October, 1999 
SCAMIT Newsletter 
Vol. 18, No.6 
evolution of larval forms within the group, and 
suggest that the auricularia larva has evolved 
more than once. The symmetry of the title (bi- 
penta-bi-decaradial) is actually the 
evolutionary “track” taken by one group, the 
Rhopalodinidae. These animals have a 
decaradial symmetry derived from a biradial 
precursor, which in turn was derived from the 
typical pentaradial symmetry of the phylum. 
The phylum symmetry was derived from a 
bilateral base. This pathway yields a symmetry 
history of biradial, pentaradial, biradial, and 
lastly decaradial for this highly modified 
holothurian group. 
On a smaller scale Heupel and Bennett (1999) 
discuss the association of the praniza larvae of 
gnathiid isopods with sharks. Although the 
adults of these isopods are free-living in the 
benthos, the larvae are fish parasites. The 
individual parasites could be found at a variety 
of locations on the host (in this case the 
epaulette shark, HemiscyIlium ocellatum ), but 
most were found attached to the gill filaments. 
It is not currently known if any of our local 
Gnathia species are associated with particular 
fish hosts, or which hosts are involved. 
In recent years the impacts of trawling 
activities, particularly those of the large 
commercial trawling operations, have been 
increasingly recognized. With trawl sampling a 
standard part of NPDES monitoring for larger 
agencies, one must also wonder about the 
effects of the trawling associated with 
monitoring studies. While Prena et al (1999) 
used a large gear rather than the smaller otter 
trawl used locally, their experimental data can 
also shed light on our situation. They did report 
impacts of trawling on the epifauna. Thick 
shelled mollusks were the least damaged of the 
considered taxa, with crustaceans sustaining 
intermediate levels of damage, and relatively 
exposed and slow moving echinoderms the 
most affected. Biomass within experimentally 
trawled areas was about 25% less than that in 
reference areas upon re-trawl. 
Samples taken in Bight ‘98 from around the 
northern Channel Islands were frequently 
found to consist primarily of biogenic 
sediments. These bottoms have, in addition to 
some fine particles, large amounts of bryozoan 
debris, foraminiferal tests, barnacle plate 
fragments, mollusk shell fragments, 
echinoderm spine and test fragments, and other 
calcareous constituents. These bottoms are in 
many respects analogous to coral/coralline 
algal sediments in more tropical areas. Santa- 
Isabel et al (1998) report on the polychaetes of 
such a biogenic sand bottom off Brazil, and 
provide data with which Bight’98 biogenic 
sand samples can be compared. 
Ballast water transport of NIS (non-indigenous 
species) between widely separated areas in 
different parts of the world ocean is now well 
documented. After introduction into a new 
potential range, however, a successful invader 
needs to expand it’s initial beachhead. Lavoie 
et al (1999) discuss this aspect of species 
introductions, emphasizing the role that ballast 
water continues to play in dispersal of 
introduced species along a continental coast¬ 
line. 
While becoming established, an invading 
species can manifest impacts on existing 
populations as it elbows its way into the local 
ecosystem. Crooks and Khim (1999) 
experimentally investigate the nature of the 
impact of the introduced mytilid clam 
Musculista senhousia on the community it has 
invaded. Since Musculista is a nest building 
clam living in aggregations, it can have a 
profound effect on associated organisms just in 
it’s physical habitat modification. It also has 
the potential of biologically modifying the 
habitat by its activities of respiration, filtration, 
particle fixation (as mucous bound fecal 
strings), and larval predation. By using 
artificial mats simulating the physical 
disturbance of a Musculista surface nest 
aggregation, the authors teased out the physical 
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