. The biology of marine animals. Marine animals; Physiology, Comparative. WATER, SALTS AND MINERALS 75 jelly coat. Eggs denuded of jelly swell or shrink in anisotonic media, and disintegrate in sea water of salinity less than 14%0, whereas eggs protected by jelly will develop even in distilled water. Larvae show volume regulation in hypotonic sea water (down to 22%0) presumably due to salt loss (Fig. ). Sex cells and larvae of the California mussel Mytilus californianus are susceptible to dilutions below 29-6%0, and survival declines below this concentration. This species is characteristic
. The biology of marine animals. Marine animals; Physiology, Comparative. WATER, SALTS AND MINERALS 75 jelly coat. Eggs denuded of jelly swell or shrink in anisotonic media, and disintegrate in sea water of salinity less than 14%0, whereas eggs protected by jelly will develop even in distilled water. Larvae show volume regulation in hypotonic sea water (down to 22%0) presumably due to salt loss (Fig. ). Sex cells and larvae of the California mussel Mytilus californianus are susceptible to dilutions below 29-6%0, and survival declines below this concentration. This species is characteristic of coasts with high salinity, and the narrow salinity tolerance of the larvae is one factor restricting its distribution (75, 149). There is space to examine only certain aspects of water and salt relations in fish eggs and larvae. Oviparous selachians produce what Needham has termed a cleidoic type of Qgg which is independent of the medium for its. 20 40 60 80 100 Time (minutes) Fig. Volume Regulation in Larvae of a Polychaete, Marphysa gravelyi Smoothed curves showing percentage increases of volume in waters of lowered salinity. (After Krishnamoorthi (75).) supply of water and salts. The egg membrane is largely impermeable to urea, and the accumulation of this substance as the result of protein metabolism gives rise to final concentrations approaching those of the adult. The eggs of marine teleosts are at first permeable to water and salts, but during the course of development osmoregulatory ability develops and the chloride content of the embryo is reduced. In contrast, eggs of the euryhaline killifish Fundulus heteroclitus are nearly impermeable to water and salt, and display ionic and osmotic regulation from earliest stages. The genital products, eggs and sperm, are initially in osmotic equilibrium with the parents' fluids. Plaice eggs (Pleuronectes platessa), which are hypotonic to sea water when laid (eggs A 0-70, sea water A 1-91), will develop in 20% sea water,
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