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The aim of this diploma thesis is to compare natural and human-influenced malacocenoses in the vicinity of the villages Krasíkov and Domaslav in the district of Tachov, Czech Republic. Inventory research was conducted between 2012 and 2013. A total of 36 gastropod species were found, and a total of 1088 snail shells were collected. On some of the surveyed sites (the farm Krasíkov, Domaslav, the pond near Ovčí vrch) the influence of anthropic stress is evident. Four species found during this study are also listed in the Red List of Threatened Species of the Czech Republic (Aegopinella nitidula, Balea perversa, Ena montana, Vertigo pusilla). Based on the results of the research, two variants of the didactic use of a such malacological research were created in the teaching of natural science and biology. Keywords: Mollusca, Gastropoda, malacocenosis, species diversity, ecology of mollusk assemblages, Krasíkov.

Theory predicts that when prey can reach a size refuge from predation, prey vulnerability to predation is a function of hatchling size, growth rate, and the handling limitations of its predator, which collectively influence the amount of time prey spend vulnerable. I examined the mechanistic role of prey size for the predator-prey interaction between predatory crayfish (Procambarus fallax) and apple snail prey (Pomacea paludosa and P. maculata) and found that crayfish feeding rates decreased with snail size, such that smaller hatchling P. maculata were more than twenty times more vulnerable than hatchling P. paludosa. Experimental manipulations of productivity increased apple snail growth rates, reducing the effects of predatory crayfish on P. maculata survivorship, but not P. paludosa survivorship. My results indicate that when prey can reach a size refuge from predation, increased system productivity decreases predator limitation of that prey. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Developmental modularity may facilitate morphological evolution by allowing phenotypic change of a developing body component without negatively impacting other components. I examined foregut development in Amphissa columbiana, a predatory neogastropod with a highly derived foregut and in Crepidula fornicata, a phytoplankton-feeder with a less derived foregut, for evidence of developmental modules. Histological sections revealed that the post-metamorphic buccal cavity and radula of both species form as a ventral outpocketing (ventral module) from the larval esophagus (dorsal module). However, in Amphissa columbiana the ventral outpocketing is semi-isolated from the larval esophagus and also produces an “anterior esophagus” that is not developmentally homologous to the “anterior esophagus” of herbivorous caenogastropods. Semi-isolation of the ventral and dorsal modules of the developing neogastropod foregut allows precocious development of the post-metamorphic foregut during the larval stage without compromising larval feeding. Therefore, development of diverse variants of the post-metamorphic foregut are freed from larval constraints. / Graduate / 2020-08-03

Cone snails are carnivorous marine mollusks, utilizing their neuropeptide-rich venom for prey capture. The venom of Conus brunneus, a wide-spread Eastern Pacific vermivore, has not been extensively studied. In the current work, peptides from the dissected venom were characterized and tested using preliminary bioassays. Six peptides (A-F) were isolated and tested. Three peptide identities were determined by comparison with previously reported data: bru9a (A), bru3a (F), and an a-conotoxin (E). Preliminary screening in a stroke-related model of induced glutamate excitotoxicity in primary neuronal cells and PC12 cell cultures indicated potential neuroprotective activity of peptide fractions A, D, and F. Further testing is necessary to determine and verify structure, activity, target, and mechanism of action of the promising peptides from C. brunneus, which may prove effective neuropharmacological agents to treat stroke. / by Rebecca A. Crouch. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Melongena corona and closely related congeners are a conspicuous part of the marine intertidal benthic communities of Florida and southeastern Alabama. Significant genetic differentiation among adjacent populations has been conjectured based on variation in shell morphology, habitat discontinuity, low levels of adult motility, and the presence of an aplanic lecithotrophic larval stage. Furthermore, studies of the highly variable shell morphology often have resulted in confusing specific and subspecific definitions of these gastropods, which are often referred to as the "corona complex". Variation in shell morphology may indicate local adaptation or environmentally induced phenotypic plasticity. In this study I utilized mitochondrial DNA sequences in order to reconstruct the phylogenetic relationships of crown conchs, and nuclear microsatellite loci to investigate the patterns of relatedness within and among populations inhabiting the southeastern United States. Approximately 500 individuals from 20 populations throughout the known range of the Crown Conch were genotyped at eight microsatellite loci. Additionally, a 1200bp portion of the cytochrome oxidase subunit I gene was sequenced along with a 490bp fragment of the 16s ribosomal gene from individuals representing all known species and subspecies of the genus Melongena. Phylogenetic analyses completed with these data provide no support for current taxonomic designations within this group and these genetic data indicate that the corona complex is composed of a single polymorphic species. Furthermore, microsatellite data reveal population structure consistent with restricted gene flow between extant populations and phylogeography heavily influenced by historical sea-level fluctuations during the Late Pleistocene.

<p>Traces of unsuccessful predatory attacks can be found in the hard parts of shell-bearing organisms as repaired shell injuries and are often preserved in the fossil record. These repaired shell injuries can help to deduce the relationship between predator and prey in the past. Gastropods afford an excellent opportunity for study since their shells are easily recognized from the Cambrian onwards, and usually preserve a full record of their life history. Predation is a phenomenon which has led to a great variety of adaptations among prey organisms in their quest to avoid being eaten. Increased predation pressure seems to have been one of the factors that has fueled the evolution of predation-resistant shell morphologies.</p><p>Individual case studies examine the frequency of shell repair in assemblages of Palaeozoic gastropods from different geological periods. The Silurian species <i>Poleumita discors</i> showed a shell repair frequency of 10 %, while only 4 % of the Devonian species <i>Praenatica gregaria</i> have been repaired. The Palaeozoic bilaterally symmetrical bellorphontiform molluscs also showed low levels of shell repair.</p><p>Similar shell morphologies in the long-lived group of pleurotomarioid gastropods were examined and shell repair frequenceis calculated to investigate potential variation through geological time. The Palaeozoic species showed repair frequencies of 17.1 % and 4.2 %. The frequency increased in the Mesozoic to between 28.8 % and 46.6 %, while all shells of Recent pleurotomarioids in the study showed repaired injuries. The repaired injuries found do not change in appearance through time, which is probably a reflection of the presence of the slit in the apertural margin. Which type of injury is the most abundant can be seen to change with time, and there is also an increase in size with time. This may be a defensive strategy taken up by the pleurotomarioids as a response to more abundant predators.</p>

