Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / Historically, two species of Chrysaora are known from the Benguela Current Ecosystem: C.fulgida (Reynaud 1830) and C. africana (Vanhöffen 1902). However a third morphotype is now seen, which bears a resemblance to both. Thus a complete qualitative and quantitative analysis of the morphometric and meristic data of these three species was conducted, along with an in depth study into the cnidome as a potential tool of identification. These findings are supplemented by a genetic analysis using cytochrome c oxidase subunit I and internal transcribed spacer 1 gene markers. Three species were unambiguously identified. The genetics and morphology showed considerable divergence, with some of the features used to separate them including: tentacle number and shape, colouration and shape of the oral arm, shape of the gastrovascular pouches and the number and shape of the marginal lappets. Although the mtDNA indicated clear separation of the three Chrysaora, the nucDNA displayed some ambiguity. The cnidome showed considerable divergence and succeeded in separating these species, while the rhopalia of the three species also showed distinct differences in the lengths of the rhopalal canals and basal stems. Much of the confusion surrounding jellyfish taxonomy has been the result of observations made on predominantly preserved specimens that are in subpar quality, a hinderence which this study endeavored to overcome. / National Research Foundation (NRF)

Philosophiae Doctor - PhD / Although jellyfish are recognised recently as key components that can influence ecosystem functioning and trophic flows in the northern Benguela upwelling ecosystem, the number of published studies on their abundance, seasonality, life history and ecological roles off Namibia is strictly limited. Chrysaora fulgida is one of the most common and conspicuous medusae in the plankton off Namibia, and has flourished in the region, following the decline of the pilchard fishery at the end of the 1960s. It is said that their biomass (together with Aequorea forskalea) exceed that of the commercially important fish stocks off Namibia. In addition, this species is also capable of forming large swarms in northern Benguela where they are a nuisance to fisheries operations. The objective of this study is to try and fill gaps regarding our knowledge of the biology and ecology of Chrysaora fulgida off Namibia, with a view to improve our understanding of its success in the northern Benguela ecosystem. In the Chapter 1, a general overview on the current knowledge and population dynamics of jellyish blooms and their ecology is compiled. Other key topics of the thesis such as jellyfish life cycles and their reproduction are also introduced. Chapter 2 investigates the temporal changes in the jellyfish community in Walvis Bay over a 23-month period from biweekly plankton samples. All twelve of the recovered taxa were characteristically neritic, and included meroplanktonic Hydrozoa and Scyphozoa, as well as cydippid ctenophores and shallow water siphonophores. Whilst, ephyrae of Chrysaora fulgida were dominant overall, and peaked in abundance during mid-spring (Year 2012: 168 933 ind. 100 m-3) and late winter (Year 2013: 23 389 ind. 100 m-3), they were not present all year round, being replaced (in part) by Obelia in summer and autumn, Bougainvillia in spring and summer, and Muggiaea atlantica in summer. Seasonal changes in the composition and structure of the community were driven primarily by bottom water temperature and day length (explaining 24% of the variability in community structure), with wind speed and moon illumination playing a secondary role. The recruitment of ephyrae of C. fulgida to the plankton off Walvis Bay is confirmed not to be continuous throughout the year. Chapter 3 present the first detailed investigation on the identification, morphological development and growth of wild caught ―ephyrae‖ of the scyphozoan Chrysaora fulgida and Chrysaora africana in Walvis Bay, off Namibia. Concrete morphological dissimilarities are documented to distinguish C. africana from C. fulgida, despite the limited sample size of C. africana: coloration differences and the presence/absence of branched canals on the periphery of velar and rhopalial canal tips. In the case of C. fulgida the morphological development from an ephyra (Stage 0) to a juvenile medusa could be described successfully in six stages, whilst missing stages were noted for C. africana. In general, the development of ephyrae described here agrees with patterns described for other species in the genus from elsewhere. The ephyrae stages of C. fulgida illustrated a low overall growth rate (4.33 and 3.45% d-1, respectively) and longer ontogenic development (~164 days), respectively, than most other jellyfish species. Through the histological examination of medusa gonads, Chapter 4 investigates the sexual reproduction and maturation of both Chrysaora species, collected off Walvis Bay, Namibia. Both species were non-brooding, gonochoristic, displayed a 1:1 sex ratio and exhibited no clear sexual dimorphism features. Gametogenesis in both species was similar to that displayed by other Discomedusae, whilst some differences in gonad maturity were evident between them – Chrysaora fulgida displayed aseasonal, reproductive heterogeneity (maturing at ~300 mm diameter) and individuals were semelparous, whilst C. africana appeared strongly seasonal but iteroparous. Through stable isotope analysis (𝛿13C, 𝛿15N and C:N ratios), Chapter 5 examines the presence of tissue, ontogenetic, seasonal, spatial and interspecific variability in medusae of Chrysaora fulgida and Chrysaora africana off Walvis Bay, in the northern Benguela, Namibia. This study did not only illustrate size-associated shifts in trophic ecology, but also revealed spatial, inter-species and some tissue differences in the northern Benguela upwelling system. Size would appear to be the over-riding factor that influences the isotope signatures of Chrysaora fulgida; size being linked in turn to space. A clear negative relationship is illustratred between 𝛿15N and individual size for two scyphozoans (C. fulgida and C. africana) off central Namibia, indicating that larger jellyfish feed lower down the food chain than smaller ones in both species. This is explained by the need and ability of ephyrae and small medusae to access the microbial food web which consists of many trophic steps and hence numerous opportunities for enrichment of nitrogen isotopes, resulting in higher 𝛿15N values of smaller individuals. Chapter 6 provides a synthesis of the main findings of the thesis, and makes recommendations on ways that the research can be carried forward. / 2020-08-31

