The crayfish plague pathogen, the oomycete Aphanomyces astaci, has been decimating populations of European crayfish species for more than 150 years, and is therefore considered one of the 100 worst world's invasive species. A. astaci is highly specialised for a parasitic life, but it can be isolated from moribund crayfish and grown on synthetic media, as it is the case also for several other oomycetes (chapter 7). The life of A. astaci includes three basic forms: mycelium in host's tissues, and the infective units occurring in water, zoospores and cysts. All North American crayfish species tested so far have shown some resistance to A. astaci, i.e., they could carry the infection for long, serving as vectors of the pathogen. Massive sporulation from infected North American crayfish starts when the host is moulting, stressed, or dying (chapter 4). However, I could show in my experiments that some sporulation occurs even from apparently healthy and non-moulting American crayfish hosting A. astaci, so infected North American crayfish must be considered a permanent source of the infection (chapter 4). Five genotype groups of A. astaci have already been distinguished. Strains from a particular genotype group probably share the same original host crayfish species of North American origin. Nevertheless, they can...

Les mangroves sont des forêts côtières des régions tropicales et subtropicales, situées dans la zone de balancement des marées. Elles fournissent un grand nombre de services écosystémiques aux sociétés humaines et aux milieux adjacents (ressources, habitats, protection). Les mangroves sont continuellement affectées par des variations environnementales naturelles (salinité, température, cycle des marées) mais elles sont également le réceptacle d'effluents anthropiques (aquacultures, centres urbains). Il a été suggéré que ces forêts humides pourraient participer à la bio-épuration d'eaux usées domestiques (EUD). Les objectifs de la thèse étaient à la fois d'apporter des éléments pouvant ultérieurement servir à définir un cadre pour cet usage spécifique d'un écosystème naturel, et, sur le plan plus fondamental, d'évaluer les capacités de résistance et de résilience à court et long termes d'une mangrove soumise à une perturbation anthropique contrôlée. Le travail de thèse s'est appuyé sur un système expérimental fonctionnant depuis 2008 dans la plus grande mangrove de l'île de Mayotte. Dans ce système pilote, des EUD prétraitées sont quotidiennement déversées dans deux zones de mangroves dominées par les palétuviers Ceriops tagal ou Rhizophora mucronata et ayant des caractéristiques contrastées. Plusieurs campagnes d'échantillonnage ont permis de suivre in situ l'impact de l'excès de nutriments et d'eau douce sur la végétation, les crabes, la méiofaune et les communautés microbiennes, et de déterminer leurs capacités de résistance et de résilience. Dans ce travail, les EUD ont fortement stimulé la croissance de la végétation, modifié la structure des populations de crabes, de méiofaune, et des communautés microbiennes, et induit une hausse des densités et des activités des microorganismes impliqués dans le cycle de l'azote. Ceci n'a cependant pas entrainé de dysfonctionnement majeur de l'écosystème (perte massive de couvert végétal ou forte régression des populations de crabes). L'observation de l'écosystème sur deux ans après l'arrêt d'apports d'EUD a également mis en évidence une capacité notable de résilience de la mangrove. Enfin, les résultats de cette étude indiquent que la zone dominée par R. mucronata serait plus apte à recevoir les EUD prétraitées dans le cadre de leur bio-épuration par la mangrove car moins impactée. / Mangroves are coastal forests in (sub)tropical regions, located in the intertidal zone. They provide a many ecosystem services to human societies and neighboring ecosystems (resources, habitats, protection). Mangroves are continually affected by natural stresses (salinity, temperature, tidal cycle) but they are also subjected to anthropogenic effluents (aquaculture, urban centers). It was suggested that mangroves may be used for the bio-epuration of domestic wastewaters. This thesis aims at providing elements that will help defining the framework for this specific usage of a natural ecosystem and evaluating the long- and short-term resistance and resilience abilities of mangroves subjected to an anthropic disturbance. To reach these objectives, we used an experimental system set up in the largest mangrove of the island Mayotte. In this system, pretreated wastewaters (PW) are daily discharged in two mangrove zones dominated by Ceriops tagal or Rhizophora mucronata. Several sampling campaigns allowed to monitor in situ the impact of nutrient and freshwater excess on vegetation, crabs, meiofauna, and microbial communities and to determine their resistance and resilience capacities. In this work, PW strongly stimulated vegetation growth, altered the structure of crabs and meiofauna, modified the microbial structure and increased microbial density and activity of microorganisms involved in nitrogen cycle. However, no major dysfunction of the ecosystem (loss of vegetation, strong decrease in crab density) was observed. The monitoring of the ecosystem during two years after the PW discharge was stopped showed a marked ability of the mangrove to recover from the disturbance. Finally, the results indicate that R. mucronata mangrove zone, less disturbed, is more able to receive discharges for bio-epuration of domestic PW by mangrove ecosystem.

