Disentangling the identities and distribution patterns of the introduced beachfleas Orchestia gammarellus and Platorchestia platensis (Crustacea: Amphipoda Talitridae) in South Africa
- Diemer, Natalie, Griffiths, Charles L, Hodgson, Alan N
- Authors: Diemer, Natalie , Griffiths, Charles L , Hodgson, Alan N
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443163 , vital:74084 , https://doi.org/10.1080/15627020.2016.1268930
- Description: Two introduced beachfleas, Orchestia gammarellus and Platorchestia platensis, have been recorded from South Africa, but have been misidentified by some earlier researchers and, prior to this study, each was also known from just a few, scattered observations, such that their true distributions remained obscure. We illustrate both species to clarify the features that identify and distinguish them and determine their true distributions by re-examining historical samples and by collecting new material from estuaries and lagoons along the west and south coasts of South Africa. Adult males of O. gammarellus have slender antennae and characteristic expanded, flattened, oar-like distal segments on pereopod 7. Adult males of P. platensis have the peduncle of antenna 2 strongly swollen and have bulbous, but not flattened, distal segments on pereopod 7. Both species occur under wrack and other debris along the banks of estuaries and sheltered lagoons. Orchestia gammarellus is found only along the south-west coast, in the Berg River Estuary, Langebaan Lagoon and the Diep River Estuary. Previous records from Knysna were misidentifications of P. platensis. Platorchestia platensis is found at one west coast site, Langebaan Lagoon, but is widely distributed from Cape Point eastwards to at least Algoa Bay. Both species share the same habitats as several other native beachfleas and competitive interactions between native and introduced species merit investigation.
- Full Text:
- Authors: Diemer, Natalie , Griffiths, Charles L , Hodgson, Alan N
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443163 , vital:74084 , https://doi.org/10.1080/15627020.2016.1268930
- Description: Two introduced beachfleas, Orchestia gammarellus and Platorchestia platensis, have been recorded from South Africa, but have been misidentified by some earlier researchers and, prior to this study, each was also known from just a few, scattered observations, such that their true distributions remained obscure. We illustrate both species to clarify the features that identify and distinguish them and determine their true distributions by re-examining historical samples and by collecting new material from estuaries and lagoons along the west and south coasts of South Africa. Adult males of O. gammarellus have slender antennae and characteristic expanded, flattened, oar-like distal segments on pereopod 7. Adult males of P. platensis have the peduncle of antenna 2 strongly swollen and have bulbous, but not flattened, distal segments on pereopod 7. Both species occur under wrack and other debris along the banks of estuaries and sheltered lagoons. Orchestia gammarellus is found only along the south-west coast, in the Berg River Estuary, Langebaan Lagoon and the Diep River Estuary. Previous records from Knysna were misidentifications of P. platensis. Platorchestia platensis is found at one west coast site, Langebaan Lagoon, but is widely distributed from Cape Point eastwards to at least Algoa Bay. Both species share the same habitats as several other native beachfleas and competitive interactions between native and introduced species merit investigation.
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Macroinvertebrate communities associated with duckweed (Lemnaceae) in two Eastern Cape rivers, South Africa
- Muskett, Phillippa C, Hill, Jaclyn M, Weyl, Philip S R
- Authors: Muskett, Phillippa C , Hill, Jaclyn M , Weyl, Philip S R
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444065 , vital:74182 , https://doi.org/10.2989/16085914.2016.1241173
- Description: The functional feeding groups and diversity of macroinvertebrate communities associated with duckweed mats in the New Years River (two sites) and Bloukrans River (two sites), Eastern Cape province, South Africa, were assessed. Duckweed (Lemnaceae) is a ubiquitous family of floating macrophytes. A total of 41 macroinvertebrate families were collected monthly over a six-month period from February to July 2014. Duckweed biomass in both rivers was highly variable both temporally and spatially. The majority of identified macroinvertebrate taxa were predators and detritivores, with a small percentage of herbivores. An average of approximately 26% of the macroinvertebrate taxa found were from families that include species from more than one functional feeding group. Although overall measures of diversity and ecosystem health (Fisher’s α and Simpson’s index) remained constant over time in the New Years River, significant differences in macroinvertebrate community structure were seen between sites and months on both rivers, with dissimilarity being driven by a larger number of species in the New Years River. This high variability within macroinvertebrate assemblages probably reflects a combination of heterogeneous duckweed distribution, variation in physico-chemistry, opportunistic behaviours of macroinvertebrate predators and/or successional colonisation of duckweed mats.
