Folklore had these parasitoid worms forming
from the dropped hairs of horses when they were frequently found in horse
troughs.
The Gordian knot is an illustration of a problem
without a solution. An ox-cart which delivered a peasant named Gordias into
Phrygia who became its king, was tied up with a knot so intricate that is was
not possible to undo it, but whoever did would rule the whole of Asia Alexander the Great tried and failed so
sliced it in half with a stroke of his sword hence the Gordian knot/
A phylum of parasitoid invertebrates
comprising the marine Nectonema and freshwater Gordioida. There are 350
different known species throughout the world.
Adults can reach a length of between 50 and 100mm and in extreme cases 2m but only
up to 1mm in diameter.
They have an external dark brown cuticle,
which is almost all muscle which gives them a hard and wiry feel. This muscle
arrangement results in them twisting
into intricate knots - hence the genus name Gordius resembling the classical
Gordian Knot.
 |
Nematomorpha showing the eponymous knotting behaviou
|
They lack any excretory, respiratory or
circulatory system. The eyeless head may
have a darker band below the paler tip.
The tail end of females is rounded but
males of most genera genital papillae showing as a cleft tail. Males of Gordius genus have a crescent-shaped
fold above the two lobes.
 |
| Male nematomorpha with bifuricated anterior. |
They exist in their external adult form
purely to reproduce.
The life cycle is complex and almost wholly
parasitic.
Long strings of gelatinous eggs are laid in
freshwater.
From these develop planktonic larvae which
have a boring apparatus with which to enter its first host, aquatic
invertebrates typically diptera or trichoptera larvae. Once inside this host, they encyst in the gut
of the invertebrate.
In turn, these invertebrates are predated
upon by freshwater or terrestrial invertebrates, typically Coleoptera or
Orthoptera with Carabidae being a common host.
Once inside this host, the larvae develop
into the adult worm-like form. They grow
to fill the internal cavity of the host but also influence it to seek out and
enter water where the host drowns. Once
this is achieved, the adult Nematomorpha will abandon the host and seek a mate
to reproduce in freshwater where the next season’s eggs are laid and the adults
die.
The National Biodiversity Network shows 251
records, the majority of which were recorded in Wales and a few in Scotland. The South West has no records at
present. However over the last three
years specimens have been increasingly recorded in Cornwall and on Lundy.
Although reportedly adults emerge from
their host in late summer or early autumn, on Lundy adults are typically found
in shallow temporary puddles on the island road in November and December. In Cornwall, they have been recorded during Riverfly surveys in small
streams in April, August, September and November.
I always search shallow puddles of the picture that eludes me, that of an adult emerging from its host.
Blogs I follow
https://downgatebatman.blogspot.com/
https://maryatkinsonwildonline.blogspot.com/
