1,720,979 research outputs found
Intraspecific diversification and mitonuclear discordance in the monogenean parasite Dolicirroplectanum lacustre, co-introduced with the invasive Nile perch
No full textParasites typically speciate faster, and become more species-rich than their hosts. This especially holds in large and long-lived hosts. Most African lates perches (Latidae), some of the largest freshwater fishes, host only a single monogenean flatworm: Dolicirroplectanum lacustre. This parasite has 'failed to diverge', but displays high morphological variability, with two morphotypes identified.
The Nile perch (Lates niloticus) is a notorious invasive species. The introductions of Nile perch from lakes Albert and Turkana into lakes and rivers in the Lake Victoria region led to the impoverishment of the trophic food webs, particularly well documented in Lake Victoria. Along with the introductions of the Nile perch, its parasites were co-introduced.
To investigate the pattern of parasite co-introduction, we studied the intraspecific diversity of D. lacustre from Nile perch in Lake Albert and Lake Victoria by assessing morphological and genetic differentiation. A single morphotype is suggested to be co-introduced in Lake Victoria. Based on our results, we reported reduced genetic and morphological diversity in Lake Victoria, resulting from a founder effect. The diversification in the COI mitochondrial gene portion was directly linked with the morphotypes, while the nuclear gene portions indicated conspecificity. Mitonuclear discordance within the morphotypes of D. lacustre indicates an incomplete reproductive barrier between the morphotypes
Limited diversification in the monogenean oparasite Dolicirroplectanum lacustre on African lates perches despite a broad habitat range
No full textINTRODUCTION: While parasites often speciate faster than their hosts, African freshwater lates perches (Latidae) host only a single monogenean gill parasite, Dolicirroplectanum lacustre. This species shows limited diversification across various habitats. In contrast, marine and brackish latids in the Indo-Pacific region host a more species-rich assemblage of gill parasites. The introduction of Nile perch (Lates niloticus), an invasive species transported from lakes Albert and Turkana to the Lake Victoria basin, presents an opportunity to study the parasite’s genetic and morphological diversification.
MATERIALS AND METHODS: To understand the diversity patterns in D. lacustre, we studied its populations across multiple sites, including Lake Albert, Lake Victoria, Lake Turkana, and the Congo River. Morphological and genetic analyses were conducted to explore genetic differentiation within the species.
RESULTS: Our analysis revealed two morphotypes within D. lacustre, with one restricted to Lake Albert displaying a distinct mitochondrial haplotype. Despite this mitochondrial divergence, nuclear gene markers confirmed conspecificity. Only one of the two morphotypes was found in Lake Victoria, where D. lacustre showed reduced genetic and morphological diversity. The screening of host gills in Lake Turkana and the Congo River has expanded the known range of D. lacustre.
CONCLUSION: Despite occupying diverse freshwater habitats across Africa, D. lacustre remains a single, morphologically constrained species with minimal diversification. The co-introduction to new environments has reduced the parasite’s diversity through founder effects. Overall, diversification within D. lacustre has been limited to morphotype differentiation rather than full speciation. Further examination of populations from Lake Turkana and the Congo River will give us more insight into its diversification and that of its hosts, and comparative genomics will shed light on the genomic mechanisms behind the observed lack of speciation. Altogether, this study may highlight how the stability of aquatic environments may limit diversification potential in host-parasite systems
Investigating the Gill-Oxygen Limitation Theory (GOLT) in the context of gill parasite diversification
No full textThe Gill-Oxygen Limitation Theory (GOLT) claims that the two-dimensional surface area of gills in Water-Breathing Ectotherms (WBE) is the limiting factor in the supply of oxygen to support the growth of their three-dimensional bodies. This limitation would lead to a shift in a range of physiological processes, most notably a slowing down of growth. Given how GOLT could affect all aspects of growth in WBE, we hypothesise that its effects would be stronger on larger-bodied than on smaller-sized species and that it would affect freshwater taxa more than marine species. Indeed, freshwater WBE, especially those occurring in the tropics, often have to cope with large fluctuations in oxygen concentrations. Hence, we propose African lates perches, Lates spp., the largest tropical freshwater fishes that are entirely dependent on their gills for gas exchange, as a model to test the predictions of the GOLT. We will also study their gill parasites, and investigate how they affect gill function.
