Editing Catfish (section)

===Internal anatomy===
{{Multiple image
| image1            = Blue catfish skeleton.jpg
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| caption1          = Blue catfish (''[[Blue catfish|Ictalurus furcatus]])'' skeleton, [[Museum of Osteology]]
| image2            = Kryptopterus 2.jpg
| caption2          = The internal organs of [[glass catfish]] (such as ''[[Kryptopterus vitreolus]]'') are visible through their transparent bodies
| align             = left
}}

In many catfish, the "humeral process" is a bony process extending backward from the [[pectoral girdle]] immediately above the base of the pectoral fin. It lies beneath the skin, where its outline may be determined by dissecting the skin or probing with a needle.<ref>{{cite web|url=http://filaman.ifm-geomar.de/Glossary/Glossary.cfm?TermEnglish=humeral%20process|archive-url=https://web.archive.org/web/20071217212539/http://filaman.ifm-geomar.de/Glossary/Glossary.cfm?TermEnglish=humeral%20process|archive-date=17 December 2007|title=Term : humeral process|publisher=[[FishBase]]|year=2007}}</ref>

The [[retina]]e of catfish are composed of single [[cone cell|cone]]s and large [[rod cell|rod]]s. Many catfish have a [[tapetum lucidum]], which may help enhance [[photon]] capture and increase low-light sensitivity. [[Double cone (biology)|Double cone]]s, though present in most [[teleost]]s, are absent from catfish.<ref name="Douglas">{{cite journal|last=Douglas|first=Ron H.|author2=Collin, Shaun P.|author3=Corrigan, Julie|date=15 November 2002|url=http://jeb.biologists.org/cgi/reprint/205/22/3425|title=The eyes of suckermouth armoured catfish (Loricariidae, subfamily Hypostomus): pupil response, lenticular longitudinal spherical aberration and retinal topography|publisher=The Journal of Experimental Biology|volume=205|issue=22|pages=3425–3433|journal=Journal of Experimental Biology|doi=10.1242/jeb.205.22.3425|pmid=12364396|bibcode=2002JExpB.205.3425D |access-date=9 June 2007|archive-date=30 September 2007|archive-url=https://web.archive.org/web/20070930044830/http://jeb.biologists.org/cgi/reprint/205/22/3425|url-status=live}}</ref>

====Sexual characters====
[[Sexual dimorphism]] is reported in about half of all families of catfish.<ref>{{cite journal|url=http://www.mapress.com/zootaxa/2006f/zt01125p056.pdf |archive-url=https://web.archive.org/web/20061031234339/http://www.mapress.com/zootaxa/2006f/zt01125p056.pdf |archive-date=2006-10-31 |url-status=live|title=''Synodontis acanthoperca'', a new species from the Ogôoué River system, Gabon with comments on spiny ornamentation and sexual dimorphism in mochokid catfishes (Siluriformes: Mochokidae)|first=John P.|last=Friel|author2=Vigliotta, Thomas R.|journal=[[Zootaxa]]|volume=1125|pages=45–56|year=2006|access-date=22 June 2009|doi=10.11646/zootaxa.1125.1.3}}</ref> The modification of the [[anal fin]] into an [[penis|intromittent organ]] (in internal fertilizers) as well as accessory structures of the reproductive apparatus (in both internal and external fertilizers) have been described in species belonging to 11 different families.<ref name="Mazzoldi">{{cite journal|title=Variation of male reproductive apparatus in relation to fertilization modalities in the catfish families Auchenipteridae and Callichthyidae (Teleostei: Siluriformes)|first=C.|last=Mazzoldi|author2=Lorenzi, V. |author3=Rasotto, M. B. |journal=Journal of Fish Biology|year=2007|volume=70|issue=1 |pages=243–256|doi=10.1111/j.1095-8649.2006.01300.x|bibcode=2007JFBio..70..243M }}</ref>

The anatomical organization of the [[testicle|testis]] in catfish is variable among the families of catfish, but the majority of them present fringed testis: Ictaluridae, Claridae, Auchenipteridae, Doradidae, Pimelodidae, and Pseudopimelodidae.<ref name="Barros"/> In the testes of some species of Siluriformes, organs and structures such as a spermatogenic cranial region and a secretory caudal region are observed, in addition to the presence of seminal vesicles in the caudal region.<ref name="Brito"/> The total number of fringes and their length are different in the [[Caudal (anatomical term)|caudal]] and [[cranial]] portions between species.<ref name="Barros">{{cite journal|title=Reproductive apparatus and gametogenesis of ''Lophiosilurus alexandri'' Steindachner (Pisces, Teleostei, Siluriformes)|first=Marcelo D. M.|last=Barros|author2=Guimarães-Cruz, Rodrigo J. |author3=Veloso-Júnior, Vanderlei C. |author4= Santos, José E. dos |journal=Revista Brasileira de Zoologia|volume=24|issue=1|pages=213–221|year=2007|doi=10.1590/S0101-81752007000100028|doi-access=free}}</ref> Fringes of the caudal region may present tubules, in which the lumen is filled by secretion and [[Spermatozoon|spermatozoa]].<ref name="Barros"/> Spermatocysts are formed from cytoplasmic extensions of [[Sertoli cell]]s; the release of spermatozoa is allowed by breaking of the cyst walls.<ref name="Barros"/>

The occurrence of [[seminal vesicle]]s, in spite of their interspecific variability in size, gross morphology, and function, has not been related to the mode of fertilization. They are typically paired, multichambered, and connected with the [[sperm duct]], and have been reported to play glandular and storage functions. Seminal vesicle secretion may include [[steroid]]s and steroid [[glucuronide]]s, with [[Hormone|hormonal]] and [[Pheromone|pheromonal]] functions, but it appears to be primarily constituted of [[mucoprotein]]s, acid [[mucopolysaccharide]]s, and [[phospholipid]]s.<ref name="Mazzoldi"/>

Fish [[Ovary|ovaries]] may be of two types - gymnovarian or cystovarian. In the first type, the [[oocyte]]s are released directly into the [[coelom]]ic cavity and then eliminated (released outside the body). In the second type, the oocytes are conveyed to the exterior through the [[oviduct]].<ref name="Brito"/> Many catfish are cystovarian in type, including ''[[Pseudoplatystoma corruscans]]'', ''[[Pseudoplatystoma fasciatum|P. fasciatum]]'', ''[[Lophiosilurus alexandri]]'', and ''[[Loricaria lentiginosa]]''.<ref name="Barros"/><ref name="Brito">{{cite journal|title=Reproduction of the surubim catfish (Pisces, Pimelodidae) in the São Francisco River, Pirapora Region, Minas Gerais, Brazil|last=Brito|first=M.F.G.|author2=Bazzoli, N.|journal=Arquivo Brasileiro de Medicina Veterinária e Zootecnia|volume=55|issue=5|year=2003|doi=10.1590/S0102-09352003000500018|page=624|doi-access=free}}</ref>