Biology Reference
In-Depth Information
Fig. 26.
Morphological differentiation of anal fi n rays of
Gambusia affi nis
Arabic numerals
indicate fi n rays number from the ventral side of the fi n. Roman numerals indicate the location
of the differentiation areas. Note the differentiation in fi n rays number 3,4,5 in a (A) male and
the same in a (B) female (from Turner, CL. 1941. Biol Bull, 80: 371-383, reprinted with kind
permission from the Marine Biological Laboratory, Woods Hole, MA)
Color and pigmentation play an important role in camoufl age, warning,
theromoregulation, protection from ultra-violet radiation and courtship
display. For instance, 99% males of
G. holbrooki
are silver and the remaining
1% is melanic. Melanic males have greater survival and larger gonopodium
(Horth et al., 2010). Tezuka et al. (2011) have reported that among the
melanics of
G. reticulata
, genetic variations in
melanocortin 1 receptor
(
MC1R
)
gene coutribute to polymorphism of melanin pigmentation. Determining
the complete coding sequence of
MC1R
, two alleles are recognized in
G. reticulata,
the one with 963-bp is less melanic than the other with 969-bp.
However, the relation between
MC1R
genotype and black pigmentation
disappears in the F
2
progenies.
Sabbah et al. (2010) have brought indicative evidence for the neural basis
for sexually dimorphic visual behavior, i.e., females and males sample their
visual environment differently, suggesting that the difference in detection of
optical signals has a role in sexual selection in tuning color vision. A large
number of publications are available on this topic, especially with reference
to the explosive speciation rate among the African cichlids (e.g., Allender
et al., 2003). Male body coloration is an important discriminatory factor
used by females in mate choice. To gain insight into the molecular basis of
