Tina Tirelli

Use of different approaches to model presence/absence of Salmo marmoratus in Piedmont (Northwestern Italy)

Abstract In Piedmont (Italy) the environmental changes due to human impact have had profound effects on rivers and their inhabitants. Thus, it is necessary to develop practical tools providing accurate ecological assessments of river and species conditions. We focus our attention on Salmo marmoratus , an endangered salmonid which is characteristic of the Po river system in Italy. In order to contribute to the management of the species, four different approaches were used to assess its presence: discriminant function analysis, logistic regression, decision tree models and artificial neural networks. Either all the 20 environmental variables measured in the field or the 7 coming from feature selection were used to classify sites as positive or negative for S. marmoratus . The performances of the different models were compared. Discriminant function analysis, logistic regression, and decision tree models (unpruned and pruned) had relatively high percentages of correctly classified instances. Although neither tree-pruning technique improved the reliability of the models significantly, they did reduce the tree complexity and hence increased the clarity of the models. The artificial neural network (ANN) approach, especially the model built with the 7 inputs coming from feature selection, showed better performance than all the others. The relative contribution of each independent variable to this model was determined by using the sensitivity analysis technique. Our findings proved that the ANNs were more effective than the other classification techniques. Moreover, ANNs achieved their high potentials when they were applied in models used to make decisions regarding river and conservation management.

Importance of feature selection in decision-tree and artificial-neural-network ecological applications. Alburnus alburnus alborella: A practical example

Abstract Recent advances in computing technology have increased interest in applying data mining to ecology. Machine learning is one of the methods used in most of these data mining applications. As is well known, approximately 80% of the resources in most data mining applications are devoted to cleaning and preprocessing the data. However, there are few studies on preprocessing the ecological data used as the input in these data mining systems. In this study, we use four different feature selection methods (χ 2 , Information Gain, Gain Ratio, and Symmetrical Uncertainty) and evaluate their effectiveness in preprocessing the input data to be used for inducing artificial neural networks (ANNs) and decision trees (DTs). The presence/absence of fish is the data item used to illustrate our models. Feature selection is fundamental in order to increase the performances of the models obtained. Accuracy of classification improves when a small set of optimally selected features is used. DTs and ANNs are very useful tools when applied to modeling presence/absence of Alburnus alburnus alborella . ANNs generally performed better than DT models.

Monitoring crayfish using a mark-recapture method: potentials, recommendations, and limitations

Crayfish are regarded as useful indicators of environmental quality and freshwater biodiversity. However, reliable methods for monitoring their populations are needed so that this potential can be fully utilised. We report and discuss methodological aspects of the white-clawed crayfish (Austropotamobius pallipes complex) survey conducted in Piedmont, Italy, with the use of mark-recapture. The results suggest that the method can serve as a convenient tool for estimating the size of crayfish populations and inferring their temporal trends. The two populations investigated appeared closed except for wintertime and July. Consequently, the Robust Design, which is regarded as the most reliable mark-recapture approach, can be easily applied. The minimum effective sampling plan for monitoring purposes should comprise one primary period per year, conducted in the summer–autumn season, and consisting of three capture sessions. If gaining insight into the ecology of the investigated species is the prime objective and sufficient resources are available, the optimal plan should include two primary periods (in spring and the summer–autumn season) of five capture sessions each. Capture sessions need to be separated by roughly 2-week intervals in order to avoid the strong, but short-term, negative effect of capturing crayfish on their recapture chances. As the model without heterogeneity in capture probabilities ensures better estimate precision we recommend that data collected for both sexes are analysed separately. Taking into consideration higher male catchabilities and sex ratio being invariably 1:1, it also seems beneficial to estimate only male numbers and double them to achieve total population sizes.

The role of water chemistry in the distribution of Austropotamobius pallipes (Crustacea Decapoda Astacidae) in Piedmont (Italy).

Over the last decades, the populations of Austropotamobius pallipes have decreased markedly all over Europe. If we evaluate the ecological factors that determine its presence, we will have information that could guide conservation decisions. This study aims to investigate the chemical-physical demands of A. pallipes in NW Italy. To this end, we investigated 98 sites. We performed Principal Component Analysis using chemical-physical parameters, collected in both presence and absence sites. We then used principal components with eigenvalue > 1 to run Discriminant Function Analysis and Logistic Regression. The statistics on the concentration of Ca(2+), water hardness, pH and BOD(5) were significantly different in the presence and in the absence sites. pH and BOD(5) played the most important role in separating the presence from the absence locations. These findings are further evidence that we should reduce dissolved organic matter and fine particles in order to contribute to species management and conservation.

Reproductive biology of Mediterranean hermit crabs: male reproductive apparatus of Clibanarius erythropus (Decapoda Anomura)

Abstract The male gonopores, internal male reproductive apparatus, and spermatophores of the Mediterranean hermit crab Clibanarius erythropus are described, using interference phase microscopy and scanning electron microscopy. A discussion on the relationship between the gonopore morphology and the different kinds of setae accompanying them, and the reproductive biology of these crabs is presented. Each testis merges into a tubular duct made up of four zones: 1) the collecting tubule with free sperm; 2) the proximal zone, where the ampulla of the spermatophore starts to be formed; 3) the medial zone, where the ampulla is completed, the stalk lengthens and the pedestal is formed; 4) the distal zone, where the mature spermatophores are stored. In the mature spermatophore the two halves of the ampulla meet at the distinct lateral ridge. Sizes of the different parts of the spermatophore are given and their morphology described. The importance of the morphology of the paguroid gonopore, male reproductive system, and spermatophore is confirmed for phylogenetic studies within the Paguroidea and Anomura.

