Macrobrachium miyakoense Komai & Fujita, 2005

Fujita, Yoshihisa, Davie, Peter J. F. & Ng, Peter K. L., 2015, A new stygobitic prawn of the genus Macrobrachium Spence Bate, 1864, from anchialine caves in Christmas Island, Indian Ocean; with a rediagnosis of M. miyakoense Komai & Fujita, 2005 (Crustacea: Decapoda: Caridea: Palaemonidae), Raffles Bulletin of Zoology 63, pp. 610-625 : 612

Macrobrachium miyakoense Komai & Fujita, 2005

( Figs. 1–3 )

Macrobrachium miyakoense – Komai & Fujita, 2005: 14 ; De Grave & Fransen, 2011: 327.

Material examined. 1 female (RUMF-ZC-2664), pocl 21.8 mm, Ueno Ana-ga Cave , Miyako Island, 24°43’13.9”N, 125°19’19.5”E, Ryukyu Islands, Japan, baited trap, coll. by Y. Fujita, 15 September 2009 ; 1 male (RUMF-ZC-2665), pocl 18.9 mm, Ueno Ana-ga Cave , Miyako Island, Ryukyu Islands, Japan, baited trap, coll. by Y. Fujita, 15 August 2010 .

Supplementary description. Compared to types, rostrum ( Figs. 1A , 2A ) directed anteriorly, sharply pointed distally, reaching/over-reaching distal end of antennular peduncle, not reaching distal margin of antennal scale, 0.45–0.52 of carapace length; dorsal margin with 10 teeth, 4 on carapace posterior to orbital margin; ventral margin with 4 or 5 teeth. Eye ( Figs. 1B , 2B ) reduced; stalk short, oblique, weakly swollen anteriorly; cornea small, oblique, faceted with dark pigments, 1.91–1.97 times wider than deep, 0.82–0.83 stalk width; ocellus absent. Epistome weakly bilobed by shallow depression. Male (RUMF-ZC-2665): second pereiopods ( Fig. 1C, D, E ) moderately robust, similar in form, unequal in length; left 1.68 times longer than right; surface from dactylus to ischium covered with numerous minute spinules, sparsely setose. Left (major) cheliped robust; ischium 0.68 of merus length; merus 1.01 of carpus length; carpus 0.58 length of chela; palm subcylindrical, 0.43 of chela length, dactylus 1.38 of palm length, 0.59 of chela length; cutting edge of fingers not gaping, with low, blunt teeth on proximal margins. Right (minor) cheliped ( Fig. 1F, G ) slender; ischium 0.78 of merus length; merus 1.12 of carpus length; carpus 0.55 length of chela; palm 0.40 of chela length; dactylus, 1.46 of palm length, 0.59 of chela length; cutting edge of fingers almost smooth, not gaping. Female (RUMF- ZC-2664): second pereiopods ( Fig. 2C, D, E ) moderately slender, similar in form, equal in length; surface of dactylus to ischium covered with sparsely minute spinules and setose; ischium 0.72–0.75 of merus length; merus 1.14–1.16 of carpus length; carpus 0.55–0.56 length of chela; palm 0.39 of chela length; dactylus 1.60–1.61 of palm length, 0.62 of chela length; cutting edge of fingers not gaping, with very low, blunt teeth on proximal margins.

Remarks. Macrobrachium miyakoense was originally described from two young males (pocl 14.70 mm and 12.60 mm). The present full-grown specimens are similar in morphology to the type specimens, but some adult characters differ markedly. We have therefore amended the original description of Komai & Fujita (2005) accordingly and provided new figures.

Figures

Fig. 1. Macrobrachium miyakoense Komai & Fujita, 2005, adult male (pocl 18.9 mm) from Miyako Island, Ryukyu Islands, Japan (RUMF- ZC-2665). A, rostrum, carapace, and cephalic appendages, lateral view; B, eye (left side), ventral view (left), dorsal view (right); C, left second pereiopod, lateral view; D, same, chela (setae and spinules omitted); E, same, basal part of fingers, dorsal view; F, right second pereiopod, lateral view; G, same, basal part of fingers, dorsal view. Scale bars = 1.0 mm.

Fig. 2. Macrobrachium miyakoense Komai & Fujita, 2005, adult female (pocl 21.8 mm) from Miyako Island, Ryukyu Islands, Japan (RUMF-ZC-2664). A, rostrum, carapace, and cephalic appendages, lateral view; B, eye (left side), ventral view; C, left second pereiopod; D, right second pereiopod; E, same, basal part of fingers, dorsal view. Scale bars = 1.0 mm.

Fig. 3. Macrobrachium miyakoense Komai & Fujita, 2005, coloration of live specimens. A, adult male (RUMF-ZC-2665), dorsal view; B, same, lateral view; C, adult female (RUMF-ZC-2664), dorsal view; D, same, lateral view.