Talk:Pleurobranchaea
Review
The Genus Pleurobranchaea: In the second sentence (and later in the same paragraphs), the claim is made that notaspids may be ancestors to nudibranchs. I am unfamiliar with this hypothesis and the reference provided does not support the statement. The Kocot paper, and others, have stated that nudibranchs and notaspids are likely to be sister groups and share a common ancestor. This is very different than saying that one arose from the other.
The Genus Pleurobranchaea, 2nd paragraph: The word "mumble" is used to describe notaspids eating sponges, which seems a bit odd.
Lifestyle, 1st paragraph: It is stated that Pleurobranchaea is nocturnal and this is supported with laboratory studies. However, the cited paper looked at serotonin sulfate levels, not behavior or activity. It seems a stretch to make a claim that an animal is diurnally or nocturnally active based on circulating levels of a particular hormone.
Chemical Ecology, 1st paragraph: There is a preposition ("with"?) missing in the second sentence.
Reproduction, 2nd paragraph: Omit the "A" at the start of the paragraph.
Figure 4 is not very clear without revision or further explanation.
Locomotion, Escape..., 1st paragraph: CPG is defined as an abbreviation, even though it was defined earlier. Also, later in the paragraph, it is stated that As neuron connectivity/function is potentially homologous to trunk CPGs in annelids and chordates. Homology implies a common ancestor with such connectivity/function, which I find highly unlikely. I would suggest that it is much more likely that this is a case of convergent evolution.
Figure 8 is not referred to in the next and seems more appropriate for the text above in the foraging sections.
Review reply
Reviewer: The Genus Pleurobranchaea: In the second sentence (and later in the same paragraphs), the claim is made that notaspids may be ancestors to nudibranchs. I am unfamiliar with this hypothesis and the reference provided does not support the statement. The Kocot paper, and others, have stated that nudibranchs and notaspids are likely to be sister groups and share a common ancestor. This is very different than saying that one arose from the other.
Gillette: The hypothesis that notaspids were ancestors to nudibranchs is an old chestnut. An interesting discussion from 100 years ago is given by Evans (Evans, T.J. 1914. The anatomy of a new species of Bathydoris, and the affinities of the genus. Scottish National Antarctic Expedition. Trans. R. Soc. Edinb. 50: 191–209, plates 17 and 18). At the time, at least one taxonomist had derived all the nudibranchs from the pleurobranchids, with Tritonia as an intermediate link for its primitive characteristics. Over beers I would support that, but retreat somewhat here in the article.
The paragraph is rewritten to simply discuss the possibility of a pleurobranchoid (the term replacing “notaspid”) origin of the nudibranchs, without an immediate expected resolution since it is rather like asking whether the ancestor of the two chimpanzee species and humans was a chimpanzee. The speculation remains that the common ancestor of the nudibranchs might have been rather like existing species of Pleurobranchaea, the major genus of the subfamily Pleurobranchaeinae, rather than members of the subfamily Pleurobranchinae (Berthella, Pleurobranchus spp., etc.), based on loss of shell. Perhaps like the basal pleurobranchaeinid Pleurobranchella nicobarica.
The common ancestor would be expected to show the strong primitive character of a true side gill, like all the Pleurobranchoidea. It should also show other characters intermediate to the more primitive pleurobranchoids and the nudibranchs. For instance, loss of the internal shell. Thus, Pleurobranchaea spp. retain the primitive character of a true side gill but they lose the shell early in ontogeny like the nudibranchs. In contrast, the other pleurobranchoids, the subfamily Pleurobranchinae, retain a significant internal shell, a primitive character found in the most basal Pleurobranchoid (Martynov AV and Schrödl M (2009) The new Arctic side-gilled sea slug genus Boreoberthella (Gastropoda, Opisthobranchia): Pleurobranchoidean systematics and evolution revisited. Polar Biol (2009) 32:53–70). Thus, it is both parsimonious and heuristic to hypothesize that one or more Pleurobranchaea-like creatures split off from the ancestral pleurobranchoid line to eventually give rise to both the Pleurobranchaeinids and many of the nudibranchs. It will be greatly interesting to observe progress in this area that might test that, even in the absence of a fossil record.
Reviewer: The Genus Pleurobranchaea, 2nd paragraph: The word "mumble" is used to describe notaspids eating sponges, which seems a bit odd.
Gillette: “mumble”: “to mouth or chew clumsily” is an alternative and likely original use of this word.
Reviewer: Lifestyle, 1st paragraph: It is stated that Pleurobranchaea is nocturnal and this is supported with laboratory studies. However, the cited paper looked at serotonin sulfate levels, not behavior or activity. It seems a stretch to make a claim that an animal is diurnally or nocturnally active based on circulating levels of a particular hormone.
Gillette: I am embarrassed to have not remembered that the behavioral data were not included in that paper! I have changed the paragraph to rely solely on divers’ observations. Thanks.
Reviewer: Figure 4 is not very clear without revision or further explanation.
Gillette: I have added explanatory legend.
Reviewer: Locomotion, Escape..., 1st paragraph: CPG is defined as an abbreviation, even though it was defined earlier. Also, later in the paragraph, it is stated that As neuron connectivity/function is potentially homologous to trunk CPGs in annelids and chordates. Homology implies a common ancestor with such connectivity/function, which I find highly unlikely. I would suggest that it is much more likely that this is a case of convergent evolution.
Gillette: It was the A-cluster in general that I was speaking of, not just the As cells. Were I specifically addressing the serotonergic As cells, I would have mentioned the dorsal raphe nuclei of vertebrates, and drawn the parallels listed in: Evolution and Function in Serotonergic Systems, Integr Comp Biol 46(6):838-46, 2006.) Such homologies are not as far-fetched as once thought. See Nomaksteinsky et al. (BMC Biology 2013, 11:53I) and look at the Tosches and Arendt (2013) paper. I'd like to retain the suggestion, however wild-eyed, in terms of the question "Are there some deep homologies?".
Reviewer: Figure 8 is not referred to in the next [section] and seems more appropriate for the text above in the foraging sections.
Gillette: Sorry, the wrong version was inserted. I got rid of one figure and properly numbered the rest.
Gillette: One more notable change was in the discussion of taurine’s effect on acid secretion. I had forgotten that we did previously suggest why it worked so, and I have also added a neat supporting reference found recently. Thanks for your useful input!
