Gut content.
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As an interesting example, take Herichthys minckleyi
at times when there are population explosions in snails in Cuatro Cienegas, the variant population of minckleyi with more powerful crushing jaws and teeth predominate, but eventually, as the snail population ebbs and fish increase, piscivores minkleyi with jaws and teeth adapted to capturing fish prey become dominant.
As fish prey wane, the detritus eating variant population of minckleyi take over.
And yet they are (so far) considered only to be a single species. Because in any spawn, of any variant, there are percentages of all 3 jaw types.
Many years ago I had (what I believed to be) the detritus morph
One such study below
Herichthys minckleyi - SciELO México
at times when there are population explosions in snails in Cuatro Cienegas, the variant population of minckleyi with more powerful crushing jaws and teeth predominate, but eventually, as the snail population ebbs and fish increase, piscivores minkleyi with jaws and teeth adapted to capturing fish prey become dominant.
As fish prey wane, the detritus eating variant population of minckleyi take over.
And yet they are (so far) considered only to be a single species. Because in any spawn, of any variant, there are percentages of all 3 jaw types.
Many years ago I had (what I believed to be) the detritus morph
One such study below
Herichthys minckleyi - SciELO México
Similar situation in A. citrinellum. Same species, but different body shapes, lip sizes (fleshy lips, non fleshy lips) as well as different jaw structures, depending on the feedng strategy of each collective group of fish. I mentioned this in the following sticky that I posted several years back. https://www.monsterfishkeepers.com/...ellus-a-potential-case-of-f1-midevils.439705/
Cost of morphological specialization: feeding performance of the two morphs in the trophically polymorphic cichlid fish,Cichlasoma citrinellum
https://www.ncbi.nlm.nih.gov/pubmed/28312073
Abstract
The feeding performance on soft and hard prey of two morphs of the trophically polymorphic Neotropical cichlid fish, Cichlasoma citrinellum, was investigated in the laboratory. The molariform morphs, specialized to feed on hard prey, are able to crack snail shells that are twice as hard as those cracked by the papilliform morphs. During ecological bottlenecks in food resources this ability should allow molariform morphs to exploit alternate, less preferred prey sources that are not available to papilliform morphs. Analysis of stomach contents revealed that molariform morphs feed significantly more often on hard snails than do papilliform morphs (Meyer 1989a). The performance advantage of the trophically specialized morphs when feeding on hard prey is countered by their less efficient performance on soft diets. The morphologically generalized papilliform morph feeds more efficiently on soft prey. The abundance of preferred soft prey, seasonal fluctuations in prey availability and the frequency of ecological bottlenecks may determine the relative abundance of these two morphs in natural populations in Nicaraguan lakes.
Cost of morphological specialization: feeding performance of the two morphs in the trophically polymorphic cichlid fish,Cichlasoma citrinellum
https://www.ncbi.nlm.nih.gov/pubmed/28312073
Abstract
The feeding performance on soft and hard prey of two morphs of the trophically polymorphic Neotropical cichlid fish, Cichlasoma citrinellum, was investigated in the laboratory. The molariform morphs, specialized to feed on hard prey, are able to crack snail shells that are twice as hard as those cracked by the papilliform morphs. During ecological bottlenecks in food resources this ability should allow molariform morphs to exploit alternate, less preferred prey sources that are not available to papilliform morphs. Analysis of stomach contents revealed that molariform morphs feed significantly more often on hard snails than do papilliform morphs (Meyer 1989a). The performance advantage of the trophically specialized morphs when feeding on hard prey is countered by their less efficient performance on soft diets. The morphologically generalized papilliform morph feeds more efficiently on soft prey. The abundance of preferred soft prey, seasonal fluctuations in prey availability and the frequency of ecological bottlenecks may determine the relative abundance of these two morphs in natural populations in Nicaraguan lakes.
By the ease of which my citrinellus crushes large dense pellets, I suspect that he is a molariform morph. lol
Good read, thanks.As an interesting example, take Herichthys minckleyi
at times when there are population explosions in snails in Cuatro Cienegas, the variant population of minckleyi with more powerful crushing jaws and teeth predominate, but eventually, as the snail population ebbs and fish increase, piscivores minkleyi with jaws and teeth adapted to capturing fish prey become dominant.
As fish prey wane, the detritus eating variant population of minckleyi take over.
And yet they are (so far) considered only to be a single species. Because in any spawn, of any variant, there are percentages of all 3 jaw types.
Many years ago I had (what I believed to be) the detritus morph
One such study below
Herichthys minckleyi - SciELO México
Great summary - thanks for sharing. Speaking of opportunistic as some have mentioned, I stumbled across some “wild bird mealworms” - by far the favorite treat of all my fish, though I feed quite sparingly due to a high protein and fat content
Are these two types breeding within there own group or cross b
read your sticky when I first joined, I have made a similar point that vendors will have to start giving exact locations within the lakes as I have heard rumours that A citrinellum could be split into 2 or 3 diffrent spp soon.
IMO all wild caught fish should be sold with precise collection locations as possible.