REPRODUCTIVE BIOLOGY OF MEDITERRANEAN HERMIT CRABS: FINE STRUCTURE OF SPERMATOPHORES AND SPERMATOZOA OF DIOGENES PUGILATOR (DECAPODA: ANOMURA) AND ITS BEARING ON A SPERM PHYLOGENY OF DIOGENIDAE

Abstract The spermatophore morphology and spermatozoal ultrastructure of Diogenes pugilator are described. The spermatophore is typically tripartite made up of an ampulla, a very long stalk and a foot. The two halves making up the ampulla meet at a lateral ridge. The sperm is ovoidal in shape and composed of a large, almost cylindrical, acrosome, which occupies most of the cell volume, capped by a conical operculum, and cupped posteriorly by a cytoplasmic region comprising the nucleus and three arms. The sizes of the different parts of the spermatophore and of the sperm are given and their exterior morphology and ultrastructure described and compared to congeners. The available spermatozoal and spermatophore data is used to place D. pugilator within a sperm phylogeny of the hermit crab family Diogenidae.

Intraspecific relationships of the hermit crab Diogenes pugilator : predation and competition

The population of the hermit crab Diogenes pugilator is numerically quite substantial in the examined area, therefore it is analysed if the population was subject to any pressure by predators and by other species of hermit crabs living in that zone. It was found there is a potential pressure by predators which might influence it. Only Liocarcinus depurator is able to keep the population trend of D. pugilator under control. With regard to the relationships with the other species of hermit crab, D. pugilator dominates only over Pagurus anachoretus, while in the other cases, there was just competition for food.

Support vector machines to model presence/absence of Alburnus alburnus alborella (Teleostea, Cyprinidae) in North-Western Italy: Comparison with other machine learning techniques

Alburnus alburnus alborella is a fish species native to northern Italy. It has suffered a very sharp decrease in population over the last 20 years due to human impact. Therefore, it was selected for reintroduction projects. In this research project, support vector machines (SVM) were tested as possible tools for building reliable models of presence/absence of the species. A system of 198 sites located along the rivers of Piedmont in North-Western Italy was investigated. At each site, 19 physical-chemical and environmental variables were measured. We verified that performances did not improve after feature selection but, instead, they slightly decreased (from Correctly Classified Instances [CCI]=84.34 and Cohens k [k]=0.69 to CCI=82.81 and k=0.66). However, feature selection is crucial in identifying the relevant features for the presence/absence of the species. We then compared SVMs performances with decision trees (DTs) and artificial neural networks (ANNs) built using the same dataset. SVMs outperformed DTs (CCI=81.39 and k=0.63) but not ANNs (CCI=83.03 and k=0.66), showing that SVMs and ANNs are the best performing models, proving that their application in freshwater management is more promising than traditional and other machine-learning techniques.

Pebrilla paguri (Ciliophora, Folliculinidae) on four Mediterranean hermit crab species

Abstract The present research aims at broadening the range of possible Pebrilla paguri hosts, by analysing various Mediterranean hermit crab species, as well as at investigating their preferential distribution on the crustacean body. For each crab carrying P. paguri on its exoskeleton, the position and number of the ciliates loricae were recorded and mapped. Pebrilla paguri loricae were observed only on 16.6% of the hermit crabs examined, with a greater number being observed on Calcinus tubularis and Paguristes eremita, compared to the two other crab species. A reason for this may be that the former are not very active in feeding, motion, and interaction. The highest frequency of P. paguri was observed on the abdomen, telson, and uropods, whereas only a few were found on the cephalotorax. This localisation is discussed in relation to the epibionts preference for parts of the crabs body that are normally kept deep inside the molluscan shell and characterised by scarce water flow and illumination. These conditions will promote bacterial proliferation and accumulation of the organic residuals, which will become available for P. paguri as food. The preferential distribution of ciliates on the left side of the crabs body can be seen as a way to avoid damage by rubbing against the shells columella.

Finding of Pebrilla paguri (Ciliata, Folliculinidae, Heterotricha) epibiont inside the shells of two hermit crab species, Calcinus tubularis and Clibanarius erythropus (Decapoda, Anomura, Diogenidae)

Ever since its discovery, Pebrilla paguri was considered to be an exclusive epibiont of hermit crabs. In fact, up to now, it has never been recorded on substrata other than the hermit crab exoskeleton. The finding of its loricae on non‐consecutive exuviae, released by the same specimen of Calcinus tubularis, suggested that the motile stage may transform into the sessile form and attach itself to the shell occupied by the crab. All the shells occupied by the C. tubularis and Clibanarius erythropus specimens showing the ciliate on the exoskeleton were identified to genus level; for each shell genus a map of the inner morphology was drawn in order to record the position and number of the loricae. The present research showed that P. paguri is not an exclusive hermit crab epibiont: it also attaches itself to shells, and particularly to the three largest whorls, corresponding to the portion occupied by the crab body. The presence of P. paguri in the shell may be determined by the preference for substrata characterized by a particular water stream or light levels. The results obtained show that the P. paguri substrata choice is more similar to that of other folliculinids, and more varied than previously reported.