a b c d e f Farrell, Anthony P, ed. (1 June 2011). Encyclopedia of Fish Physiology: From Genome to Environment. Stevens, E Don; Cech Jr., Joseph J; Richards, Jeffrey G. Academic Press. p.2315. ISBN 978-0-08-092323-9. Archived from the original on 6 December 2016 . Retrieved 13 March 2016.

To identify fish species, their tail shape is a key trait. Sharks and rays have heterocercal tails, where the upper lobe is larger than the lower lobe. Whereas, bony fish have homocercal tails with equal-sized lobes. Research published in 2014 indicates that the adipose fin has evolved repeatedly in separate lineages. [8] Fish tails have different shapes, sizes, and structures. Recognizing these shapes helps us identify fish species and understand their environment, behavior, and biology. Here are some common tail shapes: The AquaPenguin, developed by Festo of Germany, copies the streamlined shape and propulsion by front flippers of penguins. [95] [96] Festo also developed AquaRay, [97] AquaJelly [98] and AiraCuda, [99] respectively emulating the locomotion of manta rays, jellyfish and barracuda.Prosser, C. Ladd (18 March 1991). "Introduction: Definition of Comparative Physiology: Theory of Adaptation". In Prosser, C. Ladd (ed.). Environmental and metabolic animal physiology. New York: Wiley-Liss. pp.1–2. ISBN 0-471-85767-X. OCLC 22906165. Archived from the original on 3 July 2021 . Retrieved 3 July 2021. Michael, Bright. "Jaws: The Natural History of Sharks". Columbia University. Archived from the original on 24 December 2011 . Retrieved 29 August 2009. This section will explore how to identify fish species by their distinctive tail shape characteristics, including those with homocercal, heterocercal, rounded, forked, and lanceolate tail shapes. Understanding these nuances will equip anglers and fish enthusiasts with the knowledge to distinguish different species of fish by their tail shapes. Ichthyosaurs are ancient reptiles that resembled dolphins. They first appeared about 245million years ago and disappeared about 90million years ago.

N. A. Campbell and J. B. Reece (2005). Biology, Seventh Edition. Benjamin Cummings, San Francisco, California.

How to Obtain Fish Tails

Certain rays of the pectoral fins may be adapted into finger-like projections, such as in sea robins and flying gurnards Andreev, Plamen S.; Sansom, Ivan J.; Li, Qiang; Zhao, Wenjin; Wang, Jianhua; Wang, Chun-Chieh; Peng, Lijian; Jia, Liantao; Qiao, Tuo; Zhu, Min (September 2022). "Spiny chondrichthyan from the lower Silurian of South China". Nature. 609 (7929): 969–974. Bibcode: 2022Natur.609..969A. doi: 10.1038/s41586-022-05233-8. ISSN 1476-4687. PMID 36171377. S2CID 252570103. B) - Protocercal means the vertebrae extend to the tip of the tail and the tail is symmetrical but not expanded (as in the first fishes and the cyclostomes, and a more primitive precursor in lancelets)

a b c d e Ostrander, Gary Kent (2000). The Laboratory Fish. Elsevier. pp.154–155. ISBN 978-0-12-529650-2. Archived from the original on 6 December 2016 . Retrieved 13 March 2016. The first mammals appeared during the Permian period (between 298.9 and 252.17million years ago). Several groups of these mammals started returning to the sea, including the cetaceans (whales, dolphins and porpoises). Recent DNA analysis suggests that cetaceans evolved from within the even-toed ungulates, and that they share a common ancestor with the hippopotamus. [81] [82] About 23million years ago another group of bearlike land mammals started returning to the sea. These were the seals. [83] What had become walking limbs in cetaceans and seals evolved independently into new forms of swimming fins. The forelimbs became flippers, while the hindlimbs were either lost (cetaceans) or also modified into flipper (pinnipeds). In cetaceans, the tail gained two fins at the end, called a fluke. [84] Fish tails are usually vertical and move from side to side. Cetacean flukes are horizontal and move up and down, because cetacean spines bend the same way as in other mammals. [85] [86] Similar adaptations for fully aquatic lifestyle are found both in dolphins and ichthyosaurs. Stein PSG (1999). Neurons, Networks, and Motor Behavior. MIT Press. pp.38–44. ISBN 978-0-262-69227-4. Under a tough membranous shell, the tunica albuginea, the testis of some teleost fish, contains very fine coiled tubes called seminiferous tubules. The tubules are lined with a layer of cells ( germ cells) that from puberty into old age, develop into sperm cells (also known as spermatozoa or male gametes). The developing sperm travel through the seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly created sperm cells mature (see spermatogenesis). The sperm move into the vas deferens, and are eventually expelled through the urethra and out of the urethral orifice through muscular contractions.

1. Crescent or Rounded Tail

Reimchen, T E; Temple, N F (2004). "Hydrodynamic and phylogenetic aspects of the adipose fin in fishes". Canadian Journal of Zoology. 82 (6): 910–916. doi: 10.1139/Z04-069. a b c d e Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp.385–386. ISBN 978-0-03-910284-5. Standen, EM (2009). "Muscle activity and hydrodynamic function of pelvic fins in trout (Oncorhynchus mykiss)". The Journal of Experimental Biology. 213 (5): 831–841. doi: 10.1242/jeb.033084. PMID 20154199. Immune organs vary by type of fish. [70] In the jawless fish (lampreys and hagfish), true lymphoid organs are absent. These fish rely on regions of lymphoid tissue within other organs to produce immune cells. For example, erythrocytes, macrophages and plasma cells are produced in the anterior kidney (or pronephros) and some areas of the gut (where granulocytes mature). They resemble primitive bone marrow in hagfish.