188 



REAKA AND MANNING 



meral spot and other bright coloration, G. insularis uses 

 the highest number of threat displays in its interactions, 

 strikes relatively often, and rarely retreats in a contest; 

 consequently, this species can be classified as a very 

 aggressive species. Gonodactijlus smithii also is highly 

 aggressive, striking but also retreating quite frequently. 

 Members of this species perform some of the most expan- 

 sive threat displays, thus exposing one of the most 

 dramatic meral spots (carmine surrounded by black and 

 white concentric circles) seen in any stomatopwd. Inter- 

 specific tests indicate that H. glijptocercus dominates 

 G. insularis. and that G. insularis wins contests with 

 G. smithii. Gonodacfylus incipiens and G. plati/soma are 

 characterized by low levels of fighting activity and subordi- 

 nate social relationships to the other species in Enewetak. 



HABITAT 



Field work in 1972 allowed us to quantitatively analyze 

 the distribution of shallow water stomatopods from several 

 major types of habitat in Enewetak (Reaka, 1973; Reaka 

 and Manning, 1987b). These habitats include: 



1. Dead coral rubble 



2. Soft rubble and vermetid rocks 



3. The calcareous bases of "microatolls" (colonies of 

 Porites in which the center has died and often was riddled 

 with boring organisms) 



4. Open reef benches of consolidated calcareous accre- 

 tion (Table 3) 



Dingle et al. (1973), Caldwell and Dingle (1975), and 

 Caldwell and Brunenmeister (1975) provide additional 

 information about the occurrence of stomatop)ods in partic- 

 ular habitats on Enewetak. 



Coral rubble habitat is found on the reef platform as 

 isolated heads, in small patch reefs, or along the reefward 

 algal ridge on the east side of Enewetak. These habitats 

 usually are <0.5 m deep and contain G. incipiens, 

 G. micronesica, and H. gl^iptocercus. Stomatopods also 

 are collected from coral rubble in somewhat deeper habi- 

 tats (<1 m deep) in the channel between Enewetak and 

 the sandy islets on the northeast side of Enewetak, 

 between these sandy islets and Japtan, and on the 

 northeast side of Japtan. These rubble habitats contain 

 G. incipiens, G. micronesica. G. platysoma (small), 

 G. smithii (small), and H. gfyptocercus. In addition to the 

 above species, a population now classified as G. insularis 

 (Manning and Reaka, 1982) was found in the rubble on the 

 northeast flank of the sandy islets (Dingle et al., 1973; 

 Reaka, 1980a). By the summer of 1972, however, the 

 rubble had been partly buried by sand, and no G. insularis 

 could be found. Our later analysis suggests some morpho- 

 logical differences between the population found in 1971 

 and G. insularis (Manning and Reaka, 1982), and the pos- 

 sibility remains that the former population represents an 

 additional (possibly now extinct?) species in the closely 

 related G, falcatus lineage. Of the species found in dead 

 coral rubble, G. incipiens is the most common (45% of the 



40 individuals collected), followed by H. gli/ptocercus 

 (25%), small G. smithii (18%), G. micronesica (10%), and 

 small G. plat\/soma (3%). 



Stomatopods inhabit soft rubble and vermetid rocks on 

 the shoreward and reefward sides (<1.5 m deep) of the 

 moat on the north side of Aomon. In 1972 G. insularis 

 inhabited only the shoreward side of this moat (<1 m 

 deep). Gonodacti^lus incipiens and small G. plat^/soma and 

 G. smithii also are found here; the distribution of small 

 G. smithii extends into the somewhat deeper reefward 

 areas of the moat. Of the stomatopods collected from the 

 Aomon moat (N = 33), G. insularis is the most common 

 (45%), followed by small G. smithii (27%), G. incipiens 

 (15%), and small G. plati/soma (12%). 



Stomatopods also can be collected from the bases of 

 the microatolls at depths of 0.5 to 2.0 m on the reef flat 

 northeast of Enewetak. Gonodactyilus smithii is abundant 

 (72% of the 43 individuals quantified) and reaches large 

 body sizes in this habitat. Although their numbers were 

 not thoroughly quantified, our field notes indicate that 

 G. plat\isoma also attains large sizes and is "abundant." 

 The smaller species occurring in this habitat, G. incipiens 

 and H. glt^ptocercus, also reach relatively large sizes but 

 are less common (9% each of the quantified individuals; 

 however, quantification was less systematic in this than in 

 other habitats, and further sampling is needed). Caldwell 

 and Dingle (1975) suggest that large individuals of 

 G. plat\;soma occupy relatively open caverns under 

 microatolls, while individuals of G. smithii and the smaller 

 species inhabit borings further inside the center of the 

 Porites colony. Despite their abundance, individuals of 

 G. smithii are rarely observed away from their protective 

 coral colony (Reaka, personal observation). 



Individuals of two species, G. plati;soma and G. in- 

 cipiens, are commonly observed moving rapidly about on 

 the open reef adjacent to the microatolls, particularly on 

 low or incoming tides. As in the microatolls where they 

 find refuge, the G. incipiens and G. plat^/soma observed 

 on the open reef flat are relatively large in size. Our field 

 notes indicate that individuals of G. plat^/soma are particu- 

 larly abundant in this habitat. The shallow reef benches 

 (<0.5 m deep) on the east side of Enewetak and the east 

 side of Japtan also yield stomatopods. These reef benches 

 are scoured by wave action and frequently are exposed at 

 low tides. Stomatopods (G. incipiens, H. givptocercus) are 

 collected from tubular holes in the solid reef substrate or 

 as they dart about in the tide pools at low tide. 

 Gonodact^^lus incipiens was the most common stomatojxxl 

 in this habitat (7/9 or 78% of the quantified individuals), 

 although further sampling is needed to assess the relative 

 abundance of H. gl^/ptocercus. 



In 1972 a heavy rainfall during a mid-day low tide 

 caused a massive reef kill in this shallow exposed habitat 

 (Reaka, 1980a; Leviten and Kohn, 1980). Despite their 

 high activity levels and probable high metabolic rates, 

 stomatopods are remarkably tolerant of harsh physical con- 

 ditions (low O2, high temperatures, etc.; Reaka, personal 

 observation). During this reef kill, mortality among the 



