Research Article |
Corresponding author: Anatoly B. Babenko ( lsdc@mail.ru ) Academic editor: Louis Deharveng
© 2015 Anatoly B. Babenko, Arne Fjellberg.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Babenko AB, Fjellberg A (2015) Subdivision of the tribe Oligaphorurini in the light of new and lesser known species from North-East Russia (Collembola, Onychiuridae, Onychiurinae). ZooKeys 488: 47-75. https://doi.org/10.3897/zookeys.488.8123
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The paper is devoted to a taxonomic review of Oligaphorurini from the north-eastern part of Palaearctic. Two new species, i.e. Oligaphorura ambigua sp. n. and O. duocellata sp. n., are described. Four species, O. nataliae (Fjellberg, 1987), O. interrupta (Fjellberg, 1987), O. pingicola (Fjellberg, 1987), and Micraphorura alnus (Fjellberg, 1987), are redescribed on base of the types and new material, and remarks on other species known for the region, O. groenlandica (Tullberg, 1876), O. ursi (Fjellberg, 1984), O. aborigensis (Fjellberg, 1987), and M. absoloni (Börner, 1901), are given to clarify their generic affiliation. Finally, merits and disadvantages of the current subdivision of the tribe are discussed and a key to the northern species of the tribe is provided.
Taxonomy, new species, Oligaphorurini , north-eastern Asia
Two undescribed species of the tribe Oligaphorurini from the upper reaches of Kolyma River (North-East Russia, Magadan region) do not fit the current generic subdivision of the tribe, which is mainly based on revisions made by
Recently
Chribellphorura | Archaphorura | Micraphorura | Oligaphorura | Dimorphaphorura | ||
---|---|---|---|---|---|---|
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Apical vesicle on Ant.4 | present | absent | |||
Tibiotarsal setae | clavate | pointed | ||||
Anal spines | present | absent | present | |||
Furcal rudiment | finely granulated area | small pocket or finely granulated area | finely granulated area, sometimes with a kind of pocket | cuticular fold or deep pocket | finely granulated area | |
Dental setae | four in line | four in two rows | two in line | four in two rows | four in line | |
Manubrial setae | one row | two rows | two rows | two (seldom one) rows | one row | |
Unpaired setae on Abd.6 | p 0 | m 0 | p0 or a0 and p0 | a0 and p0 | a0 and p0 | |
Species involved | allanae | serratotuberculata and some species that have not yet been described | absoloni, pieninensis | groenlandica, montana, uralica, judithae, koreana, linderae | differens | |
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Anal spines | absent | present | |||
Setae on area furcalis | 2+2 setulae + 2+2 setae | 1+1 setulae + 1+1 setae | 2+2 setulae + 2+2 setae | |||
Species involved | serratotuberculata | absoloni, pieninensis | groenlandica, judithae | |||
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AO | in subapical position | normal | “So far the independence of Dimorphaphorura calls for further ground” | ||
Anal spines | absent | present or (rarely) absent | ||||
Distal tibiotarsal setae | 11 | 11 or fewer | ||||
Furcal rudiment | cuticular furrow or finely granulated area | |||||
Dental setae | two or four in one row | four in two rows | ||||
Manubrial setae | number of rows varied | |||||
Abd.5–6 | fused | separated | ||||
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Anal spines | present | present or absent | |||
Distal tibiotarsal setae | 11 | 11 | 5–11 | |||
Furcal rudiment | cuticular furrow | cuticular fold | finely granulated area | |||
Dental setae | 1+1 | 2+2 | absent | |||
ma setae | 2 (at a level with dental setae) | 2 (at a level with posterior row of dental setae) | 2–4 | |||
mm setae | 4–6 | 3–6 | 2 | |||
mp setae | 4–5 | 4–7 | 4–6 |
In 2014 a complete revision of the genus Dimorphaphorura has been undertaken (
A, AB, AC and ABC – four types of labium in Onychiuridae in accordance with the presence of thickened and blunt-tipped setae on corresponding labial papillae (
ABD – the fifth type of labium in Onychiuridae (
Abd.1-6 – abdominal segments
A-B, T-setae, setae M and Y – tibiotarsal setae (
Ant.1-4 – antennal subsegments
AO – antennal organ on Ant.3
a0, m0, and p0 – unpaired axial setae on terga
CNC – Canadian National Collection (Ottawa)
d0 – unpaired axial seta on area frontalis of the head
ma-, mm- and mp- row – anterior, medial and posterior rows of setae on manubrial field (
ms – microsensillum
MSPU – Moscow State Pedagogical University
PAO – postantennal organ
pso – pseudocellus(i)
psx – parapseudocellus(i)
q-setae – proximal setae on furcal field of Onychiuridae (
Th.1-3 – tergal segments
Holotype ♂, Russia, Magadan District, upper reaches of Kolyma River, Bolshoi Annachag Mt. Range, field station “Aborigen” [61°56'N, 149°40'E], mountains above station, rather dry moss/lichen in rock crevices, 1600 m alt., 23 vii 1979, A. Fjellberg leg. (MSPU).
