Larval growth in the estuarine crab Chasmagnathus granulata: the importance of salinity experienced during embryonic development, and the initial larval biomass

Abstract

The importance of salinity experienced during embryonic development and initial larval biomass on larval growth was studied in the South American estuarine crab Chasmagnathus granulata. Ovigerous females were maintained at three salinities (15, 20, and 32&) from egg laying to hatching of zoea 1. Larvae from all treatments were reared under constant conditions of photoperiod (12:12), temperature (18°C), and salinity (first instar at 20&, subsequent instars at 32&). Biomass was measured as dry weight, carbon, and nitrogen content per individual at egg laying, hatching of zoea 1, premoult zoea 1, and zoea 4, and in 8-day-old megalopa. From hatching to premoult zoea 4, biomass was higher for larvae from prehatching salinities of 15 and 32&. There was a significant positive correlation between biomass at hatching and at premoult zoea 1 and zoea 4. Accumulated biomass during zoeal stages tended to be higher for larvae from broods with higher biomass at hatching, although this trend was not always significant. Zoea 4 either directly metamorphosed to megalopa or moulted to zoea 5, following, respectively, a short or long developmental pathway. The proportion of zoea 4 that followed the long pathway was negatively correlated with biomass of zoeal stages. Biomass at hatching was correlated with biomass of megalopae developed through the short pathway, although it was not correlated with the accumulated biomass at this stage. Megalopae developed through the long pathway (i.e. metamorphosed from zoeae 5) had higher biomass than those from the short pathway.The present results suggest that prehatching salinity and initial egg and larval biomass can be very important for larval growth.

Seasonal and interpopulational variability in fecundity, egg size, and elemental composition (CHN) of eggs and larvae in a grapsoid crab, Chasmagnathus granulatus

“…Variation in egg biomass occurred between broods from diVerent females that had been kept at the same condition, but also as a response to reduced salinity (15) during egg development. Such diVerences in egg size persisted at least to the zoea IV stage, with a tendency of increased growth rate in larvae hatched from larger eggs (Giménez and Torres 2002). Higher egg biomass observed at the beginning of the reproductive season in MC could also be caused by low salinities, which generally occur during this period due to strong rainfalls and low evaporation during the preceding autumn and winter.…”

Influence of temperature on the larval development of the edible crab, Cancer pagurus

“…Variation in environmental key factors such as food availability (Anger & Dawirs, 1982), quality (Harms et al, 1991), salinity (Giménez & Torres, 2002;Giménez & Anger, 2003) or temperature (Dawirs, 1979(Dawirs, , 1985 can have unfavourable effects on growth in the early ontogeny of decapod crustaceans (for review, see Anger, 2001).…”

Larval salinity tolerance of the South American salt-marsh crab, Neohelice (Chasmagnathus) granulata: physiological constraints to estuarine retention, export and reimmigration

“…Likewise, we excluded from our data a few exceptional cases occurring at low salinities (three individuals at 10‰, one at 15‰), where zoea-IV larvae developed to a zoea-V stage and not directly to a megalopa. This longer developmental pathway in N. granulata was morphologically described by Pestana and Ostrensky (1995), and factors favouring its occurrence as well as consequences for later larval and juvenile development were studied in detail by Giménez and Torres (2002), Giménez and Anger (2003) and Giménez et al (2004). Experiments 2 and 3: exposure to decreasing salinities from the zoea-IV or megalopa Although the reimmigration from coastal marine to estuarine and oligohaline waters presumably occurs in the megalopa and/or in early juvenile crab stages, a beginning of return already in late zoeal stages is also conceivable, as these stages show mostly demersal behaviour, which may favour an onshore transport with tidal bottom currents (Anger 2001).…”