TIPOLOGIA: dimostrazione/presentazione DESCRIZIONE: L'autotomia è una strategia difensiva largamente utilizzata dai molluschi opistobranchi come ultima risorsa contro l'attacco dei predatori. Essa consiste nel distacco/sacrificio di parti del corpo non essenziali per la sopravvivenza e che spesso contengono sostanze tossiche o disgustose. La rigenerazione dei tessuti sacrificati ha luogo con tempi che variano da pochi giorni a diverse settimane, in dipendenza delle specie e del tipo di tessuto. ATTIVITÀ PREVISTE: Verranno presentate e, compatibilmente con la reperibilità degli organismi, mostrate in acquario, specie che affidano all'autotomia ed alla rigenerazione la propria difesa dai predatori (ad es. Cyerce cristallina e Oxynoe olivacea).

To survive, organisms must continually adapt to continually evolving invading organisms. Hosts and pathogens are the key players of a continous conflict in which natural selection aids pathogens to increase virulence to escape host surveillance, and hosts to acquire adequate defence strategies. In both cases, these achievements are limited by several factors such as the genetic fitness and the number of genes required, much larger than that available in the genome. Moreover, since the pathogen usually has a very shorter life than the host, it has to fix new mutations favoring virulence much faster than the host can evolve effective defense mechanisms. Another constrain concerns the host that must avoid adverse effects which may derive from the defence system itself. Once resistance and counter resistance are genetically assessed, both the host and the pathogen evolve in response to mutually exerted pressures. This is generally referred to as the "Red Queen Paradigm", that highlights the significance of biotic versus abiotic factors that lead to constant evolutionary changes. Evolution acts at different levels: biotic factors mainly shape species diversity over short time periods, whereas changes in the physical environment such as climate changes drive evolution at a large scale, during much longer time. Much of our current knowledge of infection biology is based on studies of the immune system in humans and mice. In contrast, much less attention has been paid to immune response in lower vertebrates. Since many features of immune defence mechanisms have been acquired throughout evolution, studying the evolution of successful pathogen virulence mechanisms highlights the potential weaknesses in host immune defenses. On the other hand, investigating the defence mechanisms which species other than tetrapods have evolved to counter infectious agents may allow to identify novel molecules and strategies useful to manage an infection in the host' s favor. So far, few attempts have been made at considering host and pathogen as interacting partners into a common evolutionary framework. A short overview on how the host-pathogen interaction has been shaped by evolution will be given.

Nel saggio sono affrontati i problemi principali che impediscono la completa ricezione della teoria dell'evoluzione da un punto di vista religioso. In particolare, si dà conto della casualità e contingenza insite nel processo evolutivo, a livello molecolare come a quello macroscopico, e si offrono degli approcci religiosi innovativi che permetterebbero una risoluzione del conflitto fra scienza e religione.

Introduzione (col. 1302). - Evoluzione delle molecole proteiche (col. 1302). - Evoluzione dei genomi e dei geni (col. 1303). - Domini e modularità: prerequisiti per l'evoluzione (col. 1307).

It is discussed the persisting necessity for a change in paradigm in science and in the common way of thinking, from the exophysical perspective, typical of the classic realism, to an endophysical one, where the mutual interaction between us and the environment is not neglected. The necessity clearly results from the continuous debate on the interpretation of Quantum Mechanics in relation with the investigation of the microworld and from the unresolved problem of the compatibility of the linear, reversible and unstructured time of physics with the highly structured time of our perception endowed with an irreversible arrow. The necessity in the proposed change in paradigm is still clearer if we focus our attention to the formation of a representation of the external world in our mind, a process similar to that observed in nature in all complex self-organizing physical systems – including living organisms and human societies – producing order in competition with the second principle of thermodynamics. In such a conceptual schema, in fact, the acquisition of knowledge in man occurs in continuous and strict interaction with the environment and the result is always a new situation in which both man (with his representation of the world) and the environment are irreversibly changed.

Originating from a benthic ancestor, the suborder Notothenioidei (the dominant fish fauna component of the Antarctic sea) underwent a remarkable radiation, which led notothenioids to fill several niches. The ecological importance of notothenioids in Antarctica and their biochemical adaptations have prompted great efforts to study their physiology and phylogeny, with special attention to the evolutionary adaptation of the oxygen-transport system. We herewith report the evolutionary history of alpha- and beta-globins under the assumption of the molecular clock hypothesis as a basis for reconstructing the phylogenetic relationships among species. These studies have been extended to fish species of other latitudes, including the Arctic region. The northern and southern polar oceans have very different characteristics; indeed, in many respects the Antarctic and Arctic ichthyofaunas are more dissimilar than similar. Our results show that the inferred phylogeny of Arctic and Antarctic globins is different. Taking advantage of the wealth of information collected on structure and function of hemoglobins, we have attempted to investigate the evolutionary history of an important physiological feature in fish, the Root effect. The results suggest that the amino acid residues reported to play a key role in the Root effect may be regarded as ancestor characters, but the lack of this effect in extant species can hardly be associated with the presence of synapomorphies.

The blood of Antarctic icefishes (family Channichthyidae, suborder Notothenioidei) is completely devoid of hemoglobin. Icefishes have developed compensatory adaptations that reduce oxygen demand and enhance oxygen transport. Oxygen delivery to tissues occurs by carrying the gas physically dissolved in the plasma. To evaluate the evolutionary pathway leading to the icefish hemoglobinless phenotype, the adult and embryonic/juvenile gene complexes from a closely related, red-blooded notothenioid species were isolated and characterized. The hybridization pattern of notothenioid adult globin cDNAs showed that the genomes of three icefish species retain transcriptionally inactive alpha1-globin-related DNA sequences, which are identical truncated variants of the alpha1-globin gene of the red-blooded fish, containing part of intron 2, all of exon 3, and the 3'-untranslated region. The icefish genomes have no beta-globin genes. Furthermore, Southern blots of genomic DNA from red- and white-blooded (two species) notothenioids, probed with fragments of the genes flanking the ends of the embryonic/juvenile complex, indicated that icefishes have also lost embryonic/juvenile globin genes. It is proposed that inability to express hemoglobin arose from a single, large-scale deletional event, which removed all icefish globin genes with the exception of the 3' end of alpha1.

The Arctic fish Anarhichas minor, a benthic sedentary species, displays high emoglobin multiplicity. The three major hemoglobins (Hb 1, Hb 2, and Hb 3) show important functional differences in pH and organophosphate regulation, subunit cooperativity, and response of oxygen binding to temperature. Hb 1 and Hb 2 display a low, effector-enhanced Bohr effect and no Root effect. In contrast, Hb 3 displays pronounced Bohr and Root effects, accompanied by strong organophosphate regulation. Hb 1 has the beta (beta(1)) chain in common with Hb 2; Hb 3 and Hb 2 share the alpha (alpha(2)) chain. The amino acid sequences have been established. Several substitutions in crucial positions were observed, such as Cys in place of C-terminal His in the beta(1) chain of Hb 1 and Hb 2. In Hb 3, Val E11 of the beta(2) chain is replaced by Ile. Homology modeling revealed an unusual structure of the Hb 3 binding site of inositol hexakisphoshate. Phylogenetic analysis indicated that only Hb 2 displays higher overall similarity with the major Antarctic hemoglobins. The oxygen transport system of A. minor differs remarkably from those of Antarctic Notothenioidei, indicating distinct evolutionary pathways in the regulatory mechanisms of the fish respiratory system in the two polar environments.