Multiple Conclusion Rules in Logics with the Disjunction Property

We prove that for the intermediate logics with the disjunction property any basis of admissible rules can be reduced to a basis of admissible m-rules (multiple-conclusion rules), and every basis of admissible m-rules can be reduced to a basis of admissible rules. These results can be generalized to a broad class of logics including positive logic and its extensions, Johansson logic, normal extensions of S4, n-transitive logics and intuitionistic modal logics

Remarkable convergent evolution in specialized parasitic Thecostraca (Crustacea)

<p>Abstract</p> <p>Background</p> <p>The Thecostraca are arguably the most morphologically and biologically variable group within the Crustacea, including both suspension feeders (Cirripedia: Thoracica and Acrothoracica) and parasitic forms (Cirripedia: Rhizocephala, Ascothoracida and Facetotecta). Similarities between the metamorphosis found in the Facetotecta and Rhizocephala suggests a common evolutionary origin, but until now no comprehensive study has looked at the basic evolution of these thecostracan groups.</p> <p>Results</p> <p>To this end, we collected DNA sequences from three nuclear genes [18S rRNA (2,305), 28S rRNA (2,402), Histone H3 (328)] and 41 larval characters in seven facetotectans, five ascothoracidans, three acrothoracicans, 25 rhizocephalans and 39 thoracicans (ingroup) and 12 Malacostraca and 10 Copepoda (outgroup). Maximum parsimony, maximum likelihood and Bayesian analyses showed the Facetotecta, Ascothoracida and Cirripedia each as monophyletic. The better resolved and highly supported DNA maximum likelihood and morphological-DNA Bayesian analysis trees depicted the main phylogenetic relationships within the Thecostraca as (Facetotecta, (Ascothoracida, (Acrothoracica, (Rhizocephala, Thoracica)))).</p> <p>Conclusion</p> <p>Our analyses indicate a convergent evolution of the very similar and highly reduced slug-shaped stages found during metamorphosis of both the Rhizocephala and the Facetotecta. This provides a remarkable case of convergent evolution and implies that the advanced endoparasitic mode of life known from the Rhizocephala and strongly indicated for the Facetotecta had no common origin. Future analyses are needed to determine whether the most recent common ancestor of the Thecostraca was free-living or some primitive form of ectoparasite.</p

Sacculina nectocarcini, a new species of rhizocephalan (Cirripedia: Rhizocephala) parasitising the red rock crab Nectocarcinus integrifrons (Decapoda: Brachyura: Portunidae)

The parasitic barnacles, Rhizocephala, are a little known group within Australia with only seven described species from a coastline stretching approximately 59763 km. This study describes a new species of Rhizocephala, Sacculina nectocarcini. The description is based on a unique combination of features pertaining to the structure of the mantle papillae, the retinaculae and the male receptacles. Biological notes, prevalence and intensity of infection are reported for this rhizocephalan, infesting the red rock crab, Nectocarcinus integrifrons, collected from Western Port, Victoria, Australia. Copyright © 2006 Magnolia Press