Indigenous demosponge spicules in a Late Devonian stromatoporoid basal skeleton from the Frasnian of Belgium

This paper records the first example of a demosponge spicule framework in a single specimen of a Devonian stromatoporoid from the Frasnian of southern Belgium. The small sample (2.5 × 2 cm) is a component in a brecciated carbonate from a carbonate mound in La Boverie Quarry 30 km east of Dinant. Because of the small size of the sample, generic identification is not confirmed, but the stromatoporoid basal skeleton is similar to the genus Stromatopora. The spicules are arranged in the calcified skeleton, but not in the gallery space, and are recrystallized as multi-crystalline calcite. The spicules fall into two size ranges: 10-20 μm diameter and 500-2000 μm long for the large ones and between 5-15 μm diameter and 50-100 μm length for the small ones. In tangential section, the spicules are circular, they have a simple structure, and no axial canal has been preserved. The large spicules are always monaxons, straight or slightly curved styles or strongyles. The spicules most closely resemble halichondrid/axinellid demosponge spicules and are important rare evidence of the existence of spicules in Palaeozoic stromatoporoids, reinforcing the interpretation that stromatoporoids were sponges. The basal skeleton may have had an aragonitic spherulitic mineralogy. Furthermore, the spicules indicate that this stromatoporoid sample is a demosponge. © 2014 Lethaia Foundation. Published by John Wiley & Sons Ltd

Statistical Feature Combination for the Evaluation of Game Positions

This article describes an application of three well-known statistical methods in the field of game-tree search: using a large number of classified Othello positions, feature weights for evaluation functions with a game-phase-independent meaning are estimated by means of logistic regression, Fisher's linear discriminant, and the quadratic discriminant function for normally distributed features. Thereafter, the playing strengths are compared by means of tournaments between the resulting versions of a world-class Othello program. In this application, logistic regression - which is used here for the first time in the context of game playing - leads to better results than the other approaches.Comment: See http://www.jair.org/ for any accompanying file

DNA barcoding of sponges (Phylum Porifera) in South Africa

Abstract : South Africa is renowned for its biological diversity and is a hotspot for marine invertebrates (Griffith et al., 2010), including sponges (Porifera). Despite their pivotal role for the functionality of the marine ecosystem, a reliable estimate of the species richness of sponges in South Africa is difficult. Using morphological characters for species identification has its limitations: it is hindered by the paucity and plasticity of morphological characters (Blanquer & Uriz 2007, Sperling et al., 2011) which may result in numerous species being morphologically indistinguishable, i.e. “cryptic” species. The sponge fauna of South Africa is also understudied, although this issue has begun to be addressed, with more than 40 new species described from this region over the last 10 years. It is likely that the current estimate of sponge biodiversity nonetheless remains a considerable underestimate, and numerous suspected new species remain to be described (Samaai, pers. comm.). Over the last five years, increased efforts were placed on documenting South African biodiversity, with sponges as one of the focus groups. The present study is part of this initiative, and constitutes the first genetic study on South African sponges aimed at complementing morphological data to help resolve sponge taxonomy. The results indicate that South African sponges are not as widespread as previously thought, but comprise cryptic and genetically distinct evolutionary lineages. Importantly, the results show that sponges identified from South Africa as southern hemisphere are representatives of supposedly cosmopolitan species that have been misidentified. Moreover, some species assumed to be widespread in southern Africa actually turned out to be subdivided into regional evolutionary lineages with distinct distribution ranges. In some cases the molecular data corroborated the morphological species identification, whereas in other instances the combined approach revealed the presence of species complexes. This study represents a first step in constructing a reference library for South African sponges and to advance our understanding of the diversity, biogeography and evolutionary adaptability of South African sponges.M.Sc. (Zoology

Lichen-Moss associations in plant communities of the Southwest Admiralty Bay, King George Island, Antarctica

The phytosociology of plant communities in the Admiralty Bay ice-free areas (King George Island, South Shetland Islands, Antarctica) was investigated during the 2003/04 summer seasons. In this study associations among lichens and mosses were found, where the lichen species are dominant in the samples. A total of 10 associations are identified. For each association found in this work, descriptions are given and comments about their ecology and distribution in the study area are made. Key words: Antartic plants, phytosociology, ecology.The phytosociology of plant communities in the Admiralty Bay ice-free areas (King George Island, South Shetland Islands, Antarctica) was investigated during the 2003/04 summer seasons. In this study associations among lichens and mosses were found, where the lichen species are dominant in the samples. A total of 10 associations are identified. For each association found in this work, descriptions are given and comments about their ecology and distribution in the study area are made. Key words: Antartic plants, phytosociology, ecology

Sponges Dominant In The Alaska Intertidal: Biology, Ecology, And Genetic Diversity

Thesis (Ph.D.) University of Alaska Fairbanks, 2002The role of the sponge, Halichondria panicea, in a Kachemak Bay, Alaska, intertidal community was investigated through field and laboratory experiments. The relationship between H. panicea and co-occurring macroalgae was studied and results indicate that removing macroalgae had no effect on sponge abundance. A laboratory feeding trial investigating H. panicea and its primary predator Archidoris montereyensis showed that nudibranchs consuming symbiotic sponge had higher feeding and egg production rates than individuals eating aposymbiotic sponge. In a simulated predation event, initial sponge growth rates into experimental feeding scars were high, indicating a response mechanism to tissue damage. A naturally occurring high nudibranch recruitment into a sponge population resulted in the local decline and extinction of both sponge and predator. Genetic studies revealed that at least two sponge species likely comprise the intertidal populations investigated, Halichondria panicea and H. bowerbanki. The reproductive cycle of H. panicea at exposed, hard-substrate habitats, and H. bowerbanki at sheltered, soft-sediment sites, exhibited seasonal peaks in oocyte production and maturation. H. panicea produced embryos 3--4 months earlier than H. bowerbanki. Six genomic DNA microsatellite loci were isolated and utilized in the characterization of two Halichondria panicea populations. The two populations were differentiated from one another with no significant inbreeding or bottleneck effect detected. All individuals were genetically unique, indicating little or no cloning. Sexual reproduction appears to be the dominant mode of reproduction maintaining the populations. DNA sequence analyses suggest that at least two species are likely present in Kachemak Bay. Distributions of ITS and CO1 haplotypes corresponded to habitat type. Analyses of the data grouped Alaska haplotypes separately from European samples of Halichondria panicea and H. bowerbanki , suggesting separate species may occur in Alaska. A re-examination of sponge systematics in southcentral Alaska is needed