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Embryonic and larval development in the Midas cichlid fish species flock (Amphilophus spp.): a new evo-devo model for the investigation of adaptive novelties and species differences.

Kratochwil CF, Sefton MM, Meyer A - BMC Dev. Biol. (2015)

Bottom Line: Key morphological differences between the embryos of Midas cichlids and other teleosts are highlighted and discussed, including the presence of adhesive glands and different early chromatophore patterns, as well as variation in developmental timing.In the past, the species flocks of the African Great Lakes have received the most attention from researchers, but some lineages of the 300-400 species of Central American lakes are fascinating model systems for adaptive radiation and rapid phenotypic evolution.The availability of genetic resources, their status as a model system for evolutionary research, and the possibility to perform functional experiments including transgenesis makes the Midas cichlid complex a very attractive model for evolutionary-developmental research.

View Article: PubMed Central - PubMed

Affiliation: Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Konstanz, Germany. claudius.kratochwil@uni-konstanz.de.

ABSTRACT

Background: Central American crater lake cichlid fish of the Midas species complex (Amphilophus spp.) are a model system for sympatric speciation and fast ecological diversification and specialization. Midas cichlids have been intensively analyzed from an ecological and morphological perspective. Genomic resources such as transcriptomic and genomic data sets, and a high-quality draft genome are available now. Many ecologically relevant species-specific traits and differences such as pigmentation and cranial morphology arise during development. Detailed descriptions of the early development of the Midas cichlid in particular, will help to investigate the ontogeny of species differences and adaptations.

Results: We describe the embryonic and larval development of the crater lake cichlid, Amphilophus xiloaensis, until seven days after fertilization. Similar to previous studies on teleost development, we describe six periods of embryogenesis - the zygote, cleavage, blastula, gastrula, segmentation, and post-hatching period. Furthermore, we define homologous stages to well-described teleost models such as medaka and zebrafish, as well as other cichlid species such as the Nile tilapia and the South American cichlid Cichlasoma dimerus. Key morphological differences between the embryos of Midas cichlids and other teleosts are highlighted and discussed, including the presence of adhesive glands and different early chromatophore patterns, as well as variation in developmental timing.

Conclusions: The developmental staging of the Midas cichlid will aid researchers in the comparative investigation of teleost ontogenies. It will facilitate comparative developmental biological studies of Neotropical and African cichlid fish in particular. In the past, the species flocks of the African Great Lakes have received the most attention from researchers, but some lineages of the 300-400 species of Central American lakes are fascinating model systems for adaptive radiation and rapid phenotypic evolution. The availability of genetic resources, their status as a model system for evolutionary research, and the possibility to perform functional experiments including transgenesis makes the Midas cichlid complex a very attractive model for evolutionary-developmental research.

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Micropylar region and mucous layer. (A) At the one-cell stage, the micropylar region is surrounded by the filament tuft. (B, C) The mucous layer adheres the eggs to the substrate and/or to one another at low (B) and high magnification (C). Abbreviations: ch, chorion; mi, micropyle; ft, filament tuft; ml, mucous layer. Scale bar = 500 μm.
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Fig3: Micropylar region and mucous layer. (A) At the one-cell stage, the micropylar region is surrounded by the filament tuft. (B, C) The mucous layer adheres the eggs to the substrate and/or to one another at low (B) and high magnification (C). Abbreviations: ch, chorion; mi, micropyle; ft, filament tuft; ml, mucous layer. Scale bar = 500 μm.

Mentions: Unfertilized or newly-fertilized eggs of A. xiloaensis have an ovoid shape, with the longitudinal axis longer (2.14 ± 0.09 mm) than the transverse axis (1.42 ± 0.07 mm) and the animal pole narrower than the vegetal pole (Figure 2A). The egg is surrounded by the chorion, a translucent envelope that sticks closely to the egg (Figures 2A, 3A). This persists throughout later developmental stages, when there is almost no perivitelline space between the chorion and the vitellus (egg yolk). The vitellus is composed of large dark-yellow yolk globules/platelets of varying sizes (0.01-0.09 mm), giving it a grainy appearance, as reported previously for the Midas cichlid and closely-related Neotropical cichlids [35,40,41] (Figures 2A, 3A). The micropyle, the pore in the membrane that guides sperm to the oocyte [42], has a funnel or cone-shaped configuration. It is surrounded by a tuft of filament that can best be observed with dark field illumination (Figure 3A), and can only be seen until the first four to six cell divisions (Figure 2A-I). After spawning (both natural and by stripping) the eggs stick to each other and to the substrate, or to the petri dish under laboratory conditions, by a mucous secretion (Figure 3B, C). In contrast to zebrafish [22], the chorion does not swell and lift away from the fertilized egg during the zygote period, which lasts until the first cleavage occurs around 1.75 h (28°C).Figure 2


Embryonic and larval development in the Midas cichlid fish species flock (Amphilophus spp.): a new evo-devo model for the investigation of adaptive novelties and species differences.

