Pristionchusnematodes occur frequently in diverse rotting vegetal substrates and are not exclusively necromenic, whilePanagrellus redivivoidesis found specifically in rotting fruits

Abstract

The lifestyle and feeding habits of nematodes are highly diverse. Several species of Pristionchus (Nematoda: Diplogastridae), including Pristionchus pacificus, have been reported to be necromenic, i.e. to associate with beetles in their dauer diapause stage and wait until the death of their host to resume development and feed on microbes in the decomposing beetle corpse. We review the literature and suggest that the association of Pristionchus to beetles may be phoretic and not necessarily necromenic. The view that Pristionchus nematodes have a necromenic lifestyle is based on studies that have sought Pristionchus only by sampling live beetles. By surveying for nematode genera in different types of rotting vegetal matter, we found Pristionchus spp. at a similar high frequency as Caenorhabditis, often in large numbers and in feeding stages. Thus, these Pristionchus species may feed in decomposing vegetal matter. In addition, we report that one species of Panagrellus (Nematoda: Panagrolaimidae), Panagrellus redivivoides, is found in rotting fruits but not in rotting stems, with a likely association with Drosophila fruitflies. Based on our sampling and the observed distribution of feeding and dauer stages, we propose a life cycle for Pristionchus nematodes and Panagrellus redivivoides that is similar to that of C. elegans, whereby they feed on the microbial blooms on decomposing vegetal matter and are transported between food patches by coleopterans for Pristionchus spp., fruitflies for Panagrellus redivivoides and isopods and terrestrial molluscs for C. elegans.

Comparative genomics of 10 newCaenorhabditisspecies

“…In laboratory conditions, the females do not lay embryonated eggs (however, we cannot rule out that they lay embryos in some environment). Instead, L1 larvae exit their mother's body through the vulva, as, for example, in the genus Panagrellus in family Panagrolaimidae (Andrássy ; Félix et al ). In the closely related species C. virilis , females lay late‐stage embryonated eggs compared to most Caenorhabditis species (which accumulate few embryos in their uteri) but are not viviparous in standard laboratory conditions.…”

Fear conditioning in invertebrates

“…C. elegans is known to be found in decaying organic matter such as stems or fruits (Schulenburg and Félix, 2017). A study surveying the environments where Caenorhabditis are commonly found also discovered P. pacificus in samples of rotting stems and fruits (Félix et al, 2018). P. pacificus, like C. elegans, is a bacterivorous hermaphrodite.…”