anal fin


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anal fin

n
(Zoology) a median ventral unpaired fin, situated between the anus and the tail fin in fishes, that helps to maintain stable equilibrium
References in periodicals archive ?
The anal fin as preserved includes four rays, the anterior two of which are greatly enlarged spines, measuring up to 3 mm in diameter.
The black perch intromittent organs were first described by Agassiz (1853) who documented a smooth patch located on the anal fin with a surrounding sheath with a burrow to house the intromittent organ.
The pelvic fins, often located right behind the pectoral, are located far down the body, along with the single dorsal fin and the anal fin.
The second dorsal fin and the anal fin of Carcharias are very large and are about equal in size.
Dorsal fin 31-39; anal fin 46-50; head large, 3-4 times into SL.
The meristic counts as: dorsal fin rays XI, I, 20~22; anal fin rays II, 21~23; pectoral fin rays 16~17; pelvic fin rays I, 5; caudal fin rays 16~17; gill rakers first arch 3~4+7~8=10~12; vertebrae 33~35 (mostly 34).
On both specimens, the anus was located closer to the edge of the suctorial disk than the origin of the anal fin.
Spinous dorsal-fin membrane completely dark and without spots, dorsal and caudal fin uniform dark blue to black, thin unpigmented strip on distal margin of caudal fin; anal fin slightly lighter, gray-blue to dark gray; pelvic fins light gray with blue tips, spine white to light gray; pectoral fins mostly dark blue-black, distal half of unbranched pectoral-fin rays light gray to white.
Anal fin similar to the second dorsal fin, with one to three spine and 8-35 soft rays; separated finlets present behind dorsal and anal fins in some species.