Gastroptychus hendersoni (Alcock & Anderson, 1899)

Ahyong, Shane T. & Poore, Gary C. B., 2004, The Chirostylidae of southern Australia (Crustacea: Decapoda: Anomura), Zootaxa 436 (1), pp. 1-88 : 8

Gastroptychus hendersoni (Alcock & Anderson, 1899)

Ptychogaster hendersoni Alcock & Anderson, 1899a: 23 [type locality: off Travancore, Kerala State, India]; 1899b: pl. 45: figs. 2, 2a.— Alcock, 1901: 280.

Material examined. TASMANIA: SAM C6088 , 2 ovigerous females (29.0– 37.4 mm), 86 km SSE of South East Cape , 44°22.7’E, 147°07.3’E, 1050–1170 m, trawled, FV Belinda, K. L. Gowlett­Holmes , 12 Feb 1992 .

Remarks. The two Australian specimens of G. hendersoni Alcock, 1894 are morphologically uniform in almost all respects but vary in carapace and abdominal spination. The smaller specimen (29.0 mm) bears three spines along the carapace midline (epigastric, gastric, cardiac) whereas the larger specimen (37.4 mm) bears only one median spine (epigastric). The spination of the abdominal pleura is more pronounced in the smaller specimen, as are the acute tubercles on the fifth abdominal tergite. In contrast to the figure and account of the holotype ( Alcock & Anderson 1899a, b) (about 13 mm), both Australian specimens have less pronounced pleural spines and lack spines on the fourth abdominal tergite. A specimen from the Philippines figured by Baba (1988) (18.1 mm) also shows reduced tergal spination, and pleural spination intermediate between the holotype and Australian specimens. Apparently, abdominal spination becomes reduced with increasing size.

As noted by Baba (1991), the relative lengths of the proximal to distal portions of the telson in G. hendersoni are variable. Alcock (1901) used the relative lengths of the proximal to distal portions of the telson as one of the distinguishing characters between G. hendersoni (proximal lobe less than half­length of distal lobe) and G. investigatoris Alcock, 1894 (proximal lobe more than half­length of distal lobe). Baba (1988, 1991), however, noted that for Philippine and Loyalty Islands specimens of G. hendersoni , length of the proximal portion of the telson in G. hendersoni is longer than half that of the distal portion (0.65–0.68). In the two Australian specimens, the relative lengths of the proximal to distal portion of the telson is 0.62–0.63.

Distribution. Arabian Sea to the Philippines, the Kyushu­Palau Ridge, Loyalty Islands and now from Tasmania at depths of 787–1469 m.