Comprehensive Description

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Nymphon adareanum


(Plate III., Fig. 3.)



Specific characters : --


Body smooth and slender, with lateral processes widely separated.


Ocular tubercle short, rounded.


Palps five-jointed, proportions of last three 2.5 : 1.25 : 1.75.


Oviger ten-jointed, without denticulate spines, but with very few simple curved spines.


Legs of moderate length, with rather long setae, terminal claw with two well-developed auxiliaries.



This small species has a fairly well-built body, with the lateral processes rather widely separated, and as long as the diameter of the trunk. The trunk articulations are very distinct, and immediately behind the lateral processes. No setae of any kind are to bee seen on the body.



The Cephalon is stout but not widely expanded, showing two distinct lobes for the reception of the chelifori; it is not quite as long as the second and third trunk segments together.



The Ocular tubercle is very stout, of small elevation, rounded at the summit, and carries four well-developed eyes. It lies just in front of the first pair of lateral processes and behind the neck.



The Abdomen is of moderate dimensions, curved upwards, and not separted by an articulation from the trunk.



The length of the body is 2.75 mm., and its extreme width 1.5 mm.



The Proboscis arises on the ventral side of the trunk, and measured ventrally it is nearly one-third the length of the entire body. It is stout, gently tapering to a rounded extremity, quite smooth.



The Chelifori are well developed; the scape is single-jointed, extending beyond the proboscis; provided laterally with comparatively long setae. The chela is not very long, the palm and fingers occupying approximately equal halves; the former is covered with setae, and the fingers, rather curved, are supplied with a very moderate number of slender teeth rather widely separated.



The Palp is five-jointed, and rises underneath the chelifori (fig. 3a); as usual, the first joint is very small and the second long. Owing to distortion in mounting this appendage, the comparative length of the second and third joints cannot be very accurately stated, but the second appears to be twice the length of the third; the fourth is half the length of the third, and the fifth is longer than the preceeding, the proportions being 5 : 2.5 : 1.25 : 1.75. The terminal joint is ovoid, and fairly well supplied with comparatively long setae; the three preceeding joints have well-developed distal fringes and a small number of setae scattered along the shaft; these are most numerous on the third joint.



The Oviger is ten-jointed, and rises from a small process of the trunk, visible dorsally, just in front of the first pair of lateral processes (fig. 3b). The first three joints are very small; the second and third are subequal in length, the latter much the more slender; the fourth is longer than the three preceding ones together; the fifth is twice as long, much curved, and bears a few setae on its outer margin; the sixth is half as long as the fourth. The four terminal joints are very small, the first being the largest, and all bear two or three long setae distally. The terminal claw is long and slender, with five slender teeth set at irregular intervals. Of denticulate spines, such as characterize the genus Nymphon, there are none, but of special spines there are 2 : 2 : 2 : 1 on the four joints; these are curved blades without any other distinguishing feature.



The Legs are not very long, extending to nearly 11mm. from the trunk. Of the three coxae, the second is as long as the other two together, the first being by a little the smallest; the proportions of the remaining joints being 4 : 5: 6 : 0.75 : 2. The terminal claw is large and stout, with two well-developed auxiliaries. The lateral line is distinct throughout. The setae have a rather indistinct linear arrangement, those on the sides of the coxae are prominent, especially on the second; on the third they are more confined to the ventral surface, and the distal fringe is fairly well developed. On the femur the setae are long and straggling, chiefly lateral, and ventrally there is a row of small tubercles. On the two tibiae, but more especially the second, the setae are most abundant, largest on the first. Ventrally they are much smaller, the distal fringe of the second tibia becoming spinous. The tarsus is a very short joint with long setae dorsally, smaller and more numerous ones ventrally, which become delicate spines distally. The propodus is covered with setae dorsally, and ventrally there is a row of rather strong spines, and of these the middle ones are strongest.



The single specimen is a male, carrying young, apparently just hatched. The Genital apertures are to be found on the second coxae of the two posterior pairs of legs.



From the root of a Laminarian taken in 17 fm., Cape Adare, 24th February, 1904.” (Hodgson 1907, 23-25)


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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