Traces of unsuccessful predatory attacks can be found in the hard parts of shell-bearing organisms as repaired shell injuries and are often preserved in the fossil record. These repaired shell injuries can help to deduce the relationship between predator and prey in the past. Gastropods afford an excellent opportunity for study since their shells are easily recognized from the Cambrian onwards, and usually preserve a full record of their life history. Predation is a phenomenon which has led to a great variety of adaptations among prey organisms in their quest to avoid being eaten. Increased predation pressure seems to have been one of the factors that has fueled the evolution of predation-resistant shell morphologies. Individual case studies examine the frequency of shell repair in assemblages of Palaeozoic gastropods from different geological periods. The Silurian species Poleumita discors showed a shell repair frequency of 10 %, while only 4 % of the Devonian species Praenatica gregaria have been repaired. The Palaeozoic bilaterally symmetrical bellorphontiform molluscs also showed low levels of shell repair. Similar shell morphologies in the long-lived group of pleurotomarioid gastropods were examined and shell repair frequenceis calculated to investigate potential variation through geological time. The Palaeozoic species showed repair frequencies of 17.1 % and 4.2 %. The frequency increased in the Mesozoic to between 28.8 % and 46.6 %, while all shells of Recent pleurotomarioids in the study showed repaired injuries. The repaired injuries found do not change in appearance through time, which is probably a reflection of the presence of the slit in the apertural margin. Which type of injury is the most abundant can be seen to change with time, and there is also an increase in size with time. This may be a defensive strategy taken up by the pleurotomarioids as a response to more abundant predators.

Title from PDF of title page. / Document formatted into pages; contains 201 pages. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Melongena corona and closely related congeners are a conspicuous part of the marine intertidal benthic communities of Florida and southeastern Alabama. Significant genetic differentiation among adjacent populations has been conjectured based on variation in shell morphology, habitat discontinuity, low levels of adult motility, and the presence of an aplanic lecithotrophic larval stage. Furthermore, studies of the highly variable shell morphology often have resulted in confusing specific and subspecific definitions of these gastropods, which are often referred to as the "corona complex". Variation in shell morphology may indicate local adaptation or environmentally induced phenotypic plasticity. In this study I utilized mitochondrial DNA sequences in order to reconstruct the phylogenetic relationships of crown conchs, and nuclear microsatellite loci to investigate the patterns of relatedness within and among populations inhabiting the southeastern United States. / ABSTRACT: Approximately 500 individuals from 20 populations throughout the known range of the Crown Conch were genotyped at eight microsatellite loci. Additionally, a 1200bp portion of the cytochrome oxidase subunit I gene was sequenced along with a 490bp fragment of the 16s ribosomal gene from individuals representing all known species and subspecies of the genus Melongena. Phylogenetic analyses completed with these data provide no support for current taxonomic designations within this group and these genetic data indicate that the corona complex is composed of a single polymorphic species. Furthermore, microsatellite data reveal population structure consistent with restricted gene flow between extant populations and phylogeography heavily influenced by historical sea-level fluctuations during the Late Pleistocene. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Στην παρούσα διπλωματική εργασία θα παρουσιαστούν τα αποτελέσματα από τα μάκρο- απολιθώματα που βρέθηκαν και συλλέχθηκαν στην ευρύτερη περιοχή του Καστριτσίου. Η περιοχή του Καστριτσίου ανήκει στην υπο-λεκάνη του Ρίου που αυτή με την σειρά της ανήκει στην λεκάνη του Κορινθιακού (Kontopoulos, N. Zelilidis, A 1997 ). Η Ιζηματολογική ανάλυση της περιοχής μα έχει δείξει ότι έχουν αποτεθεί εναλλαγές λιμνοθαλάσσιων ιζημάτων και αλουβιακών ριπιδίων από το Ανώτερο Πλειόκαινο έως το Ανώτερο Πλειστόκαινο. Τα δείγματα εφόσον εντοπίσθηκαν, μεταφέρθηκαν στο εργαστήριο αρχικά για καθαρισμό και έπειτα μελετήθηκαν για να ταξινομηθούν με βάση τα χαρακτηριστικά τους. Τα δείγματα μας ανήκουν στην συνομοταξία των Μαλάκιων και διαχωρίστηκαν σε τρείς κύριες ομοταξίες των Διθύρων, των Γαστερόποδων και των Σκαφόποδων. Η λεπτομερής μελέτη των δειγμάτων μας έδειξε τα γένη τα οποία βρήκαμε και αναφέρουμε εν συνεχεία ονομαστικά: Cerastoderma edule, Ostrea edulis, Bittium reticulatum, Turritella communis, Nassarius reticulates, Antalis inaequicostata, Antalis vulgaris, Chama gryphoides, Aporrhais pespelecani. Τα Μαλάκια μας έδωσαν πληροφορίες για την θερμοκρασία, την αλατότητα, για το βάθος της περιοχής καθώς και για τα ιζήματα στα οποία αναπτύχθηκαν οι οργανισμοί κατά το Πλειστόκαινο. / -