Trophic divergence of Lake Kivu cichlid fishes along a pelagic versus littoral habitat axis

AbstractField study on the biology of Crassicutis cichlasomae Manter, 1936 (Digenea: Homalometridae) was carried out in a small swamp in a limestone factory near Mérida, Yucatán, Mexico. Aquatic snails, Littorina (Littoridinopsis) angulifera, harbouring C. cichlasomae rediae, cercariae and metacercariae, served both as the first and second intermediate hosts. Feeding experiments confirmed the conspecificity of metacercariae from naturally infected snails with adults from naturally infected fish. Gravid C. cichlasomae worms were obtained from experimentally infected fish 19 days post exposure at 22–24°C. Examination of fish from the swamp in Mitza and other localities in the Yucatan Peninsula showed that the cichlids Cichlasoma urophthalmus and C. meeki were definitive hosts of C. cichlasomae. There was no pronounced preference of C. cichlasomae adults for the site of their location in the intestine of the definitive host; a slightly higher proportion (41%) of worms was only found in the anterior third of the gut. The time of miracidium development varied from 18.5 to 27.5 days; different temperature (20.1–35.7°C) or light/darkness regimes influenced only slightly the rate of embryonic development, with shorter development times at higher temperature (34.8–35.7°C) and constant darkness and/or light. With the exception of the sporocyst, all developmental stages are described and figured.

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Gene coexpression networks reveal molecular interactions underlying cichlid jaw modularity

BMC Ecology and Evolution ◽

10.1186/s12862-021-01787-9 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Pooja Singh ◽

Ehsan Pashay Ahi ◽

Christian Sturmbauer

Keyword(s):

In Silico ◽

Regulatory Networks ◽

Evolutionary Significance ◽

Cichlid Species ◽

Cichlid Fishes ◽

Gene Coexpression ◽

Modular Evolution ◽

Jaw Apparatus ◽

Coexpression Networks ◽

Pharyngeal Jaw

Abstract Background The oral and pharyngeal jaw of cichlid fishes are a classic example of evolutionary modularity as their functional decoupling boosted trophic diversification and contributed to the success of cichlid adaptive radiations. Most studies until now have focused on the functional, morphological, or genetic aspects of cichlid jaw modularity. Here we extend this concept to include transcriptional modularity by sequencing whole transcriptomes of the two jaws and comparing their gene coexpression networks. Results We show that transcriptional decoupling of gene expression underlies the functional decoupling of cichlid oral and pharyngeal jaw apparatus and the two units are evolving independently in recently diverged cichlid species from Lake Tanganyika. Oral and pharyngeal jaw coexpression networks reflect the common origin of the jaw regulatory program as there is high preservation of gene coexpression modules between the two sets of jaws. However, there is substantial rewiring of genetic architecture within those modules. We define a global jaw coexpression network and highlight jaw-specific and species-specific modules within it. Furthermore, we annotate a comprehensive in silico gene regulatory network linking the Wnt and AHR signalling pathways to jaw morphogenesis and response to environmental cues, respectively. Components of these pathways are significantly differentially expressed between the oral and pharyngeal jaw apparatus. Conclusion This study describes the concerted expression of many genes in cichlid oral and pharyngeal jaw apparatus at the onset of the independent life of cichlid fishes. Our findings suggest that – on the basis of an ancestral gill arch network—transcriptional rewiring may have driven the modular evolution of the oral and pharyngeal jaws, highlighting the evolutionary significance of gene network reuse. The gene coexpression and in silico regulatory networks presented here are intended as resource for future studies on the genetics of vertebrate jaw morphogenesis and trophic adaptation.

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Positive selection of the long-wavelength opsin gene in South American cichlid fishes

Hydrobiologia ◽

10.1007/s10750-021-04611-z ◽

2021 ◽

Author(s):

Thomaz Mansini Carrenho Fabrin ◽

Luciano Seraphim Gasques ◽

Rodrigo Junio da Graça ◽

Sônia Maria Alves Pinto Prioli ◽

Weferson Júnio da Graça ◽

...

Keyword(s):

Positive Selection ◽

Opsin Gene ◽

South American ◽

Long Wavelength ◽

Cichlid Fishes ◽

Selection Of

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Questioning territories and identities in the precolonial (nineteenth-century) Lake Kivu region

Africa ◽

10.1017/s0001972021000267 ◽

2021 ◽

Vol 91 (3) ◽

pp. 493-515

Author(s):

Gillian Mathys

Keyword(s):

Nineteenth Century ◽

Political Power ◽

Lake Kivu ◽

Territorial Claims ◽

The Relationship ◽

The Way

AbstractThroughout Africa, contemporary boundaries are deemed ‘artificial’ because they were external impositions breaking apart supposedly homogeneous ethnic units. This article argues that the problem with the colonial borders was not only that they arbitrarily dissected African societies with European interests in mind, but also that they profoundly changed the way in which territoriality and authority functioned in this region, and therefore they affected identity. The presumption that territories could be constructed in which ‘culture’ and ‘political power’ neatly coincided was influenced by European ideas about space and identity, and privileged the perceptions and territorial claims of those ruling the most powerful centres in the nineteenth century. Thus, this article questions assumptions that continue to influence contemporary views of the Lake Kivu region. It shows that local understandings of the relationship between space and identity differed fundamentally from state-centred perspectives, whether in precolonial centralized states or colonial states.

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