Overview

Comprehensive Description

Description

“Macrobiotus furcatus n.sp. (Plate II. Figs. 6a to 6d.)

 

Specific Characters.—Large , hyaline, in form like M. hufelandi, with claws in pairs, which are united half way up as in that species, but with stronger supplementary points. Teeth slightly curved, with a small furca. Pharynx very small, oval or rhomboid, thickenings in each row,—first, short nut next gullet, then three equal rods, about twice as long as broad, then a very obscure small nut. Dark eyes. Eggs spherical, with conical processes, which are dichotomously branched twice or thrice. Length about 600 µ, pharynx of adult 46 µ long.

 

By far the most abundant Tardigrada collected. The eggs were still more numerous than the adults. By squeezing one fully developed young out of the egg, I was able to establish the identity of structure both of claws and pharynx with the commonest adult Macrobiotus in the collections.

 

This species may be regarded as the South Orkney representative of M. hufelandi (14), with which it has affinities in all points of structure. The processes on the egg are most conspicuously different, yet their form is the same, only they are dichotomously divided at the apex. Most of the processes are twice furcated, with slight traces of a third division. Some have a perforation lower down than the first fork. The egg measures 83 µ without the spines, 105µ over the spines. The pharynx differs in the complete separation of the first two rods, which in M. hufelandi are almost joined. The pharynx is relatively much smaller, but it is probably much contracted.

 

The claw are very similar to those of M. hufelandi, but the supplementary points are almost as large as the large as the main claw. I could never see clearly two distinct supplementary points on the same claw, as RICHTERS found to be the case in M. hufelandi; but the appearance in optical section (fig. 6c) supports the belief that there are two here also. Owing to diffraction effects the true form of supplementary points on the claws of Macrobiotus is difficult to make out.

 

The processes of the egg have a very remote resemblance to those of M. granulates, Richters (9), but this does not indicate any affinity whatever, as the entire organisation is different. The processes in that species are divided into several points, but they are not dichotomous.”

 

(Murray, 1906: 327-328)

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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