Response of gastropod grazers to food conditions, current velocity, and substratum roughness

Abstract

a b s t r a c tFreshwater snails are widely distributed in running water systems. Most of them are feeding on biofilms attached to substrata. We used gastropods with different morphology and potentially different traits to analyse the effect of water currents and substratum roughness on the interactions between grazers and biofilms. The gastropods were exposed to naturally grown biofilms from the River Rhine that differed in age and in their artificial substratum roughness (mimicked by abrasive paper). The experiments were conducted in endless channels with paddle wheels where the current velocity could be set steplessly. The freshwater pulmonates Ancylus fluviatilis and Physella acuta as well as the freshwater prosobranchs Bithynia tentaculata and Potamopyrgus antipodarum were used as model organisms in this investigation. The time the snails remained on the test area related to the substratum roughness, and current velocity was used to compare the performance of the four snail species on different aged biofilms. In one experiment, the locomotive activity of snails was traced.Gastropods left substrata without biofilms and did not show different responses to biofilms of diverse ages with significant differences in their biochemical contents. Grazing by snails altered the biofilms in their chlorophyll-a content, ash-free dry mass, and ash mass. A current velocity above 0.12 m s −1 drove B. tentaculata, P. acuta, and P. antipodarum off the test areas, only A. fluviatilis remained unaffected by the applied current velocities (up to 0.23 m s −1 ). The substratum roughness had no direct influence on the retention time of snails and their locomotive activity on the substrata, whereas the chlorophyll-a content of the biofilm strongly influenced snail activity. Substratum roughness had only an indirect influence on the behaviour of snails contrary to studies on marine snail species.

Factors Explaining the Distribution of Physella acuta (Draparnaud, 1805) in Freshwaters of Morocco

“…This phenomenon is particularly noticeable in the Moulouya, Za and Melloulou Rivers [28,29,37]. This finding is congruent with those of previous studies on the sensitivity of P. acuta to flow velocity [53,54]. It is indeed known to inhabit standing water ecosystems such as wetlands, ponds, lakes and downstream stretches of rivers [18].…”

Stromatolites on the rise in peat-bound karstic wetlands

“…3). Elevated snail mortality implies periods of reduced predation on microbial films, the food source of the aquatic snails 47 . The coexistence of macroinvertebrates and marine stromatolites has recently been reported for a site in South Africa 16 , suggesting that metazoan co-occurrence may play a reduced role in limiting stromatolite growth 48,49 .…”

Pengaruh Penambangan Batu Terhadap Komunitas Makrozoobentos Di Sungai Logawa

“…Kecepatan arus berpengaruh terhadap jenis organisme. Menurut Hoffman et al (2006) dan (Schoessow et al, 2016), kecepatan arus dapat mempengaruhi distribusi makrozoobentos dan dapat mengurangi jenis organisme yang tinggal sehingga hanya jenis-jenis yang melekat saja yang bertahan terhadap arus. Kecepatan arus yang sangat lambat dalam suatu perairan juga menyebabkan perairan tersebut didominasi oleh substrat berlumpur yang banyak mengandung bahan organik (Husnayati et al, 2012).…”