Arachnids

Microwhip scorpions (Palpigradi)

The microwhip scorpions (Palpigradi) is an order of tiny invertebrates belonging to the Arachnida class. The largest known species in the group, Koenenia draco from Sicily, is 2.8 mm in size. Like all arachnids, they hunt their prey with pedipalpi. Long thin whip at the end of the body distinguishes them from the rest of the class. The microwhip scorpions are primarily distributed in the tropics, where they live in soil. Until today, 79 species have been known, classified into two families: Eukoeneniidae and Prokoeneniidae. In Europe, only members of the family Eukoeneniidae occur and only two species are endogean, while others have been found mostly in caves.

In Croatia, we find species from the genus Eukoenenia. They inhabit caves in regions of Istria, Lika and Southern Dalmatia, and mountains Ćićarija, Velebit and Biokovo. Like all microwhip scorpions, they are small in size, up to 1.5 mm including the whip. From the Lika region, subspecies Eukoenenia spelaea hauseri is described, and from southern Dalmatia Eukoenenia pretneri. Both are troglobiotic (genuine inhabitants of cave habitat). E. pretneri is the endem of Croatia and was recorded only in the type locality.

BIBLIOGRAPHY:

  • Bedek, J., Gottstein Matočec, S., Jalžić, B., Ozimec, R. & Štamol, V. (2006): Catalogue of cave type localities of Croatian fauna. Nat. Croat., Vol. 15, Suppl. 1: 1-154.
  • Gottstein Matočec, S. (ed.), Bakran-Petricioli, T., Bedek, J., Bukovec, D., Buzjak, S., Franičević, M., Jalžić, B., Kerovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & Tvrtković, N. (2002): An overview of the cave and interstitial biota of Croatia. Nat. Croat., Vol. 11, Suppl. 1: 1-112.
  • Matoničkin, I (1991): Beskralješnjaci: biologija viših avertebrata. Školska knjiga, Zagreb. pp. 642.

Spiders (Araneae)

Spiders are the most numerous order in the class of Arachnids. More than 46 000 species of spiders have been identified in the world today and for Croatia some 800 species and subspecies. Spiders play an important role in virtually all terrestrial ecosystems including the underground habitats.

All spiders produce silk, from organs called spinnerets, and they use it to build webs on which they spend most of their lives. Silk is also used for trapping insects and other prey, for traveling longer distances and as an aid in climbing, to form smooth walls for burrows, for building egg sacs and many other things. Most spiders live for about a year and through several moults (shedding of old chitinous exoskeleton) they reach the adult stage when they become sexually mature. Cave spiders are thought to live longer then their epigean (non- cave) relatives. All spiders are predators; they hunt their prey on the ground or catch it in a web, and cave spiders are at the top of cave food webs. Like other cave-adopted groups, cave spiders show some typical adaptations to life underground: thinning of the integument, loss of pigment and reduction of visual apparatus, legs elongation, increase in the number of sensory hairs and so on.

Many troglophile spiders, such as genera Meta and Metellina, can be seen in cave entrances and twilight zones. Deeper inside the caves, in the area of total darkness, live troglobiotic spiders that are well adapted to the underground conditions. Some of them build webs on the walls of cave chambers or between the boulders on cave floor to catch their pray, whereas others – like the Dysderidae family – don’t build webs, but dwell under stones or on the walls of underground passages where they actively hunt their prey.

Currently, 70 cavernicolous taxa from 10 families are recognised for Croatian fauna; 37 of them are troglobionts and 33 troglophiles. The most numerous is the family Linyphiidae (sheet weavers or money spiders) with 30 taxa, and it`s genus Troglohyphantes with 21 taxa. Other significant families are Dysderidae, Nesticidae, Leptonetidae and Agelenidae. There are 36 cave spider species described from caves in Croatia. New species for Croatian fauna or for science in general are constantly being discovered. 30 taxa are endemic to Croatia and most of them have very restricted distribution areas.

Devastation of underground habitats inevitably threatens spiders and other cave animals. 12 spider taxa are listed in the Red Book of Croatian Cave Dwelling Fauna.

CONTACT:
Martina Pavlek – martina.pavlek@hbsd.hr

BIBLIOGRAPHY:

  • Nentwig, W., Blick, T., Gloor, D., Hänggi, A. & Kropf, C. (2017): Spiders of Europe. Version 03 [online]. Available from http://www.araneae.unibe.ch/
  • Pavlek, M. (2016): Overview of cave spiders in Croatia – 150 years of research. 20th International Congress of Arachnology, Golden, SAD – abstract.
  • World Spider Catalog (2017). Natural History Museum Bern, version 18.0. Available from http://wsc. nmbe.ch.

