Stegastes beebei

Lore & Background

The Galapagos ringtail damselfish has an oval, compressed body with one pair of nostrils. The margin of the preopercle is serrated, and the bone under the eyes is serrated without a notch. Its mouth is small and protrusible with a single row of long, close-set teeth. It has a single continuous dorsal fin, a bluntly forked caudal fin, and moderately large, rough scales covering the body and most of the head, including the snout to the nostrils. The lateral line is incomplete, ending under the end of the dorsal fin base.

Adults are dark brown with darker scale outlines, often featuring a white band on the caudal peduncle, blue irises, and white or yellow outer edges of the pectoral fin. Juveniles are dark with a red nape, upper back, and spiny dorsal fin, and a dark ocellus at the rear base of the dorsal fin. They are somewhat territorial, chasing away small intruders, and are omnivorous, grazing on algae and nibbling at small crustaceans and anemone tentacles.

Breeding involves distinct pairing, with demersal eggs that adhere to the substrate; males guard and aerate the eggs. The species is named after American naturalist and explorer William Beebe of the New York Zoological Society.

Reader's Guide

Stegastes beebei is a species of damselfish documented from coral and rocky reefs in the eastern Pacific, specifically off Panama, Malpelo Island (Colombia), Cocos Island (Panama), and the Galápagos Islands. Its significance lies in its role as a common, territorial reef inhabitant at depths up to 15 meters. The species is notable for its distinctive adult coloration—dark brown with a white caudal peduncle band and blue irises—and its juvenile pattern featuring a red nape and dorsal fin with a dark ocellus. As an omnivore, it contributes to reef ecology by grazing algae and consuming small crustaceans and anemone tentacles. Its reproductive strategy involves oviparous pairing, with males providing parental care by guarding and aerating the demersal eggs. The species was named in honor of William Beebe, an American naturalist and explorer associated with the New York Zoological Society, reflecting its discovery and description within the context of early 20th-century natural history exploration. The morphological details, such as the serrated preopercle, single row of teeth, and incomplete lateral line with 20 scales, help distinguish it from related damselfish. The maximum recorded length of 17 cm places it among the moderate-sized members of its genus.

Did You Know?

• The Galapagos ringtail damselfish grows up to 17 cm in length.
• It has an incomplete lateral line with 20 scales (rarely 19).
• The specific name honors American naturalist and explorer William Beebe.