Function of byssus threads in young postlarval Mytilus

The mussel farming industry of the Galician region (NW Spain) requires that 60 to 70% of its seed supply is taken from rocky shore areas. However there are almost no quantitative data for a recruitment and settlement pattern. In the Ria d e Vigo a continuous settlement throughout the year with a major settlement season from May to September was found, reflecting the presence of spawning mussels throughout the year and the occurrence of a major spawning period during the spring. The observed settlement pattern indicates the direct settlement of larvae from the plankton onto the adult beds and a n immigration of mussels previously settled on other substrates. This pattern could b e a response to the ecological and environmental conditions that occurred on the Galician rocky shores, but could also be a differential characteristic between Mytilus edulis and M. galloprovinc~alis.

mentioning

confidence: 47%

Settlement of mussels Mytilus galloprovincialis on an exposed rocky shore in Ria de Vigo, NW Spain

Cáceres-Martı́nez¹,

Robledo²,

Figueras³

1993

“…Verwey (1966) pointed out that mussel post-larvae spin long threads, which may facilitate their upward transport by turbulence and apparently help them in finding a new attachment. Blok & Tan Maas (1977) considered that the mucous threads of Mytilus edulis are involved chiefly in settlement by becoming ensnared on the substrate. Martel & Chia (1991a) proposed the same function in the mucus produced by the gastropod Lacuna spp.…”

Section: Discussionmentioning

confidence: 99%

Settlement and post-larvae behaviour of Mytitus galtoprovincialis: field and laboratory experiments

Cáceres-Martı́nez¹,

Robledo²,

Figueras³

1994

Field sampling carried out in the Rfa de Vigo (NW Spain) from 1991 to 1993 showed that Mytdus galloprovincialis settle directly from the plankton onto substrates exposed to various environmental conditions: exposed rocky shore; protected rocky shore; exposed, raft mussel-culture area; and protected, raft mussel-culture area. For direct settlement, competent larvae may use a wide variety of substrates: filamentous nylon ropes; the byssus and intricately arranged material in the bottom of mussel beds; filamentous, thallus and membranous algae; and rugosities on adult mussel shells. The peak of settlement occurred from spring to early autumn and differences in the settlement abundance among localities were influenced by currents. After this peak, the settlement of larger post-larvae continued, associated with the increase in storms during autumn that detach them from their original substrates. This dispersion phase allows for the possibility of colonising, or recruiting on other areas, even during the post-spawning season when the presence of small post-larvae is at its minlmum. Laboratory experiments carried out with post-larval stages from 0.250 to 2.000 mm showed that under static water conditions they crawl and form clumps, but do not search for a specific substrate. If they are not disturbed, they may remain in their original place of settlement. Conversely, under moving water conditions they attach to a wide variety of substrates, particularly to byssal filaments and thalli of red algae Ceramium rubrum. The contact and attachment to substrates is carried out with a long mucous thread that also aids in forming clumps. The use of this mucus to settle results in a 'preference' for natural filamentous substrates but also in settlement on rugous hard surfaces. An alternative hypothesis to the primary and secondary settlement pattern previously described in the literature for Mytilus edulis is suggested.

“…Byssus drifting has been described for most common bivalves of the Wadden Sea, such as the blue mussel Mytilus edulis (de Blok & Tan-Maas 1977, Lane et al 1982, 1985, Caceres Martinez et al 1994) and the cockle Cerastoderma edule (de Montaudouin 1997). The byssus drifting of M. balthica has been described by Sörlin (1988) and Beukema & de Vlas (1989).…”

Section: Introductionmentioning

confidence: 97%

Changes in distribution and decrease in numbers during migration of the bivalve Macoma balthica

Hiddink¹,

Wolff²

2002

The population development of the 1998 year class of the bivalve Macoma balthica was studied by repeated sampling of a tidal flat area in the eastern Dutch Wadden Sea from May 1998 to August 2000. The juveniles migrated twice, once in mid-1998 from their primary settlement locations in the low sandy intertidal to the nursery in the high intertidal (spring migration, 25% of all juvenile M. balthica relocated from low to high intertidal) and once in late 1998/early 1999 from the nursery to the low intertidal and the subtidal (winter migration, between 8 and 15% of all 0-group (less than 1 yr old) M. balthica relocated from high to low intertidal). During winter, M. balthica migration was most intensive at the lowest temperatures. Relative to the abundance on the tidal flats, the 1+ group (older than 1 yr) M. balthica (i.e. from the second summer onwards) were rare in the tidal channels of the Wadden Sea and were only slightly more common in the North Sea adjacent to the tidal inlet. During both the spring and winter migration, many bivalves disappeared from the tidal flat population. This could partly be explained by normal mortality and by emigration to the subtidal channels and the North Sea. The remaining mortality was probably due to the risks inherent in migration: predation during pelagic floating or not reaching the right locations. The number of bivalves that disappeared was very high. In spring, slightly more disappeared than relocated. In winter, > 4 times more bivalves disappeared than relocated. Migration is obviously a very dangerous activity, therefore great advantages must be associated with the nursery use that makes such migrations necessary. An analysis of literature data on the density of M. balthica shows that in the eastern Dutch Wadden Sea, 90% of the population lives in the intertidal, about 10% in the adjacent North Sea, and a negligible fraction in the subtidal channels of the Wadden Sea.