Biology Reference
In-Depth Information
Hermaphroditism
Sequential
Serial
Simultaneous
Gamete exchanging
Self-fertilizing
Marian
Okinawan
Bidirectional
Cyclical
Lythrypnus
dalli
Duscyllus
aruanus
Kryptolebias
marmoratus
Serranus tortugarum
Gobiodon
histrio
Paragobiodon
echinocephalus
Protogynous
Protandrous
Monogyny
Monandry
Diandry
Digyny
Sarpa salpa
Halichoeres pictus
Lates calcarifer
Monochromatic
Dichromatic
Serranus baldwini
Sparisoma viride
Fig. 2.
Patterns of functional hermaphroditism in fi shes (from Pandian 2011, modifi ed)
serials change sex naturally once in the former but many times in the
latter. The sequentials are further divided into (i) female to male sex
changing protogynics and (ii) male to female sex changing protandrics.
In the monandric protogynics, secondary males arise indirectly from sex
changing females but in the diandrics primary males also arise directly, in
addition to secondary males arising from sex changing females. For detailed
information on sex-change mechanisms, Ross (1990) may be consulted.
Marian and Okinawan hermaphrodites simultaneously possess the ovarian
and testicular tissues in their gonads but essentially function as male or
female and may change sex rarely (e.g., Asoh, 2003; Pandian, 2010). A dozen
or so self-fertilizing and gamete exchanging simultaneous hermaphrodites
usually do not change sex.
Hermaphroditism is polyphyletic and derived from rudimentary or
juvenile hermaphroditic secondary gonochores. Documented in about
2% of teleosts, the presence of hermaphroditism is scattered across 20
taxonomic families in nine orders (Avise and Mank, 2009). Simultaneous
hermaphroditism is reported from Cyprinidontiformes, Perciformes,
Auloformes and Anguilliformes; protandry is known from Perciformes,
Stoniformes, Siluriformes and Clupeiformes, while the protogynics from
Cyprinidontiformes, Synbranchiformes, Perciformes and Anguilliforms
(Sadovy de Mitcheson and Liu, 2008).
1.3 Patterns of sex differentiation
In fi shes, sex differentiation is a more labile and fl exible process, subjected to
natural and artifi cial induction of sex reversal through environmental (Pandian
et al., 2012), endocrine (Pandian, 2012) and ploidy (Pandian, 2011) manipulations.
