Scientia Marina, Vol 71, No 2 (2007)

Relative growth of the semi-terrestrial crab Pachygrapsus marmoratus: an information-theory approach

Nikos Prototapas
Department of Zoology-Marine Biology, Faculty of Biology, University of Athens, Greece

Stelios Katsanevakis
Department of Zoology-Marine Biology, Faculty of Biology, University of Athens, Greece

Maria Thessalou-Legaki
Department of Zoology-Marine Biology, Faculty of Biology, University of Athens, Greece

George Verriopoulos
Department of Zoology-Marine Biology, Faculty of Biology, University of Athens, Greece


The patterns of allometric growth of the grapsid crab Pachygrapsus marmoratus were investigated with an information-theoretic approach. This approach is beneficial, more robust, and may reveal more information than the classical approaches (e.g. hypothesis testing). No differentiation in allometric growth was detected between right and left chelar propods in either sex. Significant sexual differentiation in the allometric growth of chelar propods, abdominal somites and telson was found. It was shown that the allometry of chelar propodus width may be used to identify puberty in males, as there is a marked breakpoint at a carapace width of ~16.0 mm. For females, puberty was identified by the breakpoint in the allometry of the third and fourth abdominal somites at a carapace width of ~16.5 mm. In many cases (e.g. in chelar propods of males, or in most abdominal somites and the telson in females) the classic allometric equation log Y = log a + b log X has no essential support and non-linear allometric models between the log-transformed morphometric characters have to be used.


AIC; allometry; breakpoint; crab; growth; information-theory

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