June 6, 2014 | 33
While on a family holiday recently I visited Dan yr Ogof, the famous National Show Cave for Wales. Besides being interesting for the expected geological and speleological reasons, Dan yr Ogof is set within landscaped gardens that, bizarrely, feature one of Europe’s largest ‘dinosaur parks’. Great plastic models of tyrannosaurs, sauropods and all manner of other prehistoric creatures litter the surrounds – it seems people somehow associate geological attractions with life-size models of extinct animals. Anyway, I’m not here to talk about those, but instead about some other, less spectacular animal models on display at Dan yr Ogof. Namely, the model salamanders that ‘live’ in small, shallow pools within one of the several caves.
I actually visited Dan yr Ogof as a child, many years ago, and remember the salamanders from then. These models [see adjacent image] of long, pink, aquatic animals depict White olms Proteus anguinus anguinus, the famous cave-dwelling proteid salamanders of the Dinaric karst region in south-eastern Europe. The models are about right in proportions and digit number (olms only have three fingers and two toes), but lack the bushy external gills of the real thing. White olms are committed to cave life, though the recently discovered Black or Brown olm P. a. parkelj is not as specialised and inhabits surface waters. I’ve written about olms a few times on Tet Zoo before, see the links below for more.
There are also some model Fire or Spotted salamanders Salamandra salamandra. Like olms, Fire salamanders don’t occur in Wales or elsewhere in the UK, and – in contrast to continental Europe – there isn’t any indication (so far as I know) that they occurred here in the geological past either (Böhme 2010). Fire salamanders are spectacular, robust, predominantly terrestrial salamandrid salamanders that can reach 30 cm in total length. A substantial amount of geographical variation in size and pigmentation has led to the naming of numerous subspecies and other variants (see Köhler & Steinfartz 2006), and some populations once included within S. salamandra are now classified as distinct species (see Steinfartz et al. 2000).
Fire salamanders aren’t, ordinarily, cave-dwellers, but they might sometimes be found within them: amphibians of many kinds often wander into caves, either to take refuge from conditions outside (it being variously too dry, too hot, or too cold), or because they get washed in by floodwaters or such. There are many tales of people finding, or knowing of, frogs and toads that have obviously been living in a given cave for years or even decades (cavers often talk of ‘rescuing’ frogs and toads found deep inside caves and returning them to the surface. I appreciate the sentiment, but are you sure you’re ‘rescuing’ the animal? It might have been there deliberately). It doesn’t take much imagination to see how such animals might, over generations, give rise to cave-dwelling specialists that lack pigmentation, have atrophied eyes, and are behaviourally and ecologically specialised for cave life. Maybe amphibians are pre-adapted for this so-called stygobiontic or troglodytic lifestyle since many find mates using olfactory or chemosensory cues, have long lifespans and low metabolisms, and are well suited for perpetual existence in wet, cool, dark conditions.
Why have anurans (frogs and toads) never produced a dedicated stygobiontic form (so far as we know)? Firstly, their reliance on acoustic cues to find mates might make it difficult for them to survive for generations in places where roaring water is often a common feature*. Secondly, their (typically) herbivorous tadpoles might also not be able to survive in the majority of caves. Then again, roaring water is not present in all caves; furthermore, anuran breeding biology is incredibly flexible in evolutionary terms, numerous lineages feeding or nourishing their tadpoles somehow, and many having abandoned the tadpole phase entirely. And, actually, there are several anurans that do frequent caves (examples: the North American Pickerel frog Lithobates palustris, Australian Cave-dwelling frog Litoria cavernicola and Puerto Rican Rock coqui or Guajón Eleutherodactylus cooki), it’s just that they frequent cave mouths and are not anywhere near as specialised as olms or other cave-dwelling salamanders. Cave caecilians? Hmm, not yet I think.
* Yes, there are anurans that have evolved acoustic signals that combat the problems of being close to waterfalls, and yes there are anurans that use visual signals (like waving their limbs around) in place of acoustic ones, but (1) these innovations are rare and restricted to a couple of unusual lineages, and (2) visual cues might not work well in pitch-darkness.
One last thing. Dan yr Ogof doesn’t just have models of cave-dwelling salamanders: there are two pale, cave-dwelling trout as well. I refuse to talk about them. Goddam fish.
Anyway… go to Wales, see model salamanders in a cave.
For previous Tet Zoo articles on salamanders (including olms), see…
Refs – -
Böhme, M. 2010. Ectothermic vertebrates, climate and environment of the West Runton Freshwater Bed (early Middle Pleistocene, Cromerian). Quaternary International 228, 63-71.
Köhler, G. & Steinfartz, S. 2006. A new subspecies of the fire salamander, Salamandra salamandra (LINNAEUS, 1758) from the Tendi valley, Asturias, Spain. Salamandra 42, 13-20.
Steinfartz, S., Veith, M. & Tautz, D. 2000. Mitochondrial sequence analysis of Salamandra taxa suggests old splits of major lineages and postglacial recolonizations of Central Europe from distinct source populations of Salamandra salamandra. Molecular Ecology 9, 397-410.