Tanaoa pustulosus (Wood-Mason in Wood-Mason & Alcock, 1891)

Published, First, 2009, New records of crabs (Decapoda: Brachyura) from the New Zealand region, including a new species of Rochinia A. Milne-Edwards, 1875 (Majidae), and a revision of the genus Dromia Weber, 1795 (Dromiidae), Zootaxa 2111, pp. 1-66 : 25-26

Tanaoa pustulosus (Wood-Mason in Wood-Mason & Alcock, 1891)

( Figs 7a, b, 8a, b, 9a, b)

Randallia pustulosa Wood-Mason in Wood-Mason & Alcock, 1891: 266. — Alcock 1896: 196. — Doflein 1904: 42, pl. XIV figs 1–5. — Ihle 1918: 246. — Yaldwyn & Dawson 1976: 95, figs 2–5. — McLay 1988: 100, fig. 20.

Tanaoa pustulosus — Galil 2003: 404, figs 1D, 3G, H.

Material Examined: East of North Cape: NIWA stn Z11043 , 1 male, 31.9 mm x 31.5 mm, 34°57.81’S, 175°12.64’E, 614– 602 m, Kaharoa, stn KAH0204/01, 13 Apr. 2002 ( NIWA 48569 ) ; NIWA stn Z11044 , 1 male, 31.5 mm x 32.3 mm, 34°57.62’S, 175°10.79’E, 581– 553 m , RV Kaharoa, stn KAH0204/02, 13 Apr 2002 ( NIWA 4873 ) ; NIWA stn Z11045 , 1 ovigerous female, 43.9 mm x 43.0 mm, 34°57.63’S, 175°10.44’E, 554– 518 m, Kaharoa, stn KAH0204/03, 13 Apr. 2002 ( NIWA 48575 ) .

Remarks. With their almost rounded body and long chelipeds, the two species of Tanaoa Galil, 2003 , are very distinctive species that are unlikely to be confused with any other New Zealand crabs. Besides T. pustulosus , a second species, T. distinctus ( Rathbun, 1893) has been collected at 472 m depth north of North Cape. These two species can be distinguished by the anterolateral margin with 5 or 6 prominent tubercles larger than the rest (margins bear many low tubercles in T. distinctus ) and intestinal region with a prominent tubercle anteriorly and upcurved spur-like tubercle posteriorly (intestinal region only has low tubercle posteriorly).

Tanaoa pustulosus has been reported from the Kermadec Is and Bay of Plenty, east North I., but at much shallower depths (330–475 m). The other leucosiids recorded from New Zealand are Bellidilia cheesmani ( Filhol, 1886) , Ebalia tuberculosa (A. Milne Edwards, 1873) , and Merocryptus lambriformis A. Milne Edwards, 1873 . As ambush predators, these crabs spend much of their lives buried in soft sand, with only the eyes exposed.

The ovigerous female T. pustulosus carried a large number of small eggs (diameter = 0.38–0.4mm) that were well protected by the tightly sealed brood chamber formed by the edges of the abdomen fitting into the elevated sternal rim as is typical in leucosiids. Fusion of abdominal somites 4–6 aids the formation of the brood chamber. The small egg size indicates that this species has indirect planktotrophic development and helps to explain the wide distribution of this species (see below).

Distribution. Tanaoa pustulosus inhabits the Indo-West Pacific region: East Africa, Seychelles, Mozambique Channel, Comoro Is, Madagascar, Reunion, Laccadive Sea, Andaman Sea, Japan, Taiwan, Philippines, Indonesia, New Caledonia, New Zealand, Fiji, Caroline Is, Agalega Is, and Geyser Reef, The specimens reported here fall within the known depth range 85–977 m ( Galil, 2003).