Novorostrum decorocrus Osawa, 1998

Ferreira, Luciane Augusto de Azevedo & Tavares, Marcos, 2020, The rare porcelain crab Novorostrum decorocrus Osawa, 1998 (Anomura: Porcellanidae) from Indonesia, Nauplius (e 2020007) 28, pp. 1-5 : 2-4

Novorostrum decorocrus Osawa, 1998

( Figures 1A–D ; 2A–F )

Novorostrum decorocrus Osawa, 1998: 170 ; Fujita and Osawa, 2005: 763 (description of larvae); Osawa and McLaughlin, 2010: 112 (list).

Material examined. 1 male cl 3.0 mm, cw 3.0 mm, MZUSP (40088), Tial, Ambon, Indonesia, 9 September 1991, intertidal zone, D. L. Rahayu coll. and don.; 1 ovigerous female cl 4.3 mm, cw 4.3 mm ( MZUSP 40089 ), same data .

Distribution. Japan (Iriomote Island, Ryukyu Islands) and Indonesia (Tial, Ambon Island) ( Osawa, 1998; present study).

Remarks. The Indonesian specimens agree well with Novorostrum decorocrus from the Ryukyu Islands as described and illustrated by Osawa (1998): (i) cheliped propodus bluntly toothed along the extensor margin, and with a weak crenulated longitudinal ridge adjacent to the extensor margin on the dorsal surface ( Figs. 1B ; 2B, E ); (ii) cheliped carpus with several, small, acute or blunt teeth on the dorsal flexor margin ( Figs.1B ; 2B,E ); and (iii) propodus and carpus of P2–P4 (ambulatory legs) bluntly toothed on the extensor margins( Figs.1C ; 2C, F ). In these respects, N. decorocrus differs markedly from N. indicum , N. securiger , and N. phuketense , whose chelipeds have no teeth along the extensor margins of the propodi, as well as no small teeth on the dorsal flexor margins exclusive of a broad, blunt proximal lobe; and the propodus and carpus of P2–P4 lack blunt teeth on the extensor margins ( Osawa, 1998; Osawa and Chan, 2010). Novorostrum decorocrus further differs from N. indicum in having the carapace subtrapezoidal in dorsal view ( Figs. 1A ; 2A, D ), rather than broadly subtriangular with narrower front.

Female and male ( MZUSP 40089, 40088) of N. decorocrus differ from each other in that the cheliped palm of the female has more distinct longitudinal ridges and concavities along the dorsal midline than that of the male, as also noticed by Osawa (1998). In addition, the female differs from the male in having the carapace surface more strongly uneven with deeper longitudinal grooves, the front more strongly trilobate, with the median lobe more distinctly produced than the lateral lobes ( Figs. 1A ; 2A ), and the ambulatory legs with more pronounced rugae and tubercles on the lateral surfaces ( Figs. 1C ; 2C ).

Fujita and Osawa (2005) estimated 12–14 days as the planktonic period of the zoeal phase of N. decorocrus under laboratory conditions, at a water temperature of 28.0°C–28.5°C, and offered for consideration that the distribution range of N. decorocrus could possibly be wider than known at that time. The present record of N. decorocrus from much farther south ( Ambon Island, Indonesia) than its type locality in southern Japan, provides empirical support to Fujita and Osawa’s (2005) proposition.

Figures

Figure 1. Novorostrum decorocrus Osawa, 1998, ovigerous female,cl 4.3 mm, cw 4.3 mm (MZUSP 40089).A, Carapace,dorsal view. B, Right cheliped, dorsal view. C, Left second ambulatory leg, lateral view. D, Right ocular peduncle, cornea and antenna, dorsal view. Scale bars: (A–C) = 1 mm, (D) = 0.5 mm.

Figure 2. Novorostrum decorocrus Osawa, 1998. A–C, Female, cl 4.3 mm, cw 4.3 mm (MZUSP 40089). D–E, Male, cl 3.0 mm, cw 3.0 mm (MZUSP 40088). (A, D) Cephalothorax, abdomen, and P5, dorsal view. (B, E) Right cheliped, dorsal view. (C, F) Left second ambulatory leg, lateral view. Scale bars = 1 mm.