Gonodactylus chiragra ( Fabricius, 1781 )

Gonodactylus chiragra ( Fabricius, 1781)

Squilla chiragra Fabricius, 1781: 515 [type locality Ambon, Indonesia, by neotype selection ( Manning, 1981: 217)].

Gonodactylus chiragrus .— Krauss, 1843: 60.

Gonodactylus chiragra .— White, 1847: 84.— Kemp, 1913: 4, 11, 147, 155, fig. 2, pl. 9, fig. 107 (part).— McNeill, 1926: 316 (part).— Hale, 1929: 34.— Stephenson, 1952: 11.— Stephenson & McNeill, 1955: 250–252 (part).— Stephenson, 1962: 34.— Manning, 1966: 108, 113–114 (part).— McNeill, 1968: 89.— Moosa, 1986: 381; 1991: 155–156.— Manning, 1991: 2; 1995: 71–75, pls. 5–8, figs. 8e, f, 9a, b, 10a, 11a, 27a, 28–30.— Gosliner et al., 1996: 195.— Ahyong & Norrington, 1997: 100–101.— Debelius, 1999: 273.—Ahyong, 2001: 67–70, fig. 34.— Poupin et al., 2019: 6, fig. 2B.

Material examined. KZN: SAMC-A 008451, 1 ♀ (TL 56 mm), St. Lucia Bay, 28°21’40.8”S 32°24’26.1”E, [no date—suspected to be Stebbing’s (1917) specimen and listed by Barnard’s (1950) locality summary], depth unknown, coll. H.W. Bell-Marley.

Diagnosis. Ocular scales broad, flattened, separate, together broader than half rostral plate width. Rostral plate basal portion with anterior margins strongly concave in adults; anterolateral angles blunt or rounded; lateral margins subparallel or slightly divergent anteriorly; apical spine shorter or longer than base. Lateral margin of TS6–7 subequal. AS 6 spination better presented in smaller specimens. Telson with LT tooth indicated by shallow notch in margin of telson between anterolateral angle and apex of IM tooth; mid-dorsal carinae blunt, neither sharp nor crested dorsally; MD carina unarmed posteriorly; accessory MD carinae forming “anchor”; with 11–14 SM denticles. Uropodal exopod proximal segment outer margin with 10–13 movable spines.

Colour in alcohol. Body faded dark orange to brown.

Colour in life (after Ahyong 2001). Raptorial claw with ‘meral spot’ dark blue to maroon. ♂: Body dark green to brown; pereopods yellow, with orange-red dactyl; uropodal exopod distal segment yellow-orange. ♀: Mottled grey-green and white; pereopods with distal segment pale yellow.

Measurements. ♀ (n = 1) TL 56 mm. A1 peduncle 0.52CL. A2 scale 0.57CL. AWCLI 806. The largest known specimen at TL 105 mm recorded by Kemp (1913).

Distribution and habitat. Indo-West Pacific from French Polynesia to Japan, Australia and Indo-Malayan region to Madagascar, Mozambique and South Africa in the Western Indian Ocean. Common in the upper intertidal of coral reef flats, but also known from the nearshore or onshore rocky reefs.

Remarks. Gonodactylus chiragra was the first stomatopod reported from South African waters ( Krauss 1843) and was reported on in early revisions of the South African mantis shrimp fauna ( Stebbing 1917; Barnard 1950; Manning 1969a). Barnard (1950) speculated that Krauss’ specimen from Durban may be attributed to G. platysoma Wood-Mason, 1895 ; however, without the specimen, this is unverifiable. Furthermore, G. platysoma can easily be distinguished in the genus by the absence of a lateral tooth of the telson and to date; no specimen of that species has been reported from South Africa.

Gonodactylus chiragra is distinguished by the shape of the rostral plate with the anterior margins of the basal portion being strongly concave in adults. Ahyong (2001) describes some rostral plate variation with the anterior angles blunt to rounded, while the lateral margins are subparallel or slightly anteriorly divergent. Furthermore, the anterior margins have been recorded to be sometimes only slightly concave, which overlaps with descriptions of G. childi and G. botti . Ahyong (2001) suggests the relatively short telson to distinguish G. childi and the strongly inflated mid-dorsal carinae of G. botti to be distinguishable from G. chiragra .