Comprehensive Description

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Description

Cilunculus acanthus n. sp. (Fig. 207-209)

 

 

MATERIAL EXAMINED: --

 

Eltanin Sta. 268, 10 males, 6 females, 1 juv.

 

Holotype, 1 ovigerous male, U.S.N.M. No. 112003; allotype, female U.S.N.M. No. 113004; Paratype male B.M. (N.H.) Regn. No. 1966.3.11.4; female paratype, B.M. (N.H.) Regn. No. 1966 3.11.5

 

 

DESCRIPTION: -- Based on 16 adults and 1 juvenile.

 

 

PALP: Palp 9-segmented, terminal segments with a dense armature of long spines ventrally.

 

 

PROBOSCIS: Proboscis shape B:1, not much longer than wide, mouth large, triangular.

 

 

TRUNK: Trunk rather stout but graceful; lateral processes widely separated and diverging so that their ends describe an ellipse; trunk somites articulated, raised posteriorly in ring-like expansions. Each trunk somite except the last has a tall pointed median dorsal tubercle on the posterior swelling, that of the cephalic somite being the lowest; ocular tubercles two or three times taller than the trunk tubercles, slender and pointed; eyes indistinct, near the tubercle apex; abdomen about three-quarters the trunk length, swelling to its largest diameter near the tip; a very long, erect, slender spine at the median dorsal distal margin of each lateral process, lateral and dorsal spines at the middle of the abdomen.

 

 

CHELICERAE: Chelicerae 3-segmented, long spines at the end of the 2nd segment; chelae subchelate, small.

 

 

OVIGER: Oviger of male large, stout, 10-segmented, 7th segment with recurved spines, terminal segment with two heavy denticulate spines with four large denticulation on each side; single large denticulate spines on segments 8 and 9, and probably also on segment 7.

 

 

LEGS: Female slightly slenderer in general aspect, with slightly swollen femur, without the conspicuous cement gland tube; somewhat less spinose than male. Very long, straight spine at end of femur in both sexes, this is often broken off. Many, slender, curved spines on coxae and long segments of legs. These spines are several times as long as the diameter of the leg segments; long straight cement gland tubercle just beyond the middle of the femur in the male. The cement gland lies just beneath the dorsal part of the broad base of the tubercle; propodus without basal spine or heel; terminal claw about half as long as propodus; accessory claws absent.

 

                                                                                                 
 

Dimensions

 
 

Holotype

 
 

Allotype

 
 

 
 

Male

 
 

Female

 
 

Trunk length

 
 

3.5 mm

 
 

3.75 mm

 
 

Proboscis length

 
 

1.8

 
 

2.0

 
 

Proboscis width (max)

 
 

1.5

 
 

1.5

 
 

Abdomen length

 
 

2.8

 
 

3.0

 
 

Cephalic somite length

 
 

1.5

 
 

1.25

 
 

2nd lateral process width

 
 

3.3

 
 

3.3

 
 

Third leg:

 
 

Coxa 1

 
 

0.8

 
 

0.8

 
 

Coxa 2

 
 

1.2

 
 

1.0

 
 

Coxa 3

 
 

0.8

 
 

0.8

 
 

Femur

 
 

2.5

 
 

2.4

 
 

Tibia 1

 
 

3.2

 
 

3.2

 
 

Tibia 2

 
 

2.9

 
 

3.0

 
 

Tarsus

 
 

0.1

 
 

0.1

 
 

Propodus

 
 

0.9

 
 

1.0

 
 

Main claw

 
 

0.6

 
 

0.6

 
 

Total leg length

 
 

13.0

 
 

12.9

 
 

 

DISTRIBUTION: -- The type locality is 64°1.2’S, 07°44’7” to 64°07’S, 67°44’W, depth approximately 2,700 m.

 

 

DISCUSSION: -- This species differs from others of its genus in lacking accessory claws. As Hedgpeth (1949) has suggested, the presence or absence of auxiliary claws is probably not a good generic character in the Ammotheidae (cf. Austroraptus). Cilunculus acanthus appears to be closest to C. hirsutus Clark, from New South Wales, but is distinct in the structure of the male oviger, size and position of the large femoral cement gland tube, and shape and size of the proboscis, which is shorter and more globose than in hirsutus. C. acanthus also has fewer denticulations on the ovigeral spines. The chela lacks the peg-like dactyl described for C. hirsutus; in C. acanthus it is a blunt lobe.” (Fry & Hedgpeth 1969, p. 126)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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