There are some species of fish that can produce sounds by rubbing or grinding their bones together. These noises produced by bone-on-bone interactions are known as 'stridulatory sounds'. [66]

In terms of spermatogonia distribution, the structure of teleosts testes has two types: in the most common, spermatogonia occur all along the seminiferous tubules, while in atherinomorph fish they are confined to the distal portion of these structures. Fish can present cystic or semi-cystic spermatogenesis in relation to the release phase of germ cells in cysts to the seminiferous tubules lumen. [62] Vasil’eva, E.D., Solovyeva, E.N. & Vasil’ev, V.P. (2022): Molecular Phylogeny of the Spined Loach Genus Sabanejewia (Osteichthyes: Cobitidae) Revised. The newly hatched young of oviparous fish are called larvae. They are usually poorly formed, carry a large yolk sac (for nourishment), and are very different in appearance from juvenile and adult specimens. The larval period in oviparous fish is relatively short (usually only several weeks), and larvae rapidly grow and change appearance and structure (a process termed metamorphosis) to become juveniles. During this transition larvae must switch from their yolk sac to feeding on zooplankton prey, a process which depends on typically inadequate zooplankton density, starving many larvae. Bolshakova, Y.Y. & Evseenko, S.A. (2022): A Description of the Pelagic Juvenile of Pyramodon lindas (Ophidiiformes: Carapidae) from the Western Indian Ocean. Zorina, A.A. & Chernova, N.V. (2022): Morphological variability and diagnostics of two sculpins Icelus bicornis and I. spatula (Cottiformes: Cottidae) from the Arctic.Over 97% of all known fish are oviparous, [64] that is, the eggs develop outside the mother's body. Examples of oviparous fish include salmon, goldfish, cichlids, tuna, and eels. In the majority of these species, fertilisation takes place outside the mother's body, with the male and female fish shedding their gametes into the surrounding water. However, a few oviparous fish practice internal fertilization, with the male using some sort of intromittent organ to deliver sperm into the genital opening of the female, most notably the oviparous sharks, such as the horn shark, and oviparous rays, such as skates. In these cases, the male is equipped with a pair of modified pelvic fins known as claspers.

The position of hagfish in the phylum Chordata is not settled. Phylogenetic research in 1998 and 1999 supported the idea that the hagfish and the lampreys form a natural group, the Cyclostomata, that is a sister group of the Gnathostomata. [18] [19]Silva, M.A., Ottoni, F.P., Mattos, J.L.O., Indermaur, A., Katz, A.M.& Salzburger, W. (2022): Species diversity and phylogeography of the Australoheros autrani group (Teleostei, Cichlidae) in eastern Brazil. Zarei, F., Esmaeili, H.R., Schliewen, U.K. & Abbasi, K. (2021): Taxonomic diversity and distribution of the genus Proterorhinus (Teleostei: Gobiidae) in the Caucasus biodiversity hotspot with conservation implications. Diversity of various fishes including Sharks, Stingrays, Bony fishes, Jawless fishes, and Coelacanths.

Martínez, J.G., Rangel-Medrano, J.D., Yepes-Acevedo, A.J., Restrepo-Escobar, N. & Márquez, E.J. (in press): Species limits and introgression in Pimelodus from the Magdalena-Cauca River basin. Juvenile bichirs have external gills, a very primitive feature that they share with larval amphibians.Zhao, D., Guo, Y. & Gao, Y. (2022): Natural selection drives the evolution of mitogenomes in Acrossocheilus. Poungcharean, S. & Limpivadhana. D. (2022): Morphology of developing larvae and a dichotomous key for five bubble-nesting Betta species (Teleostei: Osphronemidae).

Parker, E., Dornburg, A., Struthers, C.D., Jones, C.D. & Near, T.J. (2021): Phylogenomic Species Delimitation Dramatically Reduces Species Diversity in an Antarctic Adaptive Radiation. Gabbanelli, V., Naylor, G., Weigmann, S., Yang, L., Vazquez, D.M., Last, P., de Astarloa, J.M.D. & Mabragaña, E. (2022): Morphological and molecular evidence reveals the longnose skate Zearaja brevicaudata (Marini, 1933) to be a senior synonym of Dipturus lamillai Concha, Caira, Ebert & Pompert 2019.Torres-Hernández, E., Betancourt-Resendes, I., Solís-Guzmán, M.G., Robertson, D.R., Angulo, A., Martínez-Gómez, J.E., Espinoza, E. & Domínguez-Domínguez, O. (2022): Phylogeography and evolutionary history of the Panamic Clingfish Gobiesox adustus in the Tropical Eastern Pacific. Taxonomy Leedsichthys, of the subclass Actinopterygii, is the largest known fish, with estimates in 2005 putting its maximum size at 16 metres (52ft). Briñoccoli, Y.F., Bogan, S., Arcila, D., Rosso, J.J., Mabragaña, E., Delpiani, S.M., Díaz de Astarloa, J.M. & Cardoso, Y.P. (2022): Molecular and morphological evidence revalidates Acrobrycon tarijae (Characiformes, Characidae) and shows hidden diversity. Jegede, O.I. (2022): Karyotype of a Nigerian population of Hyperopisus bebe (Osteoglossiformes: Mormyridae) revealed another evolutionary lineage in the monospecific genus: Hyperopisus.