Chapter 23 



Crustacea Decapoda (Brach^^ura and Anomura) 

 of Enewetak Atoll 



JOHN S. GARTH,' JANET HAIG/ and 

 JENS W. KNUDSENt 



'Allan Hancock Foundation, University of Southern 

 California. Los Angeles. California 90089: 

 f Pacific Lutheran University, Department of Biology; 

 Takoma. Washington 98447 



INTRODUCTION 



A preliminary report on the Crustacea Decapoda (Bra- 

 chyura and Anomura) of Enewetak Atoll, Marshall Islands, 

 was published by the first author in 1964. It 

 reported the collecting of 19 families, 81 genera, and 147 

 species of brachyuran and anomuran crabs, mostly at 

 Enewetak Atoll, The report was based on collections made 

 by Donald J. Reish in 1956 and 1957; A. H. Banner in 

 1957; John S. Garth and Fred C. Ziesenhcnne in 1957 

 and 1959, with the assistance of J. Coatsworth, 

 L. Donaldson, T. Goreau, E. Held, R. Neshida, 

 R. Palumbo, J. Roberts, E. Ryan, and A. Smith; and 

 R. A. Boolootian, E. S. Reese, B. Sather, J. Shoup, and 

 R. A. Stevenson in 1960 and 1961. Only those species 

 were listed, however, that occurred in the two specialized 

 habitats discussed: those found in association with branch- 

 ing corals and those obtained by dredging in the lagoon. 

 (Reporting of Anomura was of a preliminary nature, giving 

 number of families, genera, and sp)ecies but listing only 

 four species, two of them to genus only, from the lagoon- 

 bottom habitat.) The overwhelming presence of the family 

 Xanthidae was noted. These comprised 45% of the genera 

 and 56% of the sp>ecies of Brachyura encountered, a cir- 

 cumstance attributed to the abundance and variety of 

 corals in which many of the xanthid species reside. 



The present report, although still of a preliminary 

 nature, is based additionally upon the more extensive col- 

 lections made by Jens W. Knudsen, who visited Enewetak 

 annually from 1965 through 1969 and again in 1971 and 

 1972; by Alan Havens, who visited the atoll in 1968, 

 1969, and 1970; and by C. Allan Child, who collected at 

 Enewetak for the Smithsonian Institution in 1969. Smaller 



collections used in preparing the report were those of 

 W. A. Bartos in 1944, F. C. Ziesenhenne in 1946, G. J. 

 Bakus and B. H. Bussing in 1965, C. V. MacCoy in 

 1967, S. L. Brunenmeister and E. Chave in 1974 and 

 1975, A. Fielding in 1976 and 1978, and P. Colin and 

 D. M. Devaney in 1980. Of the decapod crustaceans 

 obtained in the Marshall Islands during Operation 

 Crossroads in 1946 and 1947, the Portunidae (Stephenson 

 and Recs, 1967), the Xanthidae (under study by John S. 

 Garth), and the Porcellanidae (under study by Janet Haig) 

 from Enewetak could be included. Although the earlier 

 report (Garth, 1964) could compare what was then known 

 of Enewetak Brachyura and Anomura with the limited 

 work done in the Marshall Islands by the Pacific Science 

 Board's Coral Atoll Survey (Holthuis, 1953), a much bet- 

 ter comparison of the Enewetak fauna with those of other 

 atolls of the northern Marshall Islands can now be made 

 with reference to the earlier Operation Crossroads collec- 

 tions. The Porcellanidae from Marshall Islands other than 

 Enewetak are also being studied by Haig. 



Records of previous anomuran and brachyuran collect- 

 ing in the Marshall Islands at atolls other than Enewetak 

 are those of Balss (1938) from Ailinglablab, Ebon, Jaluit, 

 Kwadelin (Kwajalein), Namu, and Namorik of the Ralik 

 group; Likieb and Majeru (Majuro) of the Ratak group; of 

 Miyake (1939) from the above plus Arno of the Ratak 

 group; of Miyake (1943) (Porcellanidae only) from Jaluit; of 

 Holthuis (1953) from Ailuk, Arno, Bikar, Jemo, Kwajalein, 

 Lae, Likiep, Pokak, Taka, Ujae, Ujelang, Utrik, and 

 Wotho; and of Stephenson and Rees (1967) (Portunidae 

 only) from Bikini, Rongelap, and Rongerik. 



LAND CRABS 



The first decapod crustaceans encountered at 

 Enewetak, as at any mid-Pacific atoll, and the only ones 

 likely to be seen by many visitors, are the semiterrestrial 

 and terrestrial species. These are the species that spend 

 most of their lives at high-tide mark or above it, returning 

 to the sea only to deposit their eggs, which require sea- 

 water for hatching and for nurturing the larval stages. 

 Anomuran crabs having this habit are hermit crabs of the 



235 



