1063-0740/05/3105- © 2005 Pleiades Publishing, Inc.
Russian Journal of Marine Biology, Vol. 31, No. 5, 2005, pp. 318–321.
Original Russian Text Copyright © 2005 by Biologiya Morya, Kalachev, Yurchenko, Reunov.
The structural variation of accessory cells (nutritive
phagocytes) in some species of sea urchins has been
investigated using light [1–3, 10, 11, 13, 18, 19] and
electron microscopy [3, 7, 14, 17]. Nutritive phago-
cytes of males and females undergo a number of similar
morphological transformations in the course of the
gonadal cycle [10, 18, 19]. Before the beginning of
gametogenesis, they store nutrients and thus increase in
volume [3, 10, 11, 18]. During differentiation of germ
cells, reserve nutrients are mobilized from the nutritive
phagocytes [14, 18, 19]. In doing so, the accessory cells
become markedly reduced in size. After spawning, they
again increase in size, resorbing unspawned gametes
[18, 19]. The ultrastructural mechanisms that ensure
these changes in the nutritive phagocytes have thus far
been understood poorly. In particular, such an impor-
tant function as gamete resorption has not been
described adequately at the electron microscopic level.
Moreover, the opinion exists [4–6, 13] that gamete
resorption is a key regulator of gametogenesis.
The aim of the present electron microscopic study is
to describe the ultrastructural mechanisms of resorption
of residual sperm in the postspawning gonad of the sea
MATERIALS AND METHODS
Specimens of the sea urchin
(A. Agassis, 1863) were collected from May to
September 2002 in Yamar Bay (Sea of Japan, Peter the
Great Bay). For electron microscopy, pieces of the
gonad were preﬁxed (2 h, 4
C) in a 2.5% glutaralde-
hyde solution (0.2 M cacodylate buffer, pH 7.4) with
the addition of NaCl to achieve the osmomolarity of
seawater and then ﬁxed with 2% OsO
(1 h, room tem-
perature). After dehydration in alcohol and acetone
solutions of increasing concentrations, the material was
embedded in Araldite–Epon. Sections were stained
with 2% uranyl acetate and lead citrate and examined
and photographed in a JEOL-100S transmission elec-
To quantify various phagosome types in accessory
cells, the gonads of three males were investigated.
Three blocks were prepared from each individual and
cut with an ultratome. One section of good quality from
each block was examined. The absolute and relative
number of phagosomes containing sperm and phago-
somes containing residual bodies, as well as mixed pha-
gosomes was determined. The percent of each group of
phagosomes in their total number was calculated.
BIOLOGY OF ONTOGENESIS
Phagocytic Activity of Accessory Cells in the Gonad
of the Sea Urchin
A. V. Kalachev, O. V. Yurchenko, and A. A. Reunov
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received January 12, 2005
—The ultrastructural mechanism of postspawning sperm resorption in the testes of the sea urchin
is described. Two types of phagosomes (containing sperm and containing residual
bodies) are formed in the cytoplasm of nutritive phagocytes. The phagosomes fuse with electron-dense glob-
ules, and their contents are gradually destroyed. Afterward, phagosomes are transformed into electron-transpar-
ent vacuoles, which are ﬁnally compressed by the surrounding cytoplasm.
sea urchin, accessory cells, nutritive phagocytes, testes.
Postspawning process in the gonad of the sea urchin
(a) Resorption of sperm and (b) residual bod-
ies; (c) phagosomes containing only sperm and (d) only residual bodies in the cytoplasm of nutritive phagocytes; (e) fusion of pha-
gosomes with electron-dense globules and (f) phagosome after fusion; (g) late phagosome; (h) formation of light-colored areas in
the phagosome contents. Designations:
Electron-dense globules are marked with asterisks. Arrow-heads point to processes of a nutritive phagocyte surrounding a sperm.
Scale: a, d–h—1
End of Fig. 1. (i) Phagosome ﬁlled with a ﬂocculent matrix; (j) compression of electron-transparent vacuole by cytoplasm of nutri-
tive phagocyte. Arrows indicate areas of cytoplasm compressing an electron-transparent vacuole. Scale 1