anal fin

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anal fin

[′ān·əl ‚fin]
(vertebrate zoology)
An unpaired fin located medially on the posterior ventral part of the fish body.
References in periodicals archive ?
Diagnosis: Papiliolebias francescae differ from the others member of this genus by the following unique features: dorsal and anal fins pointed in males (vs.
carti reaches or surpasses the vertical through the origin of the anal fin and, in adults, extends posteriorly to the vertical through the origin of the dorsal fin (Lucena 2000).
First dorsal fin with micromelanophores on membrane between first two spines, larger black spots on subsequent membranes, second dorsal fin with black spots on membranes basally, and third dorsal and anal fins with dusky bands along margins.
Scales cycloid; head scaled except interorbital space, snout and chin; opercle covered by seven large scales; cheek with two horizontal rows of scales below eye; naked lower flange of preopercle thin, greatest width at angle about 2 in orbit diameter in holotype; base of dorsal and anal fins with single row of large elongated scales, one per membrane; last pored scale on lateral line at base of caudal fin enlarged and pointed; terminal scale on midline just posterior to last pored scale very enlarged and pointed; no scales on paired fins; pelvic fins with median ventral process of two elongate scales about three-fourths the length of pelvic spine, thin axillary scale of each pelvic fin about three-fourths the length of pelvic spine.
Also, the pilotfish has a deeply forked tail and its bands extend onto the dorsal and anal fins.
The insectivores, with positive scores, presented wider heads, caudal fins with a tendency toward bifurcation and larger anal fins, while the omnivores were more compressed (see Table 6 and Figure 4).
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).
The pelvic, pectoral and anal fins of juvenile acquire a yellowish tone.
Melanotaenia laticlavia is also distinguished by the dark upper and lower caudal-fin margins (also shared by M irianjaya), the possession of a dark submarginal stripe and prominent white outer margin on both dorsal and anal fins (only on the dorsal fin of other Ayamaru complex species), broad blue grey zone on lower side (tapering porteriorly), and a red spot on the operculum, which although common in the genus, is either rudimentary or absent on other Ayamaru complex species.
Dorsal and anal fins each flanked basally by 10-12 half scales, remainder of dorsal and anal fins without scales; large, diamond-shaped scales covering pelvic-fin base, remainder of pelvic fin and pectoral fin without scales; 6 rows of body scales extending onto base of caudal fin; upper and lower caudal lobes each with a single, enlarged, horizontally elongate scale.
This particular sunfish was observed often by various scientists, actively swimming upright using its dorsal and anal fins in simultaneous coordinated strokes.