Aj. Sanchez et A. Razguzman, DISTRIBUTION PATTERNS OF TROPICAL ESTUARINE BRACHYURAN CRABS IN THE GULF-OF-MEXICO, Journal of crustacean biology, 17(4), 1997, pp. 609-620
Distribution patterns are defined for 20 brachyuran crab species of La
guna de Terminos based on the range of salinity and the habitats occup
ied by each. Habitats include unvegetated soft substrates. macroalgae,
and sea grasses. ''Wide'' and ''restricted'' distributions relate spe
cies abundance to a wide and a narrow salinity range, whereas ''associ
ated with the habitat'' and ''not associated with the habitat'' consid
er the presence of a species in one or several types of habitat. Fourt
een species were grouped in the restricted and associated with the hab
itat pattern, of which the 3 spider crabs and the 10 mud crabs were as
sociated with submerged aquatic vegetation in salinities above 18 part
s per thousand, and the swimming crab Callinectes exasperatus was dist
ributed in an adjacent limnetic lagoon on unvegetated soft substrates.
The mud crab Dyspanopeus texanus was placed in the wide and associate
d with the habitat pattern, since it is a euryhaline species and was a
lways found on macroalgae and sea grasses. Three other swimming crabs
and two other mud crabs were found on all sorts of substrates along a
wide range of salinity and were included in the wide and not associate
d with the habitat pattern. Six faunistic groups were formed after ana
lysis of the abundance data, using an ordination method with axes defi
ned by salinity and type of habitat. Four functional guilds of brachyu
ran crabs are proposed, based on the 3 distribution patterns, the 6 fa
unistic groups, and the 2 subsystems and 4 areas previously described
for the lagoon. Guild A grouped 2 swimming crabs and 1 mud crab distri
buted along the areas of the lagoon directly influenced by river runof
f, where detritus-rich unvegetated soft substrates and macroalgae are
common. Guild B included: (I) the 3 spider crabs and most of the mud c
rabs of which seven restricted and associated with the habitat species
congregated in the northcentral-northeastern subsystem of the lagoon,
where the greatest heterogeneity of habitats, dense sea-grass beds an
d poly-euhaline environments, is common; (2) 5 restricted and associat
ed with the habitat species mostly distributed in this subsystem were
also collected in areas influenced by river runoff during the dry seas
ons when salinity was above 24 parts per thousand; and (3) 2 wide and
not associated with the habitat species were mostly found in this subs
ystem, but extended their distribution to areas without submerged vege
tation and lower salinities. Guild C was represented by D. texanus, wh
ich was found throughout most of the lagoon on macroalgae and sea-gras
s beds. Guild D included Callinectes sapidus and C. similis that were
distributed throughout the lagoon independently of a particular type o
f habitat.