Paratypes 6♂, 5 ♀, and 4 juveniles, same data as holotype (MSPU); 1♂, 2 ♀, and 1 juveniles, same data but moss, lichens on rock, 1650 m alt., 23 vii 1979, A. Fjellberg leg. (MSPU).
Colour white. Size of adults 0.73–0.92 mm. Body slender and elongated, Abd.3-4 clearly widened, Abd.6 short and hardly visible in dorsal view (Fig.
Pseudocellar formulas (pso) as follows, dorsal: 42/133/33354, ventral: 11/000/1111, parapseudocelli (psx) invisible. Each upper subcoxa with two pso, dorsal and ventral. Localization of pso as in Figs
This new species resembles two congeners recently described from the European part of Russia, namely Oligaphorura humicola Shvejonkova & Potapov, 2011 and O. kremenitsai Shvejonkova & Potapov, 2011. All three species lack anal spines and have no cuticular fold on the sternum of Abd.4. Apart from this, the former is characterized by a set of pso on both dorsal and ventral sides on a body, as well as on upper subcoxae identical to that in O. ambigua sp. n., and also has no ms on Th.3 and ventral psx. O. kremenitsai differs from both O. ambigua and O. humicola having more pso on Th.2-3 (42/144/33354 as a whole). Some differences like the uncommon position of anterior pso on head and submedial ones on Abd.4-5 in O. humicola and O. kremenitsai or their reduced tibiotarsal chaetotaxy may be a result of small body size (< 0.6 mm). Nevertheless, the palp structure (ABD-type) in humicola/kremenitsai and the loss of labial papilla C probably reflects a certain genetic distance.
The presence of only four papillae in AO is also an unusual condition in the tribe, shared only with Micraphorura absoloni (Börner, 1901), Oligaphorura palissai (Yosii, 1971) and Dimorphaphorura sophyae Weiner & Kaprus’, 2014. The clear cuticular papillae on antennal tip are also quite characteristic.
The name reflects the uncertain generic position of the new species.
Known only from the type locality, the alpine belt in the upper reaches of Kolyma river.
Holotype ♂, Russia, Magadan District, upper reaches of Kolyma River, Bolshoi Annachag Mt. Range, field station “Aborigen” [61°56'N, 149°40'E], mosses on slope, 1400-1500 m alt., 27.vii.1979, leg. A. Fjellberg (MSPU).
Paratypes 1♂, 1♀, and 1 juvenile, same data as holotype (MSPU).
Colour white. Size of adults 1.2–1.3 mm. Body slender and elongated. Antennae slightly shorter than head, club-like with Ant.4 clearly wider than Ant.3. Subapical organite on Ant.4 peg-like, basal microsensillum set on level with proximal whorl of setae. AO consisting of 5 long papillae, 2 sensory rods, 2 granulated sensory clubs clearly differing in shape (Fig.
Pseudocellar formulas (pso) as follows, dorsal: 32/(1)233/33343, ventral: 11/000/1111(2), parapseudocelli (psx) hardly visible (probably due to long preservation), but psx on unpaired anal lobe present. Upper subcoxae with 2-(2)3-3 pso, one dorsal and 1-2 ventral. Localization of dorsal pso as in Fig.
