Cumulative effects of low salinity on larval growth and biochemical composition in an estuarine crab, Neohelice granulata

Abstract

Throughout the larval development of a highly euryhaline crab, Neohelice (= Chasmagnathus) granulata, we studied effects of reduced salinities (15 and 25 ‰ vs. seawater control at 32 ‰) on larval dry mass (W ) and biochemical composition (total lipid and protein). In the early zoeal stages (I, II), reduced salinity caused delayed moulting, while W and biochemical composition at ecdysis remained unaffected. This suggests that the capability of the Zoea I for hyper-osmoregulation (demonstrated in a previous study) mitigated potential effects of hypo-osmotic stress on biomass accumulation and biochemical composition, but did not prevent a developmental delay. After continued rearing at low salinities, later larval stages showed increasingly negative effects on growth. The Zoea IV, for instance, revealed at 15 ‰ significantly reduced W, lipid and protein contents compared to higher salinities, probably as a consequence of weak osmoregulatory capabilities in the zoeal stages II and III. Likewise, average daily rates of biomass accumulation (taking into account salinityinduced variations in development duration) were lower at reduced salinities. These negative effects on larval growth persisted throughout the Megalopa, in spite of a strong capability in this stage to hyper-osmoregulate. This indicates that the mitigating force of osmoregulation in the final larval stage was not strong enough to offset cumulative effects of a continuous exposure to osmotic stress lasting from hatching throughout the more stenohaline zoeal stages. Osmoregulation in N. granulata has implications for population dynamics in the field, where salinity conditions prevailing during the development in the plankton may influence larval condition and survival at metamorphosis, eventually affecting recruitment.

Importance of plasticity and local adaptation for coping with changing salinity in coastal areas: a test case with barnacles in the Baltic Sea

“…Fitness advantages of rapid initiation of growth include improved competition for space [ 70 ], increased tolerance to fluctuating environmental stressors [ 71 , 72 ] as well as size-based predator avoidance [ 73 ]. Reduced growth under environmental stress has been shown in other marine species [ 74 , 75 ]. The delay in early growth that we observed in 6 PSU may be due to altered physiology (e.g.…”

Influence of temperature and light regime on the larval development of the common spider crab Maja brachydactyla Balss , 1922 (Brachyura: Majidae)

“…The influence of the culture conditions during previous stages over the megalopa seems to be a latent effect (Pechenik, ); that is, environmental conditions experienced at early stages affect development or other traits at later stages. Latent effects have been reported in decapod crustaceans in response to food limitation or osmotic stress (Giménez, ; Torres, Giménez, & Anger, ). The zoea I of M. brachydactyla reared at constant darkness had lower dry mass, carbon and nitrogen content per individual, and C:N ratio than larvae reared in the presence of light; but in general (excepting for 300 lx treatment), no variations were observed among treatments when the larvae reached the megalopa stage.…”

The capacity of crab megalopae to autotomize body appendages and the consequences upon their feeding ability–the price to pay to live another day

“…It is important to note that if eyestalk damage occurs after the megalopa has reached the PRS, not only will it be able 330 to metamorphose, but the molt cycle will be abbreviated and the timing to metamorphosis will be anticipated (Snyder and Chang 1986). Due to the levels of physiological stress associated with the eyestalk damage and the ''violence of the attack'' required to damage these appendages ''not designed to be left behind'', C. maenas megalopae will probably never be recorded in the wild exhibiting this It has already been documented in brachyuran crabs that reduced larval fitness may be ''carried-over'' metamorphosis into the benthic phase (Gime´nez, 2006), which can negatively affect the juvenile survival and growth (Gime´nez et al 2004;Torres et al 2008). Physical damage induced to megalopae can promote smaller body sizes of newly metamorphosed crabs (unpublished data).…”