Biology Reference
In-Depth Information
Stage 1
Stage 2
Genital
papilla
Penis
Penis
Va s deferens
Capsule gland
Stage 3
Stage 4
Penis
Penis
Va s deferens
Va s deferens
Stage 5
Stage 6
Penis
Penis
Obstructed papilla
Aborted capsules
FIGURE 9.1
Imposex development stages.
The Relative Penis Size Index (RPSI), established by Bryan et al. (1986), is based on penis
length of females and defined as:
=
(
mean female penislength
mean male peni
)
3
RPSI
×
100
.
3
(
sslength)
The mean of encountered imposex development stages (Figure 9.1) is the second index.
This Vas Deferens Sequence Index (VDSI) was proposed by Gibbs et al. (1987).
9.1.2.3 Do Any Other Factors Influence Imposex Development?
The RPS and VDS indices permit a specific estimation of TBT pollution only if no other
factors intervene with imposex development.
Analyses of museum samples revealed that imposex did not occur before TBT use (Bright
and Ellis 1990). The first evidence for imposex was reported by Griffith and Castagna (1962),
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