- Full Text:
- Authors: Muskett, Phillippa C , Hill, Jaclyn M , Weyl, Philip S R
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444065 , vital:74182 , https://doi.org/10.2989/16085914.2016.1241173
- Description: The functional feeding groups and diversity of macroinvertebrate communities associated with duckweed mats in the New Years River (two sites) and Bloukrans River (two sites), Eastern Cape province, South Africa, were assessed. Duckweed (Lemnaceae) is a ubiquitous family of floating macrophytes. A total of 41 macroinvertebrate families were collected monthly over a six-month period from February to July 2014. Duckweed biomass in both rivers was highly variable both temporally and spatially. The majority of identified macroinvertebrate taxa were predators and detritivores, with a small percentage of herbivores. An average of approximately 26% of the macroinvertebrate taxa found were from families that include species from more than one functional feeding group. Although overall measures of diversity and ecosystem health (Fisher’s α and Simpson’s index) remained constant over time in the New Years River, significant differences in macroinvertebrate community structure were seen between sites and months on both rivers, with dissimilarity being driven by a larger number of species in the New Years River. This high variability within macroinvertebrate assemblages probably reflects a combination of heterogeneous duckweed distribution, variation in physico-chemistry, opportunistic behaviours of macroinvertebrate predators and/or successional colonisation of duckweed mats.
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Song analysis of South African pygmy bladder cicadas (Hemiptera: Cicadidae: Cicadettinae: Tettigomyiini).
- Sanborn, Allen F, Phillips, Polly K F, Villet, Martin H
- Authors: Sanborn, Allen F , Phillips, Polly K F , Villet, Martin H
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442319 , vital:73975 , https://doi.org/10.1093/aesa/saw024
- Description: The callings songs of five species from three genera of South African pygmy bladder cicadas are analyzed. The call of each species has a distinct temporal pattern and frequency spectrum. The songs are of significantly lower frequency than would be predicted based on body mass or body length. Comparison of bladder cicada calls from Australia and South Africa show similar lower than predicted frequencies in species of independent evolutionary origin. The inflated abdomen found in these cicadas appears to be a convergent adaptation to permit more efficient song production at lower carrier frequencies that increase the distance the songs will travel.
- Full Text:
- Authors: Sanborn, Allen F , Phillips, Polly K F , Villet, Martin H
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442319 , vital:73975 , https://doi.org/10.1093/aesa/saw024
- Description: The callings songs of five species from three genera of South African pygmy bladder cicadas are analyzed. The call of each species has a distinct temporal pattern and frequency spectrum. The songs are of significantly lower frequency than would be predicted based on body mass or body length. Comparison of bladder cicada calls from Australia and South Africa show similar lower than predicted frequencies in species of independent evolutionary origin. The inflated abdomen found in these cicadas appears to be a convergent adaptation to permit more efficient song production at lower carrier frequencies that increase the distance the songs will travel.
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Sperm ultrastructure and spermatodesm morphology of the spittle bug Locris transversa (Thunberg 1822)(Hemiptera: Cercopidae)
- Hodgson, Alan N, Ridgeway, Jaryd A, Villet, Martin H
- Authors: Hodgson, Alan N , Ridgeway, Jaryd A , Villet, Martin H
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442333 , vital:73976 , https://doi.org/10.1080/07924259.2016.1157104
- Description: The structure of the spermatozoon and spermatodesm of the spittlebug Locris transversa (Thunberg 1822) was investigated by light and transmission electron microscopy. Males produced only one size class of sperm, which was 93–106 μm long. During spermatogenesis groups of spermatozoa are arranged around, and attached by their acrosomes to, a small central extracellular matrix to form a ball-shaped spermatodesm. Spermatodesmata were found in the testis, vas deferens and seminal vesicle of males and spermatheca of females. The sperm are filiform, each consisting of a ~15-μm-long head containing an anteriorly positioned conical ~2-μm-long acrosome and ~13-μm-long nucleus, and a midpiece and tail with a 9+9+2 axoneme. The acrosome, which has two posterior extensions that lie along one side of the anterior region of the nucleus, contains longitudinally orientated microfilaments. The nucleus has two unequal anterior extensions, whereas posteriorly it is flattened laterally to accommodate a putative centriolar adjunct and anterior ends of the two mitochondrial derivatives. The basal body lies posterior to the nucleus. The mitochondrial derivatives are elongated and extend for almost the entire length of the tail. The tail has glycogen within its centre, and towards its terminal end large deposits of glycogen surround the mitochondrial derivatives and axoneme. Compared to other members of the Cicadomorpha, the spermatozoa and spermatodesms of cercopids so far studied have some structural features in common with cicadellids and others in common with cicadas; therefore, if sperm features are to be useful in phylogenetic studies of cicadomorphs, attention must be given to examining key taxa to establish which character states are plesiomorphic or apomorphic.
