sea gooseberry, either of two cosmopolitan genera of invertebrate marine animals in the phylum Ctenophora: the Hormiphora and the Pleurobrachia. The genera, widely distributed in all the oceans, are represented by 90 species. Sea gooseberries are wholly planktonic in their life cycle, lacking any sessile (attached) stages. They feed on other small planktonic animals such as arrow worms. Their bluish-white luminescence sometimes colours the waves at night. They constitute an important part of the diet of the European herring.
The body of the sea gooseberry is gelatinous, transparent, and roughly spherical to pear-shaped. Along the sides of its body run eight equally spaced longitudinal rows of comblike plates, each of which consists of thousands of fused cilia. As these tiny hairlike structures beat in sequence, they propel the animal. Their beating is coordinated by a sense organ at one end of the animal’s body. A mouth at the opposite end leads into a stomach from which extend eight branches that are visible through the transparent body. Several anal pores are present near the sense organ. Two long extensile, branched tentacles protrude from pouches on the sides. The tentacles are armed with colloblasts, special cells that have sticky heads which serve to ensnare prey.