<p>Two species of Chrysaora are described from the northern Benguela ecosystem: C. fulgida and C. africana. These species can be diagnosed by a combination of morphological features including lappet and tentacle number, shape of lappets, colouration patterns (alive), shape of the proximal portion of radial septa, gastrovascular pouch shape, point of attachment of gonads and the presence or absence of small raised nematocyst warts on the exumbrellar surface. Objective, quantitative statistical analyses coupled with molecular sequence data support the qualitative morphological dissimilarity observed, as these analyses unambiguously diagnose C. fulgida and C. africana as two distinct species. There is a strong superficial resemblance between the C. fulgida material described here and the preserved specimens of C. hysoscella examined at the Natural History Museum, London. Thorough investigation does however allow the separation of these two species. Morphological features found to be dissimilar were the proximal portion of the manubrium, gastrovascular pouch shape and the presence or absence of sperm sacs. Objective, quantitative statistical analyses support these findings. Nuclear sequence variation suggests considerable divergence between the two species but additional molecular work is needed.</p>

<p>Two species of Chrysaora are described from the northern Benguela ecosystem: C. fulgida and C. africana. These species can be diagnosed by a combination of morphological features including lappet and tentacle number, shape of lappets, colouration patterns (alive), shape of the proximal portion of radial septa, gastrovascular pouch shape, point of attachment of gonads and the presence or absence of small raised nematocyst warts on the exumbrellar surface. Objective, quantitative statistical analyses coupled with molecular sequence data support the qualitative morphological dissimilarity observed, as these analyses unambiguously diagnose C. fulgida and C. africana as two distinct species. There is a strong superficial resemblance between the C. fulgida material described here and the preserved specimens of C. hysoscella examined at the Natural History Museum, London. Thorough investigation does however allow the separation of these two species. Morphological features found to be dissimilar were the proximal portion of the manubrium, gastrovascular pouch shape and the presence or absence of sperm sacs. Objective, quantitative statistical analyses support these findings. Nuclear sequence variation suggests considerable divergence between the two species but additional molecular work is needed.</p>

Magister Scientiae (Biodiversity and Conservation Biology) / Two species of Chrysaora are described from the northern Benguela ecosystem: C. fulgida and C. africana. These species can be diagnosed by a combination of morphological features including lappet and tentacle number, shape of lappets, colouration patterns (alive), shape of the proximal portion of radial septa, gastrovascular pouch shape, point of attachment of gonads and the presence or absence of small raised nematocyst warts on the exumbrellar surface. Objective, quantitative statistical analyses coupled with molecular sequence data support the qualitative morphological dissimilarity observed, as these analyses unambiguously diagnose C. fulgida and C. africana as two distinct species. There is a strong superficial resemblance between the C. fulgida material described here and the preserved specimens of C. hysoscella examined at the Natural History Museum, London. Thorough investigation does however allow the separation of these two species. Morphological features found to be dissimilar were the proximal portion of the manubrium, gastrovascular pouch shape and the presence or absence of sperm sacs. Objective, quantitative statistical analyses support these findings. Nuclear sequence variation suggests considerable divergence between the two species but additional molecular work is needed. / South Africa

>Magister Scientiae - MSc / Two species of Chrysaora are described from the northern Benguela ecosystem: C. fulgida and C. africana. These species can be diagnosed by a combination of morphological features including lappet and tentacle number, shape oflappets, colouration patterns (alive), shape of the proximal portion of radial septa, gastrovascular pouch shape, point of attachment of gonads and the presence or absence of small raised nematocyst warts on the exumbrellar surface. Objective, quantitative statistical analyses coupled with molecular sequence data support the qualitative morphological dissimilarity observed, as these analyses unambiguously diagnose C. fulgida and C. africana as two distinct species. There is a strong superficial resemblance between the C. fulgida material described here and the preserved specimens of C. hysoscella examined at the Natural History Museum, London. Thorough investigation does however allow the separation of these two species. morphological features found to be dissimilar were the proximal portion of the manubrium, gastrovascular pouch shape and the presence or absence of sperm sacs. Objective, quantitative statistical analyses support these findings. Nuclear sequence variation suggests considerable divergence between the two species but additional molecular work is needed.

