It is always nice to dive in the midst of this cloud of electric blue fishes, are the Black Castagnola – Chromis chromis – the small specimens have the electric blue livery. Small ones are photophobic, that is, they do not tolerate sunlight, so it’s easy to meet them in dark caves, or in shady areas far from sunlight. As they grow, they change color, changing the beautiful fluorescent blue livery into the black one.
From ancestors live in flocks like adults but on the bottom near caves where to take refuge from predators. They are not afraid of the man, even though approaching them swim with fast and lightning strikes, they do not actually flee, it is probably their flock strategy to confuse predators. As adults they live by occupying the entire water column, always on rocky backdrops or in the vicinity of submerged wrecks and reefs.
Chromis-chromis, the damselfish or Mediterranean chromis, (belongs to the order Perciformes, suborder Percoidei) is a small species of ray-finned fish of the family Pomacentridae from the Eastern Atlantic and Mediterranean.
Chromis chromis has an oval and laterally compressed body with an noticeably large eye. Its mouth is strongly protractile, reaching to below the centre of the eye, with small canine-like teeth set in 3 rows on the jaws. The preoperculum is not serrated and the anterior gill arch has 30 slender gill rakers. There are 13-14 spines and 10-11 soft rays in the dorsal fin and in the anal fin has 11 spines and 10-12 soft rays. Its body is covered in large scales, including the head, and there are 24-30 scales along the lateral line. The youngest fish are a brilliant iridescent blue in colour; older juveniles have blue stripes with the dorsal and anal fins outlined in blue while the adults are dark brown with the centres of each scale a paler golden brown or grey-brow and with the edge of the caudal fin lacking any colour, especially in the centre of the fork. The males become a vivid pale violet. There is a single pair of nostrils.
It can grow up to a size of 25 centimetres in length, with a common length of 13 centimetres.
Chromis chromis inhabits littoral, mainly in rocky areas from 2 to 40 metres in depth, in small shoals in midwater above or near rocky reefs and above sea-grass meadows.
In This movie we show you the youthful and the adult phase of the damselfish.
(extract from Wikipedia)