Several uncommon features, like 2+2 pseudocelli and few setae on Th.1, the presence of pseudocelli on several abdominal sterna, the absence of setae on thoracic sterna, and a furcal remnant in the form of a finely granulated area with 4 small setae behind it, permit easy identification of the new species. In addition to O. duocellata sp. n. nine known species of the tribe possess pseudocelli on several abdominal sterna. Three of them, Archaphorura serratotuberculata (Stach, 1933), A. alavensis Simón & Luciáñez, 1994, and A. marcuzzii (Cassagnau, 1968) are usually considered as representatives of the genus Archaphorura due to the absence of anal spines. The presence of ventral pso in the former species is uncertain as specimens from Moscow vicinity contrary to those from Poland (see
The only known species of the tribe with AS and pso on several abdominal sterna (M. multiperforata (Gruia, 1973), M. uralica (Khanislamova, 1986), are within Micraphorura on the www.collembola.org or treated as Dimorphaphorura (D. olenae Weiner & Kaprus’, 2014). M. multiperforata is a unique species with dorsal pso multiplication, whereas M. uralica seems to be the most similar to O. duocellata sp. n. having also more than 2 pso on subcoxae (a unique character) and no setae on thoracic sterna, a character which is known only for species from eastern parts of Asia and North America, i.e. Oligaphorura nuda (Fjellberg, 1987), O. judithae (Weiner, 1994), O. linderae (Weiner, 1994), O. montana Weiner, 1994, O. pseudomontana Sun & Wu, 2012, and O. chankaensis Sun & Wu, 2012.
Named after the presence of 2+2 pso on Th.1, a character previously unknown for the tribe.
Known only from the type locality.
Aphorura absoloni Börner, 1901: 422.
Micraphorura absoloni (Börner): www.collembola.org
Juveniles from Magadan (NE Russia) have a furcal field with 2+2 setae behind the cuticular furrow, followed by 3+3 q-setae (Fig.
Onychiurus (Archaphorura) nataliae Fjellberg, 1987: 281.
Micraphorura nataliae (Fjellberg): www.collembola.org
holotype, ♂, “USSR, Chukotka, Chaun Bay [68°44'N, 170°36'E], upland heath, soil, 13.viii 1977” (CNC 165046, type No 20114); paratypes: 1 juv. same data (CNC 165136, type No 20113); 3♀, same place, Loc. S-1, Sept. 1975 (CNC 165135, type No 20112), all S.F. MacLean leg.
15 specimens, Russia, Novosibirsk Islands, Kotel’nyi, Balyktakh river [75°03'N, 140°10'E], various habitats, vii 1994, A. Babenko leg.
Colour white. Size 0.8–0.9 mm. Body shape cylindrical. Antennae about as long as head, Ant.3-4 broad, club-like. Ant.4 with subapical organite and microsensillum located in proximal row of setae. AO consists of 5 long and thin papillae, two sensory rods, two granulated sensory clubs (internal straight, external much bigger and bent), 5 guard setae, and a lateral microsensillum which is set below the organ. Ant.1 and 2 with 8 and 14-15 setae, respectively. PAO with 3-4 lobes, slightly longer than nearest pseudocellus. Labrum with 4/5-2-2 setae but variations also seen. Apical part of labium with thick terminal setae on papillae A and C, usually complete number of long guard setae (7) and 4 spiniform ones, 6 proximal setae present. Basal fields of labium with 4+5(6) setae. Maxillary palp simple with two sublobal hairs. Maxillae not modified.
Pseudocellar formula (pso) as follows, dorsal: 32/033/33343, ventral: 2/000/0000, parapseudocelli (psx) invisible. Each subcoxa with one pso, psx invisible (absent ?). Granulation fine, clearly coarser around pseudocelli on all segments. Dorsal chaetotaxy almost symmetrical, setae smooth, macrosetae clearly differentiated only on abdominal tip, sensory setae indistinct. Th.1 with (5)6+6 setae. Lateral ms present only on Th.2. On head p1 clearly above p2, its position on Th.2-Abd.3 rather variable but usually more or less at a level with p2. Abd.1-3 with setae p4 present as a rule. Abd.5 with m1 curved, thinner and shorter than the straight a1 and p1, the latter usually shorter than anterior macrosetae a1. Unpaired setae: d0 absent, Abd.5 often with seta p0 present, Abd.6 with two axial macrosetae, a0 clearly shorter than a2. Thoracic sterna with 0, 1+1, 1+1 setae. Furca as small cuticular furrow in some distance from anterior border of sternum. Chaetotaxy of furcal field in juveniles as in Fig.
Originally described as Onychiurus (Archaphorura) nataliae, the species is now listed under Micraphorura on www.collembola.org. Nevertheless the chaetotaxy of the manubrial field in juveniles of this species is identical with that found in northern parthenogenetic populations of O. groenlandica (Tullberg, 1876) (cf. Fig.
In the interactive key on www.collembola.org the species keys out with Oligaphorura interrupta (Micraphorura on www.collembola.org) which can easily be distinguished by higher number of abdominal pso, presence of ms on Th.3 and absence of ventral setae on Th.2.
