STOMATOPOD CRUSTACEA 



187 



Other hand, G. insularis. G. smithii, and H. glyptocercus 

 arc less vagile, often occur In more protected and shore- 

 ward habitats, and undoubtedly suffer less predation than 

 G. Inciplens, G. platiisoma, and G. micronesica. Gonodac- 

 fylus plafysoma and G. incipi'ens are the most heavily 

 speckled and mottled species, and transverse banding is 

 most developed in these two species and G. micronesica. 

 Green is the predominant color in 17%, 47%, and 50%, 

 respectively, of the traits of G. incipiens, G. platysoma, 

 and G. micronesica. Green coloration is found on only 8%, 

 8%, and 0%, respectively, of the traits in G. insularis, G. 

 smithii, and H. glyptocercus (see Reaka and Manning, 

 1987b, for details). Thus, we conclude that fish predation 

 is likely to be a selective factor promoting drab greenish 

 coloration and speckling and banding patterns that camou- 

 flage the individual against algae and the grainy calcareous 

 substrate. 



On the other hand, species with elaborate aggressive 

 displays (see section on behavior) bear the most brightly 

 colored structures; 62% and 58%, respectively, of the 

 traits in G. smithii and G, insularis, but only 33%, 29%, 

 and 20%, respectively, of those in nonagressive species (G. 

 Incipiens, G. micronesica, and G. platiisoma, respectively) 

 include predominantly red and yellow hues. (See Reaka 

 and Manning, 1987b, for analysis.) Haptosquilla glypto- 

 cercus is one of the most uncolorful species, with only 9% 

 of its traits (the antennules) bearing bright coloration; indi- 

 viduals of this species show extremely aggressive behavior 

 but lack complex displays. 



Similarly, bright colors are concentrated on anterior 

 structures associated with threatening and attacking behav- 

 ior (see Table 2 and quantified data in Reaka and Man- 

 ning, 1987b). Red, maroon, or orangish antennules are 

 found in G. smithii. G. micronesica, G. platiisoma, H. glyp- 

 tocercus, and G. incipiens, respectively. Red antennae are 

 frequent in G. insularis, G. smithii, and G. plati/soma. 

 Gonodactiilus insularis and G. smithii usually bear red or 

 yellowish antennal scales. Maxillipeds often are yellowish in 

 G. incipiens, G. insularis, and G. smithii. Gonodacti;lus 

 smithii bears a red meral spot, and the carpus and prop- 

 odus in G, micronesica and G. platysoma are red. Bright 

 colors also characterize posterior structures used in defen- 

 sive combat (red urofxxlal spots in G. smithii; red or yel- 

 low urop>odal endopods and exo{x>ds in G. insularis and G. 

 smithii, respectively; red telson carinae in G. micronesica). 



Color polymorphism of the body is greatest in 

 G. smithii and G. insularis; G. insularis and G. incipiens 

 have the most color piolymorphlc apjpendages. Therefore, 

 color polymorphism among individuals in the population is 

 greatest either in species with elaborate aggressive com- 

 munication (e.g., graded displays in G. insularis, 

 G. smithii) or in sp>ecies that occur in association with 

 these species (G. indpiens). These observations suggest 

 that color pwlymorphism may function for individual recog- 

 nition of aggressive communication. 



Severjil deviant color patterns, particularly in 

 G. platiisoma, were found on the northern island of 

 Aomon, which was closer to sources of radiation from 



atomic testing than many of the southern islands in the 

 atoll. Deviations in the red coloration of the anterior rap)- 

 torial appendage, in the blue sp)ots on the orange back- 

 ground of the basal segment of the uropod, and in the 

 sequence of concentric colors on the lateral "eye sp)ots" 

 were observed in the population of G. platysoma collected 

 from Aomon. Comparisons with other populations of this 

 species collected from farther south on the atoll revealed 

 that these deviations were not explained by body size, sex, 

 or habitat. 



BEHAVIOR 



Stomatopods are highly visual, active predators that 

 have some of the most complex behavior known in inver- 

 tebrates (Caldwell and Dingle, 1975; Reaka, 1980b; Reaka 

 and Manning, 1981). The gonodactylids and protosquillids 

 on Encwetak (Table 1) inhabit preformed burrows in cored 

 or calcareous substrate that cannot be enlarged; these 

 species show the most intense and complex aggressive 

 behavior. Members of the genus Pseudosquilla cdso show 

 relatively elaborate behavior and strong aggression and 

 occupy either holes in coral or excavations under coral. 

 Lysiosquilllds burrow in sand, can enlarge their burrows, 

 have less elaborate behavior, and can grow to very l2irge 

 sizes (Caldwell and Dingle, 1975; Reaka, 1981; Reaka and 

 Manning, 1981, 1987a). 



The second maxllliped of stomatopods is enlarged into 

 a raptorial appendage that is used to smash and stab com- 

 jjetitors for burrows, predators, or hard-bodied prey. 

 Intense, potentially lethal fighting behavior is observed 

 among members of the same and different species in both 

 the field and laboratory. Aggressive behaviors Include 

 strikes (a smashing blow with the hammer-like raptorial 

 appendage or a stab with the open, needle-sharp dactyl); 

 a variety of aggressive lunges and chases; and graded 

 threat displays in which the raptorial app>endages are 

 lowered and spread, exposing the conspicuous meral spots. 

 Defensive behaviors include colling the armored telson in 

 front of the body with the uropods spread wide. In cored- 

 dwelling species this stance may effectively block the 

 entrance of a burrow against an intruder. In addition, these 

 mantis shrimps exhibit several retreat behaviors, including 

 submissive postures in which the head and telson are 

 lowered and their associated structures c>re tucked along- 

 side or under the body. 



The agonistic behavior of different species of cored- 

 dwelling stomatopKxls In Enewetak has been addressed in 

 several studies (Caldwell and Dingle, 1972, 1977; Reaka, 

 1973; Dingle, Highsmith, Evans, and Caldwell, 1973; 

 Caldwell and Brunenmeister, 1975). We provide new data 

 and synthesize all previous research on the aggressive 

 behavior of these mantis shrimps in a comprehensive study 

 elsewhere (Reaka and Manning, 1987b), but we provide a 

 brief summary here. 



Haptosquilla gl^iptocercus delivers the most strikes, but 

 this relatively uncolorful species is exceptionally prone to 

 retreat from opponents and is less likely to use threatening 

 displays than G. smithii or G. insularis. Sp>orting a yellow 



