Sexing mollusks by DNA


Larval Mass
Hello. According to an article in Science News (Mar 7, 2004?):

Mammals with an XX set of chromosomes become female. Those with XY become male. The Y chromosome is much smaller than the X.

Birds with a ZZ set of chromosomes become male. Those with ZW become female. The W chromosome is much smaller than the Z.

My question:

Which chromosomes determine sex in a mollusk? Is it simple to see, as in birds and mammals, or does it depend on individual genes on one or several chromosomes? Is there a general rule for all mollusks, or do different species sex out differently?

Thank you. Mark Wood, Nanakuli, Hawaii.

Steve O'Shea

Colossal Squid
Mark, I feel terrible that I've not been able to respond to this query to date. I've been a little distracted at work of late.

I do have papers on cephalopod karyotypes, but I cannot remember who wrote them (and my literature colelction is organised by author, alphabetically, and is quite large). I searched today for the references in the most obvious places, but did not find them. I also spent an inordinate amount of time searching the web for phrases like 'karyotype Cephalopoda', 'karyotype squid', 'karyotype octopus', and did the same through the majority of electronic journals that I have access too, also searching cephbase. In each search I turned up zip.

I can see how frustrating this might be for you. There are papers on this subject matter, I know for sure, 100%; what I'll have to do is start at A and work my way to Z, and will do so this weekend to locate them; when I do I'll be able to post something online for you.

In the event anyone else finds something in the interim, please post away.


Colossal Squid
Hi I'm in the same boat as Steve, I have squid genetics papers but........!

I will have a hunt when I get some time :lol:

One thing I do know from bitter experience that squid DNA can be immensely difficult to extract. The tissues contain large quantities of mucopolysaccharides (slime!) which can inhibit precipitation of DNA :evil:

I believe a Russian (I think) researcher called Sokolov has gone some way to immproving this situation!



O. vulgaris

Yes, Sokolov wrote a paper called "An improved method for DNA isolation from mucopolysaccharide-rich molluscan tissues" (J. Moll. Stud. (2000), 66, 573-575). He didn't use Cephs for his study though... He used Polyplacophora, Gastropoda and Bivalvia...
Another paper concerning DNA-Extraction from molluscan tissue is Winnepenninckx et al. "Extraction of high molecular weight DNA from molluscs" (Trends Genet. 1993 Dec;9(12):407.)...
Octopus DNA was successfully extracted with the Chelex-Method (see "Sequence divergence of mitochondrial DNA indicates cryptic biodiversity in Octopus vulgaris and supports the taxonomic distinctiveness of Octopus mimus Cephalopoda; Octopodidae", Marine Biology (2000) 136: 29-35).

I am currently working with Sepia DNA (actually I am just starting) and I use the QiaGen Tissue Kit for DNA-Extraction... It seems to work well so far...


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