Coenobita pseudorugosus

 

Coenobita pseudorugosus Nakasone, 1988

紅日陸寄居蟹
アカツキオカヤドカリ

 

 

Published on 18-April-2016

Updated on 25-May-2016


Common name

NA.


Remark

Below are some information about Coenobita pseudorugosus until now.

1998
According to < Land hermit crabs from the Ryukyus, Japan, with a Description of a New Species from the Philippines (Crustacea, Decapoda, Coenobitidae) >, Coenobita pseudorugosus record from Philippines(Cebu Island) is most closely related to Coenobita rugosus. Shield length can reach 12mm.

Small individuals with a broad dark brown transverse band at anterior one third of shield and two longitudinal dark brown stripes on posterior portion. Large individuals sometimes with two dark brown patches behind anterior margin of shield. Lateral borders of shield with a dark brown transverse band on anterior part. Eyestalks are dark brown.




There is series of 7 to 10 ridges (////) on upper outer surface of palm of left cheliped, lower margin nearly straight in distal half and not four-cornered in an external form. Palm is dark-brownish, lacking a distinct large patch of dark brown on the outer surface. Palm with scattered round granules in addition to oblique teeth on outer surface, numerous especially on its lower portions, both fingers also with numerous round granules on outer surface. Palm of left cheliped with a longitudinal white stripe on middle portion and the other part dark-brownish.




Outer surface of dactylus and propodus of left 3rd walking leg flat, smooth and  separated from dorsal surface by a well-marked longitudinal crest. Dactylus of left 2nd and 3rd walking legs each with a dark brown patch at proximal part. Propodus of left 3rd walking leg with a broad dark brown band on middle portion, dactylus of other walking legs with a white band at distal one-fourth, other area dark-brownish. Carpus of 1st and 3rd walking legs with a longitudinal dark brown stripe, merus with dark brown ring distally.




Male coxae of 5th legs of both sides produced unequal and right coxa produced in to elongate tube, distinctly longer than left one, its tube turning to the left and curved ventrally.




Tony: Specimens collected by Nakasone (1988) in Philippines, body colour is similar to Coenobita violascens, but shape of male coxae of 5th legs is different.



2002
According to < Ecology of subtropical hermit crabs in SW Madagascar: Refuge-use and dynamic niche overlap >, Coenobita pseudorugosus occur on SW Madagascar shores on the edge of a semi-desert.

Tony: No detail description and image.


2004
According to < Recent topics on taxonomy of hermit crabs from Japanese waters - Family Coenobitidae >, when Coenobita pseudorugosus is alive, their shield are from beautiful red to orange (specimen from Maldives, below image), like the sky at dawn, so Asakura use this as Japanese name.




Coenobita pseudorugosus from Philippines(Cebu Island) was recorded as new species. Beside the report of this type locality, recently there is a report from Madagascar of Indian Ocean. Asakura also have a specimens collected in Maldives of the Indian Ocean.

After Asakura saw the illustration of Coenobita scaevola which has been identified in the report of Tirmizi and Siddiqui (1982. The Marine Fauna of Pakistan), the shape of male coxae of 5th legs was same as Coenobita pseudorugosus. Asakura has observed specimens Coenobita scaevola from Red sea. Asakura thought that the shape of eye in Tirmizi and Siddiqui’s illustration is close to Coenobita pseudorugosus rather than Coenobita scaevola. There is a high possibility that Coenobita scaevola in report of Pakistan is Coenobita pseudorugosus.


To sum up above information, it is clear that Coenobita pseudorugosus has a wide distribution range from Philippines of Western Pacific Ocean, Pakistan (not confirm) to Madagascar and Maldives of the Indian Ocean.

Tony: Asakura (2004) named Coenobita pseudorugosus by using specimen from Maldives, not Nakasone's specimen from Philippines? Did Asakura compare the specimens between Maldives and Philippines?

The report of Barnes D. K. A. (2002, 2003) did not have detail description of Coenobita pseudorugosus in SW Madagascar. I think it needs further investigation to proof if Coenobita pseudorugosus is also distributed in Madagascar and Maldives.



2008
According to < Morphological and Molecular Evidence for a Stepwise Terrestrial Evolution and Species Delimitation on the Coenobita Phylogeny >, 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.
 
Tony: I also believed that Asakura's (2004) Coenobita pseudorugosus recorded in the Maldives represent juvenile Coenobita perlatus. Hope that author will provide images of Coenobita pseudorugosus that distributed in Taiwan in the future.


2011
A land hermit crab enthusiast, Félix J. Wáng posted some images in forum and believed that they are Coenobita pseudorugosus. Félix said he has tried to match the claw and male sexual tube shape with Nakasone's (1988) information. Nakasone (1988) said in that article he found the Coenobita pseudorugosus in Philippines. Félix have seen some Philippines specimens that do have similar characteristics with the hermit crabs that the images Félix display (Such hermit crabs also came from Central Indonesia - close to Philippines).

Tony: Félix said he matched the claw and male sexual tube shape, but the images of the shape of male sexual tube he posted is not same as Nakasone’s descriptions, but the shape is similar to Coenobita lila..





2016

Tony: Got a reply from David Barnes, author of < Ecology of subtropical hermit crabs in SW Madagascar: Refuge-use and dynamic niche overlap, 2002 > and thank you to him to share the images of Coenobita pseudorugosus with me.

Coenobita pseudorugosus in SW Madagascar are very similar to Coenobita rugosus, the easiest way to separate them is left cheliped of Coenobita pseudorugosus is 5 sided and Coenobita rugosus is 4 sided according to David Barnes.

In SW Madagascar, colour of Coenobita pseudorugosus is typically lighter. Their habitat, behavior and morphology are different with Coenobita rugosus.





Status

To be confirmed.




Reference link

coenobita.e-monsite.com

coenobitaspecies.com

Reference article

Barnes D. K. A., 2002. Ecology of subtropical hermit crabs in SW Madagascar: Refuge-use and dynamic niche overlap


Barnes D. K. A., 2003. Ecology of subtropical hermit crabs in SW Madagascar: short-range migrations

Greenaway P., 2003. Terrestrial adaptations in the Anomura (Crustacea: Decapoda)

Hung-Li Yuan, 2008. Morphological and Molecular Evidence for a Stepwise Terrestrial Evolution and Species Delimitation on the Coenobita Phylogeny


Nakasone Y., 1988. Land hermit crabs from the Ryukyus, Japan, with a Description of a New Species from the Philippines (Crustacea, Decapoda, Coenobitidae)

Poupin J., 1994. Quelques crustacés décapodes communs de Polynésie française

朝倉彰(Asakura A.), 2004. ヤドカリ類の分類学,最近の話題  オカヤドカリ科 (Asakura A., 2004. Recent topics on taxonomy of hermit crabs from Japanese waters - family Coenobitidae)