Oligaphorura groenlandica (Tullberg, 1876)

Babenko, Anatoly B. & Fjellberg, Arne, 2015, Subdivision of the tribe Oligaphorurini in the light of new and lesser known species from North-East Russia (Collembola, Onychiuridae, Onychiurinae), ZooKeys 488, pp. 47-75 : 56

Taxon classification Animalia Collembola Onychiuridae

Oligaphorura groenlandica (Tullberg, 1876)

Lipura groenlandica Tullberg, 1876: 41.

Oligaphorura groenlandica (Tullberg): www.collembola.org

Remarks.

Pomorski’s (1996) description of the furcal area of the first instar was as follows: … q-chaetotaxy - 3 chaetae, area furcalis with 2+2 setulae below cuticular furrow and 2+2 setae at base [all together 4+4 setae]. It was based on a single specimen from a bisexual population from Wolin Island on the Polish shore of the Baltic Sea. Weiner’s description ( 1996): … small, finely granulated cuticular fold or quite a deep pocket with 2 setae on its posterior edge, sometimes with 1+1 additional setae and two other dental setae posteriorly, with manubrial setae on both sides and with other manubrial setae usually in two rows is more complicated. According to the interactive key on the www.collembola.org Oligaphorura should have two dental setae on the fold or posteriorly and three manubrial rows of setae behind them. In fact, the type species of the genus, Oligaphorura groenlandica (or more correctly the most common parthenogenetic form of this species) has no cuticular fold or clear furrow, just an area with fine granulation in anterior third of the sternum of Abd.4 ( Fjellberg 1998). In adults, the position of setae of the furcal area is rather irregular due to weak polychaetosis (Fig. 17) and juveniles clearly differ from that described by Pomorski with only 3+3 setae in front of the 3+3 q-setae (Fig. 18).

Unfortunately, this parthenogenetic form is not the only one present in the northern areas of the Palaearctic. On Taimyr Peninsula and Novosibirsk Islands another bisexual form was found. Probably the same (or similar) form exists in southern Norway ( Fjellberg 1998) and Poland ( Pomorski 1998). Its furcal area is more similar to the described pattern for Oligaphorura groenlandica by Pomorski (1996) with cuticular fold and 4+4 setae between the fold and q-setae in the first instar juveniles (Fig. 26). In adults, two “dental” setae set in front of three irregular manubrial rows of setae (Fig. 25). These two forms are very similar and apart from the furcal area, differ only in size (the parthenogenetic form is larger) and in differentiation of the medial setae on Abd.5: “microsetae” m1 (thin and pointed) are much longer than macrosetae a1 and p1 (straight and truncate) in the true parthenogenetic Oligaphorura groenlandica . Bisexual specimens usually have m1 curved and short and a1 and p1 long and straight. There are also some differences in psx formulas: 10/000/222201+1m, upper subcoxae with 2-2-2 psx in the bisexual form and 10/000/222101m, subcoxae 1-1-2 in the parthenogenetic one. Unfortunately the number of psx in the latter form is not stable. Some specimens lack postlabial psx or one of psx on anterior abdominal sterna, others may have additional psx on Abd.4 or on paired anal lobes; and anterior psx on subcoxae of fore and middle legs can be just invisible due to position. Pomorski (1998) gave slightly different formula for the Polish specimens: 1/000/122101m. Thus several similar forms do exist in Palaearctic, but the real Oligaphorura groenlandica described by Tullberg from Greenland and Svalbard probably belongs to the main parthenogenetic form with circumpolar distributional range lacking cuticular fold on the sternum of Abd.4.