REFRACTILE BODIES IN THE DEVELOPING AND MATURE SPERMATOZOA OF CHILDIA GROENLANDICA (TURBELLARIA: ACOELA) AND THEIR POSSIBLE SIGNIFICANCE

Abstract

1. Living and fixed mature spermatozoa of Childia groenlandica (Turbellaria: Acoela) have conspicuous refractile bodies present behind the oval nucleus, in a double longitudinal row in the tail; an undulating membrane is also evident, as well as (in some cases) a slender head filament which is not a flagellum but which may be the result of an acrosome reaction. The living spermatozoa are 50-60 microns long and moderately motile. In living and fixed specimens, the refractile bodies are found at least as early as the secondary spermatocyte stage and increase in numbers rapidly during the spermatid stages. 2. The following results were obtained with cytochemical tests of the refractile bodies: (a) Feulgen, for DNA, negative; (b) methyl green-pyronin and azure B, for RNA, positive before and after RNase and PCA extraction; (c) alcian blue/ PAS for polysaccharides, positive before and after diastase digestion, for small accumulations of acid mucopolysaccharide (s) in centers, only, of refractile bodies; (d) Sudan IV and Sudan black B, for lipids, negative; (e) Gomori, for alkaline phosphatases, positive; (f) azo dye-simultaneous coupling, for alkaline phosphatases, questionably positive in small central area; (g) Gomori, for acid phosphatases, very questionably positive at peripheries; (h) azo dye-simultaneous coupling, for acid phosphatases, negative. The refractile bodies stained heavily after toluidine blue, safranin, Janus green, Wright's stain and Mallory's triple stain; they did not stain after Harris' acid haematoxylin, eosin or light green, nor (supra vitam) with neutral red, Nile blue sulfate or Janus green B. 3. By electron microscopy, the refractile bodies were found to have an electrondense oriented substructure of definite lamellae in the central region; this is surrounded by a ruffled membrane which is separated from the central region by a variable distance averaging approximately 0.15 micron. The fine structure of the refractile bodies is strikingly reminiscent of that of certain other cell inclusions in other forms, most notably the granules of basophil leucocytes and mast cells. This resemblance is reflected, to some extent, in their cytochemical characteristics. 4. The hypothetical significance of the refractile bodies is discussed in relation to the possibilities that they may (a) play a lysosome-like role in fertilization of the egg, or (b) remove the block to development which occurs after fertilization and during the first cleavage metaphase until the eggs are laid in sea water.