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The purpose of this paper is to investigate the relative growth and heterochely in the hermit crab Petrochirus diogenes. Hermit crabs were collected in the Ubatuba region, SP, from 1993 to 1996; using a commercial fishing boat equipped with two double-rig nets. Body mass of each individual was weighed and their cephalothoracic shield and chelar propodus size were measured. Body mass and chelar propodus size were regarded as dependent variables and plotted against length of cephalothoracic shield according to the allometric equation y = a x x(b). A total of 479 individuals were obtained being 307 males and 172 females. Cephalothoracic shield width follows an isometric growth for both sexes. Otherwise, right cheliped dimensions show different relative growth patterns and left cheliped ones present a positive allometry in males and females. Unlike brachyurans, ontogenetic changes in the growth rate of chelar propodus are not clearly discernible, which prevents the accurate detection of allometric variations. In both sexes, the right cheliped is larger than the right one. Cheliped size is a sexual dimorphic feature with males bearing larger chelipeds than females. Heterochely may be particularly adaptive in agonistic interactions and precopulatory behaviour in P diogenes.

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The communities of brachyuran crabs living on soft bottoms off Ubatuba in SE Brazil were studied with respect to their structure, bathymetric distribution, composition, diversity and indices of similarity. The data were analyzed using multivariate techniques of classification and ordination. Most of the individuals caught during summer were the swimming crab Portunus spinicarpus at the 35 m isobath, which contributed to the much-decreased diversity in this season and site. Multivariate analysis indicated that the species were distributed according to depth and also in relation to environmental gradients. KEY WORDS: Sublittoral communities · Distribution patterns · Species composition · Crustacea · BrachyuraResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 279: 193-200, 2004 15 m isobaths. Extra trawls were made monthly in the middle zones of these bays along the 20, 25, 30, 35 and 40 m isobaths (Fig. 1), here considered as an outer zone. An ecobathymeter coupled with a GPS was used to record the depths at the sampling sites.After each trawl, the brachyuran crabs were sorted, placed in plastic bags, labeled, and stored on shaved ice. In the laboratory, specimens were counted and identified according to Melo (1996). The classification adopted for brachyurans was that of Martin & Davis (2001). Salinity (‰) and temperature (°C) were measured in bottom-water samples, obtained each month for each transect, by means of a Nansen bottle.Sediment samples were collected seasonally with a 0.06 m 2 Van Veen grab. In the laboratory, the sediment was oven-dried at 70°C for 72 h. For analysis of grain size composition, two 50 g sub-samples were separated, treated with 250 ml of a 0.2 N NaOH solution and stirred for 5 min to release silt and clay particles. Sub-samples were then rinsed on a 0.063 mm sieve. Sediments were sieved through 2 mm (gravel); 2.0-1.0 mm (very coarse sand); 1.0-0.5 mm (coarse sand); 0.5-0.25 mm (medium sand); 0.25-0.125 mm (fine sand); 0.125-0.063 mm (very fine sand); smaller particles were classified as silt-clay. Cumulative particle size curves were computer-plotted using the phi scale and phi values corresponding to the 16th, 50th and 84th percentiles were read from the curves to determine the mean diameter of the sediment. This was calculated by the formula Md = (ϕ 16 + ϕ 50 + ϕ 84 )/3. The value of phi was calculated by the formula ϕ = -log 2 d, where d = grain diameter (mm).The organic matter content of the sediment was calculated by the difference between the ash-free dry weights of three 10 g substrate subsamples incinerated in porcelain crucibles at 500°C for 3 hr.All the procedures for sediment analysis followed Hakanson &Jansson (1983) andTucker (1988).Data analysis. Species diversity was calculated using the Shannon-Wiener index (Pielou 1966):where s is the number of species and P i is the proportion of the i th species. Evenness (J ') was calculated as indicated by Pielou (1975)Prior to the multivariate analysis, the data were simpli...

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