Open Reading Frame brings together a selection of recent publication highlights from elsewhere in the open access ecosystem. This week we take a look at the past few weeks in biology.
Solving a porpoise whodunit
Over the last decade, hundreds of severely mutilated harbour porpoises have washed up along the south-eastern coastline of the North Sea. The cause of these deaths has been the subject of fierce debate. Conservationists claim the local fishing industry is to blame, either through collisions with boats or by porpoises drowning in fishing nets, their corpses later mutilated by scavengers. Fisherman respond that these deaths are merely the results of natural predation. A team of Dutch researchers have now revealed who they believe to be the culprit: the grey seal. They found traces of grey seal DNA in bite marks on three freshly killed porpoises and, by trawling back through the autopsy reports of many previously beached porpoises, found that the wound patterns were consistent with attack by grey seal. Moreover, the wounds suggest these animals were attacked when still alive, going against the theory that seals are just scavenging porpoises killed by another source. Is the fishing industry off the hook? Not quite; the researchers suggest fishing could be responsible for this change in grey seal behaviour, either by making the fish seals usually eat scarcer or by providing seals with ‘practice’ in predating porpoises in the form of the individuals that do drown in fishing nets.
Leopold et al. Proceedings of the Royal Society B
For insect farmers, only the right bacteria will do
When we think of a species that grows its own food, we naturally think of humans. However a number of insect species also act as farmers, cultivating fungi for food. Species from three distinct orders of insects – ants, termites and beetles – are known to engage in this sort of behaviour, cultivating several different fungal phyla. A crucial third party in these relationships are bacteria. The bacterial microbiota growing on insect cultivated fungi acts as a kind of ‘ancillary gut’, degrading the fungi to the point where they can be digested by the insects. While the insects and fungi that engage in these behaviours are diverse, a new study suggests that the bacteria involved are not. Leaf-cutter ants from Central America, African fungus growing termites and European ambrosia beetles all have highly similar microbiotas, comprised primarily of the same three bacterial genera. In a nice example of convergent evolution, phylogenetically and geographically diverse insects and fungi have all evolved to use the same bacteria as the common glue binding them together in these symbiotic relationships.
Aylward et al. mBio
Show me the way to go home
Many animals show a remarkable ability to navigate long distances. In birds, turtles, mammals and fish this ability is known to be at least partly due to spatial learning, the ability to use landmarks to navigate. Much less is known about navigational abilities in amphibians, partly because many of them are rather sedentary animals who do not travel long distances. Poison dart frogs are an exception to this. Adults travel long distances through South American rainforests to transport newly hatched tadpoles from terrestrial to aquatic habitats. New research suggests that they accomplish this through spatial learning. Frogs were captured and released several hundred metres away from their home territories; they were then tracked using an attached miniature transponder. Those released on the mainland (and so in areas they would have previously travelled through) took a very direct route back to their territory; a number of these frogs ended up just a few metres away from where they were captured. Those frogs released the same distance away, but on a nearby island (where, unable to cross the river, they could not have been to before) wandered in random directions. This implies that frogs require spatial cues to navigate, as opposed to using cues (e.g. distant visual, olfactory or acoustic beacons) that would not be affected by being in a nearby but unfamiliar area. The presence of spatial learning in amphibians, the root branch of all land vertebrates, suggests this ability appeared early in the evolution of vertebrates.
Pašukonis et al. Biology Letters
Making the most of former forest
Where forest is cleared for agriculture, it may in time become less productive, uneconomic to farm and is subsequently abandoned (often in favour of felling further pristine forest). A study in Ecuador, where this problem is acute, finds that restoration of the land can reap both ecological and economic benefits. This study looked at abandoned farmland reused for cultivation of native or exotic trees, and intensive or low-input pasture, comparing the economic benefits of each and various measures of the ecological condition of the land against that for abandoned land. The authors did not use biodiversity as a measure of ecosystem quality, as they note that this is very low compared to pristine forest even for long-abandoned land, and say it is better to aim for a good quality novel habitat. Compared to leaving the land untended, either intensively managing the land for pasture or using it for growing trees can be both economically and ecologically beneficial, and both more so than non-intensive pasturing. Which is the best option will depending on the circumstances of the individual farm, availability of government funds and individual preferences.
Knoke et al. Nature Communications
These are the beetles you are looking for
As relationships between animals go, it’s quite a creepy one. Pristionchus pacificus is a nematode worm that lives on a host beetle, with a preference for the oriental beetle Exomala orientalis. But P. pacificus is not a parasite, instead it engages in ‘necromeny’ – patiently waiting for its host to die so it can feed on the bacteria breaking down the corpse. The beetles produce a sex pheromone, ZTDO, which has become used by the nematode as a signal attracting it to its preferred host species. In this study the authors identify a nematode protein, OBI-1 (surely a Star Wars reference), that may clear the pheromone from the nematode to aid tracking the faint scent, or could be part of a signal detection system. They also find that ZTDO not only acts as an attractant for the nematodes but can also halt their development or kill them. This raises fascinating questions about the sequence of evolutionary events that occurred when the multiple functions of ZTDO and OBI-1 arose, and whether the host and nematode are now in a stalemate, leading to the latter’s unusual necromenic lifestyle.
Cinkornpumin et al. eLife
Written by Christopher Foote, Executive Editor for the BMC Series, and Tim Sands, Executive Editor for the BMC Series.