Stegastes leucostictus
A damselfish of western Atlantic shallows, also called beau gregory.
The beau gregory, or beaugregory, is a damselfish that stays close to the seafloor in the western Atlantic’s shallow waters. This oval, laterally compressed fish can reach about 10 cm in length. Its color varies, but it is typically dark blue or brown along the top of the head and back, with yellowish sides. It has a large dorsal fin with 12 spines and 13 to 16 soft rays, and an anal fin with 2 spines and 12 to 14 soft rays. The tail fin is slightly forked, while the pectoral and pelvic fins lack spines. Its mouth sits at the tip of the snout. Juveniles display blue stripes and spots on the head, a dull blue sheen on the upper front body, and a large black eye-spot ringed in blue where the dorsal fin spines meet the soft rays. As the fish matures, this spot shifts upward onto the fin. A dark spot above each pectoral fin helps tell this species apart from others in its genus.
This fish lives in shallow waters down to about 10 meters deep, from Florida and the Gulf of Mexico south to Brazil. It is a bottom-dweller, usually staying within 50 cm of the seabed. Its habitats include seagrass meadows, rocky or coral reefs, sandy flats, and sometimes mangroves. It mainly eats seaweed, but also feeds on marine worms, amphipods, foraminiferans, and gastropod molluscs. Males guard a territory and rarely interact with neighbors, though they will attack a same-species male introduced in a bottle within that territory. Dominance depends on territory quality; the owner of a high-quality territory is dominant, and if removed, a subservient male that moves in will itself become dominant. During breeding, a male and female form a pair bond. Eggs are hidden inside an empty shell or under a stone, and the male guards the nest, fanning the eggs with his fins to keep them oxygenated. The bluehead wrasse preys on these eggs. A male damselfish can assess the threat level from one or more wrasse and respond by chasing, harassing, or adopting a head-lowered threatening posture.
Quick Facts
- Taxon
- Stegastes leucostictus
Facts from the source article.
Lore & Background
Stegastes leucostictus is a demersal fish, normally remaining within 50 cm of the seabed. Its favoured habitats are seagrass meadows, rocky or coral reefs and sandy flats, and it is sometimes found amongst mangroves. The species feeds mainly on seaweed, but also consumes marine worms, amphipods, foraminiferans and gastropod molluscs. A juvenile S. leucostictus has blue stripes and spots on its head and a dull blue sheen on the top of the head and the upper part of the front half of the body. It has a large, black eye-spot ringed in blue, centered where the dorsal fin spines join the soft rays. As the juvenile develops, this spot moves upwards onto the fin. Also, a dark spot just above each pectoral fin distinguishes this species from others in the genus.
Reader's Guide
Stegastes leucostictus is notable for its territorial and social behaviors as described in the source. A male damselfish guards a territory, but seldom interacts with its neighbours, although it will attack a male of the same species introduced in a bottle placed in its territory. Dominance is related to the quality of the territory it occupies; the owner of a high-quality territory exhibits dominance, and if it is removed and a subservient male moves in, it in turn develops dominance. During the breeding season, a male and a female form a pair bond. The eggs are hidden inside an empty shell or under a stone, and the male guards the nest and fans the eggs with its fins to keep them well oxygenated. The wrasse, Thalassoma bifasciatum (bluehead), preys upon the eggs of S. leucostictus. A male damselfish can evaluate the level of the threat posed by one or more wrasse and react appropriately, either chasing the other fish, harrying it, or adopting a head-lowered, threatening posture. These observations highlight the species' adaptive responses to predation and its role in shallow-water ecosystems.
Did You Know?
- Stegastes leucostictus is commonly known as the beau gregory or beaugregory.
- The male damselfish can evaluate the threat level of the wrasse Thalassoma bifasciatum and react with chasing, harrying, or a head-lowered posture.
More in Clownfish and Damselfish, Part 2 1-24
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