Macrobiotus blocki sp. nov. (fig. 10, 11, phot.14—20)
Length 150—560 μm. The body is white, some specimens with brown, sparsely distributed pigment. Eyes in the “anterior” position, large. Mouth opening is situated terminally and surrounded by a wreath of lamellae. Buccal apparatus of harmsworthi-type (Fig. 10a, b), buccal cavity wit ha wreath of delicate granulation which is well visible in larger specimens only (immersion, phase contrast; fig. 10c, d). The posterior part of buccal cavity with single wreath composed of bigger andelongated granules with three transversal swllings below them (fig. 10b, c); in two specimens the median swelling (medio-dorsal ridge) is distributed and situated between posterior wreath of granulation and in buccal cavity is usually less developed than on the dorsal side. Between the wreath and transversal ridges on ventral side most often there occur an addition belt of irregularly distributed granules (fig. 10d). Also the medio-ventral ridge is often divided into two or three parts. The buccal tube is twice bent (47 μm in length, outher diameter 6 μm—dimensions in the speciment 390 μm long) and with distinct apophyses. Pharynx oval (36 X 33 μm), with three macroplacoids and a rather large microplacoid (fig. 10b). Firt macroplacoid is the biggest (5 μm), second one the smallest (4 μm).Third macroplacoid is a little smaller than the first (4.5 μm) or sometimes of its length. The claws are rather stumpy and “V”-shaped, especially on I-IIIrd pair of legs. The claws lunules of I-IIIrd pair are small, smooth (fig. 10e). The claws of IVth pair have a little bigger lunules provided with tiny and irregular teeth (fig. 10f). Main branches of all claws with distinct accessory spines. Claws of IVth pair are 15 μm long.
The egg white, spherical or rarely oval. The chorion processes are conical, their tips are sharply pointed and mostly strongly elongated (fig. 11a-I, phot. 14, 15, 18-20). The tips with characteristic ornamentation composed of roundish bubbles (?) arranged usually in a row of decreasing size towards the apex. There are up to dozen or so bubbles, each one to 3 μm in diameter. The metioned ornamentation is very variable (fig. 11a-I, phot. 14-20) even within the same egg (fig. 11h); in a few cases the tips were quite smooth (phot. 20). Each process has characteristic finger-like appendices at the base which ends are usually a little thickened (fig. 11a, b, e, f, phot. 16-20). They are visible from above as a wreath of sparsely distributed thickenings (dots), up to dozen or so with the neighbouring ones though often they are situated very near one another; but when connected the characteristic “pseudoareolation” is formed. The processes surface is covered with very sparsely distributed, woundish or oval dots (pores?) of diameter up to 1 μm (mostly 0.5-0.8 μm). Often the dots are also developed on the finger-like appendices which are quite smooth (excluding “pseudoareolation”) or covered with minute, sparsely and irregularly distributed granulation. Diameter of eggs without processes 70-90 μm, with processes 90-130 μm. Height of processes 10-25 μm, diatmeter of their bases (including finger-like appendices) is 8-14 μm. The circumferences of eggs with 15-24 processes. A dozen or so eggs, with well developed embryos.
The eggs are distinguished by great variability of shape processes and ornamentation of their tips. The characteristic wreath of thickenings (appendices) at the processes bases was sometimes poorly developed.
Macrobiotus blocki sp. nov. belongs to species of “harmsworthi group” in which the specimens are very similar to each other, and the main differences occur in the structure of eggs. The eggs or the new species are most similar to Macrobiotus harmsworthi coronatus BARROS, 1942. Furthermore, the thickenings at the base of chorion processes in M. harmsworthi coronatus BAR. Never touch each other (fig.11j), and the number of processes on the circumference of eggs is comparatively smaller than in the new species. Adult specimens of M. blocki sp. nov. differ also from the compared species by fine, irregular spines on the lunules of the claws of the IVth pair of legs (in M. harmsworthi coronatus BAR. The lunules are smooth) and furthermore, the new species has a comparatively longer and narrower buccal tube and a narrower buccal cavity. Main differences in egg structure between these species are given in Table III (comp. also fig. 11).
Localities: Enderby Land-1(2+2 eggs), 2(317+303 eggs, including holotype), 3(18+18 eggs)
Type repositories. Holotype, 260 paratypes and 363 eggs in the collection of DAM, 19 paratypes and 35 eggs in NMNH, 28 paratypes and 12 eggs in BAS, 29 paratypes and 13 eggs in NMNZ.
The species is dedicated to Dr. William BLOCK, British Antactic Survey, Cambridge.”
(Dastych, 1984: 394-397)
