Freethought & Rationalism Archive

Oolon Colluphid · 07-29-2003, 01:16 AM

Here I go again...

Browsing this time (not on the loo though

) through Eckert Animal Physiology, I see that certain parasitic barnacles (Cirripedia) are so derived that they lack a gut. Well, I bet they do have one, then lose it... I don�t suppose anyone has further details, links, pics or anything, please...?

Cheers, Oolon

Wounded King · 07-29-2003, 02:41 AM

There doesn't seem to be any specific work on the gut development of Cirripedia. There has been some on segmentation in the cyprid larvae however. They appear to lack the Abdominal A hox gene which may be one reason why the adult lacks an abdomenal section and have some caudal expression, but not in the vestigial abdomen where you might expect to see it.

Quote:

Nicolas Rabet, Jean-Michel Gibert, �ric Qu�innec, Jean S. Deutsch, Emmanu�le Mouchel-Vielh

The caudal gene of the barnacle Sacculina carcini is not expressed in its vestigial abdomen.

Dev Genes Evol (2001) 211:172�178

We report the characterization of a caudal gene from the rhizocephalan cirripede Sacculina carcini and its embryonic and larval expression patterns. Cirripedes are maxillopodan crustaceans that are devoid of any complete abdominal segment at the adult stage. We currently explore the genetic basis of this peculiar body plan. In a previous study we have shown that they probably lack the abdominalA gene, while possessing the other Hox genes shared by arthropods. However, at least a part of the genetic program might be conserved, since the engrailed.a and engrailed.b genes are expressed in a posterior region that we interpret as a relic of an ancestral abdomen. Here we show first that the Sacculina caudal gene is expressed early in embryogenesis, which makes it the earliest genetic marker evidenced in the development of Sacculina and of any other crustacean species. It is expressed later in the embryo in the caudal papilla, a posterior proliferating zone of cells. During the larval stages, the caudal gene is first expressed in the whole thoracic region; then its expression regresses to the posterior end of the larva. Surprisingly, it is never expressed in the vestigial abdomen. This lack of expression of the Sacculina caudal gene in a posterior region, at odds with what is known in all other studied metazoan species, might be correlated with the defective development of the abdomen.

07-31-2003, 09:50 PM

Everytiem I hear the term *parasite*, it brings back gruesome images from parasitiology in the *book of horrors*.

Oolon Colluphid what were you trying to show in your post?

Max

Wounded King · 08-01-2003, 06:03 AM

Oolon's probably looking for another item to add to his list of sub-optimal designs, which he uses to beat creationists and ID proponents over the head.

MrDarwin · 08-01-2003, 06:37 AM

Even the most derived, morphologically modified barnacles, e.g., Sacculina, go through the nauplius larval stage typical of most crustaceans, so I imagine it would at least start out with a gut (unless it doesn't feed as a larva, in which case a gut would be really, really superflous).

Wounded King · 08-01-2003, 07:30 AM

Good point the nauplius stage is feeding, the cyprid stage is not.

Coragyps · 08-01-2003, 08:59 AM

For the rest of us who don't know a Sacculina from a sack of potato chips: Link. Happy nightmares.

07-29-2003, 01:16 AM	#1
Oolon Colluphid Contributor Join Date: Sep 2000 Location: Alibi: ego ipse hinc extermino Posts: 12,591	Parasitic barnacles help please! Here I go again... Browsing this time (not on the loo though ) through Eckert Animal Physiology, I see that certain parasitic barnacles (Cirripedia) are so derived that they lack a gut. Well, I bet they do have one, then lose it... I don�t suppose anyone has further details, links, pics or anything, please...? Cheers, Oolon

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07-31-2003, 09:50 PM	#3
YHWHtruth Guest Posts: n/a	Everytiem I hear the term parasite, it brings back gruesome images from parasitiology in the book of horrors. Oolon Colluphid what were you trying to show in your post? Max

08-01-2003, 06:03 AM	#4
Wounded King Veteran Member Join Date: Mar 2003 Location: Edinburgh Posts: 1,211	Oolon's probably looking for another item to add to his list of sub-optimal designs, which he uses to beat creationists and ID proponents over the head.

08-01-2003, 06:37 AM	#5
MrDarwin Veteran Member Join Date: May 2001 Location: Washington, DC Posts: 4,140	Even the most derived, morphologically modified barnacles, e.g., Sacculina, go through the nauplius larval stage typical of most crustaceans, so I imagine it would at least start out with a gut (unless it doesn't feed as a larva, in which case a gut would be really, really superflous).

08-01-2003, 07:30 AM	#6
Wounded King Veteran Member Join Date: Mar 2003 Location: Edinburgh Posts: 1,211	Good point the nauplius stage is feeding, the cyprid stage is not.

08-01-2003, 08:59 AM	#7
Coragyps Veteran Join Date: Aug 2001 Location: Snyder,Texas,USA Posts: 4,411	For the rest of us who don't know a Sacculina from a sack of potato chips: Link. Happy nightmares.

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