I estimated 93.1 % of the increase in the welfare of soil animals resulting from increasing cropland comes from decreasing nematode-years. So my most important assumption is that nematodes have negative lives. I have now looked a bit more into how nematodes die, and my best guess continues to be that they have negative lives.
C. elegans shares its natural environment with a diverse animal community, in particular arthropods, molluscs and other nematodes, some of which also feed on microbes proliferating upon plant decomposition. Many are potential dispersal vectors as well as predators of C. elegans. Frequently co-occurring predators include fungi, which, depending on the species, invade the nematode through spores attaching to the cuticle or the intestine, or use trapping devices that immobilize the animal and perforate it (Figure 2). Nematophagous mites, springtails and nematodes are other potential predators often encountered in the C. elegans habitat.
The broader nematode community associated with C. elegans comprises microbivorous nematodes, often including other rhabditid nematodes, such as Oscheius sp., diplogastrids or panagrolaims, which likely compete with C. elegans for microbial food resources. Also found in rotting fruits are fungal-eating and predatory nematodes. Sometimes, C. elegans co-occurs with other Caenorhabditis species in the same location or even in the same few square millimetres of substrate. Given the rapid proliferation upon food availability, intraspecific competition for food is probably substantial.
C. elegans also constantly interacts with a variety of obligate and non-obligate parasites, such as fungi, microsporidia, bacteria and viruses (Troemel et al., 2008; Félix et al., 2011; Félix and Duveau, 2012; Hodgkin et al., 2013) (Table 1). These parasites infect their host via the two most exposed parts of the nematode, the cuticle and the intestine. Some non-invasive bacteria form a biofilm along the nematode’s cuticle or directly stick to it (Hodgkin et al., 2013). Other bacteria proliferate in the nematode gut, which may induce constipation and likely impairs nutrient uptake (Félix and Duveau, 2012). The most intrusive parasites enter and proliferate inside the nematode body. Some pierce the cuticle (e.g., Drechmeria coniospora [Couillault et al., 2004], Figure 2J), while others enter intestinal cells via the apical membrane (e.g., microsporidia and Orsay virus [Troemel et al., 2008; Félix et al., 2011]).
I estimated 93.1 % of the increase in the welfare of soil animals resulting from increasing cropland comes from decreasing nematode-years. So my most important assumption is that nematodes have negative lives. I have now looked a bit more into how nematodes die, and my best guess continues to be that they have negative lives.
From Félix and Braendle (2010):
From Frézal and Félix (2015):