Biology Reference
In-Depth Information
C
A
B
Fig. 40.
Upper panel: Transverse cross-sections of mature ovotesis of
Diplectrum
formosum
showing compartmentalization (A) t = ripe testicular and o = ovarian tissues and (C) between
sd = sperm duct with spermatozoa and as = accessory structure. Ho = Hydrated oocytes are
present within the ovarian portion (x20). Lower panel: Villi-like projections (v) from the wall
of the accessory structure in the ovotestis with the presence of hydrated oocytes (ho) (x400)
(from Bubley and Pashuk, 2010). Life history of a simultaneous hermaphroditic fi sh
Diplectrum
formosum.
J Fish Biol, 77: 676-691 (reproduced by permission of The Fisheries Society of the
British Isles/John Wiley & Sons Ltd)
A combination of low density, limitation of space, reduction in allocation
for female function to 56% from 77% and shortened spawning period has
driven a few gamete exchanging simultaneous hermaphrodites to switch
over to pure male (Fig. 39). Thus, all individuals of
S. baldwini
and
S. fasciatus
commence life as simultaneous hermaphrodites but the largest individuals
in any location lose the female function and become functional males; these
males hold territories and harems consisting of one to seven females.
Marian hermaphrodites: Thanks to the series of publications by
St. Mary, the existence of Marian hermaphrotism in about fi ve goby species
belonging to genus
Lythrypnus
has been established (Fig. 2). Marian
hermaphrodites have simultaneously different fractions of both ovarian
and testicular tissues in their gonad, as in simultaneous hermaphrodites but
nonetheless function either as male or female at any point of time. Unlike
the Okinawan hermaphrodites, the Marians are solitary. Depending upon
the quantum of tissues present in the gonad, there can be pure males, male-
biased hermaphrodites, female-biased hermaphrodites and pure females. In
L. zebra, L. spilus
and
L. phorellus
, pure males are absent but their function is
carried by male biased hermaphrodites. According to St. Mary, they may be
capable of bidirectional sex change but successful sex change is described
in
L. zebra
only (see Pandian, 2010).
Okinawan hermaphroditism has been described in two species
Gobiodon
okinawae
from the Lizard Island (Cole and Hoese, 2001) and
Dascyllus
aruanus
from Papua New Guinea (Cole, 2002). They more or less resemble
Marian hermaphrodites but are colonials. In some of their colonies, a male
is absent and a male-active hermaphrodite takes over the function of the