Kratochwil CF, Sefton MM, Meyer A - BMC Dev. Biol. (2015)

Micropylar region and mucous layer. (A) At the one-cell stage, the micropylar region is surrounded by the filament tuft. (B, C) The mucous layer adheres the eggs to the substrate and/or to one another at low (B) and high magnification (C). Abbreviations: ch, chorion; mi, micropyle; ft, filament tuft; ml, mucous layer. Scale bar = 500 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4352272&req=5

Fig3: Micropylar region and mucous layer. (A) At the one-cell stage, the micropylar region is surrounded by the filament tuft. (B, C) The mucous layer adheres the eggs to the substrate and/or to one another at low (B) and high magnification (C). Abbreviations: ch, chorion; mi, micropyle; ft, filament tuft; ml, mucous layer. Scale bar = 500 μm.
Mentions: Unfertilized or newly-fertilized eggs of A. xiloaensis have an ovoid shape, with the longitudinal axis longer (2.14 ± 0.09 mm) than the transverse axis (1.42 ± 0.07 mm) and the animal pole narrower than the vegetal pole (Figure 2A). The egg is surrounded by the chorion, a translucent envelope that sticks closely to the egg (Figures 2A, 3A). This persists throughout later developmental stages, when there is almost no perivitelline space between the chorion and the vitellus (egg yolk). The vitellus is composed of large dark-yellow yolk globules/platelets of varying sizes (0.01-0.09 mm), giving it a grainy appearance, as reported previously for the Midas cichlid and closely-related Neotropical cichlids [35,40,41] (Figures 2A, 3A). The micropyle, the pore in the membrane that guides sperm to the oocyte [42], has a funnel or cone-shaped configuration. It is surrounded by a tuft of filament that can best be observed with dark field illumination (Figure 3A), and can only be seen until the first four to six cell divisions (Figure 2A-I). After spawning (both natural and by stripping) the eggs stick to each other and to the substrate, or to the petri dish under laboratory conditions, by a mucous secretion (Figure 3B, C). In contrast to zebrafish [22], the chorion does not swell and lift away from the fertilized egg during the zygote period, which lasts until the first cleavage occurs around 1.75 h (28°C).Figure 2

Bottom Line: Key morphological differences between the embryos of Midas cichlids and other teleosts are highlighted and discussed, including the presence of adhesive glands and different early chromatophore patterns, as well as variation in developmental timing.In the past, the species flocks of the African Great Lakes have received the most attention from researchers, but some lineages of the 300-400 species of Central American lakes are fascinating model systems for adaptive radiation and rapid phenotypic evolution.The availability of genetic resources, their status as a model system for evolutionary research, and the possibility to perform functional experiments including transgenesis makes the Midas cichlid complex a very attractive model for evolutionary-developmental research.

View Article: PubMed Central - PubMed

Affiliation: Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Konstanz, Germany. claudius.kratochwil@uni-konstanz.de.

ABSTRACT

Background: Central American crater lake cichlid fish of the Midas species complex (Amphilophus spp.) are a model system for sympatric speciation and fast ecological diversification and specialization. Midas cichlids have been intensively analyzed from an ecological and morphological perspective. Genomic resources such as transcriptomic and genomic data sets, and a high-quality draft genome are available now. Many ecologically relevant species-specific traits and differences such as pigmentation and cranial morphology arise during development. Detailed descriptions of the early development of the Midas cichlid in particular, will help to investigate the ontogeny of species differences and adaptations.

Results: We describe the embryonic and larval development of the crater lake cichlid, Amphilophus xiloaensis, until seven days after fertilization. Similar to previous studies on teleost development, we describe six periods of embryogenesis - the zygote, cleavage, blastula, gastrula, segmentation, and post-hatching period. Furthermore, we define homologous stages to well-described teleost models such as medaka and zebrafish, as well as other cichlid species such as the Nile tilapia and the South American cichlid Cichlasoma dimerus. Key morphological differences between the embryos of Midas cichlids and other teleosts are highlighted and discussed, including the presence of adhesive glands and different early chromatophore patterns, as well as variation in developmental timing.

Conclusions: The developmental staging of the Midas cichlid will aid researchers in the comparative investigation of teleost ontogenies. It will facilitate comparative developmental biological studies of Neotropical and African cichlid fish in particular. In the past, the species flocks of the African Great Lakes have received the most attention from researchers, but some lineages of the 300-400 species of Central American lakes are fascinating model systems for adaptive radiation and rapid phenotypic evolution. The availability of genetic resources, their status as a model system for evolutionary research, and the possibility to perform functional experiments including transgenesis makes the Midas cichlid complex a very attractive model for evolutionary-developmental research.

Show MeSH