December, 1999 
SCAMIT Newsletter 
Vol. 18, No. 8 
Current. The current which flows through the 
Strait of Florida between the Florida mainland 
and keys and adjacent areas of the Bahamas is 
quite strong, and continuously flowing. 
Although the geographic separation across the 
Strait is not large, the zoogeographic separation 
is considerable. Teleplanic larvae spawned on 
one side of this current are not likely to make it 
to the other side. The authors allozyme results 
suggest that this may be the case with 
populations of “A. misakianum” on opposing 
sides of the current. Their data supports the 
suggestion that this species is actually a 
complex of cryptospecies which are (as yet) 
morphologically indistinguishable as adults. 
Existence of cryptic species which form an 
Apionsoma misakianum complex in the 
western tropical Atlantic cast doubt on the 
identity of A. misakianum populations 
elsewhere in the world, including our own. 
Further investigations of separated populations 
elsewhere, especially those where the rather 
uninformative adult morphology is combined 
with DNA and further allozyme analyses, are 
needed to test for crypto-species in other 
oceans. Stay tuned. 
The reliability of traditionally used 
morphological characters has come under 
increasingly close examination of late. Case in 
point is the radula of gastropod mollusks. 
Several studies have suggested that this 
structure, whose characteristic tooth shapes and 
numbers have been the basis of erection of 
many taxa, is subject to ecophenotypic 
variation. Reid & Mak (1999) found this to be 
true in species of the genus Littoraria, where 
substrate on which individuals were collected 
strongly influenced some aspects of the radular 
teeth. Different substrate forms of radulae were 
found within a number of species, further 
substantiating the ecophenotypic plasticity of 
the structure in question. 
The recent trend in mollusk taxonomy is to rely 
less on hard parts (shell and radula) and more 
on the organization of soft tissues in definition 
of species and higher taxa. The original 
dependence on shell characters developed in 
large part from the lack of soft tissues in most 
mollusks brought back during the major 
explorations of the last two centuries. There 
was no alternative to study of just the shell. 
Then researchers began to extract radulae from 
dried animals still in live collected shells. 
These were assumed to vary little within a 
species, an assumption that usually went 
untested. It is only recently that the study of 
preserved animals has called into question the 
reliability of hard parts (shells, jaws, and 
radula) as defining characters of mollusk taxa. 
Studies such as the present one show that 
increasing emphasis on whole animal rather 
than just hard structure characters is not just 
desirable, but necessary. 
Passamonti et al (1999) used allozyme analysis 
on a number of Mediterranean venerid clams in 
a preliminary assessment of the systematics of 
the family. They found the current arrangement 
of genera based on morphology of the shell is 
very likely incorrect. Once again 
environmental influences have led to 
significant amounts of convergence in shell 
shape and ornamentation among species whose 
chemotaxonomy suggests they are only 
distantly related. The present allozyme results 
are in substantial agreement to earlier 
examinations using 16s ribosomal DNA or 
satellite DNA. Further examination of a 
broader range of taxa within the family should 
provide a good basis for a reassessment of the 
systematics of the group, and refinement of the 
existing morphology based classification. 
A phylogenetic analysis of the gastropod 
mollusk family Columbellidae (de Maintenon, 
1999) 
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