Cave animals in Croatia

Hi everyone, and welcome to another caving post! Today, I would like to write a bit about animals that live almost exclusively in caves in Croatia and region. So, what is so special about this region?  Dinarides, or Dinaric Alps, is a mountain range on the western part of Balkan peninsula; it is about 650 km long and is made of limestone and dolomite (karst). The mountain is a home for many different species, both animal and plant alike, with some of them being endemic for the region.

A view from inside to outside of the cave; framed arch with the blackness of the cave forming an outside frame, and sky and forest being the picture in the centre.
The cave near the Big Natural Bridge; a view from the inside.

Animals in cave some specific features, such as slower metabolism, lost of sight and pigment, and lost of circadian rhythms. Also, we can roughly divide them as animals that live in water and the ones that live on rocks and/or the ground. Furthermore, we can divide them in the following categories: genuine inhabitants (they live their whole lives in caves), inhabitants which can have epigean populations (they can live both in and out), occasional inhabitants (examples include hibernation and seeking shelter), and accidental inhabitants. When looking in numbers, there are 455 described cave inhabitants in Croatia, with many species of beetles leading the board, followed by crustaceans and snails.

However, Dinaric karst is a home to many one of the kind species, such as the only  underground freshwater sponge in the world, Eunapius subterraneus (Ogulin cave sponge), and Congeria spp, the only underground freshwater bivalves. There are two species of Congeria, Congeria jalzici that is found in north Velebit and Congeria kusceri that lives in southern parts of Dalmatia and Dinara. And if you think this is the end of the “the only underground freshwater weird looking animal”, you would be wrong, because Croatia is also home to Marifugia cavatica, Dinaric cave-dwelling tubeworm. And to Velkovrhia enigmatica (also found in Slovenia and Bosnia and Herzegovina) which is the only cave hydrozoan (Cnidaria) in the world.

There are also two very interesting species found in deep caves on Velebit – Troglocladius hajdi (Diptera without eyes, and yes, it flies) and Croatobranchus mestrovi (pictured below, it’s basically a white leech). I already wrote about Proteus in another post, so I’m purposefully omitting them here.

Now, you might wonder, what’s the big deal? Well, most of these species are not very well researched and are still a big enigma to scientists. For many of these, their genomic DNA is not yet sequenced, and their evolutionary relations to species in the same taxa are not completely clear. There is also a question of how exactly these species survive, mainly what exactly they eat, since caves are not exactly blooming with life – there are no plants, but there is some bacteria.

Have you ever heard (or seen) of these species? Would you like to know more about them? Please let me know in the comments!


Literature & more information:

Cave fauna
Pijavica Croatobranchus mestrovi

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