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...fish mothers determine offspring size?
Fish mothers can tailor offspring phenotype to the environment in which young will grow up. The habitat mothers experienced as juveniles will allow them to predict their offspring's environment better than the conditions in the adult home range. In this case maternal decisions about investment in offspring quality should already be determined during the juvenile phase of mothers. Testing this hypothesis, it was foud that the females raised in a poor environment produced larger young than females raised without food limitations, irrespective of the feeding conditions experienced during adulthood. The cause was a higher investment in eggs and to faster larval growth. Apparently, mothers prepare their offspring for similar environmental conditions to those they encountered as juveniles. Under natural conditions, juveniles live in a different and much narrower range of habitats than adults.
[Taborsky, B. Mothers determine offspring size in response to own juvenile growth conditions. In Biology Letters, 2006, 2, 225-228]

...gastritis in Tropheus is caused by bacteria?
Necrotic and granulomatous gastritis is described in Lake Tanganyika cichlids. Clostridium hastiforme and flagellated protozoa were both associated with the reaction but the significance of either is unknown. Nevertheless, treatment of surviving fish with ampicillin was carried out and mortalities ceased. The possible involvement of an unsuitable diet as a predisposing factor is discussed.
[Ferguson, H.W. et al. Gastritis in Lake Tanganyika cichlids (Tropheus duboisi). In Vet Rec., 1985, 116, 687-689]

...there are the differences in a way of algae grazing between the cichlids in Lake Malawi?
Feeding angle differences among Labeotropheus trewavasae, Labeotropheus fuelleborni, Melanochromis auratus, Petrotilapia spp., Pseudotropheus elongatus, Pseudotropheus tropheops, Pseudotropheus zebra, and Pseudotropheus gracilior were examined. The median feeding angles ranged from 35 degrees to 91 degrees. There are four feeding angle groups among the eight rock-dwelling species that were examined: (1) Labeotropheus trewavasae (35°), (2) Labeotropheus fuelleborni, Melanochromis auratus, and Pseudotropheus elongatus (44-48°), (3) Pseudotropheus tropheops (53°), and (4) Petrotilapia spp., Pseudotropheus gracilior and Pseudotropheus zebra (86-91°). Feeding angles measured in the laboratory were congruent with field data and no significant effect of feeding angle was attributed to the tank chambers. No significant differences in the extent or distribution of food acquisition were observed.
[Hale, E.A. An investigation of the utility of feeding angles among Lake Malawi rock-dwelling cichlids (Teleostei: Cichlidae). Doctoral dissertation, The Pennsylvania State University, 1997]

...the environment affects the development and body shape in Tropheus?

Recent studies of environmental influences on Tropheus body composition showed significant effect of artificial conditions on the development of some physical characteristics. The morphological characteristics of the body form four forms of wild caught Tropehus were examined. Two variants were caught in the southern area of Lake Tanganyika (Mbita Island, Nakaku) and two from northern areas (Ikola, Kekese). The wild fish were compared with the offspring of these fish (F1 generation) bred in the ponds right near the lake. By measuring various physical parameters, significant differences in the mouth orientation (pond-raised fish had mouth placed in different angle than the caught fish. An inferior subterminal mouth is characteristic for wild Tropheus), the size and location of the dorsal and anal fins (fish in these ponds have shorter fins and moved further back) were revealed. Changes in the mouth orientation is attributed to change of food intake in artificially bred fish in ponds that have significantly less opportunity to scrape algae from rocks, which is the main activity and feeding behavior of Tropheus in the lake. The fish adapt to sucking the flake food in the water column. Changes in fins structure are related to the lack of flow of water in the ponds as opposed to the lake. The size and shape of the fins has a close relationship to the swimming activity of fish. The pond water is also much quieter and there is lack of predation within the ponds. Therefore, the need for fast swimming has lost its importance.
[Kerschbaumer, M. at al. Morphological distinctness despite large-scale phenotypic plasticity—analysis of wild and pond-bred juveniles of allopatric populations of Tropheus moorii. In Naturwissenschaften, 2011, 98,125–134]

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