Eight August days of searching for a small whitish worm in Greenland (see previous post “Greenland enchytraeids”): Decaying seaweed is a unique habitat and there are several species of enchytraeids other than Enchytraeus albidus at the collecting sites, most of them of the genus Lumbricillus. Being a taxonomist of enchytraeids, I took the opportunity to study them using laboratory facilities kindly provided by staff of the GINR, the Greenland Institute of Natural Resources, in Nuuk.
Enchytraeids are investigated microscopically and alive, because inner soft-bodies structures are the important characters to distinguish species. You need a sterolupe and a microscope, not much more. Specimens are gently pressed between slide and a coverslip to reduce motility, and some worms, especially the bigger ones, need a “drink” to relax: a drop of deluted ethanol, for example the big one shown below, a true giant among enchytraeids:
This particular worm was similar to E. albidus but seemed somewhat too large, and in fact it turned out to be a different species, Lumbricillus reynoldsoni Backlund, 1948 – a new species record for Greenland.
A look through the microscope may show something like this (sorry for the low-quality on-the-spot smartphone pic):
The streak in the middle is the gut. The big bodies on both sides of it are glandular sperm funnels, and the iridescent bodies on top are nuclei of mature spermatozoa aligned in parallel. These structures are crucial to recognize the species. Fortunately, all adult individuals have the same structures because enchytraeids are hermaphrodites, like earthworms. This small species is similar to Lumbricillus buelowi Nielsen & Christensen, 1959, not yet recorded from Greenland. Among hundreds of specimens I found only two individuals. All in all, six species of Lumbricillus were identified; the most abundant ones were species common in the Palearctic: L. rivalis, L. lineatus, L. pagenstecheri, L. viridis. Two species, L. reynoldsoni Backlund, 1948 and L. cf. buelowi Nielsen & Christensen, 1959 (see pics above), are rarely collected and in fact are new species records for Greenland.
The pic below shows the results of some hours of microscopical identification work: worms in the same dish belong to the same species, and they are all still alive. Only the one top right is E. albidus, the other ones are different species of Lumbricillus. Worms were later fixed in 100% ethanol for genetic studies or in hot Bouin’s fluid – a nasty mixture of picrinic acid, formaldehyde and acetic acid – for morphological studies.
These worms are now in Spain, where I live and work, and they will be investigated taxonomically at the CICA, a new research facility at the University of A Coruña. Worms in Århus are happier, still alive, and will be submitted to cooling and freezing in order to unravel the genetics of their cold tolerance capacities – but this is another story.