Hi Jill,
I have now found the scientific paper that I referred to in my previous
email. It is:
Dittmann, S. (1998). Behaviour and population structure of soldier crabs
Mictyris longicarpus (Latreille): Observations from a tidal flat in tropical
North Queensland, Australia. Marine Biodiversity 28: 177-184.
Abstract
Crabs of the family Mictyridae are common on sandflats of the
Indo-West-Pacific. Activity patterns and population structure of Mictyris
longicarpus (Latreille) were monitored in the Haughton River estuary in
northeast Australia. The emergence of the crabs at low tide was intermittent
and could not be related to lunar cycles, but the crabs were significantly
more active on sunny than on rainy or overcast days. Of a total of 1494
crabs measured over a 14 months period, nearly 2/3 were males (951 crabs).
No ovigerous females were found on the sandflat surface. Crabs active on the
sediment surface ranged in size from 4.7 to 19.7 mm carapace length (CL).
Distinct size-frequency distributions were identified for juveniles, females
and males. The mean size of juveniles was 7.3 mm and of females 11.2 mm CL.
Males showed a bimodal size-frequency distribution. The first mode (mean 8.5
mm) was clearly separated in size from the second mode (mean 15 mm). The
population structure remained almost constant throughout the year. Juvenile
and adult crabs showed different aggregation patterns and preferred
different sediment types.
Stephen Ambrose
Ryde NSW
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