1063-0740/01/2701- $25.00 © 2001
Russian Journal of Marine Biology, Vol. 27, No. 1, 2001, pp. 31–35.
Original Russian Text Copyright © 2001 by Biologiya Morya, Gnyubkina, Kondrashev.
The changeable coloration of the ﬁsh cornea was
ﬁrst discovered in the Alaska greenling
[9, 19]. The structural and functional prop-
erties of the changeable light ﬁlter they form have been
extensively studied using both light and electron
microscopy. Filters are found in more than 120 species
of various taxons, with marine ﬁshes predominating.
Each species possesses a peculiar light ﬁlter; however,
they share a common structure and include a system of
specialized chromatophores—corneal staining cells
(CSCs). The most distinctive feature of these cells is the
reversible redistribution of the pigment between the
cell body and the single process in response to changes
in illumination [3, 19].
Despite characteristic differences between CSCs
and common (dermal) chromatophores, these two
groups share a number of common features . This
makes the hypothesis of their shared ancestry probable.
There are no data on CSC development in the literature.
In this paper, we present the results of a study of CSC
ontogenesis in the sculpin
sider the formation of a corneal light ﬁlter in total.
MATERIALS AND METHODS
(Jordan et Starks) (Cottidae) larvae
were studied at the Stark Marine Biological Station of
the Institute of Marine Biology (Popov Island, Peter the
Great Bay) in 1995–1996. Specimens of this species
are often found in the shallow waters of the northern
part of the Sea of Japan .
were caught using a plankton net in April–May and
kept in an aquarium with a gravel ﬁlter at 12–15
metamorphosis. They were fed fresh marine plankton
. Larvae of the same age and from the same school
were sampled for analysis. Age was determined based
on a number of morphological characters: the sizes of
the yolk sac, the adipose droplet, and larvae them-
selves; the distinctness of the boundary between the tail
and the rest of the body; the presence of melanophore
Ten larvae were fully adapted to darkness for 2 h
and then exposed to bright (1000 lx) light every day. As
the larvae developed, the time of their exposure to light
was increased from 10 to 20, 30, 40, 60, and 90 min.
The intervals of exposure were experimentally
adjusted. The larvae were then drawn under a stereomi-
croscope, anesthetized with an MS-222 solution in sea-
water, and ﬁxed in 4% glutaraldehyde prepared on a
phosphate buffer at pH 7.4. The eyecups were removed
and the corneas prepared using hand-made glass micro-
instruments. Corneal wholemounts were coverslipped
with glycerinee–gelatinee . The wholemounts were
observed and photographed, and necessary cell mea-
surements and counts were performed under an
ERGAVAL microscope. In this paper, average values of
cell size are given. For histological studies, eyecups
containing CSCs and characterized by fully developed
light ﬁlters were ﬁxed in 4% glutaraldehyde on a phos-
phate buffer and embedded in parafﬁn. Serial sections
The Development of Specialized Chromatophores
and a Changeable Light Filter in the Cornea
of the Sculpin
V. P. Gnyubkina and S. L. Kondrashev
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received December 3, 1999
—The development of corneal staining cells (CSCs) and a changeable light ﬁlter made of CSCs was
studied in the sculpin
(Cottidae). It is shown that CSC development is complete within 9 days,
and the whole changeable light ﬁlter system, within 11 days. The development begins with the droplike chro-
matophore stage. Later on, numerous processes and a projection towards the pupillary zone are formed, accom-
panied by the appearance of granular structures in the cytoplasm. In subsequent development, the cell becomes
round. Later on, it becomes lanceolate, forming a single process extended towards the pupillary zone. On day
3 of development, the process is relatively short and wide. Beginning from this moment, the cell responds to
changes in illumination. Light ﬁlter formation starts in the dorsonasal cornea and expands dorsally, ending in
the ventral cornea 6 days after beginning. The end of light ﬁlter development coincides with the metamorphosis
of the larvae, which is consistent with the peculiarities of their ecology.
ﬁsh, vision, eye, corneal staining cells