal sclerite of leg 2, anterior view; 14, leg 3; 15, leg 4. Scale bars: 10 – 13, 30 μm; 14 – 15, 10 μm.