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Molluscan shells show great diversity in colour, which is due to many different classes of chemical compounds. The identification of the pigments found in the molluscan shells of a diverse group of marine species was done in situ using Resonance Raman spectroscopy, and found to be unsubstituted polyacetylenes. Two South African species (D. serra and J. janthina) were chosen for extraction of the pigment-containing organic component, and it was found that the vibrational bands in the Raman spectra of the extracted component shifted relative to that obtained in the molluscan matrix, indicating structural changes in the pigmentary molecules upon extraction. Published correlations were used to evaluate the possible length of the conjugated chain, and a new correlation was established using previous reported data. The conjugated chain length predicted from the new correlation of the studied pigmentary molecules ranges between ten and twelve double bonds. Copyright 2011, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Barnard, W 2006, A spectroscopic investigation of polyacetylenic molecules in the molluskan biogenic matrix, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-06262008-114600 / > E216/ag / Dissertation (MSc (Chemistry))--University of Pretoria, 2008. / Chemistry / unrestricted

The fossiliferous Yorktown Formation (Pliocene) of Virginia was used as a natural laboratory for testing predictions of ecological and evolutionary theories. Specifically, coordinated stasis and ecological locking models have testable elements that can be analyzed using data from the Yorktown Formation. The ecological locking model requires that species within an ecosystem have strong interactions in order to stabilize morphologies of multiple lineages over millions of years. Species intereactions that are strong enough to do this should also be strong enough to be a major ordering force on the composition of paleocommunities. Single and replicate samples were taken from 30 cm stratigraphic intervals within the Rushmere and Morgart's Beach Members at several localities. A total of 142 samples were collected from 5 localites, which yielded 29,000 specimens belonging to 140 species of bivalves, gastropods, and other taxonomic groups. Principle components analysis, ANOVA, MANOVA, and other analyses were used to test the occurence and recurrence of local paleocommunities, paleocommunities, and paleocommunity types. Three paleocommunity types which occured under specific paleoenvironmental conditions were defined: rubbly bottom, transitional, and muddy bottom. Within a single locality samples from the same paleocommunity type yielded very similar faunal compositions, based on the relative abundance of the contained species. However, samples from the same paleocommunity type but different localities displayed low similarity values. This is consistant with local paleoenvironmental control of paleocommunity composition being more important than strong species interactions. The pattern predicted by the model of ecologic locking is absent from these Yorktown paleocommunities. A guild analysis was performed on the data to test whether the same types of organisms recurred in a predictable fashion under similar paleoenvironmental conditions. While the guild structure of the rubbly bottom paleocommunity type did recur at several localities, the guild structure of the other paleocommunity types varied greatly from place to place. / Ph. D.

