Collembola are entognathous (mouthparts located within a 'gnathal pouch'), wingless hexapods with antennae always present. Collembolan fossils from the Devonian (ca 400 million years ago) Rhyniella praecursor (Hirst et Maulik, 1926) are among the oldest known records of terrestrial animals and hexapods. There are cca 7900 described species worldwide. Around 70 new species of Collembola have been described every year for the last 10 years. The estimated number of Collembola species is 50 000.
Collembola inhabit all different kind of habitats such as soil, litter, vegetation, caves or even water surface. Collembola are polyphagous, in general; some species are saprophagous (decomposed plants), coprophagous (excrements), necrophagous (cadavers), mycetophagous (fungi), bacteriophagous (soil micro-organisms) or pollinophagous (pollen). Some are even predacious. Collembola are at the beginning of the food chain and they are often hunted by predators such as beetles, mites, harvestman, falsescorpions, spiders etc.
Collembola are small animals, big mostly between 1 and 5 mm. The smallest are just 0,12 and the biggest are 17 mm in size. Collembola may be often recognised by a posterior ventral forked abdominal appendage, the furca, and the ventral tube. They use furca to jump and escape predators, and they are one of the greatest jumpers in the animal world.
Around 110 species have been recorded in Croatia, so far. There are about 20 troglobite Collembola found in Croatia and some of them are still undiscribed. Cave Collembola have developed series of adaptation to underground life like extremely elongated antennae and numerous chemoreceptors and chaetae on antennae and body. Their legs are longer than those of surface Collembola, and claws are more elongated which enables them to walk on wet walls and speleothems. Surface species are often in variety of different colors while cave species lost their pigment. Most of them also lost their eyes or they are reduced to just few ocelli. Cave Collembola have changed their metabolism and biological processes so they lay fewer but larger eggs, and they accumulate more fat in their bodies so they can survive longer periods without food.
Some of the cavernicolous species found in Croatia are stenoendemics like Typhlogastrura topali (Loksa & Bogojević 1967) known so far only from two caves near Dubrovnik, or Pseudosinella dallaii Gisin & Gama, 1970 known only from Veternica cave on Medvednica Mt. Some other species are widespread like Tritomurus scutellatus Frauenfeld, 1854, that can be found from Gorski Kotar and Istria to Velebit and Lika region, or like Pseudosinella heteromurina (Stach, 1929) that can be found in caves in Lika, Gorski Kotar and Kordun region. Some of the troglobitic Collembola found in Croatia have developed peculiar adaptation to cave life such as extremely long antenna like in species Verhoeffiella longicornis (Absolon, 1900).
During recent exploration many new cave species for Croatia and science have been discovered. A long work of descriptions and fulfilling of species list for Croatia is ahead.
Marko Lukić -
Bellinger, P.F., Christiansen, K.A. and Janssens, F. (1996-2007), Checklist of the Collembola of the World. http://www.collembola.org
Bogojević, J. (1968), Catalogus faunae Jugoslaviae 3./6 Collembola, Ljubljana
Fauna Europaea Web Service (2004), Fauna Europaea version 1.1, World Wide Web, URL: http://www.faunaeur.org