Five known species of the tribe possess the same number of dorsal and ventral pseudocelli as nataliae, i.e. O. pingicola (Fjellberg, 1987), O. koreana (Weiner, 1994), Dimorphaphorura raxensis (Gisin, 1961), D. chatyrdagi (Kaprus’, Weiner & Pomorski, 2002), and D. sanjiangensis Sun & Wu, 2012. O. nataliae differs from the above Oligaphorura species (O. pingicola and O. koreana) in having no ms on Th.3. D. raxensis according to
The presence of 7 long guard setae of labium in such small species as O. nataliae is an uncommon character in the tribe and needs additional confirmation being seen in few specimens. Only five other Asiatic species, D. sanjiangensis, Micraphorura changbaiensis Sun & Wu, 2012, O. aborigensis (Fjellberg, 1987) and the two new Oligaphorura species described above, share this character with O. nataliae whereas 18 species of the tribe are known as having only 6 long guards.
Onychiurus (Archaphorura) alnus Fjellberg, 1987: 282.
Dimorphaphorura alna (Fjellberg): www.collembola.org
Dimorphaphorura alnus (Fjellberg):
holotype, ♀, “ USSR, Magadan Reg., Aborigen [field station, 61°56'N, 149°40'E], deep, moist Pinus pumila litter, 27 vii 1979“ (CNC 165044, type No 20108); Paratypes, 5 ♀, same sample (CNC 165130, type No 20111); 1 ♀, same region, “Alnus litter in dense thickets, 25 vii 1979” (CNC 165129, type No 20110), all A. Fjellberg leg.; 9 specimens (in bad condition), “USSR, Chukotka, Chaun Bay [68°44'N, 170°36'E], Sept. 1975” (CNC 165128, type No 20109), S.F. MacLean leg.
1 ♂, Magadan District, Bolshoi Annachag Mts. Range, upper reaches of Kolyma River, field station “Aborigen”, valley bottom near station, moss and litter of Larix/Pinus on slope, 25 vii 1979, A. Fjellberg leg.; 5♀ and 3♂, same region, deep moist litter in thickets of Pinus pumila, 1200 m alt., 27 vii 1979, A. Fjellberg leg.; 2 ♂, same region, stand of Pinus pumila, Betula, Larix dahurica, and Alnus fruticosa, 24 vii 1979, V. Behan leg.
Colour white. Size 0.8-0.9 mm. Body shape cylindrical. Antennae about as long as head, Ant.3-4 broad, club-like. Ant.4 with subapical organite and microsensillum located in proximal row of setae. AO consists of 5 long and thin papillae, two sensory rods, two granulated sensory clubs (internal almost straight, external much larger and bent), 5 guard setae and a lateral microsensillum which is set below the organ. Ant.1 with 8 setae, Ant. 2 with (12)13 setae. PAO with 3-4 lobes, slightly longer than nearest pseudocellus. Labrum with 4/3-2-2 setae. Apical part of labium with thick terminal setae on papillae A and C, 6 long guard setae and 6 proximal setae present, basal fields with 4+5 setae. Maxillary palp simple with two sublobal hairs.
Pseudocellar formula (pso) as follows, dorsal: 32/133/33343, ventral: 2/000/0001, parapseudocelli (psx) invisible. Each subcoxa with one pso, psx absent. Granulation rather coarse, especially around pseudocelli and on Abd.6. Dorsal chaetotaxy almost symmetrical, setae smooth and fine, macrosetae poorly differentiated, sensory setae (2/011/222211) more or less distinct, Th.1 usually with 6+6 setae, Th.2-3 with lateral ms, p1 on head and Th.2-3 almost on level with other medial p-setae. Abd.5 with m1 longer than a1, subequal to p1. Unpaired setae: d0 and axial seta on Abd.5 absent, Abd.6 with two axial setae, a0 subequal to a2. Thoracic sterna with 0-1(2)-1(2-3) setae on each side of ventral line. Upper subcoxae usually with 3-3-4 setae. Furca as a small area with fine granulation in middle section of sternum of Abd.4, some setae present on sternum anteriorly to furcal remnant. In juveniles manubrial field with usual 3+3 proximal q- setae and 2+2 distal ones set in a row, in adults some additional setae sometimes present, especially in large specimens (Fig.