Submitted by FERNANDA CRERES ROSA null (fer_creres@hotmail.com) on 2016-04-04T19:15:40Z No. of bitstreams: 1 Fernanda Rosa - Dissertação Mestrado.pdf: 2522596 bytes, checksum: e6a718a620bc5e59e8744c6971a6c1c1 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-04-06T14:43:55Z (GMT) No. of bitstreams: 1 rosa_fc_me_assis.pdf: 2522596 bytes, checksum: e6a718a620bc5e59e8744c6971a6c1c1 (MD5) / Made available in DSpace on 2016-04-06T14:43:55Z (GMT). No. of bitstreams: 1 rosa_fc_me_assis.pdf: 2522596 bytes, checksum: e6a718a620bc5e59e8744c6971a6c1c1 (MD5) Previous issue date: 2016-02-26 / Chrysaora é um dos gêneros mais ricos de espécies dentro da subclasse Discomedusae Haeckel, 1880. Na América do Sul existem duas espécies do gênero Chrysaora, Chrysaora lactea (Eschscholtz, 1829) e Chrysaora plocamia (Lesson 1830). A cifomedusa C. lactea é uma das mais comuns e amplamente distribuídas medusas de Scyphozoa na costa. A distribuição dessa espécie é contínua desde o Golfo do México até a costa norte da Argentina (Morandini e Marques 2010). Já a espécie C. plocamia apresenta um incomum padrão de distribuição, ocorrendo em ambos os lados do sul da América do Sul; região oriental do Pacífico Sul (Peru, Chile) e oeste do Atlântico Sul (Argentina), sofrendo forte influência das correntes oceânicas. Assim, o objetivo principal do projeto foi realizar um levantamento da distribuição do gênero Chrysaora na América do Sul. Adicionalmente buscou-se confirmar a ocorrência da espécie C. plocamia no litoral do Uruguai, analisar a estrutura morfológica e molecular das populaçõesde C. lactea distribuídas ao longo do Atlântico Sul Ocidental e comparar os indivíduos entre as diferentes regiões. Foram realizadas análises morfológicas e morfométricas, o estudo da composição dos nematocistos através das medidas e análises estatísticas, além de análises moleculares, através da avaliação do marcador molecular mitocondrial (16S) dos indivíduos da espécie C. lactea e C. plocamia, de diferentes localidades. Os resultados apontam que a distribuição da espécie C. lactea é continua desde o Uruguai até o norte do Brasil e que possivelmente não há incidência de espécies crípticas nessa região analisada. Já a espécie C. plocamia está associada às águas frias neríticas do Atlântico e Pacífico, notando-se a presença dessa espécie também na região do Uruguai. / Chrysaora is one of the richest genera within the subclass Discomedusae Haeckel, 1880. In South America, there are two species of the genus Chrysaora, Chrysaora lactea (Eschscholtz, 1829) and Chrysaora plocamia (Lesson 1830). The scyphomedusa C. lactea is one of the most common and widely distributed Scyphozoa jellyfish on the coast. The distribution of this species is continuous from the Gulf of Mexico to the north coast of Argentina (Morandini e Marques 2010). C. plocamia has an unusual distribution pattern, occurring on both sides of southern South America, eastern South Pacific (Peru, Chile) and western South Atlantic (Argentina). The objective of this study was to promote a survey of the distribution of the genus Chrysaora in South America. Additionally, we confirmed the occurrence of C. plocamia in Uruguay coast, analyzed the morphological and molecular structureof C. lactea distributed over Western South Atlantic comparing individuals between different regions, especially looking for the incidence of cryptic species. Morphological and morphometric analyzes were performed, as well as the study of the composition of nematocysts by measurements and statistical analysis, in addition to molecular analysis by evaluating the mitochondrial molecular markers 16S of individuals of C. lactea and C. plocamia from different locations. The results showed that the distribution of the species C. lactea is continuous from the Uruguay to the Northern Brasil and there was no incidence of cryptic species. Also, C. plocamia is associated with cold inshore waters of the Atlantic and Pacific, noting the presence of this species also in Uruguay.