Despite its inhospitable appearance and lack of any ... - Udine Cultura

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46 ■ Poriferans Among all stygobionts, sponges are certainly the least frequent and most primitive. These essentially marine organisms (there are few freshwater species belonging to the spongillid family) frequently colonise coastal caves shrouded in partial darkness. There is, however, at least one exception to this rule: Higginsia ciccaresei, a sponge which has recently been collected by scuba divers exploring the Zinzulusa Grotto in the Salento (Apulia). The species is endemic to the cave, and was found at a distance of 250 m from its entrance, at a depth of 12 m, in total darkness. The morphological characteristics of this species, like its depigmentation, have led researchers to consider it a stygobiont. ■ Platyhelminthes Flatworms are a primitive phylum of free-living or parasitic organisms. Stygobiont planarian worms are Atrioplanaria morisii generally depigmented, eyeless, with slow reproductive cycles and high numbers of chromosomes. In Italy, although very little is known about these organisms living in phreatic environments, which are certainly inhabited by many minute creatures (micro-turbellarians), some species living in karstic waters are well documented. Dendrocoelum collinii lives in pre-Alpine caves and in France, and D. italicum in Lombard caves, although the taxonomic position of Italian populations of both species requires revision. The genus Atrioplanaria is found in caves in Sardinia, central-southern Italy (A. racovitzai) and southern Piedmont (A. morisii); Polycelis benazzii lives in Ligurian caves. The taxonomy of these genera is uncertain, due to the fact that it requires examination of living specimens and the use of complex histological and karyological methods. This is why these animals are seldom included in lists of fauna. However, being predators, their trophic role in underground ecosystems may be of local importance. The taxon of temnocephalid flatworms is of uncertain position. These ectoparasitic species sometimes abound on the gills of crustaceans like stygobiont amphipods and decapods, whose haemolymph they suck. Very small (2 mm maximum), these animals have tentacles and adhesive discs with which they attach themselves to their hosts. In Italy, only three genera have been found so far (Bubalocerus, Scutariella, Troglocaridicola); they are parasitic on stygobiont shrimps of the genus Troglocaris which live in saturated karstic waters in the Karst areas of Trieste and Gorizia. ■ Molluscs All Italian stygobiont molluscs belong to the gastropod class, in particular to the hydrobioidean superfamily (spring snails). Although they are common in Italian groundwater, with about 70 species described, and are found in all types of habitats - except for the vadose zone of karstic aquifers - spring snails are still little known from the taxonomic viewpoint. This is because many species are only known by their Hadziella ephippiostoma shells, which are found in springs and hyporheic water, suggesting that the elective habitat of these populations is the deep, almost inaccessible underground environment. Many empty shells are found in river sediments, and therefore their unknown underground habitat may in fact be very far from where they were actually found. This is why their genera and species described in the past need to be revised. The shells of spring snails have various shapes. They are generally towershaped, conical and cylindrical, often truncated. Some genera have disc- and spiral-shaped shells. Stygobiont species of spring snails are usually very small (for example, the adults of the genus Hauffenia have a diameter of 2 mm and are only 0.7 mm high). The opening of the shell is generally large and round, closed with a thin, horny, egg-shaped lid, the operculum, which protects the soft tissues of these animals. They move by means of a complex set of muscles, the foot, which flattens ventrally and adheres to the substrate allowing the snails to crawl. Stygobiont spring snails feed on micro-particles of organic matter, encrusting micro-organisms and bacterial biofilms, which are scraped and ground by their radula, an organ bearing several rows of minute teeth. Except for a few species living in brackish water, most Italian spring snails live in freshwater and are crenobionts (spring-loving) or stygobionts. 47
48 Shells of gastropods Iglica vobarnensis, Paladilhiopsis virei and Hauffenia subpiscinalis (from top to bottom, ca. 30x) Crenobiont species (genera Bythinella and Graziana) may enter groundwater bodies and burrow into interstices, probably in search of food, and therefore behave as stygophiles. A large number of endemic species of the genera Bythiospeum, Iglica, Istriana, Hadziella, Paladilhiopsis and Phreatica are strictly stygobiont, and live deep within karstic and alluvial underground networks in northern Italy. Some species, living in Alpine-Dinaric areas, are exclusive to the eastern Pre-Alps and are often strict endemics (like Paladilhiopsis robiciana, Phreatica bolei, Hauffenia tellinii and Belgrandia stochi). The area with the fewest species is the Piedmont Alps, with some endemic species of the genera Alzoniella, Iglica and Pseudavenionia. The Apennines host a small number of local endemics of the genera Pezzolia, Alzoniella, Pauluccinella, Orientalina, Fissuria and Islamia. Exclusive inhabitants of Sardinia are the genera Sardhoratia and Sardopaladilhia. Sicily hosts only one crenobiont species, Islamia cianensis. Thermal waters contain particular species of Bythinella and Belgrandia. ■ Polychaetes Polychaete worms are generally sea animals, and only a few species colonise anchialine coastal waters (land-locked bodies of water with a subterranean connection to the sea), and even fewer species are adapted to underground freshwater. Among them are two stygobiont species of great biogeographical interest. The nerillid Troglochaetus beranecki is an ancient thalassoid species (that is, one with marine affinities) originating from members of psammon in Tertiary epicontinental seas, from which it invaded underground freshwater. The characteristic of this species is its vast distribution area. In Europe, Troglochaetus beranecki is found in large rivers (Rhone, Garonne, Rhine, Weser, Danube, Oder, Elbe), in Finland and in Alpine streams. It has also been found in interstices in river beds of Colorado and Montana (up to 3050 m), although further molecular analyses are required to establish whether all these populations are really conspecific. Fewer numbers are found in caves of Switzerland, Germany, Poland, Hungary and Romania. In Italy, the species has recently been found in interstitial environments (Trentino) and in caves (Lessini Hills and Carnic Pre-Alps). This distribution is very wide, and includes ice-covered areas where underground fauna is minimal if not totally absent, and the rare stygobiont organisms have a remarkable capacity for adaptation, which enabled them to colonise these areas in post-glacial periods. 49
Page 1 and 2: Fauna FABIO STOCH Despite its inhos
Page 3: 44 45 Methods for sampling and anal
Page 7 and 8: 52 collected in phreatic waters in
Page 9 and 10: 56 ● Cyclopoid copepods. So far,
Page 11 and 12: 60 those associated with percolatin
Page 13 and 14: 64 Species of genus Niphargus; top:
Page 15 and 16: 68 ■ Decapods Italian fauna has o
Page 17 and 18: 72 Stygofaunal provinces in Italy T
Page 19 and 20: 76 aquifers in the Sabini mountains
Page 21 and 22: 80 ■ The ecology of aquifers Acco
Page 23 and 24: 84 85 The discovery of a new submer
Page 25 and 26: 88 anastomoses, often adjacent to t
Page 27 and 28: 92 93 The saline springs of Poiano:
Page 29 and 30: 96 Modified sensory setae on the an
Page 31 and 32: 100 Theoretical evolutionary sequen
Page 33 and 34: 104 Sketch showing degrading phases
Page 35 and 36: 108 109 Stygodiversity in the Presc
Page 37: 112 animal groups still living on t

Despite its inhospitable appearance and lack of any ... - Udine Cultura

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