Chapter 26 



Protochordates of Eneivetak Atoll 



LUCIUS G. ELDREDGE 



Universify of Guam. The Marine Laboratoiy, 



UOG Station. Mangilao. Guam 96913 



INTRODUCTION 



Protochordates are members of two acraniate 

 subphyla — Tunicata and Cephalochordata. Tunicates 

 include the sessile ascidians and the pelagic larvaceans and 

 thaliaceans. Few of either subphyla have been recorded 

 from Enewetak. 



TUNICATA 



Even though ascidians are known to be abundant and 

 diverse at Enewetak, only 10 species have been reported 

 in the literature (Eldredge, 1967). These names are pro- 

 vided in the checklist (Table 1). All of the forms known to 



occur at the atoll belong to the family Didemnidae. Of 

 these reported in 1967, two name changes were executed 

 by Kott (1980). The original specimens of Diplosoma 

 virens should now be named Diplosoma similis, and the 

 unidentified Trididemnum sp. should be named T. clinides. 

 Enewetak is the type locality and the only known location 

 of Didemnum gintonicum from a coral knoll at Kinedrol 

 (Chinieero) and Diplosoma hiatti from the reef between 

 Japtan and Jinimi (Chinimi). 



The remaining species have widespread distributions. 

 Diplosoma macdonaldi is found in the tropical and subtropi- 

 cal waters of the Atlantic and Pacific, and Diplosoma (Lis- 

 soclinum) fragile is known from Bermuda and the West 

 Indies as well as from Japan, Malaysia, and other Pacific 

 islands. These two species and Didemnum moselei;! and 

 Diplosoma similis axe found in Hawaiian waters. Didemnum 

 moselet;i is also known from Japan, Philippine Islands, 

 Malaysia, Australia, Tasmania, New Caledonia, south Ara- 

 bia, and from several other Pacific island locations. The 



TABLE 1 

 Checklist of Ascidians and Cephalochordates of Enewetak AtoU 



Phylum CHORDATA 

 Subphylum TUNICATA 

 Class ACIDIACEA 



Order ENTEROGONA 



Suborder APLOUSOBRANCHIATA 

 Family DIDEMNIDAE 



Didemnum gintonicum Eldredge: Eldredge, 1967. 

 Didemnum grande (Herdman): Eldredge, 1967. 

 Didemnum moseleiii (Herdman): Eldredge, 1967. 

 Didemnum quincuciale Michaelson: Eldredge, 1967. 

 Diplosoma similis (Sluiter): Kott, 1980. 



Diplosoma (Diplosoma) uirens Hartmeyer: Eldredge, 1967. 

 Diplosoma (Diplosoma) hiatti Eldredge: Eldredge, 1967. 

 Diplosoma (Diplosoma) macdonaldi Herdman: Eldredge, 1967. 

 Diplosoma (Lissoclinum) fragile (Van Name): Eldredge, 1967. 

 Trididemnum clinides Kott: Kott, 1980. 



Trididemnum sp.: Eldredge, 1967. 

 Trididemnum ci>chps Michaelson: Eldredge, 1967. 

 Subphylum CEPHALOCHORDATA 



Family ASYMMETRONTIDAE 



Notasi/mmetron caudatum (Willey): Schultz (1953). 



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