Abstract The main results of research on invertebrate biology and ecology in the lagoons of the Po River Delta (Sacca del Canarin, Sacca di Scardovari, Sacca di Goro) are presented and related to the more significant approaches followed in ecological research during the last two decades. The lagoons, which are intrinsically eutrophic water bodies, have recently undergone intense eutrophication due to the dramatic increase in the Po river nutrient loading. A shift towards a dystrophic state was indicated by the appearance of large Ulva rigida beds in spring and by extensive anoxia during the summer due to the decomposition of the huge macroalgal biomass. Particularly severe dystrophic crises occurred in the Sacca di Goro. Zooplankton and zoobenthos changes were analyzed according to the variations in hydrographic features as well as those in the trophic state of the water. The significance of population dynamics studies in evaluating biological responses to environmental stresses is emphasized. Investigati...

Abstract Rivers have been considered for a long time simply as vehicles transporting water and not as ecosystems. In Italy there has been a massive transformation of the lotic habitats, particularly with regard to the riparian zones and to the quality of waters. The structure and function of the populations and communities of organisms represent indicators of the changes which take place in the environment. Numerous indices, based on the study of the macroinvertebrate communities, have been proposed for evaluating the quality of the river environments in Europe. In Italy, a concrete result of the river monitoring programme, based on analysis of the macroinvertebrate communities, is the biological quality maps of hydrographic networks. The macroinvertebrate communities play an important role in the process of transforming the organic material input and as indicators of the quality and structural and functional integrity of the lotic environment.

Abstract The genetic diversity obtained by comparing mitochondrial DNA regions (the slowly evolving protein‐coding gene cytochrome b and the tRNAGlu gene) of three lamprey species belonging to different genera, Petromyzon marinus, Lethenteron zanandreai, and Lampetra planeri, is reported. The low degree of intergeneric variability detected, as compared with differences described for other fish taxa, supports the view of a recent evolutive separation of both Lethenteron and Lampetra from Petromyzon.

Abstract Twenty population and community measures (with structural measures including richness, diversity indices, and biotic indices, and functional measures including functional feeding‐group components) that have been proposed for use in benthic biomonitoring were examined in terms of within‐habitat variability (using coefficients of variation), accuracy (i.e., indications of impact when impact occurred; no indications of impact when impact did not occur), and taxonomic effort required (e.g., from simple discrimination among taxa to generic identification of taxa and determination of trophic status). Based on 54 samples from a uniform riffle of a California mountain stream, coefficients of variation ranged from 7% for Simpson's diversity index to greater than 100% for several measures. Richness measures, Margalef s diversity index, the Family Biotic Index, and the ratio of individuals of the scraper functional‐feeding group to total number of individuals were accurate in detecting acid and thermal stre...

Abstract Systematic observations on seasonal incidence of the red admiral (Vanessa atalanta L.) in central‐northern Italy were made in the course of four successive years. Our data show that our region is characterized by regular bidirectional migration which is particularly remarkable in October, during autumn migration to the overwintering sites. Red admirals’ migration is highly directional: individuals fly along straight lines at the mean speed of 14 km/h, and produce highly oriented distributions of their vanishing bearings. This directional preference is not the result of passive displacement caused by winds, but is the expression of an internal tendency based on the use of a compass mechanism. Red admirals’ seasonal incidence in our area significantly differs from that reported for the northern range of this butterfly species. This study constitutes the base of a long‐term investigation aimed at clarifying the phenology and other aspects of migration of this butterfly species (origin and destinatio...

Abstract The snakes of southern Jordan are studied on the basis of recent collections (1990–1993). A total of 24 snake species belonging to five families are included. Notes on their ecology and distribution are also given.

Abstract Depending on the species, the teleost cortical alveolus (CA) has from one to several layers of small to large cortical vesicles forming a continuous or discontinuous collar in the peripheral ooplasm. The histochemical composition of the CA, which also varies among species, is made of neutral glycoprotein, carboxylated glycocon‐jugate, neutral glycoprotein plus carboxylated glycoconjugate, sulfated glycoconjugate, neutral glycoprotein plus sialic acid‐rich glycoprotein. The CA was sudanophobic in all species analyzed. The morphology and contents of the CA seem to express common characters among many of the groups studies. Variations in the morphology and contents of the CA may be related to different mechanisms of polyspermy blockade.