Fish (eggs) out of water: evolutionary divergence in terrestrial embryonic plasticity in Trinidadian killifish.

Externally laid eggs are often responsive to environmental cues; however, it is unclear how such plasticity evolves. In Trinidad, the killifish (Anablepsoides hartii) is found in communities with and without predators. Here, killifish inhabit shallower, ephemeral habitats in sites with predators. Such shifts may increase the exposure of eggs to air and lead to possible desiccation. We compared egg-hatching plasticity between communities by rearing eggs terrestrially on peat moss or in water. The timing of hatching did not differ between communities when eggs were reared in water. Eggs from sites with predators responded to terrestrial incubation by hatching significantly earlier compared with water-reared eggs. These responses were weaker in sites with no predators. Such divergent trends show that the presence of predators is associated with evolutionary shifts in hatching plasticity. Our results provide evidence for local adaptation in embryonic plasticity at the population scale.

Use of fluorescence imaging and indocyanine green during laparoscopic cholecystectomy: Results of an international Delphi survey.

BACKGROUND: Published empirical data have increasingly suggested that using near-infrared fluorescence cholangiography during laparoscopic cholecystectomy markedly increases biliary anatomy visualization. The technology is rapidly evolving, and different equipment and doses may be used. We aimed to identify areas of consensus and nonconsensus in the use of incisionless near-infrared fluorescent cholangiography during laparoscopic cholecystectomy. METHODS: A 2-round Delphi survey was conducted among 28 international experts in minimally invasive surgery and near-infrared fluorescent cholangiography in 2020, during which respondents voted on 62 statements on patient preparation and contraindications (n = 12); on indocyanine green administration (n = 14); on potential advantages and uses of near-infrared fluorescent cholangiography (n = 18); comparing near-infrared fluorescent cholangiography with intraoperative x-ray cholangiography (n = 7); and on potential disadvantages of and required training for near-infrared fluorescent cholangiography (n = 11). RESULTS: Expert consensus strongly supports near-infrared fluorescent cholangiography superiority over white light for the visualization of biliary structures and reduction of laparoscopic cholecystectomy risks. It also offers other advantages like enhancing anatomic visualization in obese patients and those with moderate to severe inflammation. Regarding indocyanine green administration, consensus was reached that dosing should be on a milligrams/kilogram basis, rather than as an absolute dose, and that doses >0.05 mg/kg are necessary. Although there is no consensus on the optimum preoperative timing of indocyanine green injections, the majority of participants consider it important to administer indocyanine green at least 45 minutes before the procedure to decrease the light intensity of the liver. CONCLUSION: Near-infrared fluorescent cholangiography experts strongly agree on its effectiveness and safety during laparoscopic cholecystectomy and that it should be used routinely, but further research is necessary to establish optimum timing and doses for indocyanine green.

Convergence of life-history phenotypes in a Trinidadian killifish (Rivulus hartii).

Convergent evolution is characterized by the independent evolution of similar phenotypes within similar selective environments. Previous work on Trinidadian killifish, Rivulus hartii, demonstrated repeatable life-history differences across communities that differ in predation intensity. These studies were performed in rivers located on the south slope of Trinidad's Northern Range Mountains. There exists a parallel series of rivers on the north slope of these mountains. As on the south slope, Rivulus is found across a gradient of fish predation. However, the predatory fish species in north-slope rivers are derived from marine families, whereas south-slope rivers contain a predatory fish fauna characteristic of the South American mainland. If predator-induced mortality and the associated indirect effects are the causal factors selecting for life-history patterns in Rivulus, and these are similar in north- and south-slope rivers, then the specific predatory species should be interchangeable and we would expect convergence of life-history phenotypes across slopes. Here, we characterize the life-history phenotypes of Rivulus from north-slope communities by measuring number of eggs, egg weight, reproductive allotment, reproductive tissue weight, and size at maturity. We find similar patterns of life-history divergence across analogous predator communities. Between slopes, minor differences in Rivulus life-history traits exist and one potential cause of these differences is the abundance of Macrobrachium prawns in north-slope rivers.

Experimentally induced life-history evolution in a killifish in response to the introduction of guppies.

Life-history theory predicts that increased predation on juvenile age/size-classes favors delayed maturation and decreased reproductive investment. Although this theory has received correlative support, experimental tests in nature are rare. In 1976 and 1981, guppies (Poecilia reticulata) were transplanted into localities that previously only contained a killifish, Rivulus hartii. This situation presents an opportunity to experimentally test this life-history prediction because guppies prey upon young Rivulus. We evaluated the response to selection in Rivulus by measuring phenotypic and genotypic divergence between introduction and upstream "control" localities that lack guppies. Contrary to expectations, Rivulus from the introduction sites evolved earlier maturation and increased reproductive investment within 25 years. Such evolutionary changes parallel previous investigations on natural communities of Rivulus, but do not comply with predictions of age/size-specific theory. Guppies also caused reduced densities and increased growth rates of Rivulus, which are hypothesized indirect effects of predation. Additional life-history theories show that changes in density and growth can interact with predator-induced mortality to alter the predicted trajectory of evolution. We discuss how these latter frameworks improve the fit between theory and evolution in Rivulus.