Top Tweets for #intercontinentally

3 months ago

How do #intercontinentally #distributed #freshwaterfish spread when their dispersal necessarily requires overcoming #saltwaterbarriers? The #Aplocheiloidei are a taxon of #toothcarps (#Cyprinodontiformes); these species are found in regions including South Africa, India, and South America. Among them are species known as #seasonalfish, some of which live no longer than a year because they cannot survive the seasonal #dryingup of their #habitats. Consequently, their entire life cycle unfolds rapidly within that single year of life. Much like certain crustacean taxa, such as the #Triopsidae, these fish have evolved, through independent (#convergent) #evolution, a #dormantstage in the form of #droughtresistant #eggs; these eggs survive the dry season and hatch only afterwards, allowing the fish to quickly complete their entire #lifecycle. How do species with embryos in a state of #diapause manage to overcome #oceanicbarriers? V. Borisov et al. (2026) investigated the hypothesis that eggs serve as the #dispersalstage in #Aplocheilus #lineatus, a species with a #disjunctdistribution across Madagascar and India. Unlike more derived species within the taxon, A. lineatus is not an #annualfish; however, it produces dormant stages adapted to survive periods of #highstress. In experiments involving eggs #incubated in #saltwater, the authors demonstrated that the eggs, or rather, the #embryos, are #salttolerant; when exposed to saline environments, they respond with prolonged #embryonicdevelopment and reduced consumption of endogenous nutrient reserves. The researchers conclude that the embryos are capable of #surviving transit through seawater. This raises the question of which mechanism facilitates dispersal over such great distances. The explanation offered is #passivedrift, whereby the eggs adhere to #plantdebris and are dispersed along with it. According to the authors, the adhesive nature of the eggs makes this possible. In my view, if it could be demonstrated that egg adhesiveness is an evolutionary adaptation to a life-history strategy in which dispersal via plant debris is obligatory, this could represent a case of #phoresy mediated by non-motile plant debris. © #StefanFWirth, August 2026, Berlin Please support my science writing efforts; I rely on even the smallest donations: https://t.co/4nN4eRHB6I Reference: V. Borisov et al. (2026): https://t.co/i9UFaJb0wG #Photos: 1+2) Aplocheilus lineatus in side view (aquarium setting), author: Graf zu Pappenheim, 2023, licensed under https://t.co/swnuRrM1Ow

wirthstef's tweet photo. How do #intercontinentally #distributed #freshwaterfish spread when their dispersal necessarily requires overcoming #saltwaterbarriers?

The #Aplocheiloidei are a taxon of #toothcarps (#Cyprinodontiformes); these species are found in regions including South Africa, India, and South America. Among them are species known as #seasonalfish, some of which live no longer than a year because they cannot survive the seasonal #dryingup of their #habitats. Consequently, their entire life cycle unfolds rapidly within that single year of life. Much like certain crustacean taxa, such as the #Triopsidae, these fish have evolved, through independent (#convergent) #evolution, a #dormantstage in the form of #droughtresistant #eggs; these eggs survive the dry season and hatch only afterwards, allowing the fish to quickly complete their entire #lifecycle.
How do species with embryos in a state of #diapause manage to overcome #oceanicbarriers?

V. Borisov et al. (2026) investigated the hypothesis that eggs serve as the #dispersalstage in #Aplocheilus #lineatus, a species with a #disjunctdistribution across Madagascar and India. Unlike more derived species within the taxon, A. lineatus is not an #annualfish; however, it produces dormant stages adapted to survive periods of #highstress. In experiments involving eggs #incubated in #saltwater, the authors demonstrated that the eggs, or rather, the #embryos, are #salttolerant; when exposed to saline environments, they respond with prolonged #embryonicdevelopment and reduced consumption of endogenous nutrient reserves. The researchers conclude that the embryos are capable of #surviving transit through seawater. This raises the question of which mechanism facilitates dispersal over such great distances. The explanation offered is #passivedrift, whereby the eggs adhere to #plantdebris and are dispersed along with it. According to the authors, the adhesive nature of the eggs makes this possible.
In my view, if it could be demonstrated that egg adhesiveness is an evolutionary adaptation to a life-history strategy in which dispersal via plant debris is obligatory, this could represent a case of #phoresy mediated by non-motile plant debris.

© #StefanFWirth, August 2026, Berlin

Please support my science writing efforts; I rely on even the smallest donations:
https://t.co/4nN4eRHB6I

Reference:
V. Borisov et al. (2026):
https://t.co/i9UFaJb0wG

#Photos:
1+2) Aplocheilus lineatus in side view (aquarium setting), author:
Graf zu Pappenheim, 2023, licensed under https://t.co/swnuRrM1Ow

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