The Physiology of Sea-Urchin Spermatozoa

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Abstract
1. The effect of adding sea water containing different concentrations of versene to suspensions of sea-urchin spermatozoa (Echinus esculentus) has been investigated, as regards their respiration, motility and fertilizing capacity. 2. The respiratory Dilution Effect is progressively reduced and finally abolished when, instead of sea water, sea water containing 10-6, 10-5, 10-4 or 10-3 M versene is added to sperm suspensions. 3. At the same time versene greatly delays the senescence of the spermatozoa, both as regards their motility and fertilizing capacity. For example, after seventeen hours, a 105 sperm/ml. suspension in sea water containing 10-3 M versene has 125 times the fertilizing capacity of a suspension containing 107 sperm/ml. without versene. 4. The change in the ratio of seminal plasma to sea water which occurs when a dense suspension is diluted does not explain the Dilution Effect. 5. These results are discussed in relation to the hypothesis which accounts for the Dilution Effect in terms of trace metals, particularly copper, normally occurring in sea water, and the amounts available per spermatozoon under various conditions of dilution.