Mesofaunal borers in seagrasses: world-wide occurrence and a new record of boring polychaetes in the Mexican Caribbean

In the last decade, an increasing number of mesofaunal crustaceans and polychaetes have been reported to bore into seagrass tissues. Crustacean borers have been found in seagrasses from different oceans (Indo-West Pacific, Mediterranean, and Caribbean), but until present, boring polychaetes had only been registered in the Mediterranean. Here, a new record of polychaete borers within sheaths of the seagrass Thalassia testudinum (Banks ex Konig) off the Mexican Caribbean coast (Puerto Morelos) is reported. The polychaetes were found in sheaths of plants collected at two stations in a shallow meadow (3-4 m depth), and except for slight morphological differences, were similar to Lysidice ninetta Andouin and Milne Edwards, Lysidice collaris Grube, and Nematonereis unicornis Grube; taxa previously recorded in sheaths of the Mediterranean seagrass Posidonia oceanica (L.) Delile. A synthesis of present knowledge of fauna burrowing into seagrass tissues, suggests the. existence of specific associations between particular seagrasses and specialized members of crustaceans (orders Isopoda and Tanaidacea) or polychaetes (family: Eunicidae). The boring crustaceans can be classified as mesoherbivores because they consume the living tissues they burrow into. Each species bores into specific tissues which are either leaf blades, leaf sheaths, rhizomes or seeds. The polychaetes, in contrast, bore into the dead sheath tissues which remain attached to the vertical rhizomes after abscission of the green blades, and can thus considered to be detritivores. (C) 2003 Elsevier Science B.V. All rights reserved.