It is often hypothesised that marine species with mobile planktonic phases are capable of widespread dispersal and may therefore be genetically homogenous throughout their distribution. Studies that have demonstrated positive correlation between duration of plankton phase and levels of gene flow reinforce the prediction that life history characteristics of marine species determine the potential extent of genetic and demographic connectivity throughout their distributions. This prediction has however been challenged by studies that have employed genetic markers highly sensitive to both historical and contemporary demographic changes. Disparities between dispersal potential and measured levels of gene flow have been demonstrated both among historically disconnected ocean basins and within semi-enclosed areas of strong hydraulic connectivity. These studies and others highlight a need for greater focus on factors that may influence population structure and distribution for marine species. In this thesis, I have examined genetic structure within and among populations of an estuarine species of mud crab Scylla serrata (Forskal, 1775) using a number of genetic markers and methods. The species is widely distributed throughout mangrove and estuarine habitats of the Indo - West Pacific (IWP); it is generally assumed that life-history characteristics of S. serrata promote high levels of population admixture and gene flow throughout its distribution. Alternatively, factors that have promoted population genetic structure for a variety of IWP marine species may also have affected S. serrata populations. By investigating genetic structure at several spatial scales of sampling, I was able to address a variety of hypotheses concerning the species distribution, dispersal, and genetic structure. Episodic changes to marine habitat and conditions experienced within the IWP during the Pleistocene may have affected genetic structure for a broad variety of marine taxa. The relative strength of this hypothesis may be assayed by comparative genetic studies of widespread IWP taxa with high dispersal capacity. In order to ascertain levels of historical and contemporary gene flow for S. serrata, I investigated the phylogeographic distribution of mitochondrial DNA haplotypes sampled throughout the species range. Adults were sampled from three west Indian ocean locations (N=21), six west Pacific sites (N=68), and two sites from northern eastern Australia (N=35). Temperature gradient gel electrophoresis and sequencing of 549 base pairs of the mitochondrial cytochrome oxidase I (COI) coding gene identified 18 distinct haplotypes. Apart from that seen in northern Australia, haplotype diversity was low (h < 0.36) at each of the locations. Total nucleotide diversity in the entire sample (excluding northern Australian locations) was also low (p = 0.09). Haplotypes clustered into two clades separated by approximately 2% sequence divergence. One clade was widespread throughout the IWP (clade 1) whereas the other was strictly confined to northern Australia (clade 2). Genealogical assessment of sequenced haplotypes relative to their distributions suggested that a historical radiation of clade 1 S. serrata throughout the IWP occurred rapidly and recently (<1Myr bp) from a west Pacific origin. The evidence of fixed unique haplotypes at the majority of locations suggested that contemporary maternal gene flow between trans-oceanic sites was limited. Contrary to reports for other widespread species of IWP taxa, there was no evidence of lengthy periods of regional separation between Indian from Pacific Ocean populations. However, results may indicate a separation of northern Australian crabs from other locations before and during the IWP radiation. I speculated that this isolation might have resulted in the formation of a new species of Scylla. Additional sampling of mud crabs from the Australian coastline allowed an examination of the diversity and distribution of clade 1 and 2 haplotypes among recently formed shelf-connected coastal locations, and across a historical bio-geographic barrier. Over 300 individuals were sampled from multiple locations within coastal regions (western, northern and eastern) of Australia and analysed for mutational differences at the COI gene. Analysis of molecular variance partitioned by sampling scale (Among regions, within regions, and within all locations) indicated mitochondrial haplotypes were structured regionally (P < 0.001), which contrasted with evidence of genetic panmixia within regions. Regional genetic structure broadly correlated with hydrological circulation, supporting the contention that release and transport of propagules away from the estuary may allow genetic connectivity among widespread shelf-connected S. serrata populations. That similar patterns of maternal gene flow were absent among trans-oceanic populations may indicate that the spatial scale of effective dispersal for this species is generally limited to areas of coastal shelf. The two clades of haplotypes were geographically separated either side of the Torres Strait, a narrow sea channel connecting the northern