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Fig. 2. Germ cell features (A,C,E) and panoramic views of testes (B,D,F). (A) Two
very early spermatogonia which have peripherical condensed chromatin in their
nucleus, a single nucleolus and lightly colored and scarce cytoplasm. On the
left hand side of the picture it is possible to observe a cluster of
spermatogonias that have probably undergone further mitosis, given their
smaller size. Scale bar, 10 µm. (B) Resting testis from a fish captured in
July. The tubules are filled with spermatogonia. Scale bar, 20 µm. (C) Cyst
of early spermatocytes. Note that the chromatin is in the initial phase of
condensation. Scale bar, 10 µm. (D) Recovering testis from a fish captured
in October. The tubules are mainly filled with cysts of spermatocytes. It is
also possible to observe cysts of spermatids. Scale bar, 20 µm. (E)
Spermatids oriented inside the cysts, with their heads towards the periphery
and their tails towards the center. On the right hand side there is free sperm
in the lumen Scale bar, 10 µm. (F) Mature testis from a fish captured in
December. The germinal epithelium has become thinner, cysts of spermatocytes
remain but testis is dominated by pools of free sperm in the lumen. Scale bar,
20 µm. The maturing testis, present in October and November is not shown.
(G) Relative distribution of three different groups of germ cells in testis of
freshly captured males in June (N=4, non-breeding season), October
(N=4), and December (N=4, breeding season). White,
spermatogonia; hatched pattern, spermatocytes; black, spermatids and sperm.
sc, spermatocyte; sd, spermatid; sg, spermatogonia; sp, sperm.
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