|Developmental ecophysiology of the beachflea Orchestia gammarellus (Pallas) (Crustacea: Amphipoda). 2. Embryonic osmoregulation|
Morritt, D.; Spicer, J.I. (1996). Developmental ecophysiology of the beachflea Orchestia gammarellus (Pallas) (Crustacea: Amphipoda). 2. Embryonic osmoregulation. J. Exp. Mar. Biol. Ecol. 207(1-2): 205-216
In: Journal of Experimental Marine Biology and Ecology. Elsevier: Tokyo; Oxford; New York; Lausanne; Shannon; Amsterdam. ISSN 0022-0981, more
Developmental stages; Ecophysiology; Osmoregulation; Salinity effects; Amphipoda [WoRMS]; Orchestia gammarellus (Pallas, 1766) [WoRMS]; Marine
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The osmotic concentrations of the periembryonic fluid (PF) of a number of key embryonic stages of the semi-terrestrial beachflea Orchestia gammarellus, cultured in vitro, were measured over a wide range of external concentrations (150-1250 mOsm/kg). Similarly the haemolymph concentration of immediate post-hatch (<24 h) individuals was measured over the same concentration range. All embryonic stages displayed a well-developed hyper-hypo-osmotic regulation pattern, maintaining the PF between concentrations of 500-900 mOsm/kg over an external concentration range of 150-1250 mOsm/kg. In post-hatch individuals, however, hyper-hypo-regulation was much weaker (approaching isosmotic in higher concentrations), the haemolymph being maintained at concentrations between 320 and 1100 mOsm/kg over a concentration range of 150-1250 mOsm/kg. Experiments in which early embryos were cultured in a number of seawater dilutions (25%-50% sea water) showed > 50% survival and normal development of O. Gammarellus embryos in culture only occurred at concentrations of greater than or equal to 40% sea water. The results are discussed in relation to the female control of the embryonic environment and the environmental osmotic stresses experienced by the different developmental stages. It is suggested that fluctuating osmotic stress has acted as a strong selection pressure on early developmental stages thus affecting the ontogeny of osmoregulation in O. Gammarellus embryos.