Coenobita pseudorugosus(EN)

According to < Morphological and Molecular Evidence for a Stepwise Terrestrial Evolution and Species Delimitation on the Coenobita Phylogeny > in 2008, Coenobita pseudorugosus is also distributed in Taiwan. Coenobita pseudorugosus differs from Coenobita rugosus in their outer surfaces and outlines of left chelae, and in the right coxa of the 5th leg of the male. However, two possible objections will be raised to Nakasone’s descriptions: one is that during calcification the new soft skeleton of the chelae and other walking legs is molded to fit the shape of the shell (Greenaway, 2003), thus the difference in left chelae between the two species becomes more open to question; the other is that based on our observation on the right coxa of the 5th leg of the male. The difference is too slight to separate Coenobita pseudorugosus from Coenobita rugosus, and the young crabs of the two species are especially liable to be confused.

With regard to Coenobita pseudorugosus recorded by Asakura (2004), according to the colourful picture presented by this author, it might be merely a juvenile Coenobita perlatus, and not, as Asakura (2004) believed, a real Coenobita pseudorugosus. The main reason is that the colours of their claws and shields are quite different from those described by Nakasone (1988); Nakasone’s (1988) specimens are of dark-brown colour, while Asakura’s (2004) ones are of bright reddish-orange colour just like Coenobita perlatus. During the period of this investigation, in Indonesia several specimens of terrestrial hermit crabs were captured that are closely similar to Asakura’s (2004) Coenobita pseudorugosus recorded in the Maldives. But according to our identification we believe that they represent juvenile Coenobita perlatus.

After our analysis of species delimitation, we could be sure that Asakura (2004) misidentified juvenile specimens of Coenobita perlatus as Coenobita pseudorugosus.

Moreover, Nakasone (1988) suggested that Coenobita pseudrugosus was distinguishable from Coenobita rugosus from the plam; the palm of Coenobita pseudorugosus is dark-brownish, lacking a distinct large patch of dark brown on the outer surface, but that of Coenobita rugosus has a distinct large of dark brown. Based on this easily distinguishable character, as well as according to our unpublished artificial larval cultivation data, the juvenile crabs hatching from one single ovigerous female of Coenobita rugosus exhibited two types of morphology, which were Coenobita rugosus and Coenobita pseudorugosus. Therefore, we suggest that Coenobita pseudorugosus is not a valid species, but merely a synonym or a variety of Coenobita rugosus.