Separation and biological effects of CNS factors affecting water balance in the decapod crustacean Thalamita crenata

Primary culture and characteristic morphologies of neurons from the cerebral ganglion of the mud crab, Scylla paramamosain

Crustacean neurons, obtained from the cerebral ganglion of the mud crab Scylla paramamosain, were successfully cultured in vitro. They maintained typical morphological characteristics and showed better outgrowth in modified Medium 199 (M199) medium than that in Liebowitz's L-15 medium. Fetal bovine serum (FBS), muscle extracts, and hemolymph of the mud crab S. paramamosain were added as supplements. Only 20% FBS could promote neuron outgrowth, while muscle extracts and hemolymph of S. paramamosain did not improve neuron outgrowth. For cell dissociation, both collagenase type I and trypsin worked well as determined by initial cell viability and following cell outgrowth potential. More than six kinds of cells with different morphological characteristics were identified in the neuron outgrowth. They were "small cells", "veilers", "branchers", "multipolar cells", "super-large cell", and "bipolar cells". Among all of the cells, bipolar cells were identified for the first time in crustacean neurons culture and they could live longer than other cells. The neurons could grow for more than a week before retraction and eventual degradation.

Involvement of the central nervous system in neuroendocrine mediation of osmotic and ionic regulation in the freshwater shrimp Macrobrachium olfersii (Crustacea, Decapoda)

The presence of putative neurofactors within the central nervous system, i.e., the eyestalks (ES), ventral nerve cord (VNC), and supra-esophageal (SEG) and thoracic ganglia (TG), which are involved in osmotic and ionic regulation, was investigated in the euryhaline, freshwater shrimp, Macrobrachium olfersii. Homogenates were prepared from shrimps exposed for 6 hr to a high salinity medium (HSM, 21/1000 S) and were injected into shrimps subsequently maintained for 1, 3, or 6 hr in freshwater (FW, 0/1000 S) or HSM. Osmolality and sodium, chloride, and calcium concentrations were determined in single hemolymph samples removed at each time interval. Heart rates and wet weights were measured before and after experimental treatments. Exposure to HSM increased [Na+] and [Cl-] and heart rate. Injection of ES homogenate increased osmolality, [Na+] and [Cl-], and wet weight in shrimps maintained in FW; VNC homogenate also increased hemolymph [Cl-] in shrimps maintained in FW after injection, but reduced heart rate in shrimps subsequently exposed to HSM. Injection of TG homogenate reduced heart rate to a lesser extent in shrimps maintained in FW. Hemolymph [Ca2+] was not altered by homogenate injection. The exposure period of 6 hr to HSM appears to result in the accumulation of factors within the central nervous system that regulate the osmotic and ionic concentrations of the hemolymph, in addition to exerting antidiuretic and cardio-depressor actions. The coordinated action of these factors is intimately involved in the hyporegulatory processes that permit the survival of M. olfersii in media of elevated salinity.

Neuroendocrine regulation of osmotic and ionic concentrations in the hemolymph of the freshwater shrimp Macrobrachium olfersii (Wiegmann) (Crustacea, Decapoda)

Putative neuroendocrine mediation of osmotic and ionic responses to acute exposure to high salinity medium was investigated in the freshwater shrimp Macrobrachium olfersii (Wiegmann). Homogenates of supra-esophageal or thoracic ganglia, prepared from shrimps exposed to seawater of 21% S for 6 hr, were injected into the abdominal musculature of shrimps previously exposed to freshwater and subsequently exposed to either freshwater or seawater (21% S). Osmotic, sodium, chloride, potassium, magnesium, and calcium concentrations were determined in hemolymph samples removed by intracardiac puncture at time = 0, 1, 3, or 6 hr after homogenate application. Control shrimps were injected with filtered seawater, isosmotic to the hemolymph, and treated similarly. In control shrimps, the osmotic, Na+, Cl-, K+, Mg2+, and Ca2+ concentrations in the hemolymph increased (P less than or equal to 0.05) after 1-hr exposure to seawater. In shrimps injected with homogenates of supra-esophageal ganglion and exposed to seawater, osmotic and ionic concentrations in the hemolymph did not vary with exposure time; in injected shrimps exposed to freshwater, Na+, Cl-, K+, and Mg2+ concentrations decreased (P less than or equal to 0.05) with time. In shrimps injected with homogenates of thoracic ganglion and exposed to seawater, hemolymph osmotic, K+, and Mg2+ concentrations increased (P less than or equal to 0.05); Na+, Cl-, and Ca2+ concentrations remained unchanged. In injected shrimps exposed to freshwater, hemolymph osmotic concentration alone increased (P less than or equal to 0.05) after 1 hr, all other ionic concentrations remaining unchanged. These data suggest that neurofactors apparently located within the ganglia of the central nervous system of M. olfersii may alter the apparent ionic permeabilities of this shrimp, depending on the salinity characteristics of the external medium. The data support the notion that invasion of the freshwater biotope by estuarine crustaceans has necessitated the evolution of specific physiological mechanisms capable of compensating for the osmotic dilution and ion loss typically encountered by such organisms.

Neuroendocrine control of hydromineral regulation in the American lobster Homarus americanus H. Milne-Edwards 1837 (Crustacea, Decapoda). 1. Juveniles

Juvenile lobsters survive well in salinities above 10.2% (300 mOsm/kg), and their osmotic and ionic (Cl-, Na+, Ca2+) regulation in dilute sea water is slightly hyperosmotic, similar to that of adults. Approximately a month after eyestalk ablation, osmotic and ionic (Cl-, Na+) regulation becomes isosmotic, water content increases, and survival rate in dilute sea water declines, but these changes can be partially reversed by implantation of eyestalk neuroendocrine tissue. Regulation of Ca2+, in contrast, is only slightly affected by eyestalk ablation. These results indicate that osmotic regulation and regulation of hemolymph Na+ and Cl- concentrations are at least partly controlled by eyestalk neuroendocrine factors in this species.

[Influence of environmental salinity on the diffusion fluxes of water in the Isopod Sphaeroma serratum (Frabricius)]

1.--In Sphaeroma serratum, the diffusion fluxes of water are 3 or 4 times more important in sea water (SW) than in diluted (50%) sea water. In 100% and in 50% SW influx equals the outflux. 2.--When the animal is quickly transferred from 100% SW to 50% SW, and from 50% SW to 100% SW, the outflux is instantaneously and entirely reset. 3.--The main factor of the instantaneous resettlement of the outflux seems to be the variation of the concentration of Na+ or Cl- or both together in the external medium; the Ca2+ and Mg2+ concentrations do not seem to have any effect on the diffusion flux. 4.--The validity of our results is discussed (theory of unstirred layers, blood-circulation, oxygen interchange, ultrastructure). Our results are compared with those obtained in other Crustaceans and in Fishes.