The Pigeon River watershed has been the focus of a ¬¬major recovery project to reintroduce fish and other aquatic species into the river where they were historically present. A paper mill at Pigeon River Kilometer/Mile (PRKM 102.1/PRM 63.2) began operations in 1908 and discharged effluents which had a detrimental impact on the aquatic wildlife. Recent modifications to the mill have significantly improved effluent quality such that most aquatic organisms are recolonizing the river. The present study is a baseline survey of crayfish species in the Pigeon River and its tributaries; it also includes a comparison of the mean Catch Per Unit Effort (CPUE) in four different reaches of the stream and documents diversity upstream and downstream of the paper mill. Crayfish are important to the aquatic ecosystem and food web because they serve as cutters that help to break down leaf litter and carrion and are also a food source for predators. Crayfish were collected using modified minnow traps and electroshocking and by snorkeling along ‘turning’ rocks; the method used was based on characteristics of the stream reach sampled, including water depth, flow, transparency, and type of substrate. A total of 1,320 crayfish specimens representing seven species was collected during the eight month study. Crayfish were found in nine Pigeon River tributaries , in the main stem of the Pigeon River upstream of the paper mill (PRKM 102.1/PRM 63.2), and below the Progress Energy Dam (PRKM 61.1/PRM 38.0). No crayfish were found downstream of the paper mill in the river itself; however, crayfish were found downstream from the Progress Energy Dam down to the Pigeon River’s confluence with the French Broad River.

The crayfish claw opener neuromuscular junction (NMJ) is a biological model for studying presynaptic neuromodulation by serotonin and synaptic vesicle recycling. Serotonin acts on crayfish axon terminals to increase the release of the neurotransmitter glutamate, but a complete understanding of its mechanisms of action are unknown. In order to sustain enhanced neurotransmission over long periods of time, it was hypothesized that serotonin recruits (activates) a population of previously non-recycling vesicles to become releasable and contribute to neurotransmission. To determine if serotonin activates a distinct population of synaptic vesicles, FM1-43 fluorescence unloading experiments were performed on crayfish excitatory opener axon terminals. These experiments could not resolve a serotonin-activated population of synaptic vesicles, but instead revealed that synaptic vesicles change behaviour in axon terminals independent of serotonin, with vesicles becoming less likely to exocytose and unload FM1-43 dye over time. The change in behaviour was hypothesized to be due to conversion of vesicles from a recycling (releasable) status to a reserve (reluctant to release) status. Synaptic vesicle pool localization was then tested using photoconversion of FM1-43 and transmission electron microscopy techniques. The spatial location of FM1-43-labeled vesicles fixed 2 minutes following 20 Hz stimulation did not reveal retention of vesicles specifically near release sites and the distribution of FM1-43-labeled vesicles was not significantly different between early (2 min) and late (180 min) time points. Terminals fixed 30 seconds following stimulation, however, contained numerous endosome-like structures - the most frequently observed structures resembled large vesicles, which were the equivalent of 2-5 regular vesicle sizes. These results suggest that crayfish axon terminals recycle vast amounts of membrane in response to sustained 20-Hz stimulation and endocytosis appears to occur via multiple routes with the most common being through large vesicle intermediates. / Graduate

In this study, branchiobdellids were collected from crayfish captured from two adjacent sites in Denton County, Texas. Identification of the branchiobdellid, Cambarincola vitrea Ellis, was first made and then work was extended to include several topics of ecological interest.

This thesis investigates the impact of two invasive ecosystem engineers on the river banks. Invasive species generate significant global environmental and economic costs and represent a particularly potent threat to freshwater ecosystems. Ecosystem engineers are organisms that modify their physical habitat. Therefore this thesis will explore the interaction of these two types of species and their impacts on the example of the impact of signal crayfish and Himalayan balsam The obtained results indicate that there are few avenues through which invasive ecosystem engineers can influence river bank processes. While many uncertainties remain, due to the intrinsic complexity of river ecosystems, a multitude of anthropogenic stressors that they are increasingly subjected to and a wide array of ecosystem services that rivers provide to people, it is important to consider the role of invasive ecosystem engineers in river management practices. on river banks. The work included analyses and development of conceptual models for the understanding of invasive ecosystem engineers, followed by four research chapters aimed at answering specific questions. A study of signal crayfish impact is primarily focused on the impact of burrows that crayfish dig as shelter and their influence on riverbank erosion. The interaction between habitat characteristics, the occurrence of burrows and erosion is analysed on three different levels of spatial scale: bank section in reach, reach in the catchment and bank section in the catchment. Bank section in reach survey (Chapter 4) focused on a reach heavily impacted by crayfish burrowing on the River Windrush, UK, in order to study the maximum effect of burrowing. Also, smaller spatial extent enabled detailed study of three sets of variables as well as an assessment of the impact that signal crayfish population density has on burrowing. Reach in catchment spatial scale expanded the survey to cover 103 river reaches in the Thames catchment and was based on a combination of habitat information from publicly available online data sets, primarily the River Habitat Survey database and rapid field surveys that recorded burrows and erosion. Bank section in catchment-scale was based on the same 103 sites, but the main focus of field observations were ten metres long bank sections for which habitat, burrows and erosion information were collected. Overall, burrowed banks were more likely to be characterised by cohesive bank material, steeper bank profiles with large areas of bare bank face, often on outer bend locations and were associated with bank profiles with signs of erosion. There were indications that signal crayfish burrowing is contributing to the river bank erosion, but no conclusive results have been made. Study of the impact of the Himalayan balsam was undertaken on eight sites at the River Brenta in Italy and it was focused on three main aspects. Firstly it was established that extent of Himalayan balsam domination over native vegetation varies widely depending on the habitat conditions and native plants encountered. Secondly, it was established that there are no conclusive differences in the extent of erosion and deposition on transects covered by native vegetation and Himalayan balsam. Thirdly, measurement of traits of individual plants showed significant differences in traits of individual plants that are known to have consequences for river bank erosion and deposition.

