Austruca cryptica

Michie, Laura A., Barnes, R. S. K., Clark, Paul F., Bennett, Wayne A. & Cragg, Simon M., 2021, Distinguishing ten sympatric species of fiddler crab (Decapoda: Ocypodidae) using a suite of phenotypic characteristics, Zootaxa 5026 (4), pp. 480-506 : 484-486

Austruca cryptica (Naderloo, Türkay and H.-L. Chen, 2010)

( Figure 3a–j )

Material examined. 12 ♀, 9 ♂, Kaledupa , Indonesia, 5º 29’ 50’’S, 123º 45’ 20’’E, mud flat in front of mangroves, coll. L. Michie, 26.08.2014 . 8 ♀, 11 ♂, Kaledupa , Indonesia, 5º 29’ 51’’S, 123º 45’ 20’’E, on the mangrove perimeter, coll. L. Michie, 26.08.2014 .

Diagnosis. Carapace: broader than long; smooth; front broad; anterolateral angles moderately acute and slightly produced; anterolateral margins short, moderately convergent; anterolateral margin moderately convergent; dorsolateral margins short or nearly absent. Major cheliped: outer surface of carpus smooth, manus with outer surface slightly granular; both fingers with enlarged proximal tooth and sub-distal teeth, present or absent.

Colouration ( Figure 3a–d ). Adult male. Carapace: mainly black with white transverse bands varying in size and number, some individuals as much white as black, occasionally pale region turquoise rather than white, anterior ventral surface of carapace and merus of third maxilliped generally black, ventral surface of third maxilliped ischium almost always white or pink. Major cheliped: dactyl and pollex generally have white tips, remainder orange or pink which extends to manus and carpus, alternatively dactyl and pollex white or in equal proportions white and orange/ pink, merus often same colour as adjacent manus and carpus. Minor cheliped & ambulatory legs: black, dark brown or grey.

Adult female. Carapace: varies greatly, mostly pink or orange, occasionally grey, frequently with a white band across posterior region. Ambulatory legs: similar to males.

Juvenile male. Carapace: usually mottled light brown/russet with pattern and darker colours developing with maturity. Major cheliped: tends to be light brown and pink at juvenile stage but becomes darker with maturation.

Juvenile female. Same as juvenile male.

Gonopod morphology ( Figure 3e–h ). G1 curved in dorso-lateral direction; distal end relatively short with pore in midline; distal protuberance (thumb as described by Crane 1975) moderately long, reaching base of flange; large protruding lateral lobe extending slightly beyond main termination; distal end curved slightly in lateral direction; pore of sperm channel in midline, marked by indentation.

Gastric mill ( Figure 3i, j ). Urocardiac ossicles complex, with 2 transverse ridges of median teeth, both large, different in shape with first strongly arched and second much broader; stem region has 4 pairs of cusps, decreasing in size distally, last one shorter, attached to plate dorsally. Lateral tooth plate with 17 comb-shaped teeth.

Biology. Austruca cryptica is a small-size species (largest male CL = 8.9 mm, CB = 15.6 mm, largest female CL = 8.2 mm, CB = 13.3 mm); one of least abundant species on shore, present on margin of mangroves in mid intertidal zone.

Distribution. Indonesia ( Michie et al. 2015), Philippines.

Remarks. The specimens examined fit the descriptions by Naderloo et al. (2010) and Michie et al (2015), specifically the distinct inclination of the apical part of the G1 and the complex morphology of the gastric mill. The large protruding lateral lobe of the G1 distinguishes A. c ryptica from other Austruca species , and the complex gastric mill morphology and colouration separates A. c ryptica from the closely related species, A. perplexa , at Ambeua.

Figures

FIGURE 3. Austruca cryptica Naderloo,Türkay &H.-L. Chen, 2010:a–d Sulawesi Tenggara, Indonesia.Adult male colouration; a, large chela; b, carapace dorsal view. Adult female colouration; c, frontal view; d, carapace dorsal view. Photos credit L. Michie. Line drawing of right G1; e, mesial view; f, lateral view; CLSM images of apical part of G1; g, mesial view; h, lateral view; SEM images of male gastric mill; i, median tooth plate, ventral view; j, left lateral tooth plate, mesial view.