Biology Reference
In-Depth Information
Body size
Weight
Age
Standard length/weight/age
Fig. 43. Fecundity model, showing the relationships of fecundity to body size (-----), weight
(—)and age (…..) of fi shes (from Pandian, 2010)
3.5 Sex chromosomes and genes
Very surprisingly, cytogenetic studies on sex chromosomes on hermaphroditic
fi shes are limited to a dozen species only, though 380 or so hermaphroditic
fi shes including those in which functional hermaphroditism remains to
be confi rmed, are known to exist and their phenomenal diversity has
allured considerable curiosity. Even among the dozen or so available
publications, none has employed molecular cytogenetic studies like those
of Ross and Peichel (2008) and Bradley et al. (2011). The conventional
karyotypic studies thus far undertaken have only reported the number of
chromosomes present (e.g., 2 = 48 Sparus aurata, Alvarez et al. (1991), or the
lack of difference in the chromosome morphology during different sexual
phases (e.g., monandric grouper E. guttatus, diandric wrasse Thalossoma
bifasciatum, Ruis-Carus, 2002) or at the best the presence of 46 homomorphic
chromosomes in K. marmoratus (Sola et al., 1997). Nevertheless, there are
a couple of observations reporting the existence of female heterogametic
serranid E. tauvina (2n = 48) and male heterogamety in the polymorphic
labrid C. julis (2n = 46, 48, 46/45 XX/XO, see Devlin and Nagahama, 2002),
although these observations require confi rmation. Interestingly, the male
heterogametic sex chromosome system of C. julis is XX/X0. It also remains
to be tested whether the haremic male hetrogametic C. julis is a somatic
female, like the nematode C. elegans, in which due to non-disjunction of a
X chromosome, males are generated (Zarkower, 2006).
 
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