and eastern regions of coastal Australia. This pattern of historical genetic separation was concordant with a number of other marine species across northern Australia, and might indicate a shared history of vicariance induced by eustasy. Alternatively, differences in diversity and distribution of the clades may be evidence of two independent expansions of clade 1 and 2 crab populations into Australian regions following post-glacial estuary formation. Overall, despite evidence of genetic panmixia within extensive sections of the Australian distribution, there was also evidence of significant barriers to maternal gene flow with both shallow and deep regional phylogeographic assortment of mtDNA haplotypes. The presence of these barriers indicated both historical and contemporary factors have imposed limits to effective dispersal by this species among coastal habitats. A subset of the Australian sample (8 locations, N = 188) was also examined for variation at five microsatellite loci developed specifically here for S. serrata. I examined variation among samples at each of the loci to: a) independently verify regional structure among crab populations previously detected using the mtDNA analysis; b) test for evidence of co-distributed non-interbreeding stocks of S. serrata within Australian waters by examining samples for segregation of alleles within microsatellite loci concordant with the two mtDNA clades. The frequency and distribution of alleles for each of the highly polymorphic microsatellites were homogenous at all levels of sample partitioning and contrasted sharply with the instances of both weak and strong regional phylogeographic assortment of mtDNA haplotypes. These contrasting results between different genomic markers were examined in relation to the species life history, and to differences in mutational rate and inheritance of the genetic markers. Several hypotheses may explain the disparity, however it is most likely that rampant homoplasy and high rates of mutation at the microsatellite in conjunction with large Ne at locations may be concerted to delay equilibrium between genetic drift and migration among populations at these highly polymorphic nuclear markers. There was also no evidence that alleles at microsatellite loci were co-segregated with mtDNA clades and therefore no evidence of segregated breeding between the clades of crabs. Whether or not this result was also driven by homoplasy at the microsatellites remains unknown. Recently established mud crab populations (~ 3-4 years old) observed in a number of southwest Australian estuaries are almost 1000 kilometres south of their previously recorded distribution on the Western Australian coast. Colonisation of the southwest region may have occurred either by a natural range expansion from northwest Australian mud crab populations or by means of translocation from any number of mud crab sources within the Indo - West Pacific. I used mtDNA analysis to verify the species and determine the potential source population(s) of the colonists, by comparing sampled genetic material from the southwest (N = 32) against that previously described for the genus. I also compared levels of diversity at mtDNA and two microsatellite loci between the colonist and suspected source population(s) to qualitatively determine if the southwest populations experienced reductions in genetic diversity as a result of the colonisation process. All colonist samples had S. serrata mtDNA COI sequences identical to one previously described as both prevalent and endemic to northwest Australia. High levels of genetic diversity among source and colonist populations at two microsatellite loci contrasted to the mitochondrial locus which displayed an absence of variation among colonists compared to moderately diverse source populations. I argued that the southwest was recently colonised by large numbers of S. serrata propagules derived from the northwest of Australia, possibly due to an enhanced recruitment event coinciding with the reported strengthening of the Leeuwin Current during 1999. Contrasting levels of diversity among nuclear and mitochondrial loci may be attributed to a difference in response by the two genomes to the colonisation process. I predict that such differences may be generally prevalent among plankton-dispersed species. Finally, I discuss aspects of the species distribution and biogeography obtained as a composite of the various results and ideas expressed in this thesis. I propose that S. serrata populations in the IWP may have experienced several cycles of extinction and population retraction from temperate areas followed by subsequent periods of colonisation and rapid coastal expansion in response to the effects of glacial episodes on coastal habitats in the IWP. I propose that persistence of this species as remnant populations of clade 1 and 2 crabs at equatorial locations during low sea level stands provided source populations for later expansions by the species into a variety of coastal areas throughout the IWP. Further analysis is required to determine if mtDNA clade 1 and 2 crabs are non-interbreeding species of mud crab.

