Dorhynchus ramusculus ( Baker, 1906 )

Ahyong, Shane T., 2008, Deepwater crabs from seamounts and chemosynthetic habitats off eastern New Zealand (Crustacea: Decapoda: Brachyura), Zootaxa 1708 (1), pp. 1-72 : 36-37

Dorhynchus ramusculus ( Baker, 1906)

( Figs 16B–C )

Stenorhynchus ramusculus Baker, 1906: 104 , pl. 1: figs 1, 1a [type locality: off Neptune Island , South Australia].

Achaeopsis thomsoni . — Rathbun 1918: 4 [not A. thomsoni ( Thomson, 1873) ].

Achaeopsis ramusculus . — Hale 1927: 124, fig. 121. — Griffin 1966: 24, 35–37. — Dell 1968c: 234, 238. — Griffin & Tranter 1986: 21. — McLay 1988: 116–117, fig. 25.

Archaeopsis (sic) ramusculus . — Dell 1968a: 23.

Archaeopsis (sic) thomsoni (?). — Clark & O’Shea 2001: 15 [not A. thomsoni ( Thomson, 1873) ].

Dorhynchus ramusculus . — Davie 2002: 293. — Poore 2004: 360, fig. 108h–j.

Material examined. Seamount 441: NIWA 3595, 1 ovigerous female (cl 8.2 mm), 34°03.30–03.09’S, 174°48.49–48.42’E, 910– 820 m, KAH0204/52, 19 Apr 2002.

West Cavalli Seamount: NIWA 3593, 1 ovigerous female (cl 7.9 mm), 34°08.56–08.88’S, 173°57.12– 57.27’E, 879– 853 m, KAH0204/33, 17 Apr 2002; NIWA 3594, 1 ovigerous female (cl 10.8 mm), 34°09.85– 09.84’S, 173°57.84–58.33’E, 820– 805 m, KAH0204/40, 18 Apr 2002.

Rumble III Seamount: NIWA 34783 , 1 female (cl 5.9 mm), 35°44.38–44.46’S, 178°29.92–30.43’E, 430– 340 m, TAN0107/50, 19 May 2001 .

Hikurangi margin: NIWA 14172 , 2 males (pcl + 10 mm), 39°26.29–27.00’S, 178°20.70’E, 940– 970 m , R440 , 16 Jun 1990 ; NIWA 9941 , 1 male (cl 13.3 mm), 38°46.00’S, 178°48.00’E, 913 m, E0719, 23 Mar 1967 ; NIWA 9939 , 1 male (cl + 10 mm), 1 ovigerous female (cl 9.6 mm), 38°46.00’S, 178°48.00’E, 913 m, E0719, 23 Mar 1967 .

Ritchie Hill: NIWA 34972, 1 damaged male, 39°28.24–27.28’S, 178°24.76–25.17’E, 865– 741 m, KAH9907/40, 3 Jun 1999.

Builders Pencil cold seep: NIWA 29382 , 1 damaged female, 39°32.47–32.83’S, 178°19.90–19.95’E, 775–810 m, TAN0616/18, 5 Nov 2006 ; NIWA 29383 , 2 males (cl 15.0 mm; 1 damaged), 39°32.59–32.62’S, 178°20.17–19.72’E, 815– 812 m, TAN0616/21, 5 Nov 2006 ; NIWA 29384 , 1 male (cl 10.7 mm, pcl 7.7 mm, cw 6.1 mm), 1 ovigerous female (pcl 7.8 mm, cw 6.5 mm), TAN0616/30 ; NIWA 29385 , 1 ovigerous females (cl 9.6 mm), 39°32.59–32.65’S, 178°20.19–19.62’E, 815–819 m, TAN0616/38, 6 Nov 2006 ; NIWA 29386 , 1 ovigerous females (cl + 9.5 mm), 39°32.59–32.65’S, 178°20.19–19.62’E, 815–819 m, TAN0616/38, 6 Nov 2006 .

Rock Garden cold seep: NIWA 29377 , 1 damaged female, 40°02.31–02.47’S, 178°08.58–08.62’E, 730– 747 m, TAN0616/06, 4 Nov 2006 ; NIWA 29378 , 1 ovigerous female (cl 11.3 mm, pcl 8.8 mm), 40°02.31– 02.47’S, 178°08.58–08.62’E, 730–747 m, TAN0616/06, 4 Nov 2006 ; NIWA 29379 , 1 male (cl 13.6 mm), 1 female (12.7 mm), 40°02.35–02.41’S, 178°08.62–09.00’E, 764–766 m, TAN0616/07, 4 Nov 2006 ; NIWA 29380 , 1 damaged male, 40°02.38–02.22’S, 178°08.55–08.86’E, 760– 700 m, TAN0616/010, 4 Nov 2006 .

Hihi cold seep, Uruti Ridge: NIWA, 2 females (cl 8.9–10.1 mm; smaller ovigerous), 41°17.71–17.65’S, 176°33.37–33.66’E, 730–747 m, TAN0616/67, 10 Nov 2006 .

Wairarapa Seep , North Tower: NIWA 29388 , 1 male (cl 11.0 mm), 41°46.95–46.83’S, 175°23.98– 24.25’E, 1040–1053 m, TAN0616/79, 13 Nov 2006 .

Remarks. The examined specimens of D. ramusculus include the first ever recorded from cold seeps. The New Zealand specimens agree well with Australian material ( Baker 1906; Hale 1927; Griffin & Tranter 1986) in having parallel to slightly divergent rostral spines and usually a small tubercle or spine on each protogastric region of the carapace (becoming increasingly obsolete with increasing size, and absent in the largest specimens). The ventral ornamentation of the rostral spines ranges from 0–3 small spines on one or both sides.

Griffin & Tranter (1986) updated Griffin (1966) in providing more reliable criteria to distinguish D. thomsoni from D. ramusculus , and showed previous Australian records of the former ( Rathbun 1918) to be based on the latter. Similarly, previous records of D. thomsoni from New Zealand ( Clark & O’Shea 2001; Martin & Haney 2005) are based on D. ramusculus . Griffin & Tranter (1986) suggested that male cheliped length might differ between D. ramusculus and D. thomsoni (1.8 versus more than 2.0 times cl), but cheliped length in males of the present series spans the range reported for both species.

Distribution. Southern Australia and northern New Zealand, from the Hikurangi Margin to Rumble III seamount, Bay of Plenty, and Cavalli seamounts; 340–1053 m.

Figures

FIGURE 16. Carapace. A, Cyrtomaia cornuta Richer de Forges & Guinot, 1995, male, cl 46.9 mm (NIWA 14182), dorsal view. B–C, Dorhynchus ramusculus (Baker, 1906), male, cl 13.3 mm (NIWA 9941), right lateral and dorsal views. D, Platymaia maoria Dell, 1963, ovigerous female, cl 55.8 mm (NIWA 14191). E, Vitjazmaia latidactyla Zarenkov, 1994, ovigerous female, cl 72.0 mm (NIWA 16800).