Criodrilidae
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The family Criodrilidae is represented by genus ''Criodrilus'' comprising limicolous (mud-dwelling) and/or aquatic
earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...
s endemic to the Palaearctic currently known only from Europe and Japan, respectively. Only three or four species are described, and the type, ''Criodrilus lacuum'', has been introduced into North and South Americas, and is found rarely in plant pots or paddy fields. The Criodrilidae are characterised by holoic
nephridia The nephridium (: nephridia) is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body. Nephridia co ...
absent from anterior segments (cf. ''Pontodrilus''), a simple gut with no gizzard and no
typhlosole In Morphology (biology), biological morphology, a typhlosole is an internal fold of the Gut (anatomy), intestine or intestine inner wall. Typhlosoles occur in bivalve mollusks, lampreys and some annelids and echinoderms. In earthworms, it is a d ...
. They are true earthworms, having a complex vascular system with
capillaries A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the in ...
, the male pores (on 15 or 13) behind the female pores (on 14) and a multicelled clitellum. They were at one time placed in the earthworm families
Glossoscolecidae The Glossoscolecidae are a large family of earthworms (annelids) which has native representatives in South and Central America. The species A species () is often defined as the largest group of organisms in which any two individuals of th ...
or
Almidae The animal family Almidae includes about six genera of Oligochaeta, segmented worms. A notable peculiarity of some species in this family is a tendency to extensions of the body wall in the vicinity of or including the male pores. These extens ...
, but at present are considered to constitute their own family. Criodrilidae species (criodrilids) are found in mud next to lakes and waterways (cf. North American ''Sparganophilus''). They feed in the low-oxygen mud and organic material, but with their highly vascularized posterior region on or near the surface. ''Criodrilus'' has no accepted common name; ''Criodrilus bathybates'' is the
Lake Biwa is the largest freshwater lake in Japan. It is located entirely within Shiga Prefecture (west-central Honshu), northeast of the former capital city of Kyoto. Lake Biwa is an ancient lake, over 4 million years old. It is estimated to be the 13 ...
earthworm.


References

http://opuscula.elte.hu/PDF/Tomus37/2_Review%20of%20Criodrilidae.pdf {{Taxonbar, from=Q284372 Haplotaxida