The Enemy Release Hypothesis proposes that introduced species often achieve larger individual sizes and greater population abundance in their introduced range because they have escaped their natural enemies - predators and parasites - that regulate populations in their native range. The main objective of this study is to test the Enemy Release Hypothesis (ERH) by investigating the identity, prevalence and intensity of parasites in two marine species introduced to New Zealand - the recently introduced but spatially restricted Asian portunid crab, Charybdis japonica, and the longer-established Asian nesting mussel, Musculista senhousia. Host choice of a native generalist parasite presented with the non-native and native mussels, and prey selection by a native predator presented with these bivalves will be examined. This is the first study of its kind in New Zealand. The parasite fauna of the only established New Zealand population of C. japonica (Waitemata Harbour, Auckland), was compared to that from (a) a population of C. japonica from its native region (Japan) and (b) to multiple populations of the native New Zealand crab Ovalipes catharus, a native New Zealand portunid. Results showed the introduced crab harboured only one species of endoparasite (a nematode), and two types of melanised lesions. Neither the parasite nor the lesions were present in the native crab populations. The native crab was host to only one parasite species, which occurred at very low prevalence, and was present in only one of the six populations examined from throughout New Zealand. Carapace width in the introduced crab was no larger than that reported in literature from its native are, but was larger than carapace widths of the Japanese sample. M. senhousia was examined from five sites within New Zealand. Parasites in M. senhousia were compared with a sympatric native bivalve, Austrovenus stutchburyi, two native mytilids, (Perna canaliculus and Xenostrobus pulex) and with samples of M. senhousia from Italy and the USA where it is introduced, and Japan where it is native. Two native generalist parasites, the pea crab Pinnotheres novaezelandiae, and a copepod, were found within M. senhousia in New Zealand, but only at low prevalence. A greater array of organisms was associated with the native bivalves. No parasites were recovered from any of the overseas samples of M. senhousia, including the Japanese samples. This may be caused by the preservation medium used, but could be a true reflection of the parasite fauna in these populations. The site where the two native parasites were exploiting M. senhousia was the only site sampled where two native mussels, P. canaliculus and X. pulex, also occurred. Consequently, effects of these two generalist parasites on the three mussel species were examined. In P. canaliculus, presence of native pea crabs was associated with lower tissue dry weight and greater shell depth. Shell width and depth were both greater in the presence of copepods. However, the prevalence of pea crabs and copepods was much lower in M. senhousia compared to the two native mussels, indicating some release from the effects of these parasites for the non-native species. Experimental choice tests showed that the pea crab, P. novaezelandiae, does not actively select M. senhousia as a host, preferring the larger native mussel, P. canaliculus. Rates of infection of M. senhousia are, therefore, likely to remain low in natural habitats where there are large numbers of native hosts. In addition, a generalist predator, the crab O. catharus, showed no preference when foraging on the three mussel species under experimental conditions. Thus, some predation pressure may be exerted on M. senhousia by this native crab in the natural environment. Investigation of multiple populations of both native and non-native species has shown large variation in parasite prevalence and intensity among populations of each species. After examining C. japonica and the comparable native O. catharus, evidence to support the ERH was found to be weak. As the native crab was relatively free of parasites, it seems unlikely that parasite infection is important within native populations and therefore, the success of C. japonica is unlikely to be caused by comparatively greater freedom from parasites (a central tenet of the ERH). There was also no evidence for host-switching by native parasites into the introduced C. japonica population. In contrast, native parasites were present at very low prevalence in the non-native mussel M. senhousia. Length of time since introduction can be an important factor in host switching between native and introduced hosts, but unless prevalence of these parasites is high, the introduced species still escapes from enemies that could control a population. Therefore every non-native species needs to be examined using multiple populations to investigate variation in parasite fauna, prevalence and intensity, as the same species, if introduced numerous times, could potentially show contrasting results for the ERH unless multiple populations are examined.

