Elacatinus horsti
A small goby that lives with sponges and eats parasitic worms.
Elacatinus horsti, the yellowline goby, inhabits the western Atlantic Ocean and Caribbean Sea. This fish reaches a length of 5 centimeters, with a rounded snout and a long, slender body. Its upper side is black, while the underside is gray and fades to white. Many individuals display a bright yellow stripe on each flank, running from the eye to the tail, often with a yellow spot or short line on the snout. In juveniles, this stripe is shorter, extending only slightly past the base of the pectoral fin. Young Elacatinus chancei look very similar, but in that species the yellow line barely reaches the pectoral fin. Another color form has a white stripe that turns bluish-gray beyond the pectoral fin. The dorsal fin is split into two parts, with seven spines and 11 to 12 soft rays; the pectoral fin has 18 rays, and the anal fin has one spine and 10 soft rays.
The yellowline goby occurs along the Gulf Coast of the United States, the Gulf of Mexico, the Caribbean Sea, the Bahamas, Curaçao, and Panama, on reefs at depths of 7 to 27 meters. It always lives in association with a tubular sponge, such as Verongia aerophoba, or a massive sponge, like Neofibularia nolitangere, feeding on the parasitic worm Haplosyllis spongicola, which thrives on these sponges. It also consumes other bottom-dwelling invertebrates and plankton. The species name honors Dutch biologist Cornelius van der Horst (1889–1951), who collected the type specimen while staying on Curaçao in 1920.
Quick Facts
- Maximum length
- 5 cm
- Dorsal fin spines
- 7
- Dorsal fin soft rays
- 11 to 12
- Pectoral fin rays
- 18
- Anal fin spines
- 1
- Anal fin soft rays
- 10
- Depth range
- 7 to 27 m
Facts from the source article.
Lore & Background
The yellowline goby has a rounded snout and a long, slim body. Its upper parts are black and the underside is grey, paling to white. Some individuals have bright yellow stripes running along each side from the eye to the tail, often with a yellow spot or short line on the snout. In juvenile fish, this stripe is shorter and extends just beyond the base of the pectoral fin. Another form of the fish has a white stripe that pales to a bluish-grey colour beyond the pectoral fin. The dorsal fin is divided into two parts. The species is always found living in association with a tubular sponge such as Verongia aerophoba or a massive sponge such as Neofibularia nolitangere, feeding on the parasitic worms Haplosyllis spongicola that live on these sponges. It also eats other invertebrates that live on the seabed and plankton.
Reader's Guide
The yellowline goby is a small reef-dwelling fish with a specialized ecological niche. It is always found in association with specific sponges, either tubular (Verongia aerophoba) or massive (Neofibularia nolitangere), and its diet centers on the parasitic worms Haplosyllis spongicola that infest those sponges. This close relationship highlights the goby's role in controlling sponge parasites. The species also supplements its diet with other benthic invertebrates and plankton. Its distribution spans the Gulf Coast of the United States, the Gulf of Mexico, the Caribbean Sea, the Bahamas, Curaçao, and Panama, at depths between 7 and 27 m. The specific name honors the Dutch biologist Cornelius van der Horst, who collected the type specimen while staying on Curaçao in 1920. The yellowline goby is one of several similar-looking species in the genus, and its juvenile form can be confused with young Elacatinus chancei, though in that species the yellow line hardly reaches the pectoral fin.
Did You Know?
- The yellowline goby grows to a maximum length of 5 cm.
- It is always found living in association with tubular or massive sponges.
- Its diet includes the parasitic worm Haplosyllis spongicola.
- The species was named after Dutch biologist Cornelius van der Horst.
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