Moult cycle and growth of the crab Halicarcinus planatus (Brachyura, Hymenosomatidae) in the Beagle Channel, southern tip of South America

DIEZ, MARIANO J.; LOVRICH, GUSTAVO A.

HELGOLAND MARINE RESEARCH

SPRINGER

Lugar: Berlin; Año: 2012

1438-387X

The crab Halicarcinus planatus is the onlyhymenosomatid crab that inhabits the southern tip of SouthAmerica and is the only decapod species that reproducestwice a year in the Beagle Channel. In this article, we studythe moult cycle in the field (moult frequency, analysis ofsize frequency distribution) and linked it with growthstudied in the laboratory (absolute and per cent growthincrement, Hiatt function). Hiatt functions were similar formales and females. Moult frequency was seasonal: in earlyaustral spring and in austral summer. In females, thepubertal moult is the terminal moult, whereas males continuemoulting after attaining the size of morphometricmaturity. Moult increment was highly variable. The relationshipbetween absolute moult increment and crab sizewas described by a quadratic function. Per cent growthincrement decreased with size, and relationships weredifferent for each sex: linear for females and quadratic formales. Seven and eight modal groups explained the sizefrequency distributions for females and males from thefield, respectively, and revealed the existence of twocohorts of recruits per year. Further modal analysis wasmainly hampered by the high variability of size incrementthat could make any moulting individual fall in its own orone of two following modal groups. The antagonismbetween growth and reproduction was evident in smallmales. We hypothesize that the terminal pubertal moult isan advantageous feature that allows females to maximize their investment in reproduction after their terminal moult,which allows this species to have two spawnings per year.