Deep-water trawling (>200 m deep) for crustaceans in the South West Indian Ocean (SWIO) yields catches of several species, including prawns (Haliporoides triarthrus, Aristaeomorpha foliacea, Aristeus antennatus and Aristeus virilis), langoustine (Metanephrops mozambicus), spiny lobster (Palinurus delagoae) and geryonid crab (Chaceon macphersoni). Infrequent deep-water trawling takes place off Tanzania, Kenya and Madagascar; however, well-established fisheries operate off Mozambique and South Africa. Regular trawling off South Africa started in the 1970’s, mainly targeting M .mozambicus and H. triarthrus. Catch and effort data for the South African fishery were regularly recorded in skipper logbooks over a 23 year period (1988 – 2010); this database was obtained from the Department of Agriculture, Forestry and Fisheries (DAFF) in order to assess abundance trends of M. mozambicus and H. triarthrus. Generalized linear models (GLM) were used to quantify the effects of year, month, depth and vessel on catch per unit effort (CPUE). By year, the standardized CPUE of M. mozambicus increased, and three factors (or a combination of them) could explain the trend: reduced effort saturation, improved gear and technology, or an increase in abundance. By month, CPUE peaked in July and was highest between depths of 300 and 399 m. The standardized CPUE of H. triarthrus fluctuated more by year than for M. mozambicus, possibly because it is a shorter-lived and faster growing species. The monthly CPUE peaked in March, and was highest between depths of 400 and 499 m. Totals of 2 033 M. mozambicus (1 041 males and 992 females) and 5 927 H. triarthrus (2 938 males and 2 989 females) were sampled at sea between December 2010 and March 2012, during quarterly trips on-board a fishing trawler. A GLM framework was used to explore their size composition, sex ratio variability, size at maturity and reproductive cycles. Male and female M. mozambicus size distributions were similar, but varied by month and decreased as depth increased. Female H. triarthrus were significant larger than males; size structure varied by month, but showed no change over depth. The sex ratio of M. mozambicus favoured males (1 : 0.89), but was close to parity in all months, except November when males predominated. H. triarthrus exhibited parity (1 : 1.002) with no significant variations in sex ratios by month. The proportion of egg-bearing M. mozambicus in the population declined between March and August (hatching period) and then increased until December (spawning period). The L₅₀ (length at 50% maturity) of M. mozambicus was estimated to be 49.4 mm carapace length (CL), and the smallest and largest observed egg-bearing females were 33.5 and 68.6 mm, respectively. No reproductively active female H. triarthrus were recorded during the sampling period. Growth parameter estimates for M. mozambicus (male and female combined) using Fabens method were K = 0.48 yearˉ¹ and L∞ = 76.4 mm CL. Estimates for the von Bertalanffy growth formula (VBGF) were: K = 0.45 yearˉ¹ and L∞ = 76.4 mm CL. H. triarthrus male and female growth parameter were estimated separately. For males they were K = 0.5 yearˉ¹ and L∞ = 46.6 mm CL using Fabens method, and K = 0.76 yearˉ¹ and L∞ = 46.6 mm CL using the VBGF. For females they were K = 0.3 yearˉ¹ and L∞ = 62.9 mm CL using Fabens method, and K = 0.47 yearˉ¹ and L∞ = 62.9 mm CL using the VBGF. CL to total weight regressions were calculated for both species; no significant differences were found between male and female M. mozambicus, although H. triarthrus females became larger and heavier than males. Comparisons with three earlier studies (Berry, 1969; Berry et al., 1975; Tomalin et al., 1997) revealed no major changes in the biology of either species off eastern South Africa. Stocks appear to be stable at current levels of fishing pressure, although some factors are not yet fully understood. Disturbance caused by continual trawling over a spatially limited fishing ground may affect distribution and abundance patterns, especially in M. mozambicus, which was less abundant in the depth range trawled most frequently. The absence of reproductive H. triarthrus in samples suggests that they occur elsewhere, and there is some evidence of a possible spawning migration northwards to Mozambique; this suggests that H. triarthrus is a shared stock between South Africa and Mozambique. The results from this thesis will add to the knowledge of M. mozambicus and H. triarthrus in the SWIO, and provide a basis for developing sustainable management strategies for the deep-water crustacean trawl fishery off eastern South Africa. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.

