(179PDaqu) Podura aquatica (Linneaus 1758)

Podura aquatica (Fig. 1) is often described as being extremely common and widespread on the surfaces of standing water. However, the map would suggest otherwise. There are surprisingly few records although where it occurs, the species can be abundant. Swarms of Collembola on puddles are very often hypogastrurids, often mis-identified as 'Podura' in the popular press. Its strongholds appear to be fens and polders - Peter Shaw confirmed Podura from Wheatham fen, Coldham where the species has been present apparently continuously since 1929 (and probably a lot longer), and seen swarms on the surface of ditches in the Netherlands.  Old accounts refer to swarms of this animal being washed up on the shores of water bodies in such numbers as to resemble soot, and when poked they jumped en masse - an action likened (rather fancifully) to gunpowder.  Perhaps Podura aquatica is declining due to pesticide use and draining of wetland habitats. 

Taxonomically too this species is odd; it gave its name to the poduromorpha and its family Poduridae used to contain Hypogastrurids and Neanurids, but recently has tended to be classed as 'Incertae sedis'.  Reassuringly for morphological taxonomist,  Xiong et al (2008) used mitochondrial DNA sequencing to place Podura back close the hypogastruridae. 

 
Podura aquatica has a prominent furca (Figs. 2 and 3) and the foot does not possess an empodium (Fig. 4). There are 8+8 ocelli in a distinctive, strangely sculpted pattern, and a post-antennal organ is absent.

 

 

 

 

Fig. 1 (above): Live specimen of Podura aquatica of 2.0 mm in length collected by Frans Janssens from the surface of a pond.

Fig. 2: Podura aquatica collected from Wicken Fen in November 1925 by C.H. Jackson.

 

Fig. 3: Dens and mucro of the furca of Podura aquatica collected from Wroxham, Norfolk in May 1950 (collector not known).

 

Fig. 4 (left): Foot of the third leg of the same specimen of Podura aquatica shown in Fig. 3.

 
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