Chapter 1 3 



Pol\;chaetes of Eneivetak Atoll 



DENNIS M. DEVANEY (deceased)* and 

 JULIE H. BAILEY-BROCKt 



'Bernice P Bishop Museum. Honolulu. Hawaii 9681 7; 

 fDepartment of Zoology. University of Hawaii 

 Honolulu. Hawaii 96822 



POLYCHAETA 



The first record of polychaetes from Encwctak is based 

 on collections made during Operation Crossroads between 

 1946 and 1952 (Hartman, 1954). Earlier reports on 

 polychaetes from the Marshall Islands (Chamberlin, 1919; 

 Gustafson, 1930) did not refer directly to Enewetak as a 

 collection locality. Just over 70 polychaete species (20 of 

 which could not be specifically determined) were identified 

 by Hartman (1954). Most of the polychaetes were col- 

 lected in shallow reef flat areas on lagoon and seaward 

 sides of windward and leeward islands. Specimens from 

 these collections have been deposited in the U. S. National 

 Museum of Natural History (USNM) and Allan Hancock 

 Foundation. Hartman suggested that many of the 

 polychaetes had an erosive effect on the reefs because 

 they are known to bore into coral rock. Most of the iden- 

 tified species are represented in other parts of the Indo- 

 West Pacific, and three new species, Dodecaceria laddi, 

 Leaena minuta, and Sphaerodorum pacificum, were 

 described from Enewetak (Hartman, 1954). Table 1 pro- 

 vides a checklist of polychaetes of Enewetak Atoll. 



Due to the importance of polychaetes as bio- 

 eroders, food for fishes and invertebrates, and components 

 of the coral reef biota, Mid-Pacific Research Laboratory 

 contracted for further collections to be made between 

 1956 and 1957. As a result, a series of identified species 

 was deposited in the reference collection at Enewetak and 

 the USNM, and three publications added 10 new species 

 to the atoll polychaete fauna (Reish, 1961, 1968; 

 Woodwick, 1964). Of the 29 newly recorded species from 

 Enewetak, 13 were cosmopolitan, eight were range exten- 

 sions from the Indian Ocean and Red Sea, and five were 

 from nontropical areas (Reish, 1968). This latter reference 

 is valuable in enumerating and in giving keys to species 

 within 29 families of polychaetes known from the Marshall 

 Islands at that time. 



Two ectocommensal polychaetes have been recorded 

 as symbionts from echinoderms at Enewetak. Hartman 

 (1954) reported Gastrolepidia clauigera associated with the 

 sea cucumbers Stichopus horrens at Bikini, Enewetak, and 

 Rongelap and with Holothuria gyrifer at Enewetak. Two 

 additional holothuroids (Actinopyga mauritiana and 

 Holothuria atra) were recorded as hosts for this polynoid 

 by Reish (1968). Devaney (1967) noted Hololepidella 

 nigropunctata as a symbiont with the brittle-star 

 Ophiocoma anaglyptica at Enewetak. Straughan (1969) 

 made the first identifications of spirorbid tube worms from 

 Enewetak. Two species were recognized. One, erroneously 

 described as a new species, is the sinistrally coiled species 

 Vinearia koehleri [as Spirorbis (Pileolaria) polyoperculatus 

 Straughan, (1969)]; the other is a dextral species, 

 Neodexiospira brasiliensis [as Spirorbis (Circeis) bellulus 

 Bush]. Young (1969) recorded a nudibranch that preyed 

 on the above two species and on a serpulid. 



Leviten (1976, 1978) recorded polychaetes from the 

 families Eunicidae and Nereididae that served as prey for 

 several conid gastropods on the seaward reef bench at 

 Enewetak Islet and elsewhere in the Indo-West Pacific. 

 Kohn (1981), in his continuing ecological studies on 

 Conus, reported representatives of eight polychaete fami- 

 lies that are prey for several of these gastropods. Some of 

 the identified polychaetes are apparently the first records 

 of these species from Enewetak where they occurred 

 mainly in the sandy lagoon among algae (Halimeda spp.). 



An understanding of the habitat preferences and diver- 

 sity of reef flat polychaetes along the seaward side of 

 Enewetak Islet was greatly enhanced through a study con- 

 ducted in 1976 and 1978 under laboratory support by 

 Bailey-Brock et al. (1980). As a result of this work, it was 

 determined that 44 polychaete taxa included 18 identified 

 species that were new Enewetak records, with representa- 

 tives of two additional families (Paraonidae and Scalibreg- 

 midae). Over 20 of the 31 syllids had been previously 

 unrecorded, but 12 have yet to be assigned specific 

 names. 



Polychaetes representing 26 families were abundant 

 infaunal components associated with selected Enewetak 

 corals and coral rubble (Highsmith, 1981). The poly- 

 chaetes were the most common invertebrates found in the 

 coral heads, with over 80% of all individuals represented 



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