Macrobiotus furciger Murray 1906

Macrobiotus furciger Murray, 1906 (Fig. 1)

Material examined. South Georgia, Grytviken: 11 specimens and 4 eggs from a moss sample.

Unfortunately the quality of some photos is not optimal due to the quality of the specimens.

Specimens and eggs found by Dastych in South Georgia perfectly coincide with the description of M. furciger. We think it opportune to add some notes to make a more detailed description of the species.

Description. Cuticle smooth, colourless, eyes present; buccopharyngeal apparatus of Macrobiotus type (Fig. 1 A, B); mouth terminal with ten peribuccal lamellae, an anterior band of small teeth, a posterior ring of triangular teeth, three dorsal and three ventral transverse ridges. Also some supplementary teeth may be present. Stylet supports inserted on the buccal tube at 76.2–77.1% of its length (pt = 76.2–77.1). Other notes about dimensional characters are indicated in Table 1. Pharyngeal bulb with apophyses, three rod­shaped macroplacoids without narrowings, microplacoid present. Third macroplacoid clearly longer than the first two (Table 1).

Claws of the hufelandi type well developed and with very developed accessory points on main branches (Fig. 1 C). Lunules present, smooth on the first three pairs of legs, finely indented on the hind legs.

Eggs laid freely, spherical, diameter 91.7–100.4 m excluding the processes, 110–123 m processes included. Distal portion of the processes (20–24 in the circumference) twice or thrice divided; the terminal branches appear as short terminal points (Fig. 1 D, E). Each subdivision may be dichotomic or multiple, i.e., two or more branches may be formed. Process surface has some small refracting areas (Fig. 1 D, E), some larger refracting areas are in the distal portion and in the branches (this character has been noted by Murray, 1906). In the largest measured egg the processes are 12–13 m high; the basal diameter is variable from 11 to 14.5 m. The base of each process has many short digitations forming a ring of dots; the egg shell has many small refracting points and therefore it has a reticular sculpture with very small meshes.

furciger aradasi sp. nov. divergens sp. nov. sicheli sp. nov.

n = 2 n = 3 n =7 n = 3 Remarks. As above mentioned, we compared material from different geographical areas. Dastych (1984) studied specimens (and eggs) from South Georgia and South Shetland Islands, described some differences concerning both animals and eggs but he attributed all specimens and eggs to M. furciger. In our opinion the specimens from South Georgia belong to Macrobiotus furciger, while the specimens from King George Island belong to a different species later described and named Macrobiotus aradasi sp. nov.

Argue (1972) recorded M. furciger from Canada but Binda & Rebecchi (1992) ascertained that the specimens and eggs studied by Argue belong to a different species they named M. pilatoi. We agree with the opinion of Binda and Rebecchi. M. pilatoi is also present in Italy.

Ramazzotti (1964) found M. furciger in Chile but he noted that the eggs have a smaller diameter than that indicated in the description of the species; therefore we think that the presence of M. furciger in South America needs to be confirmed.

Horning et al. (1978) attributed to M. furciger specimens and eggs in spite of some differences. We examined 15 specimens so named by Horning et al., and concluded that they belong to a new species later described and named Macrobiotus divergens sp. nov.

Binda (1984) attributed to M. furciger specimens and eggs from South Africa very similar but not identical to this species. After the comparison of this material with the specimens of M. furciger from South Georgia, we concluded that the specimens from South Africa belong to a new species later described and named Macrobiotus sicheli sp. nov.

Maucci & Durante Pasa (1980) attributed to M. furciger three specimens and three eggs from Andaman Islands, but the photography of one specimen (Maucci & Durante Pasa, 1980, Fig. 6) demonstrates that it surely belongs to a different species; the characters of the egg (Maucci & Durante Pasa, 1980, Figs. 7, 8) are not clearly visible and therefore the presence of M. furciger in the Andaman Islands, in our opinion, needs to be confirmed.

Also the presence of this species in Europe, in our opinion needs to be confirmed. Maucci (1986) recorded M. furciger from Italy, but some characters indicate differences from the typical material (posterior crown of the buccal armature formed by teeth thin and spaced; lunules small; egg processes without refracting areas). In our opinion also the presence of the species in Italy needs to be confirmed.

The species has been also recorded from Hungary (Iharos, 1947) Spain (Maucci, 1991), Poland (Weglarska, 1959) and Russia (Biserov, 1991), but no drawings or photographs were provided. De Coninck (1939) recorded M. furciger from Iceland but he found only specimens and no eggs, and therefore we think that this record needs to be confirmed. Dastych (1988) in the monograph on tardigrades from Poland illustrated a specimen, buccopharyngeal apparatus and claws, but he recorded the species on the basis of the record of Weglarska (1959), and he used the same drawings he used for his population from South Georgia (Dastych, 1984), and he wrote (Dastych, 1988, p. 103): “The occurrence of this species in Poland needs a confirmation.”

In conclusion, M. furciger is surely widespread in Antarctic and Subantarctic areas; some records of the species in this area may refer to a different species. The records of this species from different geographical areas in our opinion need to be confirmed.