Diphascon greveni sp. nov. (fig. 29, phot. 44, 45)
Hypsibius (Diphascon) scoticus: JENNINGS, 1976a, b.
Length 250-415 μm. The body is white, cuticle smooth. No eyes. The length of buccal tube is 100 μm (in a speciment 415 μm long), its width 2.8 μm. The mouth tube is 34 μm long. No drop-shaped thickening between the mouth tube and flexible part of buccal tube. The pharynx oval (45 X 30 μm), with two large apophyses, three macroplacoids, a microplacoid ad a septulum (fig. 29b, phot. 44, 45). The second macroplacoid is the shortest, third one the longest (I-6; II-5; III-9 μm). The macroplacoid row is 22 μm long. The septulum (2 μm) is a little bigger than the microplacoid (1 μm). Legs of I-IIIrd pair with long cuticular bars at the bases of inner claws (fig. 29a, c). The bases of all outer claws (I-IV) with small but distinct spines (fig. 29c-e). Those spines occur also on the bases of inner claws of IVth pair of legs. The bases of inner claws of I-IIIrd pair of legs are smooth (fig. 29c). Claws main branches with distinct accessory spines. The bases of outer claws main branches of IVth pair are broad and the accessory spines of the these claws are the biggest (fig. 29d, e). The outer claws of IVth pair are 24 μm long. The investigated features variability of that species is given in Table VII, VIII.
The new species is very similar to Diphascon scoticum MURRAY, 1905, and particularly to D. higginsi BINDA, 1971, and to D. mirabilis sp. nov., a species described in this paper as well.
By the habit of the body and the structure of the buccal apparatus the new species resembles D. scoticum MUR.*, however, it differs distinctly from it by possessing septulum and a different structure of claws. The bases of the claws in D. scoticum MUR. do not possess developed fine spines (they are smooth), they have smaller accessory spines on main branches of claws (particularly on outer claws of the IVth pair of legs), and between the bases of outer and inner claws there occur fine cuticular bars which are lacking in D. greveni sp. nov.
D. greveni differs from D. higginsi BINDA** by spines on the bases of outer claws of I-IIIrd pairs of legs (which are lacking in D. higginsi BINDA), considerably greater accessory spines on the main branches of claws (especially on the outer claws of IVth pair of legs), more massive claws in general, comparatively greater cuticular bars on the legs of I-IIIrd pairs, a longer and wider buccal tube. Furthermore, these species differ also by the size of macroplacoids. In the new species the second macroplacoid was the shortest, on the other hand, in the compared individuals of D. higginsi BINDA the size of macroplacoids either increased towards the back of the body or (in one specimen) two first macroplacoids were equally long. These observations agree with the original description of D. higginsi BINDA.
However, lately PILATO (1974, tab. I; 1975, tab. I) gave other lengths of macroplacoids for D. higginsi BINDA, i.e. either the second macroplacoid is the shortest, or the two first are of equal length. However, this author (l.c.) presents also original drawings of the buccal apparatus of this species (comp. also BINDA, 1971), on which the first is always shorter than the second one. Since the data from the table and drawings contradict each other, it should be presumed that there was a printer’s mistake in the tables. Therefore one can presume that the differences in the length of two first macroplacoids are also a good feature differentiating these two species.
The new species is also very similar to Diphascon mirabilis sp. nov. One of the essential differences is the occurrence in D. mirabilis sp. nov. of drop-shaped thickenings between the mouth tube and the flexible part of the buccal tube and the lack of spines on the bases of both claws of I-IIIrd pairs of legs. Other differences between these two species are given in the description of D. mirabilis sp. nov. and in Tables VII-IX
Localities: King George Island- 5(1), 8(13, including holotype), 11(1), 14(7)
Type repositories. Holotype and 19 paratypes in the collection of DAM, 1 paratype in NMNH, 1 paratype in BAS.
The new species was recorded as Hysibius (D.) scoticus MUR. by JENNINGS (1976a, b) from South Georgia, South Orkney Island, South Shetland Islands, Marguerite Bay and Alexander Island.
The species is dedicated to Dr. Hartmut GREVEN, Zoologisches Institut, Münster.
*The presence of D. scoticum MUR. in Antarctica requires confirmation, taking into consideration the revision of PILATO (1974), the description of D. greveni sp. nov. and D. mirabilis sp.nov.
**The new species was compared with specimens of D. higginsi BINDA from Poland. The determination correctness of the latter was kindly confirmed by Prof. Dr. G. PILATO.”
(Dastych, 1984: 424-428)