- Full Text:
- Authors: Hodgson, Alan N , Ridgeway, Jaryd A , Villet, Martin H
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442333 , vital:73976 , https://doi.org/10.1080/07924259.2016.1157104
- Description: The structure of the spermatozoon and spermatodesm of the spittlebug Locris transversa (Thunberg 1822) was investigated by light and transmission electron microscopy. Males produced only one size class of sperm, which was 93–106 μm long. During spermatogenesis groups of spermatozoa are arranged around, and attached by their acrosomes to, a small central extracellular matrix to form a ball-shaped spermatodesm. Spermatodesmata were found in the testis, vas deferens and seminal vesicle of males and spermatheca of females. The sperm are filiform, each consisting of a ~15-μm-long head containing an anteriorly positioned conical ~2-μm-long acrosome and ~13-μm-long nucleus, and a midpiece and tail with a 9+9+2 axoneme. The acrosome, which has two posterior extensions that lie along one side of the anterior region of the nucleus, contains longitudinally orientated microfilaments. The nucleus has two unequal anterior extensions, whereas posteriorly it is flattened laterally to accommodate a putative centriolar adjunct and anterior ends of the two mitochondrial derivatives. The basal body lies posterior to the nucleus. The mitochondrial derivatives are elongated and extend for almost the entire length of the tail. The tail has glycogen within its centre, and towards its terminal end large deposits of glycogen surround the mitochondrial derivatives and axoneme. Compared to other members of the Cicadomorpha, the spermatozoa and spermatodesms of cercopids so far studied have some structural features in common with cicadellids and others in common with cicadas; therefore, if sperm features are to be useful in phylogenetic studies of cicadomorphs, attention must be given to examining key taxa to establish which character states are plesiomorphic or apomorphic.
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The network society: A model for computing infrastructure in South African schools
- Siebörger, Ingrid, Terzoli, Alfredo
- Authors: Siebörger, Ingrid , Terzoli, Alfredo
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430651 , vital:72706 , 10.1109/ISTAFRICA.2016.7530673
- Description: Worldwide computers are being used in schools for, amongst other things, developing the knowledge and skills required for citizens to be able to operate within the 21st Century Information Age. Realising the potential of technology in uplifting the lives of its citizens the South Afri-can government has proposed the National Broadband Plan (SA Con-nect). However, unfortunately this plan only addresses the networking aspect of Information Communication Technologies (ICTs). In this pa-per we investigate appropriate Information Technologies for schools in the light of SA Connect, and propose a model for the computing infra-structure required in South African schools in order to support access to and adoption of technology and networks. This model is based on our multi-year experimentation in the Siyakhula Living Lab.
- Full Text:
- Authors: Siebörger, Ingrid , Terzoli, Alfredo
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430651 , vital:72706 , 10.1109/ISTAFRICA.2016.7530673
- Description: Worldwide computers are being used in schools for, amongst other things, developing the knowledge and skills required for citizens to be able to operate within the 21st Century Information Age. Realising the potential of technology in uplifting the lives of its citizens the South Afri-can government has proposed the National Broadband Plan (SA Con-nect). However, unfortunately this plan only addresses the networking aspect of Information Communication Technologies (ICTs). In this pa-per we investigate appropriate Information Technologies for schools in the light of SA Connect, and propose a model for the computing infra-structure required in South African schools in order to support access to and adoption of technology and networks. This model is based on our multi-year experimentation in the Siyakhula Living Lab.
- Full Text:
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