Molt cycle of the natural population of Palaemonetes argentinus (Crustacea, Palaemonidae) from Los Padres Lagoon (Buenos Aires, Argentina)

Abstract

The molt cycle of the natural population of Palaemonetes argentinus Nobili, 1901 from Los Padres Lagoon, Buenos Aires, Argentina, was studied in relation to age, sex, and environmental factors. A total of 1645 individuals (740 females, 539 males, and 366 juveniles) were collected and analyzed between December 1995 and December 1996. The results indicate that the sex ratio (males:females) remains around 1:1.4 throughout most of the year. The reproductive period extends from September until February (spring and summer), with maximum sexual activity in October and November. Two cohorts originated in the spring and in the summer were differentiated. Ovigerous females arrest their molt cycle during the intermolt period to restart it after oviposition. The duration of the intermolt period does not differ between adults and juveniles. Since the percentage of premolt individuals represents 60% of the total cycle, it was classified as a diecdysic cycle. Within the studied range of water temperatures, the observed variations in the span of the different stages, indicate that this factor does not alter the molt frequency. Like in the rest of decapods, the intermolt duration of P. argentinus is modified by ovarian maturation.

Life history traits of the grass shrimp Palaemonetes antennarius (Decapoda, Palaemonidae) in the delta of the Neretva River, Croatia

“…However, slight changes in the sex ratio were observed during the period of high reproductive activity in June and August. Furthermore, ovigerous females might be slower and therefore easier to catch than males, which are in agreement with the observations on P. argentinus Nobili, 1901 (Felix & Petriella 2003). Brood size and CL relationship confirm the pattern observed in North and South Italy (Dalla Via 1983;Hofer et al 1980).…”

Littoral Communities. Macrocrustaceans

“…This becomes more complex if we consider the beginning of the ovarian maturation. In P. varians, there is a reduction in the intermolt period when temperature increases (Jefferies 1964), whereas in P. argentinus (Felix and Petriella 2003) the increase in temperature does not modify the frequency of molt, since ovarian maturation would be producing a higher influence.…”

Intraspecific variability in life-history traits of a "freshwater shrimp", Palaemonetes argentinus

“…Intraspecific variability in life-history traits of a "freshwater shrimp", Palaemonetes argentinus (2) lations from Argentina and Brazil (e.g. Spivak 1997, Gonçalves & Fontura 1999, Félix & Petriella 2003, Dumont & D'Incao 2004, Oliveira Azevedo et al 2004). On the other hand, simultaneous comparative investigations of life-history traits in different populations have so far not been available.…”