According to Steve Hopkin (a UK Collembola expert) on his website, there are 23 species of 'littoral' (meaning intertidal/seashore) springtails found in the UK. These 23 springtails are split across two orders (Poduromorpha and Entomobryomorpha) and five families (Hypogastruridae, Neanuridae and Onychiuridae within Poduromorpha; Entomobryidae and Isotomidae within Entomobryomorpha).
As far as I can tell, in most cases it seems to be very difficult if not impossible to ID any of these 23 springtails down to species from photographs and/or a description of habitat or behaviour alone. Rather, as per Steve Hopkin's website, it is only with a view of microscopic features that identifications can be made. That being said, one can certainly go down to order or family in some cases, particularly if close-up photos of individuals are provided.
Identifying to order:
According to Dallimore and Shaw's (2013) 'Illustrated key to the families of British Springtails (Collembola)', Poduromorpha and Entomobryomorpha can be easily distinguished from one another by examining the first thoracic segment. Both Poduromorpha and Entomobryomorpha technically have three thoracic segments. In Entomobryomorpha, however, the first thoracic segment of the three is greatly reduced dorsally, such that it almost appears as if the springtail has a 'neck'. Poduromorpha, in contrast, have a clearly visible first thoracic segment. For an obvious example of the difference, compare https://www.inaturalist.org/observations/221987468 with https://www.inaturalist.org/observations/194018768.
Identifying to family:
Within Poduromorpha (12 littoral species):
- As far as I am aware, littoral Hypogastruridae cannot be confidently distinguished from littoral Neanuridae without microscopic examination (for more info see this other journal post of mine).
- It is likely that any unpigmented (i.e. white) and blind (no eyes) littoral Poduromorpha springtail is one of the three littoral species within Onychiuridae (Protaphorura macfadyeni, Thalassaphorura debilis or Thalassaphorura halophila), however this call cannot be made with 100% certainty given that the colouration of some other Poduromorpha springtails in Hypogastruridae and Neanuridae is not known for certain because photos of these species are lacking (As per the global Collembola database 5 of the 9 non-Onychiuridae littoral springtails lack photos).
Within Entomobryomorpha (11 littoral species):
- Entomobryidae are easily identified to family if it is clear that the 4th abdominal segment is notably longer than the other abdominal segments.
- Isotomidae are easily identified to family is it is clear that all the abdominal segments are of similar length.
- ID beyond family here is also likely possible...
Congregating behaviour:
I am yet to see any definitive evidence that the 'congregating' behaviour exhibited by some littoral springtails (e.g. see here) is a unique feature of a distinct subset of the 23 littoral species. Given that many of the 23 littoral species lack everything besides a basic description, and some do not even have photos in the global database, I strongly suggest that using this congregating feature as any sort of determinant for an ID is inappropriate.
As far as I am currently aware, the two Poduromorpha springtail families Neanuridae and Hypogastruridae cannot easily be distinguished from one another based on field photography alone. Rather, assuming the species is not otherwise obvious, details only visible through microscopic analysis may well be needed.
It is notable that this assertion differs with that made by Dallimore and Shaw's (2013) 'Illustrated key to the families of British Springtails (Collembola). According to that key, the choice between families can be made based on the 'distinctiveness' of the head from the thorax. In Neanuridae, it is argued, the head is indistinct, whereas in the other UK Poduromorpha families (Odontellidae, Poduridae, Onychiuridae, Tullbergiidae and Hypogastruridae), the head is distinct.
I am inclined to disagree with Dallimore and Shaw's key here because the 'distinctiveness' of the head from the thorax is not a binary property. Rather, 'distinctiveness' varies considerably along a gradient from 'clearly distinct' to 'clearly indistinct'. It is not a clear-cut matter. Furthermore, not only does distinctiveness appear to differ between species within the two families, it is also likely that distinctiveness can vary between individuals within a species (i.e. intra-specific morphological variation), and even over time for a single individual (based on environmental conditions, whether the springtail is feeding, resting, etc.).
See original discussion on these two observations:
Contrary to Dallimore and Shaw's (2013) 'Illustrated key to the families of British Springtails (Collembola)', it is not a universal rule that distinguishing UK springtails from the families Onychiuridae and Tullbergiidae (together superfamily Onychiuroidea) from UK springtails in the family Hypogastruridae (having eliminated from consideration Neanuridae, Poduridae and Odontellidae), is a simple matter of considering all white (unpigmented) springtails as Onychiuroidea and all non-white (pigmented) springtails as Hypogastruridae.
Rather, there are a few outliers to this general rule – the relatively few but still considerable species of unpigmented Hypogastruridae. Some of these resemble Onychiuroidea, at least to an untrained eye. Of those for which there are photos listed on the global Springtail database, there are at least 5 species of unpigmented Hypogastruridae:
- Ceratophysella succinea
- Ceratophysella armata
- Schaefferia emucronata
-
Xenylla grisea (juveniles)
- Mesogastrura libyca
To identifiers with experience, most of these species are quite distinctly different from Onychiuroidea, but Mesogastrura libyca in particular looks very similar to some members of the superfamily. It should also be explicated that many Hypogastruridae species lack photographs on the database and so could also easily also be unpigmented and similar in appearance to some Onychiuroidea.
I therefore urge that caution should be taken when distinguishing Hypogastruridae from Onychiuroidea on the exclusive basis of pigmentation. In cases where appropriate detail is not obvious, observations should be left at order.
One of the few UK Onychiuroidea springtails that can be distinguished from photographs alone is Kalaphorura burmeisteri. To quote Matthew Shepherd (a UK Soil Ecologist): "this is one species that can be identified by shape alone. It's the only white, blind, springless podger that his this tapering shape, fattest around the middle. Often compared to the Michelin man!"
Original source (including photos) is this facebook post.
Usá ArgentiNat con app iNaturalist
