(119PRarm) Protaphorura armata (Tullberg, 1869)

*humata (Gisin, 1952)
*nemorata (Gisin, 1952)
*subaequalis (Bagnall, 1937)
*waterstoni (Bagnall, 1937)

Numerous species within the Protaphorura armata 'group' have been described (Figs. 1 and 2). All have simple vesicles in the post-antennal organ (Fig. 3), a furca present as a tiny vestigial flap (Fig. 4), two anal spines, and empodium of the foot long and filamentous about the same length as the claw (Fig. 5).
The 'typical' PSO formula of Protaphorura armata is 33/023/33343 but there is considerable variation (Figs. 6 to 13). Brian Pitkin suggested that the number of PSO on the third thoracic segment (th3) could be used for separating Protaphorura armata (th3 with 3+3 PSO; Fig. 7) and Protaphorura aurantiaca (th3 with 2+2 PSO).
The red dots on the map show the localities of specimens with 3+3 pseudocelli (PSO) on the third thoracic segment (th3) that were checked by Steve. The green dots are literature records for Protaphorura armata and its synonyms.
Protaphorura armata is white in life whereas Protaphorura aurantiaca is normally yellow (fades to white in alcohol!). Other characters (particularly presence or absence of seta s' on abd5, and the degree of convergence of lines drawn through the two pairs of setae anterior to the anal spines) appear not to be reliable..
Occasionally, an asymmetrical arrangement of pseudocelli makes it difficult to assign a definitive species identification and it is probably safest to assign such specimens to the Protaphorura armata 'group'.

 

These are among the easier springtails to keep in culture, feeding on bakers yeast and breeding for multiple generations.  Being both amenable to culture and widespread in forest litter, these springtails (or taxa close to them) have proved useful models to study invertebrate-fungus grazing interactions.  We now know that Protaphorura (or Onychiurus as they were hitherto called) are selective fungus feeders, avoiding some (often toxic) species, and that their selective grazing can affect the outcome of competition between decomposer fungi.

 

 

 

 



Fig. 1: Specimens of Protaphorura 'armata' (1.5 mm in length) collected by Steve Hopkin from a flower pot in a garden in Reading.

 


Fig. 2: Specimens of Protaphorura 'armata' (1.5 mm in length) collected By Steve Hopkin from a flower pot in a garden in Reading.

 

Fig. 3 (above): Post-antennal organ (PAO) and four adjacent pseudocelli (1 to 4) of Protaphorura armata collected from Thornwick Bay, Flamborough in August 1934 by Bagnall. According to the 'classic' description of Protaphorura armata, there should only be three PSO in this position. Specimens have been seen repeatedly that have four PSO on one side and three PSO on the opposite side of the same animal.

Fig. 4: Vestigial furca of the same specimen of Protaphorura armata shown in Fig. 3.

 

 

Fig. 5 (above): Foot of third leg of Protaphorura armata collected from Chipstead, Surrey in October 1977 by Brian Pitkin.

Fig. 6: First (th1) and second (th2) thoracic segments of Protaphorura armata collected from Leith Hill, Surrey in October 1977 by Brian Pitkin. There are no pseudocelli (PSO) on th1. On th2 there are three PSO on the left side (1 to 3) but only two PSO on the right (* marks the position of the 'missing' pseudocellus). sc, subcoxal PSO.

 

Fig. 7: Third thoracic segment (th3) and first two abdominal segments (abd1, abd2) of the same specimen shown in Fig. 6. On th3 there are three PSO on each side (1 to 3; labelled on left side only). There are also three PSO on each side of abd1 (1 to 3; labelled on left side only).

 

Fig. 8 (above): Posterior margin of the left side of the head of Protaphorura armata collected from Thornwick Bay, Flamborough in August 1934 by Bagnall. According to the 'classic' description of Protaphorura armata, there should only be three PSO in this position. Steve noted as having seen several specimens that have four PSO on one side in this position and three PSO on the opposite side of the same animal.

 

Fig. 9 (above): Fifth (abd5) and sixth (abd6) abdominal segments of Protaphorura armata collected from 500 Acre Wood, Sussex in April 1978 by Brian Pitkin. According to the 'classic' description of Protaphorura armata, there should only be three pseudocelli (PSO) on each side of abd 5. However, there are three PSO on the left and four PSO on the right. The asterisks (*) indicate the position in which seta s' would be located if present.

 

Fig. 10 (above): Fourth (abd4) and fifth (abd5) abdominal segments of Protaphorura armata collected from Gleneagles, Scotland in August 1934 by Bagnall. 500 There are three pseudocelli (PSO) on each side of the midline of abd 5. However, the arrangement of setae is asymmetric. One of the setae (*) is bifurcated.

 

Fig.11 (above): Hind margin of the fifth abdominal segment (abd5) on the left side of Protaphorura armata collected from Tilgate Forest, Crawley in October 1977 by Brian Pitkin. According to the 'classic' description of Protaphorura armata, there should only be three pseudocelli (PSO) in this position on abd 5. However, there are five PSO (1 to 5) in this example.

 

Fig. 12: Hind margin of the fifth abdominal segment (abd5) on the left side of Protaphorura armata collected from Dalmeny near Edinburgh in August 1934 by Bagnall. According to the 'classic' description of Protaphorura armata, seta s' should be absent but it is clearly present in this example. Steve reported having seen several specimens that have seta s' present on one side but absent from the opposite side of the same animal.

 

Fig. 13 (above): Fifth (abd5) abdominal segment of Protaphorura armata collected from Boynton Woods, E. Yorks. in May 1934 by Bagnall. According to the 'classic' description of Protaphorura armata, there should be three pseudocelli (PSO) on each side of abd 5. However, there are four PSO on the left and two PSO on the right in this example.

 
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