remains of nuclei from sloughed dead keratinocytes. It
stands to reason that a captive snake that is growing
rapidly and frequently shedding the outer layers of its
keratinised epithelium might accumulate plugs of
keratin in the lumina of the inverted hemipenes.
In conclusion, it seems that the plugs are neither
accumulated sperm, i.e. sperm plugs, nor hemipenal
casts as such, although the keratinous material may at
least be partially composed of the remains of hemipenal
exuviae. To me, the term ‘cast’ implies something that
retains the shape of the organ it sloughed off, not a
sticky substance capable of stretching like chewing
gum. Also, if they were hemipenal casts, one would
expect them to appear on each and every sloughed skin
throughout the snake’s life, and they should also be
present on sloughs from juvenile, immature males. That
is clearly not the case.
GTPs and OCCs.
Returning to the process of ontogenetic colour change
(OCC), this consists of permanent colour changes allied
to the normal, progressive development of individuals
of a species. This is typically associated with changes
in size, habitat, reproductive status and other factors,
and has been noted amongst a variety of organisms
including aquatic and terrestrial invertebrates, fish
(including the Nile Perch), birds and mammals, however
it is doubtful whether a more spectacular example exists
than the colour change exhibited by juvenile Green Tree
Pythons (Emerald Tree Boas also undergo a remarkably
Left: library of sloughs from the cloacal region of juve-
nile GTPs.
Below right: typical ‘plugs’ on male GTP slough.
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