186 



REAKA AND MANNING 



whitish pink in G. incipiens, yellow with an anterior red 

 infusion in G. insularis, white in G. micronesica and 

 G. plafysoma, carmine red surrounded by a black-and- 

 white ring in G. smithii, and cream colored in H. glx/pto- 

 cercus. Our analysis, however, shows that the color of the 

 meral spot ranges from blue greenish to salmon among 

 individuals classified as G. incipiens; morphological differ- 

 ences, especially in the structure of the telson, among 

 members of this population also suggest that this taxon 

 needs further investigation. Additionally, individuals in the 

 Enewctak population of G. smithii have a carmine meral 

 spot, whereas members of other populations of G. smithii 

 bear a dark purplish red meral spot. This fact, in combina- 

 tion with the observations that G. smithii from Enewetak 

 are diminutive in body size, produce smaller eggs relative 

 to their body size, and invest a smaller profwrtion of their 

 body volume in a brood of eggs than do other populations 

 of G. smithii (Reaka, 1975a, 1979a; Reaka and Manning, 

 1987b), suggest that this population also is in need of tax- 

 onomic investigation and may represent an endemic 

 species. 



Several other invariant traits also are useful for species 

 identifications, particularly when used in combination with 

 the meral spots. Haptosquilla glijptocercus sports uniquely 

 maroon antennules and white antennae among the species 

 at Enewetak. The antennal scales of G. plat^soma are 

 white proximally but green distally. The propodus of the 

 raptorial appendage in G. smithii is iridescent blue purple, 

 set against a bright yellow background outline where it 

 folds against the merus. Lateral dark spots characterize the 

 propodus of the raptorial appendage in G. incipiens 

 (although their number increases with depth and type of 

 habitat). The propodus and dactyl of the raptorial maxil- 

 liped are uniquely red in G. micronesica. The dactyl of 

 the raptorial appendage in G. plati^soma is bright bluish 

 blue-green. Gonodact\/lus plati;soma also is remarkable for 

 the colorful concentric "eye spots" on each side of the 

 eighth thoracic and sixth abdominal segments. On the 

 thorax this spot is composed of an outer white band, fol- 

 lowed by a pale blue, red, dark blue, and finally an inner- 

 most red orange circlet of color. On the sixth abdominal 

 segment, the "eye spot" is formed of an outer band of 

 white, followed by red brown and dark blue rings and an 

 innermost patch of yellow orange. The basal segment of 

 each uropod in G. plat^/soma is orange with a light and 

 dark blue spot. The basal segment of each uropod in 

 G. smithii bears a brilliant red spot which is conspicuously 

 exposed against dark green body coloration when the uro- 

 pods are flared (particularly when the telson is coiled 

 defensively in front of the body during a fight); these spots 

 vanish when the uropods are tucked under the telson in a 

 submissive posture. In addition, G. insularis is character- 

 ized by a lineage-specific set of four black spots — two on 

 the sixth abdominal segment and two on the anterior tel- 

 son. The uropodal exopods (and usually the endopods) are 

 uniquely red in G. insularis, as are the dorsal carinae on 

 the sixth abdominal segment and telson in G. micronesica 

 (Table 2). 



In contrast to the invariable and often unique traits dis- 

 cussed above, however, the color of most traits varies 

 among individuals or with sex, developmental stage, or 

 habitat in most species. When the range of variability 

 among individuals is considered for all species (Reaka and 

 Manning, 1987b), all of the major morphological traits can 

 be ranked for relative variability of color, providing an indi- 

 cation of which traits are likely to be the most — or the 

 least — reliable indicators of species identity in general. 

 Except for the specific cases identified in Table 2 as being 

 invariable, the uropodal exopods, antennules, antennae, 

 uropodal endopods, and antennal scales, resfiectively, form 

 a set of traits that are moderately variable in color. Simi- 

 larly, when all species are considered (with invariable 

 exceptions being noted in Table 2), the color of the maxil- 

 lipeds, walking legs, and uropodal forked tips varies still 

 more among individuals; body color is in general the most 

 polymorphic of all traits. Descriptions of species and field 

 identifications based \ipon the latter characters are most 

 likely to be biased by small sample sizes. 



Color patterns vary predictably with sex in some cases 

 (Table 2). The color of the body, walking legs, and maxil- 

 lipeds are more likely to be greenish in males but may 

 shift toward other hues (especially brownish, yellowish) in 

 females of some species (G. smithii. G. incipiens, H. gl\;pto- 

 cercus). In G. incipiens, the antennae are more likely to be 

 red or orange in males but clear in females. 



The color pattern of certain traits also varies predict- 

 ably with size or age in some species. The incidence of 

 blue green or green coloration on the antennal scales or on 

 the endopods, exopods, or forked tips of the urofxxls 

 increases in larger individuals of several species 

 (G. incipiens, G. insularis, G. smithii). The color of the 

 uropodal endopod shifts toward red (matching the red of 

 the invariant exopod) as individuals of G. insularis become 

 larger. Also, the antennae and antennules of G. plat^isoma 

 change from clear to red as individuals mature. White 

 speckling on the body increases with size in G. incipiens 

 and G. smithii. 



Several color characteristics shift with habitat within 

 species, where these shifts cannot be explained by the dis- 

 tributions of individuals of different sexes and sizes in dif- 

 ferent habitats. In G. incipiens, the frequency of white 

 transverse banding on the body, dark spots on the 

 propodus of the raptorial appendage, and yellow coloration 

 on the antennules and distal fork of the uropods increases 

 from shallow (0.5 m) to deepjer (0.5 to 2.0 m) habitats. 

 The degree of color polymorphism among individuals also 

 increases with depth (antennal scales, maxillipieds, distal 

 forks of the uropods) in G. incipiens. Additionally, the 

 uropodal endopods in G. incipiens shift toward clear 

 coloration in habitats that contain assemblages of aggres- 

 sive species of stomatopods. 



Color patterns also correlate with habitat and suscepti- 

 bility to predation among species. Because they are highly 

 vagile or occupy deep, reefward, or open exposed environ- 

 ments, G. incipiens, G. plati/soma, and G. micronesica axe 

 likely to encounter considerable fish predation. On the 