The redescription completely matches the original one, although
The set of dorsal pseudocelli displayed by M. alnus is shared with several other species in the genus. Among these only four species have ventral pso present on Abd.4, i.e. M. alnus, M. pieninensis Weiner, 1988, Dimorphaphorura irinae (Thibaud & Taraschuk, 1997), and D. olenae. Micraphorura pieninensis differs from both other species in having no ms on Th.3. Dimorphaphorura irinae can be distinguished by the reduced tibiotarsal chaetotaxy (only 2 T-setae present), a full number of labral setae (4/9) and different labial type (ABC) (
Onychiurus (Archaphorura) interruptus Fjellberg, 1987: 282.
Micraphorura interrupta (Fjellberg): www.collembola.org
holotype, ♀, “USSR, Magadan Reg., “Death Valley”, Magadan-Ust’ Umchug [road], 209 km from Magadan, moss, lichen, Vaccinium, 30 vii 1979” (CNC 165045, type No 20107); Paratypes, 9♀ and 1♂, same sample (CNC 165134, type No 20106), all A. Fjellberg leg.
1 specimen, Magadan District, Bolshoi Annachag Mts. Range, upper reaches of Kolyma River, field station “Aborigen” [61°56'N, 149°40'E], alpine study area (lichen, moss, Dryas, Empetrum), 26 vii 1979, V. Behan leg.; 11 specimens, same region, Butugychag (“Death Valley”) [61°18'N, 149°11'E], moist Sphagnum, litter Betula nana, Alnus thickets, 30 vii 1979, A. Fjellberg leg.; 10 specimens, Magadan vicinities, “Snow Valley”, rich meadow (Veratrum, Angelica), 20 viii 1979; ca. 15 specimens, Northern Yakutia, Shirokostan Peninsula, Ledyanoe lake [72°25'N, 141°00'E], various habitats, 1994, A. Babenko leg.; 1 ♀, North-Eastern Yakutia, delta of Indigirka river [71°26'N, 149°45'E], Eriophorum vaginatum tussock, 1994, A. Babenko leg.; ca. 30 specimens, Magadan District, upper reaches of Ola River [60°39'N, 151°16'E], various sites, viii 2011, A. Babenko leg.
Colour white. Size 0.75 mm. Body shape cylindrical. Antennae about as long as head, Ant.3-4 broad, club-like. Ant.4 with a peg-like subapical organite, microsensillum located in proximal row of setae. AO consisting of 5 long and thin papillae, two sensory rods, two granulated sensory clubs (internal straight, external much bigger and bent), 5 guard setae and a lateral microsensillum set below the organ. Ant.1 and 2 with 8 setae and 13-14 setae respectively. PAO with 3-4 lobes, longer than nearest pseudocellus. Labrum with 4/3-2-2 setae. Apical part of labium with thick terminal setae on papillae A and C, common number of guard setae (6 long and 4 spiniform ones), and 6 proximal setae. Basal fields with 4+5(6) setae. Maxillary palp simple with two sublobal hairs.
Most common dorsal pseudocellar formula (pso) as 32/033/33353, submedial pso a and b on Abd.1-2 set close together (with pso b on level with setae p3). Variations are frequent and specimens with additional pso on some abdominal terga (usually asymmetrical) are seen. The whole formula may be expressed as follows, 32/033/3(4),3(4),3(4),(4)5,3(4). Ventral side of head with two pso as usual. Parapseudocelli (psx) invisible. Each subcoxa with one pso. Granulation fine and uniform, sometimes clearly coarser around pseudocelli. Dorsal chaetotaxy almost symmetrical, setae smooth, macrosetae short, needle-like usually blunt at tip, sensory setae more or less distinct, usually 2/011/22211 in number, sensilla like, broaden seta usually present on lower Scx.3. Th.1 with 5-6 setae on each side. Both Th.2 and 3 with lateral ms, p1 on head and Th.2-3 usually slightly in front of p2, Abd.1-3 with setae p4 usually present. Abd.5 with m1 curved, thinner and shorter than the straight a1 and p1. Unpaired setae: d0 absent, p0 frequently present on Abd.5, Abd.6 with two axial setae, a0 clearly shorter than a2. Thoracic sterna 1-3 with 0-0-1 setae, sometimes setae completely absent. Furca remnant as a small fold in some distance from anterior border of Abd.4 sternum, chaetotaxy of manubrial field in juveniles as in Fig.