Macroalgas marinhas sÃo habitadas por uma sÃrie de animais vÃgeis, incluindo moluscos, constituindo uma comunidade fital dinÃmica. Para se compreender essa comunidade, deve-se considerar, entre outros fatores, a complexidade do habitat. Alguns indicadores dessa complexidade seriam biomassa e volume algais. Acredita-se que um aumento estrutural da alga resulta em maior riqueza de espÃcies e abundÃncia de invertebrados associados. Foi investigada a malacofauna associada à rodÃfita Pterocladiella caerulecens, na zona entremarÃs da Praia da Pedra Rachada, em Paracuru, CearÃ. Foram realizadas seis coletas, sendo trÃs durante o perÃodo tipicamente seco (outubro, novembro e dezembro de 2009) e trÃs durante o chuvoso (abril, maio e junho de 2010). Foram selecionadas trÃs estaÃÃes de coleta (A, B e C), sendo estabelecida, em cada, uma parcela de 10 m x 10 m, subdividida em 100 quadrantes de 1mÂ. Foram amostrados cinco quadrantes em cada parcela, o que totalizava 15 amostras por mÃs. Os tufos de P. caerulescens foram coletados manualmente e acondicionados em sacos plÃsticos. Em laboratÃrio, as amostras foram triadas, os moluscos identificados e armazenados em etanol 70%. O volume da alga foi estimado pelo mÃtodo de deslocamento da Ãgua em recipiente graduado e a biomassa calculada atravÃs do peso seco. Foram identificadas 50 espÃcies, sendo 36 de Gastropoda, 11 de Bivalvia e 3 de Polyplacophora. De um modo geral, as trÃs estaÃÃes de coleta foram semelhantes, nÃo tendo sido observado padrÃo de distinÃÃo entre elas. A pluviometria pareceu nÃo influenciar o volume de alga, uma vez que nÃo foram observadas diferenÃas significativas entre os meses. Foi verificada correlaÃÃo positiva entre biomassa da alga e riqueza e abundÃncia de moluscos, reforÃando a ideia de que quanto maior a quantidade de alga no meio, maior a probabilidade de se encontrar diferentes espÃcies e um maior nÃmero de indivÃduos. A malacofauna se caracterizou por indivÃduos de tamanho reduzido, com hÃbitos alimentares diversificados. A macroalga estudada revelou atuar como importante substrato para moluscos, principalmente para juvenis, sugerindo que pode ser um habitat fundamental em estÃgios iniciais de desenvolvimento. / Seaweeds are inhabited by a lot of vagile animals, including molluscs, constituting a dynamic phytal community. In order to understand this community, the complexity of the habitat should be considered, among other factors. Some indicators of this complexity may be biomass and volume of the alga. It is believed that a structural increase of algae result in higher species richness and higher abundance of associated invertebrates. This work investigated the mollusks associated with the red alga Pterocladiella caerulecens, in the intertidal zone of the beach Pedra Rachada, in Paracuru city, state of CearÃ. Samples were collected during six months: three months of the dry season (October, November and December 2009) and three of the rainy season (April, May and June 2010). Three sample sites were selected (A, B and C). In each one was established a 10m x 10m plot, subdivided into 100 quadrants of 1mÂ. Five quadrants in each plot were sampled monthly, totalizing fifteen samples. The tufts of P. caerulescens were removed and placed in plastic bags. In laboratory, samples were analyzed, the mollusks were identified and stored in 70% ethanol. The volume of algae was estimated by immersing the alga in a graduate recipient with known amount of water, and the biomass was estimated by dry weight. Fifty species of mollusks were identified: 36 of Gastropoda, 11 of Bivalvia and 3 of Polyplacophora. In general, the three sites A, B and C were similar, with no pattern of distinction between them. It seems that rainfall did not influence the volume of algae, once there were no significant differences between months. Positive correlation was observed between the alga biomass and the molluscs richness and abundance. The molluscan fauna was characterized by individuals of small size, with diversed food habits. This study confirmed that Pterocladiella caerulescens acts as substrate for molluscs, mainly for juveniles, suggesting that it plays an important role in early stages of development.

The decomposition of land snail shell is a complex process involving a number of factors and influences, including the characteristics of conchs themselves. In particular, it is the shell size with which the progress and the rate of degradation are tightly bound. Post-mortem changes begin with the loss of the original colour and, in the case of transparent species, by the opacification of the shell wall. Subsequently, the periostracum disruption and dissolution of calcium layers occur. However, this sequence may be reversed for some small species (e.g. Columella aspera, Nesovitrea hammonis). Animals mechanically destroy empty shells, humic acids from the substrate cause their artificial dyeing. Fungal mycelium or colonies of Streptomyces grow on the surface of the conchs. The plant roots are also involved in shell decomposition. While degradation of large shells starts with periostracum disruption and subsequent ostracal dissolution, periostracum of small shells persists even after dissolution of ostracal layers. The phenomenon is caused by high resistance of the periostraca of small species. In the case of large shells, periostracum has primarily a "building" function during shell formation, and sometimes it is flaking off already during the snail's life. For small species, it is an important part...

第22回名古屋大学年代測定総合研究センターシンポジウム平成21(2009)年度報告

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