Ostracoda of the Italian ricefields thirty years on: new synthesis and hypothesis

Abstract

We compare data from a survey of ostracode species carried out during 1994-1998 from Northern Italian ricefields with data from the same area collected in the ’60s. Twenty-five species were recorded during a survey of 19 ricefields in 1994-98 as against 46 species found in 16 ricefields over thirty years ago. Three of these species (Ilyocypris biplicata, Chlamydotheca incisa and Chrissia sp.), as well as six among the 27 species found in the '60s but not recorded during 1994-1998, were found in Italy only in the ricefield habitat. Three species were recorded for the first time in Italy: Hemicypris dentatomarginata, Ilyocypris monstrifica and Chrissia sp. Eight taxa (Chlamydotheca incisa, Chrissia sp., Cypretta turgida, Dolerocypris sinensis, H. dentatomarginata, Isocypris beauchampi, Strandesia spinulosa and Tanycypris pellucida) were considered endemic to South America, Africa or Asia and are thought to have been introduced to Italy with useful plants, notably rice varieties. The recording of these species indicates once again the importance of man as an agent for passive dispersal of ostracode and the role of ricefields as a suitable habitat for new exotic colonising species. Heterocypris incongruens is the most widespread species and several other species (D. sinensis, Cypridopsis vidua, Ilyocypris gibba and Isocypris beauchampi cicatricosa) were found in more than 50% of the ricefields sampled: 40% of the species occur in just one or two ricefields. In Northern Italy today, species similarity between ricefields is inversely related to their geographic distance but is not spatially structured. This may be due to the fact that, in ostracodes, the production of passive dispersal resting eggs constrains regional differentiation. Species richness is significantly related to the amount of cultivated area. The decrease in species richness observed over the last thirty years or so may be related to the widespread use of pesticides in local current agricultural practices

Limnological characteristics and recent ostracods (Crustacea, Ostracoda) of freshwater wetlands in the Parco Oglio Sud (Northern Italy)

“…For example, the taxon richness of the Oglio River wetlands is comparable to that found in ricefields (Rossi et al 2003), but with a much greater proportion of autochthonous taxa. Also, the number of identified species in the Oglio wetlands was higher than that of a group of 31 lowland springs (Rossetti et al 2004).…”

“…Pseudocandona compressa has a broader distribution, being widespread throughout Europe, Turkey, Iran, Siberia and probably North America (Meisch 2000). The occurrence of Ilyocypris monstrifica is also of particular interest, since this species was known in Italy only from two ricefields in the Po River Valley and one locality in Sicily (Rossi et al 2003). It is nevertheless possible that this species has previously been reported as I. gibba, so its exact distribution remains at present unknown.…”

“…This contribution is part of a larger project to investigate the values and functions of wetlands of the Parco Oglio Sud, aimed at the management and restoration of the aquatic ecosystems (Delfini 2003). As pointed out by Rossi et al (2003), data on recent freshwater ostracods in Italy are relatively scarce, although the checklist compiled by Ghetti & McKenzie (1981) reported an extraordinary high species diversity and a large number of endemic taxa. Unfortunately, the prevalent inadequacy of taxonomic descriptions and often also the absence of collections and type repositories make it difficult to confirm the reliability of many earlier Italian records.…”

“…for the genus Herpetocypris (González Mozo et al 1996). A preliminary appraisal of the extant diversity of nonmarine ostracods (from surface, crenal, and subterranean waters) in Italy, following synonymisation of several taxa, elimination of doubtful records and inclusion of new species (e.g., Martens 1992 on Eucypridini, Martens et al 2002 on Heterocypris, Karanovic & Pesce 2000 on Mixtacandona talianae) and new records for Italy (e.g., Stoch 1998, Bellavere et al 2002, Rossi et al 2003, this paper), leads to a rough estimation of about one hundred valid species, of which c. 15% are exotic and less than 5% endemic (Rossetti & Martens in preparation).…”

Freshwater ostracods as environmental tracers

“…The widespread and massive use of fertilizers, pesticides and herbicides causes a decrease in ostracod richness (Rossi et al 2003), although some species are resistant to pesticides or organic pollution (Lim and Wong 1986). Tolerant taxa are dominant in lowland springs with high nitric nitrogen contents ([800 lM) derived from a diffuse pollution of agricultural origin (Rosetti et al 2004), whereas important increase of phosphate contents has been related to the absence of living specimens in the upper sediments of some lakes (Wünnemann et al 2006).…”