July, 1999 
SCAMIT Newsletter 
Vol. 18, No. 3 
initially, and give evidence of their con- 
specificity. Starved individuals which had 
previously spawned exclusively or primarily 
lecithotrophic larvae switched to production of 
planktotrophic larvae after a period of only 3 
days without food. Adults producing both types 
of larvae were gene sequenced, and showed the 
same level of heterogeneity at cytochrome c 
oxidase I sites observed in other marine 
invertebrate species, virtually ruling out the 
possibility that cryptic sibling species are 
involved. This appears to be another verified 
case of poecilogony. 
The assumption is always made that planktonic 
larvae are intended to, and do, provide wide 
dispersal of a population. This was tested by 
Todd et al (1998) who examined two co¬ 
occurring intertidal nudibranch species, one 
with planktotrophic (Goniodoris nodosa ) and 
one with pelagic lecithotrophic larvae 
(Adalaria proximo). Larvae of the former can 
persist in the plankton for up to 3 months, 
while those of Adalaria can delay 
metamorphosis for only a few weeks and 
generally settle after only a day or two. A series 
of populations within the region were tested for 
genetic heterogeneity to quantify gene 
exchange in each species. Populations of 
Goniodoris examined came from an order of 
magnitude larger area than did those of 
Adalaria. Despite this the Goniodoris 
populations were not significantly 
differentiated genetically. Those of Adalaria , 
however, showed very significant 
differentiation. The authors conclude that in 
species with pelagic larvae, larval behavior can 
significantly change the dispersal potential of 
any spawning event. This can render any 
extrapolations of dispersal ability based on 
laboratory larval rearing experiments suspect, a 
possibility not considered in the past. 
Just how wide is ‘wide’ anyway? Many species 
are characterized as having cosmopolitan, 
tropicopolitan, circum-subtropical, or circum- 
temperate distributions. Such claims have been 
viewed as increasingly suspect by many and 
have contributed to the on-going lumper vs. 
splitter debacle. While man’s influence has 
certainly enabled many species to expand their 
ranges by overcoming geographic barriers, 
there are many cases where human aided 
transport seems unlikely or impossible. Boury- 
Esnault et al (1999) provide another recent 
example of the rejection of broad distribution 
on close examination, in this case with 
supposedly conspecific sponge populations 
from the Atlantic and Pacific coasts of Panama. 
They found the two very distinct on 
morphological, cytological and genetic 
grounds. Neither was conspecific with the 
animal they were initially identified as, both 
being new species. The addition of genetic 
examination in the form of enzyme 
polymorphism or actual gene sequencing has 
added significant new tools to the taxonomic 
arsenal which allow objective rating of the 
relatedness of any two given examples. “Oh, 
they’re just variants” becomes a testable 
hypothesis, and the lumper vs. splitter debate 
becomes, at least locally, resolvable. 
A similar result was obtained when specimens 
from widely separated populations of a 
supposedly cosmopolitan interstitial polychaete 
were examined by Schmidt and Westheide 
(1999). Along the way they were able to 
demonstrate that a related fresh-water species 
(Hesionides riegerorum ) was most closely 
related genetically to the proximal geographic 
form. Based on their analyses several new taxa 
should be erected from Hesionides gohari, but 
the authors do not do so in the present paper. 
Variations of feeding rates are often reported to 
be related to concentration of available food, or 
temperature, but not usually to population 
density. In cases of resource limitation feeding 
rates are limited by competitive interactions, 
although such interactions are usually manifest 
in changed feeding efficiency rather than rate 
changes. Wheatcroft et al (1998) tested 
deposit-feeding rates in the polychaete 
Mediomastus ambiseta at different population 
densities and found that worms fed about an 
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