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Ahi, E. P., Singh, P., Duenser, A., Gessl, W. & Sturmbauer, C. (2019). Divergence in larval jaw gene expression reflects differential trophic adaptation in haplochromine cichlids prior to foraging. BMC Evolutionary Biology, 19, Article ID 150.
Open this publication in new window or tab >>Divergence in larval jaw gene expression reflects differential trophic adaptation in haplochromine cichlids prior to foraging
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2019 (English)In: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 19, article id 150Article in journal (Refereed) Published
Abstract [en]

BackgroundUnderstanding how variation in gene expression contributes to morphological diversity is a major goal in evolutionary biology. Cichlid fishes from the East African Great lakes exhibit striking diversity in trophic adaptations predicated on the functional modularity of their two sets of jaws (oral and pharyngeal). However, the transcriptional basis of this modularity is not so well understood, as no studies thus far have directly compared the expression of genes in the oral and pharyngeal jaws. Nor is it well understood how gene expression may have contributed to the parallel evolution of trophic morphologies across the replicate cichlid adaptive radiations in Lake Tanganyika, Malawi and Victoria.ResultsWe set out to investigate the role of gene expression divergence in cichlid fishes from these three lakes adapted to herbivorous and carnivorous trophic niches. We focused on the development stage prior to the onset of exogenous feeding that is critical for understanding patterns of gene expression after oral and pharyngeal jaw skeletogenesis, anticipating environmental cues. This framework permitted us for the first time to test for signatures of gene expression underlying jaw modularity in convergent eco-morphologies across three independent adaptive radiations. We validated a set of reference genes, with stable expression between the two jaw types and across species, which can be important for future studies of gene expression in cichlid jaws. Next we found evidence of modular and non-modular gene expression between the two jaws, across different trophic niches and lakes. For instance, prdm1a, a skeletogenic gene with modular anterior-posterior expression, displayed higher pharyngeal jaw expression and modular expression pattern only in carnivorous species. Furthermore, we found the expression of genes in cichlids jaws from the youngest Lake Victoria to exhibit low modularity compared to the older lakes.ConclusionOverall, our results provide cross-species transcriptional comparisons of modularly-regulated skeletogenic genes in the two jaw types, implicating expression differences which might contribute to the formation of divergent trophic morphologies at the stage of larval independence prior to foraging.

Place, publisher, year, edition, pages
BMC, 2019
Keywords
Haplochromine cichlids, Modularity, jaw development, Trophic specialization, Adaptive radiation, East African lakes
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-391368 (URN)10.1186/s12862-019-1483-3 (DOI)000477028400003 ()31340758 (PubMedID)
Available from: 2019-09-04 Created: 2019-09-04 Last updated: 2019-09-04Bibliographically approved
Ahi, E. P., Richter, F., Lecaudey, L. A. & Sefc, K. M. (2019). Gene expression profiling suggests differences in molecular mechanisms of fin elongation between cichlid species. Scientific Reports, 9, Article ID 9052.
Open this publication in new window or tab >>Gene expression profiling suggests differences in molecular mechanisms of fin elongation between cichlid species
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 9052Article in journal (Refereed) Published
Abstract [en]

Comparative analyses of gene regulation inform about the molecular basis of phenotypic trait evolution. Here, we address a fin shape phenotype that evolved multiple times independently across teleost fish, including several species within the family Cichlidae. In a previous study, we proposed a gene regulatory network (GRN) involved in the formation and regeneration of conspicuous filamentous elongations adorning the unpaired fins of the Neolamprologus brichardi. Here, we tested the members of this network in the blockhead cichlid, Steatocranus casuarius, which displays conspicuously elongated dorsal and moderately elongated anal fins. Our study provided evidence for differences in the anatomy of fin elongation and suggested gene regulatory divergence between the two cichlid species. Only a subset of the 20 genes tested in S. casuarius showed the qPCR expression patterns predicted from the GRN identified in N. brichardi, and several of the gene-by-gene expression correlations differed between the two cichlid species. In comparison to N. brichardi, gene expression patterns in S. casuarius were in better (but not full) agreement with gene regulatory interactions inferred in zebrafish. Within S. casuarius, the dorsoventral asymmetry in ornament expression was accompanied by differences in gene expression patterns, including potential regulatory differentiation, between the anal and dorsal fin.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-390679 (URN)10.1038/s41598-019-45599-w (DOI)000472477700007 ()31227799 (PubMedID)
Available from: 2019-08-15 Created: 2019-08-15 Last updated: 2019-08-15Bibliographically approved
Ahi, E. P., Singh, P., Lecaudey, L. A., Gessl, W. & Sturmbauer, C. (2018). Maternal mRNA input of growth and stress-response-related genes in cichlids in relation to egg size and trophic specialization. EvoDevo, 9, Article ID 23.
Open this publication in new window or tab >>Maternal mRNA input of growth and stress-response-related genes in cichlids in relation to egg size and trophic specialization
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2018 (English)In: EvoDevo, ISSN 2041-9139, E-ISSN 2041-9139, Vol. 9, article id 23Article in journal (Refereed) Published
Abstract [en]

Background: Egg size represents an important form of maternal effect determined by a complex interplay of long-term adaptation and short-term plasticity balancing egg size with brood size. Haplochromine cichlids are maternal mouthbrooders showing differential parental investment in different species, manifested in great variation in egg size, brood size and duration of maternal care. Little is known about maternally determined molecular characters of eggs in fishes and their relation to egg size and trophic specialization. Here we investigate maternal mRNA inputs of selected growth- and stress-related genes in eggs of mouthbrooding cichlid fishes adapted to different trophic niches from Lake Tanganyika, Lake Malawi, Lake Victoria and compare them to their riverine allies.

Results: We first identified two reference genes, atf7ip and mid1ip1, to be suitable for cross-species quantification of mRNA abundance via qRT-PCR in the cichlid eggs. Using these reference genes, we found substantial variation in maternal mRNA input for a set of candidate genes related to growth and stress response across species and lakes. We observed negative correlation of mRNA abundance between two of growth hormone receptor paralogs (ghr1 and ghr2) across all haplochromine cichlid species which also differentiate the species in the two younger lakes, Malawi and Lake Victoria, from those in Lake Tanganyika and ancestral riverine species. Furthermore, we found correlations between egg size and maternal mRNA abundance of two growth-related genes igf2 and ghr2 across the haplochromine cichlids as well as distinct clustering of the species based on their trophic specialization using maternal mRNA abundance of five genes (ghr1, ghr2, igf2, gr and sgk1).

Conclusions: These findings indicate that variations in egg size in closely related cichlid species can be linked to differences in maternal RNA deposition of key growth-related genes. In addition, the cichlid species with contrasting trophic specialization deposit different levels of maternal mRNAs in their eggs for particular growth-related genes; however, it is unclear whether such differences contribute to differential morphogenesis at later stages of development. Our results provide first insights into this aspect of gene activation, as a basis for future studies targeting their role during ecomorphological specialization and adaptive radiation.

Place, publisher, year, edition, pages
BMC, 2018
Keywords
Haplochromine cichlids, Maternal mRNA, Eggs, Trophic specialization, Adaptive radiation, East African lakes
National Category
Evolutionary Biology Zoology
Identifiers
urn:nbn:se:uu:diva-372382 (URN)10.1186/s13227-018-0112-3 (DOI)000451770100001 ()30519389 (PubMedID)
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-01-07Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6528-1187

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