Predation on seeds of seagrasses Zostera marina and Zostera caulescens by a tanaid crustacean Zeuxo sp.

This paper reports the first evidence of seed predation by a tanaid crustacean on seagrasses Zostera marina and Z caulescens in Otsuchi Bay, northeastern Japan. A tanaid, Zeuxo sp., was found to live in spathes of the seagrasses. Spathes with the tanaid were observed to have bored seeds. Laboratory observations revealed that the tanaid consumes seeds by drilling a hole. For both seagrass species, tanaids and bored ovules were not observed for spathes before anthesis, whereas spathes with bored seeds and density of the tanaid increased after anthesis, from June to August. In August, 14 and 27\% of seeds were found bored in Z marina and Z caulescens, respectively, suggesting that seed predation by the tanaid has considerable negative impact on seed production of the seagrasses. Some adult individuals of Zeuxo sp. in spathes had brood pouches containing eggs and juveniles. A large number of juveniles were found in spathes in August. Thus, the tanaid utilizes seagrass spathes not only as feeding site, but also as place of reproduction and a nursery. (C) 2002 Elsevier Science B.V. All rights reserved.