A new method of estimate duration of molt stages in crustaceans

A new method of estimate duration of molt stages in crustaceans

D. Hankin

A new method of estimate duration of molt stages in crustaceansThis is part of Crabs in Cold Water Regions: Biology, Management, and Economics
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Description

The methods of Drach and Tchernigovtzeff (1967) have been used to de-scribe molt stages of many crustacean species, but there have been fewattempts to estimate the duration of individual molt stages. Molt stagingoften requires destructive removal and examination of a suitably trans-parent paired structure (e.g., branchial epipod), thereby ruling out peri-odic molt staging of single individuals throughout the molting cycle. In alaboratory setting, however, it is possible to either (1) determine the initialmolt stage of a crustacean and then hold it until molting takes place, or (2)hold a freshly molted crustacean and determine its molt stage at a pre-specified date following molting. Data generated through such experiments,based on many individuals, consist of either (1) initial molt stages and corre-sponding days to molt, or (2) days post molting and associated molt stages.I show that the existing published method (Buchholz 1991) for estimatingduration of molt stages of crustaceans from type 2 laboratory data lacks arigorous derivation and may generate seriously biased estimates when moltstages have unequal expected durations. I propose alternative estimatorsof molt stage durations that have improved performance characteristics.

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