The number of pseudocelli in the species appears to be more variable than stated in the original description by
The presence of ventral setae on Th.3 in O. interrupta was used by
Only one other known species of the tribe shares the absence of pso on Th.1 combined with presence of 5 pso on Abd.4 with O. interrupta and O. nuda: Oligaphorura reversa (Fjellberg, 1987). This characteristic species differs from the above-mentioned species in having an unusual position of the dorsal pseudocelli on Abd.1-3: the medial pso a is set in a posterior position, clearly behind submedial pso b.
The species listed as O. sp. aff. nuda in
Lipura groenlandica Tullberg, 1876: 41.
Oligaphorura groenlandica (Tullberg): www.collembola.org
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 (
Onychiurus ursi Fjellberg, 1984: 71.
Oligaphorura ursi (Fjellberg): www.collembola.org
Contrary to O. groenlandica, O. ursi, another northern circumpolar species of the genus, is common in the Magadan region inhabiting different wet sites above tree-line. Recently the species was redescribed on the basis of specimens from northern China (
Onychiurus (Archaphorura) aborigensis Fjellberg, 1987: 285.
Oligaphorura aborigensis (Fjellberg): www.collembola.org
holotype, ♀, “USSR, Magadan Reg., Aborigen [67°57'N, 149°34'E], alpine snow fields, under stones, 27 vii 1979“ (CNC 165043, type No 20102); paratypes, ♀ and juv., same sample (CNC 165127, type No 20101), all A. Fjellberg leg.
Unfortunately the types of the species were partly damaged and no additional specimens were found in the available material from the vicinity of Aborigen field station. So, only few additional details can be added to the original description.
Labium with thick terminal seta only on papilla A, 7 long guard setae and 6 proximal setae, basal fields with 4+6 setae. Tibiotarsi with complete set of setae (20-20-19): each distal whorl (A+T) with 11 setae, whorl B with 7-7-6 setae, setae M and Y present on all tibiotarsi. Furcal fold straight and comparatively small, situated in mid-section of Abd.4, furcal field in the only seen juvenile with 4+4 setae between proximal q-setae and the cuticular fold (as on Fig.
The species is well defined due to the absence of sublobal setae on the maxillary outer lobe (a unique character for the tribe or even for Onychiurinae), strong differentiation of dorsal setae and the pseudocellar formula (32/133/33353) which is not especially common for the tribe being shared with only D. pseudoraxensis (Nosek & Christian, 1983), O. sabulosa Babenko, 2008, and D. jingyueensis Sun & Wu, 2012. All of them have the usual two sublobals on the maxillary palp and the macrosetae being much shorter and finer than in O. aborigensis. Apart from this the two former species are characterized by the absence of ms on Th.3.
Onychiurus (Archaphorura) pingicolus Fjellberg, 1987: 285.
Oligaphorura pingicola (Fjellberg): www.collembola.org
holotype, ♂, “Alaska, Prudhoe Bay, Dryas-turf on pingo, 16 viii 1976” (CNC 165048, type No 20099); paratypes, 5♀ and ♂, same sample (CNC 165139, type No 200100), all A. Fjellberg leg.
50 specimens, Russia, Yakutia (Sakha Republic), Suntar-Khayata Mt. Range, upper reaches of Kyubyume River [63°13'N, 139°32'E], various sites, viii 2002, O. Makarova leg.; 25 specimens, Magadan District, upper reaches of Ola River [60°39'N, 151°16'E], snow fields, 1100–1200 m alt., A. Babenko leg.; 4 specimens, Magadan District, Bolshoi Annachag Mts. Range, upper reaches of Kolyma River, field station “Aborigen” [61°56'N, 149°40'E], thick moss among rocks near snow field, 26 vii 1979, A. Fjellberg leg.; 4 specimens, same region, lichen/Ledum in northern slope, 28 vii 1979, A. Fjellberg leg.; 1 specimens, same region, Pinus pumila and lichen cover on hillside, 20 vii 1979, V. Behan leg.; 2 specimens, same region, alpine study area (lichen, moss, Dryas, Empetrum), 26 vii 1979, V. Behan leg.
