An interesting mutation of Mauritia histrio
Within particular populations
of Mauritia histrio from the East African coast, an occasional specimen
with a black blotch on the base occurs. Recently, a population with
shells predominatly blotched has been discovered in the south of
Dar-es-Salaam, Tanzania. It is provisionally named
Mauritia histrio var. maculabasis
In the widespread and highly
diverse M. maculifera from the Pacific, a basal blotch is a
characterizing feature. It is absent only in rare exceptions. To see
this feature in occasional M. histrio from the Indian Ocean reveals
that within the genetic variability of that species, a basal blotch may
or may not be found. It also suggests that a common ancestor of M.
maculifera and M. histrio was originally blotched, but the feature got
reduced in M. histrio from the Indian Ocean whereas it is retained in
M. maculifera in the Pacific. The shells of the population here called
M. histrio f. maculabasis all show darker than usual pigmentation of
the base, and all of them have some sort of black blotching. In some
cases, it is quite extreme, more so than in M. maculifera. The marginal
spotting is also remarkable, as it cosists of black spots on dark
violet-grey background, as in M. maculifera and unlike other M. histrio
from other places in Tanzania.
 Fig. 1: Mauritia histrio f. maculabasis Please note that the name maculabasis is not available as an official name in publications, and I have forgotten to list it in G3. |