PATTERNS OF MOLTING FREQUENCIES IN CORAL-DWELLING STOMATOPOD CRUSTACEA

¹ Department of Zoology, The University of Maryland, College Park, Maryland 20742

1. Four estimates of intermolt intervals (time between two molts; time from collection until first molt; time from collection until individuals either molted, were killed, or died; and total number of days stomatopods were maintained relative to total number of molts in the captive population) provided information on molting frequencies in 20 populations of coral-dwelling stomatopods.

2. Number of molts did not decline with increased maintenance time in the laboratory. The time between two molts did not vary among different groups of Gonodactylus zacae or of G. falcatus that were collected and maintained at different times. Individuals of G. zacae and G. falcatus that molted survived equivalent or longer periods than those that did not molt. Survival did not vary between males and females or with body size in G. zacae or G. falcatus. The percentages of individuals that molted during a month of laboratory maintenance in Thailand corresponded to those found in the field.

3. There were no major differences in estimates of intermolt intervals with seasons or between males and females for most species. However, in G. zacae, the time between two molts (but not other estimates of intermolt intervals) was greater in females than in males, and Pseudosquilla ciliata females showed a longer interval from collection until the first molt (but not other estimates of intermolt intervals) than males. Several females laid eggs during various portions of the intermolt cycle in G. zacae and G. falcatus; these intervals were lengthened relative to those of nonbrooding females.

4. Molting frequencies did not decline detectably with increased body size of post-juvenile stomatopods. There was no correlation of the interval between two molts and body length of individuals within populations of G. zacae, G. falcatus, or P. ciliata. In Phuket, where individuals were maintained for a relatively short time, the percentage of individuals that molted did not decline among small and large adults of G. chiragra or of G. viridis. The body lengths of individuals that molted were not significantly different from the distribution of body lengths in any of the captive populations. Thus, stomatopods appear to follow patterns of isochronal growth similar to those found in some copepods.

5. Molting rates were highly correlated with several measures of body size (mean, median, modal, and maximal body lengths) among populations. Large species maintain a high molting rate throughout adulthood, while the molting frequencies of small species level off at lower rates. Ecological and evolutionary factors affecting patterns of molting are discussed.