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Coenobita scaevola(EN)

Coenobita Scaevola Forskål, 1775

Image©papa___74

Common name

Red Sea Hermit Crab.

Size

Shield length can reach 9.5mm.

Distribution

On the coast from the Red Sea to the northern Arabian Sea, e.g. Gulf of Aden, Gulf of Oman, Sinai Peninsula, Qatar, Yemen, Iran, Pakistan, Egypt, Djibouti, Eritrea, Somalia etc.

Habitat

They are found in arid (desert) conditions with high temperature and low relative humidity. They live close to the sea and do not penetrate far inland, they mainly depend on the sea for their only water source. During the day they dig as deep as 15-20cm into the sand or live in burrows in shaded areas among coastal vegetation.

Larval stages

Seven zoeal stages.

Characteristics

Adult
Body colour is white, cream, light gray or pale pink (mainly in juveniles).

With gray granules at the anterior part of the shield.

Eyestalks
Eyestalks are compressed in shape, lateral view like a triangle.

The eyes are gray.

Antenna
The bottom part of antenna are white.

Cheliped
Left cheliped is bigger than right cheliped. There is series of ridges (////) on upper outer surface of palm of left cheliped.

Upper margins of both cheliped with brush of setae.

With gray granules at proximal part of both cheliped.

Walking legs 
With gray granules at proximal part of 2nd and 3rd walking legs.

Abdomen  
 The abdomen is short.

Male coxae of 5th legs
Right coxa produced into an elongate tube, always longer then left one.

Juvenile 
Body colour is pale pink, others are similar to adult.

Juvenile:

⇒https://www.inaturalist.org/observations/236803249

Adult:

⇒https://www.inaturalist.org/observations/236767555

Remark

According to < Coastal Hermit Crabs (Decapoda: Anomura) from Kenya, with a Review and Key to East African Species >, Coenobita scaevola may reach its southern limit on the Kenya coast but it was no found in the present study. It is possible that the absence of Coenobita scaevola from the Kenyan collection is due to Kenya being beyond the southern limit of their geographical ranges.

According to same article Table 3. < Species of the genera Birgus and Coenobita recorded from East Africa >, Coenobita scaevola have also no record in Tanzania and Madagascar.

But I found some land hermt crabs images from Kenya, Tanzania, Madagascar and Seychelles, these places are close to Arabian Sea. They are very similar to Coenobita scaevola, it is possible they are also Coenobita scaevola.

But these specimens may also be Coenobita rugosus, just like Coenobita violascens from East Africa, body colour of specimens from East Africa tend to be lighter or white in colour, so they are very similar to Coenogita scaevola.

Kenya

Tanzania

Madagascar

Seychelles

Remark 2 – Coenobita scaevola vs Coenobita rugosus

Thank you Professor Shih for providing useful article < Die Anomuren des Roten Meeres (Crustacea Decapoda Paguridea, Galatheidea, Hippidea) > published in 1969 for reference.

The article mentioned that Coenobita scaevola can be distinguished from Coenobita rugosus by some characteristics, for example below 3 points:

1. Coenobita scaevola with a tuft of long setae on the ventral margin inside of the merus of the right cheliped. This tuft of long setae is absent in Coenobita rugosus.

Thank you Dr. Khaleid Fouad Abd El-Wakeil from Egypt confirmed the investigated specimens from Dr. Elham Said Ahmed Said, Coenobita scaevola have this tuft of long setae on the right cheliped

2a. Different shape of lower margin of palm of left cheliped.

2b. Coenobita scaevola with pointed series of ridges (////) but Coenobita rugosus only with rounded series of ridges (////) (Tony: I think this point difficult to distinguish). 

2c. Coenobita scaevola with upper edge with a row of eight to nine teeth (Tony: I think this point difficult to distinguish). 