Several species and populations of African Lates spp. are infected by a single species of gill-infecting monogenean parasite: Dolicirroplectanum lacustre. This finding is surprising as, normally, parasite species diversity exceeds that of their host. Our research will apply the GOLT to understand this lack of diversification. We hypothesize that strong evolutionary pressures on the gill environment contribute to the limited parasite diversification. By measuring physiological gill stress and assessing both host and parasite stress, we aim to investigate the impact of gill function limitations on parasite and host growth. Studies suggest that monogenean parasites may impair gill function, with larger fish showing greater investment in combating these parasites. We will also examine the extent of gill damage caused by parasitic infections and use this to model how parasite infections affect fish growth. Our study will involve histopathological analyses of gill samples from infected and non-infected fish across different sizes and species. We will assess gill damage, infection levels, and stress responses, correlating these with environmental proxies such as oxygen and salinity. The results of this study will help solidify the quantitative basis of GOLT and expand its applicability to inter-specific interactions. By elucidating the relationship between gill stress, host-parasite dynamics, and environmental fluctuations, our research will contribute to a deeper understanding of the evolutionary pressures shaping parasite diversification in variable environments
With a pinch of salt: the fish gill, a surface of exchange for parasites
No full textLarge-scale patterns of species diversity suggest that stability facilitates speciation. Conversely, fluctuating environments are expected to counteract speciation in host-parasite systems. Monogenea (Platyhelminthes, Neodermata) is a group of obligate flatworm ectoparasites living mostly on the gills and skin of fishes. Monogenean gill parasites are exposed to the aquatic environment which can be highly variable in oxygen and salinity levels. In addition, they are directly exposed to the environment of the fish gill, a continuously adapting organ, due to its physiological functions.
While lates perches (Actinopterygii, Latidae) host various monogenean flatworms in the marine and estuarine environments of the Indo-Pacific region, only a single species, Dolicirroplectanum lacustre (Monogenea, Diplectanidae), infects the gills of African freshwater lates perches.
These contrasting patterns of speciation on an intercontinental scale across various aquatic habitats provide the ideal study system to investigate the influence of environmental variability on host-parasite speciation.
Thus far, we have investigated the population-level diversification of D. lacustre across several African lakes, where high levels of phenotypic plasticity have been revealed.
In order to compare the level of diversification in the parasites with that of the host, we have started the delineation of host units in African basins through morphometrics and geomorphometrics. With the aim to relate the levels of diversification to the stability in the environment of the fish gill, we will quantify the level of gill stress. Fluctuating asymmetry will be investigated using 3D CT scans, and using qPCR, ratios between mitochondrial and nuclear markers will be determined from gill tissue. We will contrast the resulting patterns of diversification in D. lacustre with the divergence of its marine congener Dolicirroplectanum penangi and the diplectanid Laticola latesi coinfecting Indo-Pacific latid Lates calcarifer
Limited diversification in the monogenean oparasite Dolicirroplectanum lacustre on African lates perches despite a broad habitat range
No full textINTRODUCTION: While parasites often speciate faster than their hosts, African freshwater lates perches (Latidae) host only a single monogenean gill parasite, Dolicirroplectanum lacustre. This species shows limited diversification across various habitats. In contrast, marine and brackish latids in the Indo-Pacific region host a more species-rich assemblage of gill parasites. The introduction of Nile perch (Lates niloticus), an invasive species transported from lakes Albert and Turkana to the Lake Victoria basin, presents an opportunity to study the parasite’s genetic and morphological diversification.
MATERIALS AND METHODS: To understand the diversity patterns in D. lacustre, we studied its populations across multiple sites, including Lake Albert, Lake Victoria, Lake Turkana, and the Congo River. Morphological and genetic analyses were conducted to explore genetic differentiation within the species.
RESULTS: Our analysis revealed two morphotypes within D. lacustre, with one restricted to Lake Albert displaying a distinct mitochondrial haplotype. Despite this mitochondrial divergence, nuclear gene markers confirmed conspecificity. Only one of the two morphotypes was found in Lake Victoria, where D. lacustre showed reduced genetic and morphological diversity. The screening of host gills in Lake Turkana and the Congo River has expanded the known range of D. lacustre.
