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Marine Animal Encyclopedia

Velvet Horn Codium tomentosum

The spongy fronds of velvet horn are made up of interwoven tubes, arranged rather like a tightly packed bottlebrush, with each tube ending in a swollen bulb. Many of these bulbs packed together make up the outside of the frond, which is usually repeatedly branched in two. Many short, fine hairs cover the seaweed, giving it a fuzzy appearance when in water. The plants are attached to rocks by a spongy holdfast.

Although this seaweed is present year-round, its maximum development is in winter, and it also reproduces during the winter months. Velvet horn, like all Codium species, is often grazed by sacoglossans, small sea slugs that suck out the seaweed’s contents, but can keep the photosynthetic chloroplasts alive and use them to make sugars inside their own tissues. The chloroplasts color the sea slugs green, which helps to disguise them from predators. There are about 50 species of Codium.

Velvet Horn habitat mapzoom image
  • Class Bryopsidophyceae
  • Size Up to 8 in (20 cm)
  • Habitat Intertidal pools, shallow subtidal rocks
  • Water_temperature 46–86°F (8–30°C)
  • Distribution Coastal waters worldwide