3. Different shape of the eyes and the eyestalks.

Gallery

Reference links

  • coenobita.e-monsite.com
  • coenobitaspecies.com

Reference articles

  • Abd Al-Kader M. Hassan., Besar M.H., Hanafy MH., Mohamed M Abu-Zaid1., 2013. Some Ecological Aspects of the Land Hermit Crab Coenobita Scaevola ( Coenobitidae ) at Wadi El-Gemal Protected Area , Red Sea
  • Achituv Y., Ziskind M., 1985. Adaptation of Coenobita scaevola (Forskal) (Crustacea, Anemura) to terrestrial life in desert-bordered shore line
  • Burggren W. W., McMahon B. R., 2009. Biology of the Land Crabs, Cambridge University Press
  • Ch. Lewinsohn., 1969. Die Anomuren des Roten Meeres (Crustacea Decapoda: Paguridea, Galatheidea, Hippidea) 1)
  • Fishelson L., 1971. Ecology and distribution of the benthic fauna in the shallow waters of the Red Sea
  • E S A Said., 2008. Taxonomical and ecological studies on hermit crabs inhabiting the Red Sea coast of Egypt. Master thesis in Zoology (Invertebrates), Zoology Department, Faculty of Science, Assiut University, Egypt
  •  
  • Fishelson L., 2009. Red Sea Explorations by Israeli Zoologists 1950–2009
  • Greenaway P., 2003. Terrestrial adaptations in the Anomura (Crustacea: Decapoda)
  • Kazmi Q. B., Siddiqui F. A., 2006. An illustrated key to the Malacostraca (Crustacea) of the northern Arabian sea part vi: Decapoda Anomura
  • Khaleid F., Abd El-Wakeil, Elham S. Ahmed, Ahmad H., Obuid-Allah, Nasser A., El-Shimy, 2009. Hermit crabs (Crustacea: Decapoda: Anomura) inhabiting the intertidal and shallow sub tidal region of Red Sea coast of Egypt
  • McLaughlin P. A., Komai T., Lemaitre R., Rahayu D. L., 2010. Annotated checklist of anomuran decapod crustaceans of the world (exclusive of the Kiwaoidea and families Chirostylidae and Galatheidae of the Galatheoidea) Part I. Lithodoidea, Lomisoidea and Paguroidea
  • Moradmand M., Sari A. R., 2007. Littoral hermit crabs (Decapoda: Anomura: Paguroidea) from the Gulf of Oman, Iran
  • Niggemann R., 1968. Zur Biologie und Ökologie des Landeinsiedlerkrebses Coenobita scaevola Forskal am Roten Meer
  • Reay P. J., Haig J., 1990. Coastal Hermit Crabs (Decapoda: Anomura) from Kenya, with a Review and Key to East African Species
  • Sallam W. S., 2012. Egg production and shell relationship of the land hermit crab Coenobita scaevola (Anomura: Coenobitidae) from Wadi El-Gemal, Red Sea, Egypt
  • Sallam W. S., Mantelatto F. L., 2010. Population features and breeding season of the land hermit crab Coenobita scaevola (Forskal, 1775) (Anomura, Coenobitidae) from Wadi El- Gemal, South Red Sea, Egypt
  • Sallam W. S., Mantelatto F. L., Hanafy M. H., 2008. Shell utilization by the land hermit crab Coenobita scaevola (Anomura, Coenobitidae) from Wadi El-Gemal, Red Sea
  • Seyfabadi J., Motazedi M., Khodabandeh S., Kheirabadi N., Safaei M., 2013. Shell selection in the land hermit crab, Coenobita scaevola (Forskal, 1775) from Larak Island, Persian Gulf, (Decapoda: Coenobitidae)
  • Seyfabadi J., Zamani Jamshidi M. M., Mahvary-Habibabadi A., 2013. Littoral hermit crabs (Crustacea: Decapoda: Anomura) of Larak Island, Persian Gulf, Iran
  • 朝倉彰, 2004. ヤドカリ類の分類学，最近の話題 － オカヤドカリ科

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