Occurrence of Leptestheria Dahalacensis Rüppell, 1837

OCCURRENCE OF LEPTESTHERIA DAHALACENSIS RÜPPELL, 1837 AND EOLEPTESTHERIA TICINENSIS (BALSAMO-CRIVELLI, 1859) (CONCHOSTRACA, LEPTESTHERIIDAE) IN EMILIA-ROMAGNA, ITALY; NEW MORPHOLOGICAL DATA BY FRANCA SCANABISSI SABELLI and STEFANO TOMMASINI Dipartimento di Biologia evoluzionistica sperimentale dell' Università di Bologna, sede di Zoologia, Via S. Giacomo 9, 40126 Bologna, Italy RIASSUNTO E segnalata la presenza di Eoleptestheriaticinensis (Balsamo-Crivelli, 1859) e Leptestheria dahalacensisRüppell, 1837 finora note solo per altre località, in alcune risaie della provincia di Ferrara (Emilia-Romagna, Italia). Viene descritto un nouvo carattere dimorfico, che consiste nella presenza nei maschi di un'area armata di corte setole sulla carena inferiore del rostro cefalico. INTRODUCTION During the collection of specimens of Phyllopoda carried out in May 1987, May 1988 and May 1989, several populations of Crustacea Conchostraca were found in rice-fields in the countryside around Ferrara, precisely in the areas called "Corte Ravenna" and "Le Contane" (Iolanda di Savioa), "Torbiera" and "Ponte Langorino" (Codigoro), and "Corte Salute" (Massa Fiscaglia). The specimens were identified as belonging to the family Leptestheriidae, viz. Eoleptestheria ticinensis (Balsamo-Crivelli, 1859) and Leptestheria dahalacensis Rüp- pell, 18371837 (Daday (Daday de de Dees,Dees, 1923; 1923; Thiery, Thiery, 1988). 1988). Males and females are pres- ent with a balanced sex-ratio in the populations of both species. Once the females are fecundated they deposit hundreds of eggs, reddish in colour, under the valve of the carapace and keep these along their sides for several days. The eggs are then left to fall to the bottom and after a required pcriod of drying of the pool water complete their development after rehydration and hatch as larva in the nauplius stage. Comparable to the condition met within other Phyllopoda this type of biological cycle is suitable to overcome any adversity in the particular environment of the rice-fields, whether this adversity is natural (drying, ultraviolet radiation, overheating, variations in salinity and pH) or artificial (chemical treatment of crops). 260 As is also known from the literature (Daday de De6s, 1923; Fox, 1951; Straskraba, 1965; Cottarelli & Mura, 1983; Thiery & Pont, 1987; Nourisson & Thiery, 1988) the geographical distribution of these two species in Italy covers the area we have explored; exact information, nevertheless, is lacking for Emilia-Romagna, as E. ticinensis is known only from Lombardy and perhaps also from Piedmont, while L. dahalacensis has only been observed in Sicily. Our records show that the two species, sympatric though never found in the same water pool, occupy a wider and still to be defined area, probably related to the growth of their characteristic habitat; consequently their distribution may have followed the introduction of rice-growing in the province of Ferrara and in other Italian regions. The record in the province of Ferrara, like that of E. ticinensis in "Moyenne Camargue" (Thiery & Pont, 1987) is noteworthy as both biotopes have the same geographical situation in common, viz. the proximity of great river deltas (Po and Rhone), with many brackish lagoons, a habitat characterized by the presence of an abundant migratory avifauna, the main means of transport of the Conchostracan eggs. The sale of seeds as a means of spreading the species must in all likelihood be excluded as infestation of rice-fields by the afore men- tioned species invariably occurs years after the first cultivation of the rice- fields. Population density in rice-fields may become so high that farmers are induced to adopt drying techniques or to use chemicals in the fields to get rid of the muddiness of the water causes by the detritivorous activity of these Phyllopoda. These methods, however, are quite useless when applied after the deposition of the eggs, these being resistant to pesticides and requiring a period of drying before further development (Fox, 1951; Tommasini & Scanabissi- Sabelli, 1989), such as those that are used for the growth of young rice plants. Observations on both species have been made with the Scanning Electron Microscope (SEM) and are recorded below, along with diagnostic characters necessary for the recognition of the two species; with the exception of those characters that have been recognized as being too variable, as for instance the shape of the carapace and the number of mctameres. Eoleptestheria ticinensis (Balsamo-Crivelli, 1859) (fig. 1) Synonymy: Lsaura ticinensis Balsamo-Crivelli, 1859; Estheria ticinensis Grube, 1865: Eoleptestheria ticinensis Daday, 1913; Daday, 1923; Eoleptestheria inojJÏnata Daday, ]8>211; Eoleptestheriachinensis Daday, 1923; U6no, 1940; Roen, 1952; Eolef?te.stheriavariabilis Rotnariuc, 1947 ; Eoleptestherias?ino.ca Marincek, 1978; Eoleptestheriaspinosa teniil*SMarincek & Valvajter, 1979; Eoleptestheriaspl'nosa magna Marincek & Valvajter, 1982 (after Rrtck, in litt.). .

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