small and large intestine in ray-finned fishes

[marcrr]

In our similarity annotations, small and large intestine are annotated as homologous among tetrapodes; but ray finned fish have small and large intestine according to wikipedia (https://en.wikipedia.org/wiki/Fish_anatomy#Intestines), and we have small intestine (UBERON:0002108) data in Bgee for zebrafish. In ZFIN there is a link to this paper: https://doi.org/10.1016/j.mod.2004.10.009 but it doesn’t discuss homology. In this zebrafish anatomy paper http://journals.sagepub.com/doi/abs/10.1177/0192623311409597 (which is worth reading in general @ANiknejad) they note "No stomach, small intestine, or large intestine can be distinguished" But in this medaka paper http://dev.biologists.org/content/143/19/3470 they distinguish a small and a large intestine, using molecular markers from tetrapods. I've also seen the terms "anterior" and "posterior" intestines, e.g. https://doi.org/10.1111/raq.12010. It would be good to clarify the divisions of the intestine in ray-finned fishes, and their relations with known anatomy in amniotes.

[ANiknejad]

GIT (gastro-intestinal-tract) it is a tricky field, indeed, and yes, specially in Actinopterygians.

https://www.ncbi.nlm.nih.gov/pubmed/?term=26732746

"Whereas GIT diversity of derived actinopterygians (teleosts) is well documented, this is not the case for the non-teleostean actinopterygians, which are represented in the modern fauna by a few depauperate lineages: bichirs and reedfish (two genera and 16 species), sturgeons and paddlefishes (five genera and 27 species), gars (two genera and seven species) and the bowfin (one species)4. These taxa exhibit plesiomorphic GIT morphologies, including the presence of a spiral valve in the posterior part of the intestine (also known as the spiral or valvular intestine) that are reminiscent of those seen in living chondrichthyans and differ from those of teleosts2,3,6."

Actinopterygii (ray-finned fishes)

[Term] id: UBERON:0010016 name: spiral valve of intestine namespace: uberon def: "Coiled structure in the lumen of the small intestine that increases the length of the route through the digestive tract.[WP,cjm,Kardong]" [http://en.wikipedia.org/wiki/Spiral_valve] synonym: "intestinal spiral valve" EXACT [] synonym: "spiral valve" BROAD [] xref: Spiral:valve is_a: UBERON:0003978 {source="cjm"} ! valve is_a: UBERON:0035118 ! material entity in digestive tract relationship: only_in_taxon NCBITaxon:7742 ! Vertebrata relationship: part_of UBERON:0002108 ! small intestine

"A spiral or scroll valve in the posterior part of the intestine is a plesiomorphic feature shared amongst chondrichthyans (including most “†acanthodians”), non-teleostean actinopterygians, non-tetrapod sarcopterygians (including extant lungfishes that possess a spiral valve and extant coelacanths that possess a scroll valve) and likely “†placoderms”8. The presence of a scroll valve has also been suggested for some early Paleozoic jawless vertebrates9,10 whereas modern lampreys, but not hagfishes, also exhibit a reduced spiral valve3,6. The spiral valve is clearly a character that appeared very early in the evolution of vertebrates."

[ANiknejad]

"Zebrafish intestinal morphology is highly homologues to that of higher vertebrates."

https://www.sciencedirect.com/science/article/pii/S0145305X1630057X

Morphological and molecular evidence for functional organization along the rostrocaudal axis of the adult zebrafish intestine. "The intestinal tract does not display the anatomical, morphological, and molecular signatures of a stomach and thus we conclude that this organ is absent from the zebrafish digestive system."

https://www.ncbi.nlm.nih.gov/pubmed/20565988

[ANiknejad]

one lineage that diverged early in the evolutionary history of Actinopterygii (ray-finned fishes) - the family Polypteridae. Commonly known as "bichirs", this clade includes 12 extant described species (as well as multiple subspecies) that inhabit freshwater rivers and lakes of tropical Africa [10]. Little is known about polypterid evolution primarily because of their long history of phylogenetic and taxonomic confusion, likely owing to their unique collection of "primitive" (e.g., ganoid scales, cartilaginous skeleton, the intestine with a spiral valve) and derived (e.g., highly modified dorsal fins, pectoral fins with lobed base covered with scales, possession of only four gill arches) anatomical features [11, 12, 13]. However, recent morphological and molecular analyses have determined that bichirs are a basal lineage of Actinopterygii (ray-finned fishes; Fig. 1) [14, 15, 16, 17, 18, 19].

https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-10-21