Colour white. Granulation distinctly enlarged on Abd.6 and on head. Size 1.0–1.1 mm. Body shape cylindrical. Antennae about as long as head, Ant.3-4 broad, club-like. Ant.4 with a subapical spherical organite and a microsensillum located in proximal row of setae. AO consists of 5 long and thin papillae, two sensory rods, two granulated sensory clubs (internal almost straight, external much larger and bent), 5 guard setae and a lateral microsensillum which set below the organ. Ant.1 and 2 with 8-9 and 15-16 setae respectively. PAO with 2-3 elongated lobes, much longer than nearest pseudocellus. Labrum with 4/5-2-2 setae. Apical part of labium with thick terminal setae on papillae A and C, 6 long guard setae and 6 proximal setae present, basal fields with 4+(5)6 setae. Maxillary palp simple with two sublobal hairs.
Pseudocellar formula (pso) as follows, dorsal: 32/033/33343, ventral: 2/000/0000, parapseudocelli (psx) 10/000/222201+1m. Each subcoxa with one pso and one psx, psx present also on femora and on border between Ant.3-4. Granulation rather fine but clearly coarser around pseudocelli and on Abd.6. Dorsal chaetotaxy almost symmetrical, setae smooth and clearly differentiated, sensory setae more or less distinct, usually 2/011/222211. Th.1 with 7-8 setae on each side, both Th.2 and 3 with lateral ms, p1 on head and Th.2-3 usually moved forward in relation to other medial p-setae. Abd.5 with microsetae m1 thin and curved, clearly shorter than mesosetae a1 and p1. Unpaired seta d0 on head absent, Abd.5 frequently with one unpaired axial seta in p-row, two axial setae present on Abd.6, a0 shorter than a2. Thoracic sterna of both Th.2 and 3 with 1+1 setae along ventral line. Furca shaped like a small fold in some distance from anterior border of Abd.4, in juveniles furcal field with 4+4 setae between proximal q-setae and the cuticular fold (Fig.
The above redescription is in full accordance with the original one, adding a few details. While originally described from Alaska,
Oligaphorura pingicola shares the number of dorsal and ventral pseudocelli with at least five known species of the tribe, namely O. koreana, O. nataliae, Dimorphaphorura raxensis, D. chatyrdagi, and D. sanjiangensis. O. koreana is very similar to O. pingicola, differing by fewer tibiotarsal setae (19-19-18 versus 20-20-19) and by absence of psx (“indistinct”). The absence of psx is also characteristic for O. nataliae which differs from O. pingicola in having 7 long guard setae on labial palp and absence of ms on Th.3, as well as 2 setae of the proximal row on labrum (4/7 as a whole). Dimorphaphorura raxensis has 9 distal setae on tibiotarsi, full number of labral setae and ABC type of labium (
Oligaphorura tottabetsuensis (Yosii, 1972), a species known from northern Japan, probably also belongs to the same group although the reported number of dorsal pseudocelli is slightly different (32/033/33333). The species is in need of redescription.
The morphological characters being widely accepted as separating genera of Onychiuridae involve the shape of the postantennal organ (PAO), structures of the antennal organ (AO), tibiotarsal chaetotaxy, arrangement of the pseudocelli (pso), presence/absence of anal spines, distribution and shape of sensory setae on the body, and the gradual reduction of the furca. In our view a genus diagnosis based exclusively on reductional stages of the furca is dubious for at least two reasons: (1) similarity in reductional stage may represent a convergence achieved independently from distant phyletic lines, resulting in a polyphyletic or paraphyletic assemblage of species; (2) many collembolan genera (Xenylla, Folsomia, Folsomides, Scutisotoma, etc.) cover species with a wide range of furcal reduction, but are still accepted as natural genera which no one would split. In Collembola at least the initial stages of furcal reduction are clearly of adaptive nature, reflecting a shift from surface activity to life in deeper strata where jumping ability is restricted. Although the species under discussion have a furca which is no longer functional, the adaptive character of the reduction probably masks the underlying genetic relationships. Moreover, the practically identical furcal remnant of the Onychiuridae genera Supraphorura Stach, 1954 and Psyllaphorura Bagnall, 1948 is obviously not a good proof for any close relationship.
On the www.collembola.org there is an interactive key which proposes the following characters for identification of Oligaphorurini genera.
Chribellphorura: antennal tip with a retractive papilla, tibiotarsi with clavate setae in distal whorl; Archaphorura: Abd.5-6 fused dorsally, Ant.3-4 fused, anal spines absent; Dimorphaphorura: furcal rudiment in a form of finely granulated area; Oligaphorura: furcal rudiment in a form of cuticular furrow or small fold; chaetotaxy: 2 dental setae on the fold or posteriorly and three manubrial rows of setae behind them; Micraphorura: similar to Oligaphorura but without 2 dental setae, so only three rows of setae can be distinguished, mm-row with 4-6 setae.