CONCLUSION: Despite occupying diverse freshwater habitats across Africa, D. lacustre remains a single, morphologically constrained species with minimal diversification. The co-introduction to new environments has reduced the parasite’s diversity through founder effects. Overall, diversification within D. lacustre has been limited to morphotype differentiation rather than full speciation. Further examination of populations from Lake Turkana and the Congo River will give us more insight into its diversification and that of its hosts, and comparative genomics will shed light on the genomic mechanisms behind the observed lack of speciation. Altogether, this study may highlight how the stability of aquatic environments may limit diversification potential in host-parasite systems
A failure to diversify on a surface of exchange: the case of Dolicirroplectanum lacustre, the monogenean parasite infecting African latids
No full textIntraspecific diversification and mitonuclear discordance in the monogenean parasite Dolicirroplectanum lacustre, co-introduced with the invasive Nile perch
No full textParasites typically speciate faster, and become more species-rich than their hosts. This especially holds in large and long-lived hosts. Most African lates perches (Latidae), some of the largest freshwater fishes, host only a single monogenean flatworm: Dolicirroplectanum lacustre. This parasite has 'failed to diverge', but displays high morphological variability, with two morphotypes identified.
The Nile perch (Lates niloticus) is a notorious invasive species. The introductions of Nile perch from lakes Albert and Turkana into lakes and rivers in the Lake Victoria region led to the impoverishment of the trophic food webs, particularly well documented in Lake Victoria. Along with the introductions of the Nile perch, its parasites were co-introduced.
To investigate the pattern of parasite co-introduction, we studied the intraspecific diversity of D. lacustre from Nile perch in Lake Albert and Lake Victoria by assessing morphological and genetic differentiation. A single morphotype is suggested to be co-introduced in Lake Victoria. Based on our results, we reported reduced genetic and morphological diversity in Lake Victoria, resulting from a founder effect. The diversification in the COI mitochondrial gene portion was directly linked with the morphotypes, while the nuclear gene portions indicated conspecificity. Mitonuclear discordance within the morphotypes of D. lacustre indicates an incomplete reproductive barrier between the morphotypes
Rethinking the Nile Perch Species Complex: Diversification and Phenotypic Plasticity in the most widespread fisheries keystone species in African Freshwaters
No full textStudying the diversity of freshwater fish species, in particular, the Nile perch complex is crucial for understanding and managing African freshwater ecosystems. As top predators, they play a significant role in regulating fish populations and influencing ecosystem functioning. Taxonomic uncertainties within the complex necessitate further investigation.
We study the morphological diversification of lates perches (Latidae) across Afrotropical freshwaters. We hypothesize morphological differentiation between Nile perches from various basins and habitats, particularly between the Congo and Nile rivers. We expect an increased morphospace in lacustrine environments compared with riverine environments, reflecting the presence of more species in the lakes. We aim to assess the status of two sympatric species in Lake Turkana.
Specimens of lates perches were collected from various historical collections and included in the morphological study. A subsample underwent X-ray or CT scanning. Morphological measurements (37 parameters) were obtained using a digital caliper. Meristic data, including fin formulas, scale counts, and vertebral counts were recorded.
Genetic data were retrieved from ten specimens of Lake Turkana (Kenya). Fin clips were collected and DNA extraction was performed, followed by Illumina sequencing (with targeted bait capture), and Sanger sequencing of the targeted markers (11 mitochondrial, 1 nuclear). Phylogenetic analyses were conducted using maximum likelihood estimation and Bayesian inference.
