Biology Reference
In-Depth Information
3
Differentiation in
Hermaphrodites
Hermaphroditism is defi ned as the expression of both male and female
reproductive function in a single individual either simultaneously or
sequentially (Sadovy de Mitcheson and Liu, 2008). In fi shes three patterns
of functional hermaphroditism have been recognized (Pandian, 2010):
simultaneous, sequential and serial (Fig. 2). Simultaneous hermaphrodites
function as male and female at the same time or within a short span of time.
They do not undergo natural sex change. However, the sequential and serial
hermaphrodites undergo natural sex change; the sequentials change sex
only once in a single direction (protogyny: female to male; protandry: male
to female) during their life time but the serials do it more than once in either
direction. The ontogenetic pathways of sexual differentiation in these sex
changing sequentials and serials are depicted in Fig. 38. Incidentally, it is
known that a fraction of individuals in sex changing sequential populations
does not undergo sex change: e.g., protogynics
Pagrus pagrus
, protandric,
Diplodus vulgaris.
Social pressure induced sequential (e.g., Cichlidae,
Crenicara punctulata,
Zupanc, 1985) and serial (e.g.,
Macropodus opercularis,
see Pandian, 2011) sex changes do occur in a few gonochores. They are
discussed elsewhere (Pandian et al., 2012).
3.1 Patterns of hermaphroditism
Due to plasticity in sexuality and flexibility in mating system, the
detection of truly functional hermaphoroditism in some 350-400 species
belonging to 34 or so families (Nakazona and Kuwamura, 1987) has been
indeed a task (see Pandian, 2010). By applying a rigorous set of criteria to
