Predation on Juvenile Lagoonal Mud Snails (Hydrobia Neglecta)

Abstract

Lagoonal mud snails have been shown to suffer approximately 50% mortality between hatching and adulthood. Experiments were conducted in the laboratory to assess the role of predators on the survival of juvenile Hydrobia neglecta (Mollusca: Gastropoda). Adult snails were collected from a lagoon in the Reedland Marshes system at Dunwich, Suffolk, and their eggs hatched in the laboratory, providing a population of juvenile snails which could be presented as a food source. The vessels, kept at environmental regimes close to that of the natural environment, were seeded with juvenile snails at field density. Predator preference was established by exposing the juvenile snails to combinations of potential predators found in the lagoon. One experiment also gave predators a choice of various juvenile snail sizes and other prey species. Juvenile snails remaining alive after the four week exposure to predators were removed, counted and measured. In the absence of other prey, the opisthobranch snail Retusa obtusa preferentially consumed 50% of the available juvenile H. neglecta over a four week period and the nemertean Lineus ruber up to 90%, making them the major contributors to juvenile H. neglecta mortality. The infaunal anemone Nematostella vectensis, did not have a significant impact on snail survival in the experiments but was observed (incidentally) in a separate non-experimental situation engulfing juvenile H. neglecta. The stickleback Gasterosteus aculeatus and the lagoonal prawn Palaemonetes varians, did not contribute directly to the observed mortality of juvenile mud snails, but were found to consume other predators, producing a system of prey preferences in the food chain. Understanding the role of predation contributes to the understanding of ecological processes occurring in rare lagoonal systems.

Spatial structure of a multi-species guild: the dominant biofilm-grazing microgastropods of seagrass

“…It is known that many are taken by small sympatric invertebrate predators (e.g. McArthur, 1998;Dupuy et al, 2010), but unfortunately knowledge of consumption of microgastropods by nekton and larger benthos is limited and contradictory. On the one hand, a number of studies have shown that few nektonic consumers take a significant number of adult microgastropods (e.g.…”

The circatidal rhythm of the estuarine gastropod Hydrobia ulvae (Gastropoda: Hydrobiidae)

“…However, the role of predation should be carefully considered because it is uncertain how predation pressure on Hydrobia is distributed along the tidal cycle. Studies indicate that Hydrobia is likely to be preyed upon by waders and other birds during low tide (Goss Custard et al ., 1977; Moreira, 1995), although fish (Aarnio & Mattila, 2000) and invertebrates (Mcarthur, 1998) prey on them at other phases of the tide. Moreover, ingestion rates along the tidal cycle have not been measured, and the true effects of ingestion by vertebrates on the mortality of Hydrobia require better quantification given that sometimes up to 90% of individuals may pass the digestive tract of flat fish alive (Aarnio & Bonsdorff, 1997).…”