Lumbriculus variegatus
Encyclopedia
Lumbriculus variegatus, sometimes known as blackworm (or even California blackworm), is the name given to at least three distinct species of worms which are identical in outward appearance. Until 2009, the species were regarded as one.black worms can split easy
These species of worms live in shallow water marsh
es, pond
s, and swamp
s, feeding on microorganism
s and organic material. They live throughout North America and Europe.
On average, an adult blackworm can have from 150 segments to 250, each of which has the ability to regenerate
into a whole new individual when separated from the rest of the animal; in most populations, this is the primary mode of reproduction, and sexually mature individuals are exceedingly rare - in large areas (including Asia, most of North America and the greater part of Europe) sexually mature individuals have never been found.
will attempt to escape, either by swimming in a helical ("cork-screw") fashion, or by reversing its body. The escape pattern used depends on where the worm is touched: anterior touch elicits body reversal, whereas posterior touch triggers helical swimming. Lumbriculus has a quick reflex that allows it to use its photoreceptors to escape. The photoreceptors can detect shadows and movement. The posterior end lifts out of the water and forms a right angle. It is then exposed to air and is used to exchange oxygen and carbon dioxide, although this exposes its posterior to its enemies. If the photoreceptors detect a shadow or movement, the posterior rapidly shortens in response to a threat.
L. variegatus is presumed to be holarctic
in distribution, although in East Asia and North America (and perhaps other places as well) it is probably replaced by the other species of the genus (many of which are known from very small areas; Lumbriculus illex
, for instance, is known only from three individuals found in a stream to the North of Vladivostok
). Mature Lumbriculus
can easily be told apart by a number of genital characters, but as few of the species in the genus ever become sexually mature, it is often difficult to know which species you are dealing with. A physical description of L. variegatus is, to a large extent, valid for the entire genus.
These species of worms live in shallow water marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
es, pond
Pond
A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including water gardens, water features and koi ponds; all designed for aesthetic ornamentation as landscape or architectural...
s, and swamp
Swamp
A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...
s, feeding on microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s and organic material. They live throughout North America and Europe.
On average, an adult blackworm can have from 150 segments to 250, each of which has the ability to regenerate
Regeneration (biology)
In biology, regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organs, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. At its most...
into a whole new individual when separated from the rest of the animal; in most populations, this is the primary mode of reproduction, and sexually mature individuals are exceedingly rare - in large areas (including Asia, most of North America and the greater part of Europe) sexually mature individuals have never been found.
Characteristics
Among the characteristics of the genus are a green pigmentation of the anterior end, its two-pointed setae, and its curious reflex escape mechanisms. When touched, LumbriculusLumbriculus
Lumbriculus is a genus of oligochaetes....
will attempt to escape, either by swimming in a helical ("cork-screw") fashion, or by reversing its body. The escape pattern used depends on where the worm is touched: anterior touch elicits body reversal, whereas posterior touch triggers helical swimming. Lumbriculus has a quick reflex that allows it to use its photoreceptors to escape. The photoreceptors can detect shadows and movement. The posterior end lifts out of the water and forms a right angle. It is then exposed to air and is used to exchange oxygen and carbon dioxide, although this exposes its posterior to its enemies. If the photoreceptors detect a shadow or movement, the posterior rapidly shortens in response to a threat.
Reproduction
Regeneration in L. variegatus follows a set pattern. If the regenerating segment originated less than eight segments from the anterior tip, this amount of segments are regenerated; if, however, the segment was originally from a more posterior position, only eight segments are regenerated. Posterior to the segment, a variable number of segments are regenerated, and the original segment undergoes transformation to become suited to the new, often more anterior position.L. variegatus is presumed to be holarctic
Holarctic
The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...
in distribution, although in East Asia and North America (and perhaps other places as well) it is probably replaced by the other species of the genus (many of which are known from very small areas; Lumbriculus illex
Lumbriculus illex
Lumbriculus illex is a fresh-water worm, the most recently described member of the genus , and is known only from 3 individuals found in Komarovka stream, north of Vladivostok...
, for instance, is known only from three individuals found in a stream to the North of Vladivostok
Vladivostok
The city is located in the southern extremity of Muravyov-Amursky Peninsula, which is about 30 km long and approximately 12 km wide.The highest point is Mount Kholodilnik, the height of which is 257 m...
). Mature Lumbriculus
Lumbriculus
Lumbriculus is a genus of oligochaetes....
can easily be told apart by a number of genital characters, but as few of the species in the genus ever become sexually mature, it is often difficult to know which species you are dealing with. A physical description of L. variegatus is, to a large extent, valid for the entire genus.