anal fin


Also found in: Encyclopedia.

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 ?
Description: Dorsal rays XI,9 (female paratype with XII,9); anal rays 111,9; first dorsal and anal soft rays unbranched, all others branched, the last to base; pectoral rays 15, the upper two un-branched; pelvic rays 1,5; principal caudal rays 13; median 11 unbranched; upper and lower procur-rent caudal rays 6, posteriormost segmented; lateral line interrupted; dorso-anterior series of pored scales 17+7 (17+6-8), scales above lateral line to base of dorsal fin 2; scales below lateral line to base of anal fin 6; median predorsal scales 5; median prepelvic scales 6; circumpeduncular scales 16; horizontal scale rows on cheek 2; gill rakers 13 (1314); branchiostegal rays 5; vertebrae 9 + 16.
macrolepidotus the anterior rays of the anal fin are elongated in mature males giving the fin a crescentic shape, in contrast to that of females where it is straight.
large mouth with thick lips; canine teeth on both jaws, strong and with an enlarged pair nearby the tip, visible when mouth is closed; vomerine tooth patch crescentic to triangular, without a medial posterior extension; preopercular margin with a weak knob; dorsal fin with 10 spines and 14 soft rays; anal fin rounded, with 3 spines and 7 soft rays; pectoral fins short, not reaching level of anus; with 16 to 18 rays; caudal fin nearly truncate.
The anal fin was an average of 1.99mm (0.35) long and 0.47 (0.16) wide and presented III spines, the first small with an average length of 0.55mm (0.35) and the second one with an average length of 0.34mm (0.11) long.
Swordfish age and growth studies have been based mainly on two different methods: modal decomposition analysis of length frequency data and the analysis of hard parts such as otoliths, dorsal and anal fin rays, and vertebrae.
The count of scales in longitudinal series is made from just behind the upper end of the gill opening (not including two or three small anterior scales) to the base of the caudal fin (not including a smaller scale that overlaps the fin base); scales in transverse series are counted from the origin of the anal fin obliquely upward to the base of the first dorsal fin; gill-raker counts were made on the first gill arch, the rakers on the upper limb listed first (only one or two counts of paratypes per species).
These characteristics included the genital papilla, the presence of papillary processes on the anal fin, and the notch on the dorsal fin (26,27).
Key differences: A spinner shark has a black-tipped anal fin, while the blacktip, in spite of its name, has a plain anal fin.
adornatus complex by the color pattern of the anal fin, which consists in longitudinal, alternating three yellow and three black stripes (vs.
rohita were non-significantly different (P greater than 0.05), anal fin length was significantly different (P less than 0.05), and all the remaining parameters were highly significantly different (P less than 0.01) among the sites.
3A), but depressed fin pale yellow with oblique rows of dark pigment; adipose fin pale with at least one dark marking dorsally; pectoral fin pale with approximately 6 wavy, irregular bars of dark brown pigment; pelvic fins bright yellow; anal fin yellow; center of caudal fin (at anterior end of fork) and posterior portion of ventral caudal lobe dark gray to brown; dorsal caudal lobe pale with light, dusky pigment on posterior margin; dorsal caudal lobe with 2-3 small brown bars on procurrent rays.
The dorsal fin is shorter than the anal fin, and its origin is slightly behind that of the anal fin.