Lineus

Lineus

Languages: English

Overview

Diagnosis

(from 1912 Wijnhoff, G. List of nemerteans collected in the neighbourhood of Plymouth from May - September, 1910) Body rounded or flattened, unusually long, very contractile. Head mostly somewhat broadened and spathulate. The worms are not able to swim ; as a rule they coil themselves up and make knots. Ocelli present in most species. Proboscis sheath short.

General Description

(from Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.)
Representatives of this genus are characterized by a slender, sometimes thread-like body, usually rounded throughout.  The body is commonly twisted and coiled into an irregular mass.  The movements are sluggish.  The animals creep over objects and readily move about on the surface of the water, but they are unable to swim.  The body is extremely contractile; the head is often slightly wider than the body, of oval shape, and is usually provided with numerous minute ocelli, often arranged in a single row on each side of the head.  A caudal papilla or cirrus, a diagonal muscular layer, and neurochord cells are all wanting.  The proboscis sheath is often short in comparison with the length of the body.

Key

(from Allan Hancock Pacific expeditions vol. 1 1943)

Genus LINEUS Sowerby

Eight species of this genus are known to occur on the North Pacific coast. Only 2 of these have been found in other parts of the world.

Key to Species

1. Tip of head not conspicuously different from body in color; body without distinct markings....2
1. Tip of head of different color from that of body or with distinct markings on body....4

2. Dusky or brownish green, dark brown, or reddish brown, commonly paler beneath ; a single row of 4 to 8 ocelli on each side of head....3
2. Yellowish, pale yellow with tinge of orange, dull orange, ocher, buff, or yellowish brown; margins of head pale or colorless; with 3 to 7 irregular red, purple, or black ocelli, of which the most anterior are largest....flavescens

3. Body contracts by shortening and thickening — not by coiling in spiral; regenerative capacity very slight....ruber
3. Body contracts by coiling in spiral ; regenerative capacity almost unlimited....vegetus

4. With conspicuous median dorsal stripe, but without transverse markings; dark brown or olive, with median dorsal stripe of white or yellow extending whole length of body and widening out on head to form broad white marking....bilineatus
4. Without conspicuous median dorsal stripe....5

5. Body with narrow transverse rings of paler color....7
5. Body without transverse rings of paler color....6

6. Pink, rosy, flesh color, or pinkish red, sometimes with tinge of blue; tip of head white both above and below, sharply marked off from rosy color of body ; often with bluish tinge after preservation....rubescens
6. With a single narrow whitish band connecting posterior ends of cephalic furrows on dorsal side of head. Body and head dark reddish brown or purple....torquatus

7. Green or brown, with numerous narrow white or yellow rings at irregular intervals; head with white ring about midway between brain and tip ....geniculatus
7. Deep brown or black; middle of head without white ring....8

8. Deep brown, chestnut, or slaty, sometimes with greenish tinge; with narrow transverse pale yellow rings at intervals along whole length of body; with 7 to 15 very inconspicuous, fine, hairlike longitudinal lines of yellow on dorsal surface; tip of head white, usually with 2 orange-colored spots....pictifrons
8. Brown, greenish black, or bluish black; without longitudinal lines ....atrocaeruleus

References

Coe, W. R. (1901).  Papers from the Harriman Alaska Expedition. XX. The nemerteans.. Proc. Wash. Acad. Sci.. 1-110.
Coe, W. R. (1904).  Nemerteans of the Pacific coast of North America. Part II. Harriman Alaska Series. 11, 111–220.
Gibson, R. (1995).  Nemertean species and genera of the world: an annotated check-list of original names and description citations, synonyms, current taxonomic status, habitats and recorded zoogeographic distribution. Journal of Natural History . 29, 271–562.
McIntosh, W. C. (Submitted).  A monograph of the British annelids. Part I. The nemerteans.. 214 pp..