False scorpions (Pseudoscorpiones)

The false scorpions (Pseudoscorpiones) are an order in the Arachnida class. They resemble the more famous scorpions, but lack segmented tail with a venomous stinger. Sizes range from 2.5 mm to 7.5 mm, and all known species are predatory. They prey on animals that can be far bigger than them by catching them with pincers on long pedipalpi and killing them with the poison (like spiders). They feed on springtails, isopods, mites and young spiders. False scorpions prefer to live on the ground, often under rocks.

There are 3 families of cavernous false scorpions in Croatia: Chthoniidae, Neobisiidae and Chernetidae, with a total of 8 genera. The most interesting endemic genera are Protoneobisium and Insulocreagris from the Neobisiidae family, relics of Pre-Tertiary fauna. The fauna of the cavernous false scorpions of the Dinarides is extremely rich, with more than 30 troglobiotic species and subspecies described only from Croatia.

BIBLIOGRAPHY:

  • Gottstein Matočec, S. (ed.), Bakran-Petricioli, T., Bedek, J., Bukovec, D., Buzjak, S., Franičević, M., Jalžić, B., Kerovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & Tvrtković, N. (2002): An overview of the cave and interstitial biota of Croatia. Nat. Croat., Vol. 11, Suppl. 1: 1-112.

Harvestmen (Opiliones)

The harvestmen (Opiliones) are an order in the Arachnida class which resembles spiders. The main difference from spiders, noticeable at a first look, is a body that is not sharply divided into the front and back part (connection between the cephalothorax and abdomen is broad). Most species have characteristically long legs. They are predators, but in the absence of prey they feed on dead organic matter.

The harvestmen in caves are most commonly found at the entrances where one can often find the troglophilic species Nelima troglodytes. In Croatia we can also find troglobiotic taxa from the Sironidae family, genus Cyphophthalmus. A total of 7 cave species are described from the mentioned genus. One small cave on the island of Hvar is the only locality where 2 mm big Lola insularis lives. From the island of Mljet Travunia jandai is described. Caves in the vicinity of Dubrovnik are inhabited by T. anophthalma. All three species do not have pigment or eyes and are completely adapted to life in caves.

BIBLIOGRAPHY:

  • Gottstein Matočec, S. (ed.), Bakran-Petricioli, T., Bedek, J., Bukovec, D., Buzjak, S., Franičević, M., Jalžić, B., Kerovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & Tvrtković, N. (2002): An overview of the cave and interstitial biota of Croatia. Nat. Croat., Vol. 11, Suppl. 1: 1-112.
  • Jalžić, B., Bedek, J., Bilandžija, H., Cvitanović, H., Dražina, T., Gottstein, S., Kljaković Gašpić, F., Lukić, M., Ozimec, R., Pavlek, M., Slapnik, R. & Štamol, V. (2010): Atlas špiljskih tipskih lokaliteta faune Republike Hrvatske, svezak 1. Hrvatsko biospeleološko društvo, Državni zavod za zaštitu prirode, Zagreb. pp. 261.

Mites and ticks (Acari)

Mites and ticks (Acari) are a very diverse group of arachnids (class Archnida), among which we find predators, parasites and herbivore which inhabit terrestrial, aquatic and marine habitats. They are usually small in size, which is why they lost segmentation of the body, and their prosoma and opisthosoma (anterior and posterior part of the body) have coalesced. Also, many organs in mites and ticks have been reduced or are even missing (e.g. a very reduced nervous system).

The mites from caves are a diverse but poorly researched group of animals. In addition to the parasitic species of ticks found on bats, there are several free-living troglophilic and troglobiotic taxa. They are predators who inhabit cracks in rocks and cave walls, the water surface and under stones. An example of such taxa is the subspecies Spelaeothrombium caecum caecum, a representative of Tertiary relict fauna with a body size of 2 mm.

Particularly interesting is a specimen from the Rhagidiidae family collected in 2010 during research of the cave system Jamski sustav Lukina jama – Trojama. The specimen was found at a depth of 980 m, has extremely troglomorphic characteristics and represents a new species for science.

In underground waters, especially those rich in organic matter, we find the members of water mites (Hydracarina) that are very small in size.

BIBLIOGRAPHY:

  • Bedek, J., Gottstein Matočec, S., Jalžić, B., Ozimec, R. & Štamol, V. (2006): Catalogue of cave type localities of Croatian fauna. Nat. Croat., Vol. 15, Suppl. 1: 1-154.
  • Gottstein Matočec, S. (ed.), Bakran-Petricioli, T., Bedek, J., Bukovec, D., Buzjak, S., Franičević, M., Jalžić, B., Kerovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & Tvrtković, N. (2002): An overview of the cave and interstitial biota of Croatia. Nat. Croat., Vol. 11, Suppl. 1: 1-112.
  • Matoničkin, I (1991): Beskralješnjaci: biologija viših avertebrata. Školska knjiga, Zagreb. ¸pp. 642.