The female reproductive biology of a Chasmagnathus granulatus population inhabiting the area near the mouth of Mar Chiquita coastal lagoon, Argentina, was studied. An increase in air temperature during the spring is related to the start of the breeding period, when well defined egg-laying and hatching pulses were observed. Hatching is synchronic during the whole summer but the egg production was not, probably due to the gradual incorporation of young females to the reproductive population. Neither egg-laying nor larval release showed a clear relation to moon phase or tidal cycles, suggesting that reproduction is not rigidly programmed in this unpredictable habitat. Females moult at the beginning of autumn, after releasing the last larvae. However, a new cohort of ovocytes, which was in primary vitellogenesis before moulting, completed the secondary ovogenesis after moulting. Consequently, ovaries remained fully developed throughout the winter.

The female reproductive biology of Chasmagnathus granulatus Dana, a semiterrestrial burrowing crab endemic to the southwestern Atlantic, was compared in two contrasting coastal habitats: San Antonio (SA, marine) and Mar Chiquita (MC, estuarial). Mature females were collected monthly for 1.5 years and the ovarian cycle was described using a qualitative scale. Gonadosomatic (GSI) and hepatosomatic (HSI) indexes were calculated. The highest GSI and HSI occurred early in the reproductive season in SA and during the non-reproductive season in MC. The beginning and duration of the reproductive season also differed between populations: it started later and was shorter in SA. In MC, secondary vitellogenesis continued when the reproductive season had finished, and the ovaries remained fully developed throughout the non-reproductive season (winter). Therefore, females of MC were ready to lay eggs as soon as spring environmental conditions appeared. However, SA females did not attain a fully developed ovary during winter. A limited food supply would restrict the available energy to complete secondary vitellogenesis at the end of the reproductive season in SA, after the last spawning. Thus, the vitellogenic cycle should be completed in the following spring, causing a delay in the beginning of the reproductive period. In addition, the higher temperature amplitude may cause the reproductive period in SA to end early.

The shrimp Palaemonetes argentinus Nobili 1901 inhabits freshwater streams, lakes and brackish coastal lagoons in the warm temperate regions of southeastern South America. Larvae and adults tolerate a wide range of salinities, exhibiting a well developed osmoregulatory capacity already from hatching. Nevertheless, effects of salinity on the embryos of P. argentinus have not been studied yet. In the present investigation, freshly layed eggs were removed from ten females and, from the time of extrusion to larval hatching, exposed in vitro to four salinities (1, 15, 25, 32 PSU; all incubated at 20°C). This technique allowed the comparison of salinity effects on embryos of the same brood, excluding maternal effects as potentially confounding sources of variation. Initial egg size and duration of embryonic development under identical conditions varied significantly among broods from different females, but showed no significant relationships with female body size. Development was most successful in eggs incubated at salinities of 1 and 15 PSU, with average hatching rates of 72% and 79%, respectively. In contrast, 20% hatched at 25 PSU, and only three individuals (1.5%) in seawater (32 PSU). Egg mortality increased consistently near the end of the developmental period, especially at 25 and 32 PSU. Larvae hatching at these relatively high salinities retained a greater quantity of yolk, while many were deformed, suggesting that hyperosmotic stress interfered with metabolic energy mobilization and morphogenetic processes. The mean time from spawning of the eggs to larval hatching was similar at 1 and 15 PSU (ca. 24 d), but lasted significantly longer at 25 and 32 PSU (26–27 d, respectively). During the first ca. 10–12 days of embryonic development, the volume of the eggs decreased slightly at 25 and 32 PSU, while an increase was observed at lower salinities (maximum: 20% at 1 PSU). During the final period of development, an increase in egg volume occurred in all treatments, being significantly stronger at low salinities (≤15 PSU). The first zoeal stage of P. argentinus can also in complete absence of food successfully develop from hatching through the moult to the zoea-II stage; this trait (facultative lecithotrophy) was not affected by salinity. Our results suggest that successful reproduction of P. argentinus in freshwater and brackish habitats with highly variable conditions of salinity and food availability is based on an early appearance of osmoregulatory functions during the embryonic phase and/or a low permeability for ions of the egg membrane, while yolk reserves persisting from the egg allow for food-independent development through the first larval stage.

The oriental shrimp Palaemon macrodactylusRathbun, 1902 was detected first in Argentina in 2000 in a fully marine environment (Mar del Plata) and more