Commercial farming of mud crab Scylla serrata is a significant industry throughout South East Asia. The limited scientific knowledge of mud crab nutritional requirements and digestive processes, however, is recognised as a major constraint to the future growth of this industry. To better understand the mechanisms of digestion in the mud crab we have analysed the diversity of digestive enzymes from the hepatopancreas. Significant protease, amylase,cellulase and xylanase activities were detected in soluble extracts from this organ. Temperature profiles for all enzymes were basically similar with optimal activities observed at 500C. Examination of pH tolerance revealed optimal activities for protease and amylase at pH 7.0 while optimal activities for cellulase and xylanase were observed at pH 5.5. Under optimum conditions,protease and amylase activities were approximately two orders of magnitude greater than those seen for either cellulase or xylanase. Interestingly, hepatopancreatic extracts were able to liberate glucose from either starch or carboxymethyl (CM)-cellulose suggesting that a range of carbohydrates may be utilised as energy sources. The effects of dietary carbohydrates on feed digestibility, digestive enzyme levels and growth were also studied by inclusion of additional starch or CM-cellulose at the expense of casein in formulated diets. It was shown that amylase, cellulase and xylanase activities in extracts from the hepatopancreas were highest in mud crabs fed diets containing 47% carbohydrate. Based on the findings, we suggest that the ability of the mud crab to modulate digestive enzyme activities may represent a mechanism to maximise access to essential nutrients when the dietary profile changes.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Os manguezais sÃo ecossistemas costeiros tropicais com elevada biodiversidade, composta por Ãrvores e arbustos com grande tolerÃncia as Ãguas salgadas ou salobras e por animais tÃpicos dessas regiÃes. Dentre os representantes da fauna, os caranguejos destacam-se tanto por seu grande nÃmero de espÃcies quanto por sua importÃncia ecolÃgica e econÃmica. Esses crustÃceos apresentam elevada densidade populacional e alta atividade de mobilizaÃÃo do solo, principalmente devido ao processo de formaÃÃo de tocas, as quais proporcionam a oxigenaÃÃo e drenagem do solo, alterando a dinÃmica dos minerais no perfil vertical do mesmo. Da mesma forma, alteraÃÃes temporais e variaÃÃes sazonais acentuadas do regime de chuva, como ocorrem na regiÃo do semi-Ãrido brasileiro, podem ocasionar oxidaÃÃo da pirita devido a substituiÃÃo de parte da Ãgua no solo por gÃs oxigÃnio durante a estaÃÃo seca, com conseqÃente aumento da liberaÃÃo das fraÃÃes de ferro a ela associada. Neste trabalho foi realizada a anÃlise dos padrÃes fÃsico-quÃmicos e das concentraÃÃes de ferro ativo e ferro pirÃtico em solos de manguezais sob aÃÃo do caranguejo UÃÃ (Ucides cordatus), comparando os valores encontrados entre os perÃodos chuvoso e seco, assim como entre esta Ãrea com uma outra com atividade da espÃcie de caranguejo Uca maracoani. Foram encontradas significativas variaÃÃes nas formas geoquÃmicas do Fe nos solos da Ãrea com U. cordadus entre as estaÃÃes seca e chuvosa, assim como quando comparada com a Ãrea com U. maracoani. Os resultados encontrados demonstram os efeitos distintos da variaÃÃo sazonal e de caranguejos sobre a biogeoquÃmica do Ferro em manguezais do semi-Ãrido brasileiro, ressaltando a necessidade de mais estudos nessas Ãreas afim de poder realizar futuramente comparaÃÃes / Mangroves are tropical coastal ecosystems with high biodiversity, consisting of trees and shrubs with high tolerance to salt, and animals typically residents of those regions. Among these, crabs demonstrate a great ecological and economic importance. These crustaceans have a high population density and high activity of soil mobilization, mainly due to the formation of burrows, which provide oxygenation and soil drainage, changing the dynamics of minerals in the vertical profile. Likewise, climate changes and seasonal marked variations of rainfall regime, as occurring in the semi-arid areas, can cause oxidation of pyrite due to replacement of the water in the soil for oxygen gas during the dry season, with a consequent increase in release