Snails, the key to the functioning of lowland streams

A laboratory experiment has made it possible to discover the fundamental role that snails of the genus Melanopsis play in the conservation of lowland stream ecosystems in the face of the threat of invasive plants.

The experiment has been carried out by the Aquatic Ecology and Aquaculture research group of the University of Almería in Spain.

In the experiment, the performance of two detritus-eating organisms (organisms that constitute an essential part of ecosystems by contributing to the decomposition and recycling of nutrients) that coexist in the streams of the southeast of the Iberian Peninsula were examined: the amphipod Echinogammarus obtusidens, and the Melanopsis praemorsa snail, when they were fed with two types of litter (native, white poplar (Populus alba) and an invasive reed (Arundo donax) and the corresponding feces produced after ingesting the litter of these species.

The study is titled “Interspecies coprophagy in small aquatic detritivores counteracts low-quality litter: Litter from native versus invasive plants.”

The results of the study indicate that the amphipod developed a low performance when fed with leaf litter, especially sugar cane, with which more than half of the individuals died. On the contrary, the amphipods fed with feces produced by the snail presented the best performance. For its part, the snail showed a fairly stable performance regardless of the species of litter it was fed with, as well as with feces from other snails.

A snail. (Photo: NPS)

These results suggest that the amphipod can act as a coprophage (organism that feeds on excrement) when it does not have high-quality litter, and that the snail plays an essential role facilitating access to the nutrients of the recalcitrant litter for other detritivores that they coexist with him through his feces. Thus, the snail can act as a keystone species by increasing nutrient availability for other detritus species in lowland streams.

The researchers propose that managers pay attention to the conservation of these detritivorous species, which are so important for the functioning of lowland stream ecosystems, controlling activities that could threaten their populations (for example, exploitation of aquifers or water pollution). superficial), especially in streams where the diversity of detritivores is reduced, such as those located in the lowlands of the Mediterranean region.

This research arises from the problem posed by invasive species, one of the main threats to the conservation of biodiversity throughout the world. In particular, it has been shown that the cane of the Arundo donax species is capable of significantly deteriorating riparian habitats, altering the structure of the vegetation and displacing native vegetation, with consequent negative effects on the abundance and diversity of the communities. that depend on it.

The study evaluates how two species of aquatic detritivores can cope with the invasion of the banks by the giant reed and shows how the ingestion of feces produced by larger detritivores can be a successful feeding strategy for amphipods in order to overcome the invasion, but also to thrive in environments where low-quality litter inputs (whether native or not) are abundant. (Source: University of Almería)