The Red-Bar Anthias (Pseudanthias rubrizonatus), belonging to the sub-family Anthiinae, is close relative of the frequently encountered Groupers of the sub-family Epinephelinae.
As with most members of its sub-family, the Red-Bar Anthias, at a maximum length of around 12cm, is significantly smaller than locally occurring members of the Grouper family.
Although a very common sub-family throughout the world's coral reefs, there appear to be very few species of Anthias in local waters.
The Red-Bar Anthias is unusual in that it appears to prefer relatively deep water (20m+) which, combined with its small size, means it is rarely encountered and easily missed.
The species has been confirmed at only a few locations such as Sail Rock, most notably around the south-facing side of the East Pinnacle, at a depth of between 25 - 30m.
A number of individuals live together in small aggregations known as "harems", in which a single dominant male aggressively defends its territory, typically consisting of mostly females and possibly one or two non-dominant males.
In common with many other reef dwelling species such as the Wrasses and many Damselfish, Red-Bar Anthias are protogynous hermaphrodites, which begin life as female, with the largest female changing to male in the event of the dominant male dying.
There exists clear sexual dimorphism between males and females, with males being significantly more colourful than females.
Male Red-Bar Anthias are easily recognised by their overall yellow/orange colouration which tends to be more intense at the head and less so posteriorly.
There may be pinkish areas, predominantly on the anterior side of the deep red bar (after which the species is named) and a pink line originating below the eye and terminating just behind the gill cover (operculum). This line is one of the few markings shared by both male and female, although it is more prominent on the male
The upper and lower edges of the caudal fin, and dorsal fin margin are blue whilst the pectoral and anal fins have a paler blue margin. A prominent red sub-margin is also present on the anal fin
The main anatomical feature that distinguishes the male from female is the presence of an elongated filament on both the upper and lower posterior edge of the caudal fin.
In contrast to the vivid colouration of the males, female Red-Barred Anthias are a more uniform orange/pink overall with translucent pectoral fins and mainly purple-ish coloured dorsal, pelvic and anal fins.
The caudal fin is partially translucent, with distinctive red/orange upper and lower posterior tips.