fraction of iron associated with it. In our study, the analysis of physical-chemical standards and concentrations of active iron and pyritic iron in soils under the action of mangrove crab (Ucides cordatus), comparing the values found between the rainy and dry seasons, and between this area with another area under the activity of the crab specie Uca maracoani. We found significant variations in the geochemical forms of Fe in soils of the area with U. cordadus between the dry and rainy seasons, as well when it was compared to the area with U. maracoani. The results demonstrate the distinct effects of seasonal variation and representatives of the fauna on the biogeochemistry of iron in the mangroves of the semi-arid region, highlighting the need for further studies in these areas in order to make future comparisons

The present study has attempted to investigate some of the more basic questions concerning the toxicity and accumulation of mercury in the purple shore crab, Hemigrapsus nudus. This rocky intertidal denizen is found in abundance along the entire Pacific coast of the United States from Sitka, Alaska, to the Gulf of California where it dominates the mid-tide pool region. Local specimens were collected just north of the Pacific Marine Stations, Dillon Beach, Marin County, California. The animal is hearty and can be kept in a state of good health for long periods of time in the laboratory with minimum care and negligible mortality. Most importantly, as a middle intertidal inhabitant, H. nudus would be among the first groups of organisms to feel the stress of environmental contamination from an industrial source located on the open coast. This, coupled with its wide distribution, indicates its possible use as an environmental monitor.

No description available.

Four experiments were conducted with crab processing waste. Addition of 1.5% propionic/formic acid prevented degradation up to 14 d. Desirable fermentation was achieved when 32% of the treated crab waste was ensiled with 32% straw, 16% molasses, and 20% water with or without .1% microbial inoculant. The pH of the silage was lowered and high concentration of lactic acid was observed. Use of .2% NaOCl or .4% H₂O₂ retarded spoilage of crab processing waste up to 7 d. Ensiling of the treated waste (32%), straw (32%), molasses (16%), and H₂0 (20%) indicated that the chemical used in preservation enhanced fermentation. Addition of .4% NaOCl and 1.5% acetic acid to the crab processing waste retarded degradation up to d 4. The trimethylamine (TMA) concentration and NH₃ evolution were highest for the untreated waste while the lowest concentration for TMA and NH₃ evolution were observed for the NaOH-treated waste. Addition of 1% NaNO₂ or combination of .4% NaOCl/CaOCl (1:1, w/w) preserved the waste for up to 10 d. The evolution of NH₃ and H2₂S, and TMA concentration were lowest for the waste treated with 1% NaNO₂. Apparent digestibility of DM, organic matter, CP, energy, NDF, ADF, cellulose and hemicellulose decreased linearly (P<.01) with level of crab waste-straw silage in diets containing 0, 50, and 100% crab waste-straw silage. Nitrogen retention increased linearly (P<.05) with level of crab waste-straw silage. The apparent absorption was higher (P<.01) and retention was positive (P<.05) for Ca, Mg, Na, K, Cu and Fe with sheep fed the highest level of crab waste-straw silage. Daily gain, feed efficiency and carcass characteristics tended to be higher for steers fed 30% crab waste-straw silage, dry basis. The flavor and overall desirability of cooked meat were not adversely affected by feeding up to 30% crab waste-straw silage, dry basis. Modifying the existing methods of quantifying chitin showed that initial decalcification or deprotinization of the samples with chemicals are not necessary. Similar values were obtained for chitin when ADF/ashing method was compared to the ADF/deacetylation method. These methods prevented loss of chitin during preparation. Digestibility of chitin was higher (58%) for sheep fed 100% crab waste-straw silage compared to the value of 37% in sheep fed 50% crab waste-straw silage. When ADF/ashing method was used in quantifying chitin, higher disappearances were obtained for samples containing 100% crab meal kept in the rumen or incubated in vitro for 72 h. / Ph. D.