The morphological data reveal a remarkably conserved morphology with local variation. Based on the combined genetic and morphological evidence, we classify Lates niloticus var. macrolepidota from the Congo River as a distinct species, elevated to Lates macrolepidotus Pellegrin, 1922. We observe east-west clinal variation, with Guinean populations showing greater similarity in meristics to L. macrolepidotus, likely influenced by the predominance of rainforest ecosystems and habitats. The endemic species from lakes Turkana and Albert exhibit morphological differences from the co-occurring L. niloticus, but without species-level genetic differentiation in Lake Turkana
Investigating the Gill-Oxygen Limitation Theory (GOLT) in the context of gill parasite diversification
No full textThe Gill-Oxygen Limitation Theory (GOLT) claims that the two-dimensional surface area of gills in Water-Breathing Ectotherms (WBE) is the limiting factor in the supply of oxygen to support the growth of their three-dimensional bodies. This limitation would lead to a shift in a range of physiological processes, most notably a slowing down of growth. Given how GOLT could affect all aspects of growth in WBE, we hypothesise that its effects would be stronger on larger-bodied than on smaller-sized species and that it would affect freshwater taxa more than marine species. Indeed, freshwater WBE, especially those occurring in the tropics, often have to cope with large fluctuations in oxygen concentrations. Hence, we propose African lates perches, Lates spp., the largest tropical freshwater fishes that are entirely dependent on their gills for gas exchange, as a model to test the predictions of the GOLT. We will also study their gill parasites, and investigate how they affect gill function.
Several species and populations of African Lates spp. are infected by a single species of gill-infecting monogenean parasite: Dolicirroplectanum lacustre. This finding is surprising as, normally, parasite species diversity exceeds that of their host. Our research will apply the GOLT to understand this lack of diversification. We hypothesize that strong evolutionary pressures on the gill environment contribute to the limited parasite diversification. By measuring physiological gill stress and assessing both host and parasite stress, we aim to investigate the impact of gill function limitations on parasite and host growth. Studies suggest that monogenean parasites may impair gill function, with larger fish showing greater investment in combating these parasites. We will also examine the extent of gill damage caused by parasitic infections and use this to model how parasite infections affect fish growth. Our study will involve histopathological analyses of gill samples from infected and non-infected fish across different sizes and species. We will assess gill damage, infection levels, and stress responses, correlating these with environmental proxies such as oxygen and salinity. The results of this study will help solidify the quantitative basis of GOLT and expand its applicability to inter-specific interactions. By elucidating the relationship between gill stress, host-parasite dynamics, and environmental fluctuations, our research will contribute to a deeper understanding of the evolutionary pressures shaping parasite diversification in variable environments
Rethinking the Nile Perch Species Complex: Diversification and Phenotypic Plasticity in the most widespread fisheries keystone species in African Freshwaters
No full textStudying the diversity of freshwater fish species, in particular, the Nile perch complex is crucial for understanding and managing African freshwater ecosystems. As top predators, they play a significant role in regulating fish populations and influencing ecosystem functioning. Taxonomic uncertainties within the complex necessitate further investigation.
We study the morphological diversification of lates perches (Latidae) across Afrotropical freshwaters. We hypothesize morphological differentiation between Nile perches from various basins and habitats, particularly between the Congo and Nile rivers. We expect an increased morphospace in lacustrine environments compared with riverine environments, reflecting the presence of more species in the lakes. We aim to assess the status of two sympatric species in Lake Turkana.
Specimens of lates perches were collected from various historical collections and included in the morphological study. A subsample underwent X-ray or CT scanning. Morphological measurements (37 parameters) were obtained using a digital caliper. Meristic data, including fin formulas, scale counts, and vertebral counts were recorded.
Genetic data were retrieved from ten specimens of Lake Turkana (Kenya). Fin clips were collected and DNA extraction was performed, followed by Illumina sequencing (with targeted bait capture), and Sanger sequencing of the targeted markers (11 mitochondrial, 1 nuclear). Phylogenetic analyses were conducted using maximum likelihood estimation and Bayesian inference.
The morphological data reveal a remarkably conserved morphology with local variation. Based on the combined genetic and morphological evidence, we classify Lates niloticus var. macrolepidota from the Congo River as a distinct species, elevated to Lates macrolepidotus Pellegrin, 1922. We observe east-west clinal variation, with Guinean populations showing greater similarity in meristics to L. macrolepidotus, likely influenced by the predominance of rainforest ecosystems and habitats. The endemic species from lakes Turkana and Albert exhibit morphological differences from the co-occurring L. niloticus, but without species-level genetic differentiation in Lake Turkana
- …