An Amphilophus citrinellus caught in a man made lake such as Lake Arenal, in Costa Rica, is most likely going to be genetically different than an A. citrinellus collected in one of the Great Lakes of Nicaragua. And as demonstrated in that sticky on potential F1 Midevils, genetically there's still a lot of questions that need to be answered. It only seems wise to breed fish from the same collection location, and not just a midas to another midas. Unless of course all one is attempting to achieve is to create aquarium strain fish. When I was actively breeding I made certain that the fish were collected at the same location, at the same time. To me this was just common sense, but not all breeders seemed that concerned back in the day. All many focussed on was whether the fish was wild caught, F1, or F whatever. Today many cross various collection locations on purpose (umbee come to mind), to create more better, more cooler strains, with way cooler names. Whatever, free world and all that, but personally I think it's daft to cross pure strains from different geographical locations.
An Amphilophus citrinellus caught in a man made lake such as Lake Arenal, in Costa Rica, is most likely going to be genetically different than an A. citrinellus collected in one of the Great Lakes of Nicaragua. And as demonstrated in that sticky on potential F1 Midevils, genetically there's still a lot of questions that need to be answered. It only seems wise to breed fish from the same collection location, and not just a midas to another midas. Unless of course all one is attempting to achieve is to create aquarium strain fish. When I was actively breeding I made certain that the fish were collected at the same location, at the same time. To me this was just common sense, but not all breeders seemed that concerned back in the day. All many focussed on was whether the fish was wild caught, F1, or F whatever. Today many cross various collection locations on purpose (umbee come to mind), to create more better, more cooler strains, with way cooler names. Whatever, free world and all that, but personally I think it's daft to cross pure strains from different geographical locations.
I posted the following 2009 study in another sticky on bloat that I wrote several years ago, which demonstrates just how great intestinal plasticity can be in response to the diet quality of various species of cichlids found in Lake Tanganyika. Dietary adaptation at it's best, and again, even within different populations of the same species, within the same body of water.
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2435.2009.01589.x/full
Summary
1. Among vertebrates, herbivores have longer digestive tracts than animals at higher trophic levels, a pattern thought to reflect a trade-off between digestive efficiency and tissue maintenance costs. However, phylogenetic influences on this pattern have rarely been considered. Taxa that have undergone diversification accompanied by dietary shifts provide a powerful opportunity to examine the relationship between diet and intestine length while accounting for phylogeny.
2. In this paper we assess the relationship between diet and intestine length in the cichlid fishes of Lake Tanganyika, which are renowned for their diversity of species and trophic strategies.
3. First, we test the effect of trophic position on intestine length across 32 species, while controlling for phylogeny. Trophic position was inferred from nitrogen stable isotopes, which provide a temporally integrated, quantitative perspective on the complex diets of tropical fish. Second, we examine patterns of intraspecific variation in intestine length of an algivorous cichlid (Tropheus brichardi) along a natural spatial gradient in algal nitrogen content.
4. Trophic position explains 51% of size-standardized variation in intestine length after accounting for phylogeny. Accounting for phylogeny does not substantially alter the relationship between trophic position and intestine length, despite the existence of phylogenetic signal in both traits. Thus, diet is a strong predictor of variation at the interspecific level.
5. There is a striking inverse relationship between intestine length and algal nutrient content among populations of T. brichardi, suggesting substantial plasticity in response to food quality, and thus a strong dietary influence on patterns of intraspecific variation.
6. Diet is a strong predictor of intestine length at both intra- and interspecific scales, indicating that fish adjust their phenotype to balance nutritional needs against energetic costs. Furthermore, functional explanations for trophic diversification of cichlid fishes in the African Great Lakes have long focused on jaw structures, but our results indicate that intestinal plasticity in response to diet quality may also be an important mechanism for accommodating trophic shifts during evolutionary radiations.
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2435.2009.01589.x/full
Summary
1. Among vertebrates, herbivores have longer digestive tracts than animals at higher trophic levels, a pattern thought to reflect a trade-off between digestive efficiency and tissue maintenance costs. However, phylogenetic influences on this pattern have rarely been considered. Taxa that have undergone diversification accompanied by dietary shifts provide a powerful opportunity to examine the relationship between diet and intestine length while accounting for phylogeny.
2. In this paper we assess the relationship between diet and intestine length in the cichlid fishes of Lake Tanganyika, which are renowned for their diversity of species and trophic strategies.
3. First, we test the effect of trophic position on intestine length across 32 species, while controlling for phylogeny. Trophic position was inferred from nitrogen stable isotopes, which provide a temporally integrated, quantitative perspective on the complex diets of tropical fish. Second, we examine patterns of intraspecific variation in intestine length of an algivorous cichlid (Tropheus brichardi) along a natural spatial gradient in algal nitrogen content.
4. Trophic position explains 51% of size-standardized variation in intestine length after accounting for phylogeny. Accounting for phylogeny does not substantially alter the relationship between trophic position and intestine length, despite the existence of phylogenetic signal in both traits. Thus, diet is a strong predictor of variation at the interspecific level.
5. There is a striking inverse relationship between intestine length and algal nutrient content among populations of T. brichardi, suggesting substantial plasticity in response to food quality, and thus a strong dietary influence on patterns of intraspecific variation.
6. Diet is a strong predictor of intestine length at both intra- and interspecific scales, indicating that fish adjust their phenotype to balance nutritional needs against energetic costs. Furthermore, functional explanations for trophic diversification of cichlid fishes in the African Great Lakes have long focused on jaw structures, but our results indicate that intestinal plasticity in response to diet quality may also be an important mechanism for accommodating trophic shifts during evolutionary radiations.
