Chapter 1 7 



Stomatopod Crustacea of Enewetak Atoll 



MARJORIE L. REAKA* and 

 RAYMOND B. MANNINGf 



'Department of Zoology/, Universitx; of Mari^hnd, 

 College Park, Mari;land 20742. f Department of 

 Invertebrate Zoology/. National Museum of 

 Natural History;. Smithsonian Institution. 

 Washington. D. C. 20560 



INTRODUCTION 



This study provides a checklist and discusses the 

 biogeographic relationships of the 12 species of Stoma- 

 topoda (mantis shrimps) now known to occur on Enewetak 

 Atoll. Five species are widely distributed throughout the 

 Indo-West Pacific region, and three species have somewhat 

 more restricted ranges in the Indo-West Pacific and Indian 

 Ocean. Four species arc endemic to the Central Pacific 

 (two to Enewetak), and three taxa need further taxonomic 

 investigation, which may demonstrate further endemism. 

 Stomatopods from Enewetak are dwarfed in body size 

 compared to their mainlaind relatives. Small size has 

 strong consequences for life history and evolutionary pat- 

 terns in stomatopods, and in particular is likely to generate 

 endemism. We provide information on the color patterns 

 of the stomatopods from Enewetak, showing which traits 

 are the most reliable indicators of species identity for taxo- 

 nomic and field research and which traits are most likely 

 to be influenced by body size, sex, or habitat. Several 

 anomalies in usually invariant color traits are found in 

 stomatopods from Aomon Island, which was closer to 

 sources of radiation from atomic testing than more south- 

 ern islands in the atoll. We also summarize what is known 

 about the habitat and fighting behavior of the coral- 

 dwelling mantis shrimps from Enewetak. For each of the 

 above topics, we identify or discuss all previous literature 

 on the stomatopods of Enewetak. 



CHECKLIST 



The stomatopod Crustacea from Enewetak Atoll were 

 first recorded by Manning (1971) and more recently by 

 Manning and Reaka (1982); these studies included the 

 description of three new species. Here we identify four 

 species {Gonodacti/lus ternatensis. Pseudosquilla ciliata, 



P. ornata. and Lt^siosquilla maculata) that have not been 

 recorded previously from Enewetak, bringing to 12 the 

 total number of species known from the atoll (Table 1). 

 We also identify here all pertinent literature in which par- 

 ticular species of stomatopods from Enewetak have been 

 discussed. 



BIOGEOGRAPHIC COMPARISONS 



Pseudosquilla ciliata is the only species of those found 

 on Enewetak that also occurs in the Atlantic. Five of the 

 species known from Enewetak (G. chiragra. G. plat\;soma, 

 P. ciliata. P. ornata. and L. maculata) are widely distrib- 

 uted throughout the Indo-West Pacific region. All of these 

 are relatively large species of stomatopods, and 

 Pseudosquilla has a particularly long larval dispersal stage 

 (Reaka, 1979a, 1980a; Reaka and Manning, 1987a). 



Three species have somewhat more restricted distribu- 

 tions in the Western Pacific, Indo-Malayan, and Indian 

 Ocean regions than the previously mentioned group. 

 Haptosquilla gl^ptocercus occurs from Enewetak to Japan, 

 northern Australia, and as far west as the Andaman 

 Islands. Gonodacty/lus smithii is known from Oceania and 

 the South China Sea and from Australia to the western 

 Indian Ocean; however, populations from the western 

 Indian Ocean and Red Sea may be referable to another 

 species, G. acutirostris De Man. Gonodactiilus ternatensis 

 is known with certainty only from localities between 

 Samoa and Indonesia. 



Of the remaining species, G. espinosus and G. in- 

 cipiens axe known only from island localities in the Central 

 Pacific, while G. insularis and G. micronesica apparently 

 are endemic to Enewetak Atoll. These four species, as well 

 as H gl\;ptocercus (which also has a relatively restricted 

 distribution), are the smallest species that occur on 

 Enewetak. 



Figure 1 shows that the typical body sizes of popula- 

 tions of all of the coral-dwelling stomatopods from 

 Enewetak are diminutive compared to those from many 

 other geographic localities, particularly the Indo-West 

 Pacific mainland areas. This fact is emphasized by compar- 

 ing lineages of the same or closely related species in dif- 

 ferent regions. For example, individuals of G. smithii attain 

 considerably smaller sizes in Enewetak than in Thailand or 



181 



