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Vol. 49 No. 1, 2010
Molting and Growth in Relation to Form Alternations in the
Male SpinyCheek Crayfish Orconectes
limosus
Miloš
Buřič*, Antonín Kouba, and Pavel Kozák
Laboratory
of Ethology, Nutrition of Fish and Crayfish, Research Institute of Fish
Culture and Hydrobiology, Faculty of Fisheries and Protection of
Waters, University of South Bohemia in České Budějovice, Zátiší 728/II,
389 25 Vodňany, Czech Republic
Miloš Buřič, Antonín
Kouba, and Pavel Kozák (2010) Morphological changes associated with
form alternations in the male spiny-cheek crayfish Orconectes limosus
are described with new findings and explanations of existing
equivocalness. Males were observed for 10 mo (from Feb. to Nov.
2008). Most males (84.4%) underwent 2 molts, with a 1 mo interval
between molts. A small proportion (8.9%) (with a higher initial
size than those that molted twice) molted once, without a form
alternation. A smaller proportion (6.7%) (with a higher initial
size than those that molted either once or twice) did not molt at
all. Molting began after water temperatures were at least 16°C
for 2 mo. Form I gonopods were longer, wider, and more robust
than form II gonopods, which were similar to those of juveniles, in
addition to possessing wider protopodites and shorter
endopodites. Chelae of form I males were longer and wider than
those in form II males. Juveniles had shorter and narrower
chelae. The chelae and abdomen of form I males were more robust
than those of form II males and juveniles, which did not differ.
A change of body ratios did not occur in crayfish which molted once
without a form alternation. Negative allometric growth of chela
length (ChL) and width (ChW), and abdominal width (AbW) was observed
after the molt in form II. The body size increased more at the
1st molt (to form II), than at the 2nd molt back to form I. ChL,
ChW, and weight (W) increments were 3 (ChL) and 4 times (ChW and W)
that of body-size increments and were dramatically higher than at the
previous molt. Form alternation seemed to have a function of
allowing the effective utilization of resources through which males
could increase in size and be attractive to females.
Key words: Invasive
species, Crayfish, Intra-sex dimorphism, Growth.
*Correspondence: Tel: 420-383-382402. Fax:
420-383-382396. E-mail:buric@vurh.jcu.cz
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