When in Gambia in February of
this year (2010), I explored the beach several
times looking for washed-up cowries. I succeeded
in one spot only, just in front of a number of
large rocks, stretching over about a hundred meters
and most of the time being submerged, see picture.
I found a couple of dozens cowries, varying in
seize from 20 to 80 mm, amidst large numbers of
shells and fragments of bivalves.Otherwise there
was only sandy beach without any rocks at all.
As
there are no coral reefs on the Atlantic coast
of West Africa, the number of cowrie-species is
very limited, the actual number even being disputable.
Cypraea pyrum (17-52
mm) is primarely a Mediterranean species and occasionally
found down the West African coast as far as Namibia.
Smaller West African variations have been described
as C. senegalensis.
C. angolensis and C.
petitiana (Lorenz and Hubert, 1993),
but I fully agree with Burgess that these are
not valid species but mere variations.
A
second West African species is C.
zonaria (15-43 mm), with a range
from Senegal as far south as the Congo River.
The dorsum is green-brown with a zone of darker
brown across. Almost identical with this species
is C. gambiensis, and
is therefore not considered as a valid species
by most authors.
C.
picta resembles C. zonaria
as well, but may be differentiated by a more elongated
shape and its teeth which are more prominent in
C. zonaria. The species
occurs in the Cape Verde Islands, while C.
zonaria does not. Nevertheless,
there is no agreement to the question whether
or not this is a valid species or a variation
of C. zonaria.
Finally,
C. sanguinolenta is
probably another variation of C. zonaria.
It is the smallest form and more elongate in shape.
A
third distinct species is C. stercoraria
(25-97 mm), the biggest of the West African cowries
and variable in both seize and shape, but the
mottled green to brown dorsum resembles that of
no other cowrie. This is the species I found on
the Gambian coast, with specimens as big as 80
mm, leaving no doubt to the nature of the species,
see picture. Some specimens were heavy with markedly
produced lateral calluses, others were flat. The
range of the species is from Senegal to as far
south as the Congo River. Locally it occurs in
fair numbers.
Summarizing,
along the West African Atlantic coast only three
valid species of cowries can be found, C.
pyrum, C. zonaria and C.
stercoraria. All three species show
a lot of variation in both seize and shape and
for that reason two out of the three species has
been divided into other species which according
to most authors are no valid ones.
