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Description

Achelia spicata (Hodgson) (Text-figs. 13 and 14).

 

 

Austrothea spicata, Hodgson, 1914-1915, p. 147

 

 

Occurrence. – Station 220, off Cape Adare, 45-50 fathoms; 23 females, 13 males. Station 355, McMurdo Sound, 300 fathoms; 1 female, 1 male.

 

 

Description. – Trunk hardly longer than its greatest width, across the second lateral processes; first two intersegmental articulations very distinct, third marked only by a faint superficial groove. Lateral processes more or less well separated, the last two pairs usually separated to the base; a pair of dorsal tubercles, the posterior the larger, on each of the first three lateral processes, and a small anterior tubercle only on the last lateral process. Cephalon a little wider than long, without anterior-lateral tubercles. Ocular tubercle much higher than wide, inclined forwards, conically tapered above the eyes; anterior part of eyes not much larger than posterior.

 

 

Proboscis about two-thirds of length of trunk, widest about the middle, where its width is less than half its length.

 

 

Abdomen horizontal, little shorter than proboscis, reaching beyond middle of second coxa of last legs, slightly clavate and bluntly pointed.

 

 

Chelophores extending to, or a little beyond, middle of proboscis. Palps with second and fourth segments equal, sixth and seventh produced ventrally, terminal segment little longer than preceding.

 

 

First coxae each with two conical tubercles of which the posterior is the larger. Femur and first and second tibiae subequal or slightly longer successively; femur from about three times as long as deep in the female to more than six times in the male. Auxiliary claws one-third as long as main claw.

 

 

Sexual differences. – Apart from the usual differences in the diameter of the femora, the males apparently tend to have the trunk more elongated and the lateral processes more widely separated than in the females; they have also the tubercles on the lateral processes more prominent and those of the first coxae forming suprs which may be as long as the width of the segment.

 

 

Variation. – The specimens examined differ among themselves in the relative length of the body, the degree of separation of the lateral processes, and the length of the legs. Two extreme types are represented in Figs. 13 and 14, but many specimens are intermediate. In the more elongated forms the spiniform tubercles on the lateral processes and first coxae are longer, as is also the conical apex of the ocular tubercle.

 

 

Two specimens differ from the typical form in the segmentation of the body. In one, there is a very distinct articulation between the last two somites; in the other, the only articulation is between the first two.

 

 

Measurements, in mm. – The measurements here given are taken from two fairly representative specimens: --

 

                                                                        
 

 
 

Male

 
 

Female

 
 

Length of proboscis

 
 

1.2

 
 

1.04

 
 

Greatest width of proboscis

 
 

0.5

 
 

0.44

 
 

Length of trunk

 
 

1.72

 
 

1.6

 
 

Width across second lateral processes

 
 

1.6

 
 

1.52

 
 

Length of abdomen

 
 

1.04

 
 

0.92

 
 

Third right leg -

 
 

Coxae

 
 

1.52

 
 

1.48

 
 

Femur

 
 

1.8

 
 

1.84

 
 

First tibia

 
 

1.88

 
 

2.0

 
 

Second tibia

 
 

2.0

 
 

1.92

 
 

Tarsus and propodus

 
 

1.08

 
 

1.2

 
 

Main claw

 
 

0.56

 
 

0.52

 
 

Auxiliaries

 
 

0.16

 
 

0.16

 
 

 

Remarks. – I have examined two of Mr. Hodgson’s syntypes. One is immature, and the other, an adult female, is of a slender type with very long legs and with the femora less dilated than is usual in this sex. In other respects it resembles very closely indeed the slender male here figured (Fig. 14) except that the lateral processes are not so well separated.” (Calman 1915, 57-60)

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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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