Aphanomyces spp. are water moulds, eukaryotic fungus-like organisms, belonging to the class Oomycota. This genus contains primary pathogens of plants and animals as well as opportunistic and saprotrophic species. One of the animal parasites (A. astaci) is the causal agent of the crayfish plague, a disease listed by the World Organisation for Animal Health (OIE). It is believed that A. astaci was first introduced into Italy from the US in the late 19th century and rapidly spread in Europe causing the decline of native crayfish. It currently threatens to wipe out the UK native white-clawed crayfish (Austropotamobius pallipes). Random amplified polymorphic DNA (RAPD-PCR) on pure isolates of A. astaci distinguished five genotypes (A, B, C, D, and E). This distinction proved to be a useful tool for epidemiological studies aimed at understanding the history and spread of the disease in Europe; furthermore, there are differences in virulence among genotypes. No discriminatory morphological or physiological characters are available and widely used markers such as the internal transcribed spacer (ITS), the divergent domains regions (D1-D2) of nuclear large subunit (LSU) rDNA, and cytochrome c oxidase subunit I (COI) also fail to discriminate between A. astaci genotypes. There are some practical drawbacks to genotype by the currently available genotyping methods. Whole genome sequencing (WGS) was used to catalogue DNA single nucleotide variants and genotype-unique genomic regions that could be exploited as phylogenetic markers. These newly developed molecular markers were tested both on pure cultures and historical samples derived from outbreaks and carrier crayfish available in our laboratories, validating these genotyping methods, which represent new diagnostic tools aiding the detection and prevention of crayfish plague.

Poikilothermic and endothermic animals demonstrate febrile response to infection with bacteria or to injection with endogenous pyrogen extract of Prostaglandin E1. Febrile response is measured in endotherms as a relative change in metabolically achieved body temperature and in poikilotherms as an increase in selected temperatures relative to previously established preferred temperatures. Final preferendum change with environmental factors or associated physiological states.

During centrally orchestrated movements, the nervous system must distinguish between appropriate and inappropriate reflexes. I studied local postural flexion reflexes of the crayfish that are evoked by unexpected touch. An isolated abdomen was used which permitted recording and stimulating of tailfan afferents, nerve cord interneurons, and postural motor neurons. Stimulation of the afferents evoked a postural flexion response of the medium tonic and large phasic motor neurons of the superficial flexor nerve; a flexion motor program was then excited by stimulating descending interneurons. Afferent stimulation evoked a smaller motor response during the motor program than before or after. These results indicate that the postural reflex responses to sensory stimulation are inhibited at a site presynaptic to the motor neurons during the flexion motor program. Application of Picrotoxin (blocked inhibition) to the primary afferent-to-mechanosensory interneuron synapse did not prevent the modulation of the postural flexion reflex during the flexion motor program.

Thesis (Ph.D.)--Bowling Green State University, 2009. / Document formatted into pages; contains vi, 78 p. : ill. Includes bibliographical references.

Dissertation (Ph.D.)--Auburn University, / Abstract. Includes bibliographic references.

The illegal sale of East Coast rock lobster (Panulirus homarus) along the N2 highway at Mfazazana on the south coast of KwaZulu-Natal, continues to create tension between the local community and conservation and other authority structures in the region. Panulirus homarus (P. homarus) is a valuable commodity in an area distant from industry and other economic prospects and is within easy reach of both the harvester, in terms of its intertidal living space and the market, in terms of the N2 and the economy in seafood prevalent in the region. P. homarus is therefore at risk by virtue of its biology and habitat, and the illegal nature of its capture tests the parameters of sustainable resource management still further. This research addresses the issue of sustainable resource use through an examination of the perceptions of the various stakeholders who are involved in the use and protection of P. homarus at Mfazazana. This study was commissioned by the Communications Section of the KwaZulu Department of Nature Conservation (KONC) in response to continued illegal harvesting and trade of P. homarus at Mfazazana. One of the mandates of the Communications Section is to initiate and maintain environmental education programmes and thus comply with the KONC mission statement (See Appendix 1a). Specific objectives of the study include: • how respondents perceive their relationship with, responsibility to and role in terms of P. homarus • how respondents perceive their relationship with, responsibility to and role in terms of the others involved with P. homarus • how present legislation is perceived by stakeholders • what options exist regarding the regulation and/or management of P. homarus • whether changes over time have occurred in the respondents' relationship with P. homarus Fishing and trading activities were inv~stigated using informal, loosely structured questionnaires which elicited qualitative information. Two main groups were selected. and respondents were interviewed either individually or in small groups. The crayfishers made up the first group and the resource managers made up the second group which included the Natal Parks Board (NPB), the KONG, the Hibberdene Tourism and Publicity Association, the Community Policing Forum, the Community Development Forum at Mfazazana and the South Coast Fishing Forum. The study provided an understanding and explanatiol] of how the elements of the locality interact with underlying structures and human agency in time to produce the conflict over the marine resource P. homarus at Mfazazana. It was found that the conflict between stakeholders, as a result of differing perceptions regarding the illegal harvesting of the resource, was obstructing the sustainable management of P. homarus at Mfazazana. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997