In summary, Archaphorura has a unique character combination, Dimorphaphorura has no furcal fold or furrow, and Oligaphorura has an additional row of setae on the manubrial field compared with Micraphorura. The monotypic genus Chribellphorura is unique and needs no further discussion to be distinguished.
This adequate but probably too simplified scheme was neglected by
The recent revision of the Palaearctic species of Dimorphaphorura by
In fact the diversity of manubrial chaetotaxy patterns in Oligaphorurini seems to be much higher than postulated so far, which obscures the current generic subdivisions. Thus four different patterns were found in juveniles of the northern species of the tribe: apart from 3+3 proximal q-setae the furcal field may have 2+2 setae (alnus, absoloni, Fig.
Chaetotaxy of abdominal sterna. 25Oligaphorura sp. aff. groenlandica (adult, Taimyr) 26Oligaphorura sp. aff. groenlandica (I instar, Taimyr) 27 Micraphorura absoloni (I instar) 28 Micraphorura absoloni (adult). Secondary setae in adults circled. Scale bars: 9 = 0.1 mm, 10–12 = 0.05 mm.
The present generic framework for Oligaphorurini is probably unique – difficult to use and hardly reflecting real relationships. There is great temptation to return to a single genus Archaphorura as Christiansen and Bellinger (1980, 1998) and
1 | Th.1 without pso | 2 |
– | Th.1 with pso | 6 |
2 | Only Th.2 with lateral ms | O. nataliae (Fjellberg) |
– | Both Th.2 and Th.3 with lateral ms | 3 |
3 | Abd.4 with 4 dorsal pso [totally 32/033/33343] | O. pingicola (Fjellberg) |
– | Abd.4 with 5 dorsal pso including 3 in submedial group | 4 |
4 | Th.2 with at least 1+1 ventral setae. Abd.1-3 with pso b moved forward above medial pso a. Dorsal pso formula as 32/033/44454 | O. reversa (Fjellberg) |
– | Th.2 without ventral setae. Abd.1-3 with pso b set behind medial pso a | 5 |
5 | Th.3 at least sometimes with 1+1 ventral setae | O. interrupta (Fjellberg) |
– | Th.3 without ventral setae | O. nuda (Fjellberg) |
6 | Th.1 with 2+2 pso and with only 4+4 setae present in adults. Thoracic sterna without setae | O. duocellata sp. n. |
– | Th.1 with only 1+1 pso and more than 4+4 setae in adults. Th.2-3 as a rule with ventral setae | 7 |
7 | Only Th.2 with lateral ms | 8 |
– | Both Th.2 and Th.3 with lateral ms | 11 |
8 | AO with 4 papillae | 9 |
– | AO with 5 papillae | 10 |
9 | Anal spines present. Upper subcoxae with 1-1-1 pso. Labrum with 9 setae. Labium of AC type | M. absoloni (Börner) |
– | Anal spines absent. Upper subcoxae with 2-(2)3-3 pso. Labrum with 7 setae. Labium of ABC type | O. ambigua sp. n. |
10 | Abd.4 with 4 dorsal pso [totally 32/133/33343]. Labium A-type | O. ursi (Fjellberg, 1984) |
– | Abd.4 with 5 dorsal pso [totally 32/133/33353]. Labium AC-type | O. sabulosa Babenko, 2008 |
11 | Maxillary outer lobe without sublobals. Formula of dorsal pso as follows 32/133/33353 | O. aborigensis (Fjellberg) |
– | Maxillary outer lobe with 2 sublobals. Formula of dorsal pso as follows 32/133/33343 | 12 |
12 | Labium of A- type | O. schoetti (Lie-Pettersen) |
– | Labium of AC type | 13 |
13 | Abd.4 with ventral pso. Labrum with 7 setae | M. alnus (Fjellberg) |
– | Abd.4 without ventral pso. Labrum with 9 setae | O. groenlandica (Tullberg) |
We express our sincere thanks to V. Behan-Pelletier, M. Potapov, O. Makarova, I. Kaprus’ and Yu. Shvejonkova for the loan of valuable material and for their constructive comments. We are also much indebted to anonymous reviewers and the academic editor, Louis Deharveng, for critical and suggestive remarks.
The paper has been supported through grants of the Russian Foundation for Basic Research (projects 11-04-00175 and 14-04-01114) and through several scientific programmes of the Russian Academy of Sciences.