Influence of peat substrate on the distribution and behaviour patterns of sand shrimp, Crangon septemspinosa , under experimental conditions

Abstract

Peat harvesting is a lucrative industry in New Brunswick, Canada, and is for the most part located along the coast. Current methods of mining peatlands are such that high levels of peat fibers are transported by runoff into fresh and marine waters. To understand better the influence of peat substrate on aquatic organisms living in peat-impacted habitats, the sand shrimp (Crangon septemspinosa) was used as a bioindicator. A series of laboratory experiments was conducted in which shrimp were provided with a choice between sand and peat. Long-term studies on starved shrimp confirmed that whereas foraging activities took place on both substrates, shrimp display an overall preference for sand (73% of all shrimp observed were on sand, n ¼ 60). When food was deposited on each of the substrates, shrimp generally opted to feed on sand (75% of all shrimp observed were on sand, n ¼ 60). After all food on sand was consumed, shrimp tended to move to peat. This was followed by a short period of foraging on both sand and peat with an eventual return to sand in most instances. The presence of food on both substrates did not influence their preference for sand. However, shrimp will move onto a peat substrate to forage if food is present only there. This observation suggests that, although there is a marked preference for sand, peat is not completely repellent to them. Finally, histological investigations of the shrimp digestive system revealed that peat was ingested with food particles and processed in the gastric mill. There was, however, no discernible discrimination between the two substances during ingestion. Finally, starved shrimp on peat substrate did not ingest peat fibers, suggesting that peat is not perceived as an alternative food source.

HABITAT CHOICE BEHAVIOR IN Macrobrachium brasiliense (HELLER, 1862) (DECAPODA, PALAEMONIDAE) UNDER LABORATORY CONDITIONS

“…Even though these animals live in a different environment and consequently differ physiologically from the species studied in this present study, both results confirm the statement by Dall et al (1990) that substrates with particles between 1.0 mm and 62.0 μm provide food availability and facilitate escape from predators. In a study on the caridean prawn Crangon septemspinosa (Decapoda, Crangonidae), Oullette et al (2003) also found that this species preferred finer substrates, and connected this choice with survival, since C. septemspinosa lives much of its life cycle on this type of substrate. This finding agrees with our observation that M. brasiliense individuals spent most of their time buried in this type of substrate.…”

Comportamento do camarão em diferentes substratos nas fases clara e escura do dia

“…Entre os principais fatores que influenciam o comportamento dos camarões estão: disponibilidade de alimento, mecanismos relacionados à escavação e aspectos associados à respiração quando enterrados. A maioria dos camarões marinhos utiliza a escavação e o enterramento como estratégia de fuga e refúgio (Dall et al, 1990;Oullette et al, 2003;Freire et al, 2011). O tipo de substrato deve permitir a expressão natural desses comportamentos, o que favorece o conforto ambiental para o animal.…”

“…Kenyon et al (1995) não observaram preferência de juvenis de P. monodon em relação aos substratos mais finos. Já Oullette et al (2003) verificaram que Cragon septemspinosa prefere areia em detrimento de substratos artificiais, o que sugere que fatores físicos, como granulometria do substrato (tamanho do grão e porosidade), são reconhecidos pelos camarões.…”

“…Assim, as condições do substrato são particularmente importantes para o seu cultivo (Dall et al, 1990). Os habitats aquáticos, sejam eles naturais ou artificiais, são caracterizados por substratos compostos de níveis granulométricos variados, desde os mais grossos, como cascalho, até os mais finos, como argila, areia fina e silte (Oullette et al, 2003).…”

Impact of peat moss released by a commercial harvesting operation into an estuarine environment on the sand shrimp Crangon septemspinosa

“…They burrow into substrates for protection from predators and to ambush passing prey (Minello et al., 1987), an activity which can be affected by the nature and size of sediment particles (Trueman and Ansell, 1969; Ruello, 1973; Moller and Jones, 1975; Aziz and Greenwood, 1982; Pinn and Ansell, 1993). Observations in our laboratory showed that when offered a choice, sand shrimp display a strong preference for a sand substrate over a peat substrate and showed difficulty burrowing completely into the peat substrate (Ouellette et al., 2003). Furthermore, sand shrimp are known to ingest substrate particles during foraging (Wilcox and Jeffries, 1974), a phenomenon also observed during our laboratory experiments (Ouellette et al., 2003).…”