Why are flatworms less likely to develop anthelmintic resistance compared to roundworms?

Question

BlackTom AI · Accepted Answer

The question asks why flatworms are less likely to develop anthelmintic resistance compared to roundworms. Each answer option should be evaluated for its relevance to the evolution and spread of drug resistance.
Option 1: Sexually reproduction. This would typically generate diverse offspring through recombination, which can accelerate the appearance and spread of resistance alleles. Therefore, this option does not explain why flatworms would be less prone to resistance; in fact, sexual reproduction can hasten resistance under selective drug pressure in many parasites.
Option 2: Asexual reproduction. A key feature of many flatworms is a tendency toward asexual reproduction (e.g., fragmentation) that produces genetically identical clones. Clonal populations have lower genetic diversity, which reduces the immediate availability of resistance-conferring variants and slows the spread of resistance once a mutation arises. This makes asexual reproduction a plausible reason for the reduced likelihood of resistance development in flatworms.
Option 3: Location in the host animal. While tissue location can affect exposure to drugs and pharmacokinetics, it does not inherently determine the evolutionary potential for resistance. Drug concentration at specific sites may influence selection locally, but it isn’t the core reason why flatworms would resist developing resistance less than roundworms.
Option 4: More life-cycle stages. Having more stages could increase opportunities for genetic mixing or selection at different points, potentially complicating resistance dynamics. However, more stages do not inherently reduce the rate at which resistance alleles arise or fix in a population, so this option does not convincingly explain lower resistance risk.
Option 5: Stricter (more specific) host specificity. Narrow host ranges can limit transmission between hosts and geographic spread, which could dampen the population size and slow selection. Still, this factor mainly affects epidemiology, not the fundamental genetic capacity to develop resistance, so it is not the primary reason flatworms would be less prone to resistance.
Overall, the most directly relevant factor among the options is the mode of reproduction. Asexual reproduction promotes clonal populations with limited genetic diversity, reducing the raw material for resistance to arise and spread, whereas sexual reproduction would typically enhance it. The other factors may influence drug exposure and transmission but do not provide as clear an explanation for reduced resistance risk as the reproductive mode does.

Why are flatworms less likely to develop anthelmintic resistance compared to roundworms?单项选择题

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