Which family is freshwater aquatic, lacks gills, and has natatorial legs for swimming, with mostly herbivorous feeding?

Which family is freshwater aquatic, lacks gills, and has natatorial legs for swimming, with mostly herbivorous feeding?

• A. Nepidae (Waterscorpions)
• B. Corixidae (Water Boatmen)
• C. Notonectidae (Backswimmers)
• D. Belostomatidae (Giant Water Bugs)

Answer: (B)

The question tests matching a freshwater aquatic bug that uses swimming legs and mainly eats plant matter. Water boatmen, belonging to Corixidae, fit this profile. They inhabit ponds and streams and swim with their hind legs that are specifically adapted like oars for propulsion. They are generally herbivorous or detritivorous, feeding on algae and plant material rather than preying on other animals. They lack true gills; instead they breathe through a surface-associated mechanism that uses a thin film of air, often described as a plastron, allowing gas exchange while staying submerged. This combination of freshwater habitat, natatorial hind legs, and predominantly plant-based feeding makes them the best match. The other families listed are primarily predators: waterscorpions are ambush predators with raptorial forelegs, backswimmers swim on their backs and hunt other organisms, and giant water bugs are large predators as well. They do not fit the herbivorous, swimming-leg, gill-less profile as neatly.

The question tests matching a freshwater aquatic bug that uses swimming legs and mainly eats plant matter. Water boatmen, belonging to Corixidae, fit this profile. They inhabit ponds and streams and swim with their hind legs that are specifically adapted like oars for propulsion. They are generally herbivorous or detritivorous, feeding on algae and plant material rather than preying on other animals.

They lack true gills; instead they breathe through a surface-associated mechanism that uses a thin film of air, often described as a plastron, allowing gas exchange while staying submerged. This combination of freshwater habitat, natatorial hind legs, and predominantly plant-based feeding makes them the best match.

The other families listed are primarily predators: waterscorpions are ambush predators with raptorial forelegs, backswimmers swim on their backs and hunt other organisms, and giant water bugs are large predators as well. They do not fit the herbivorous, swimming-leg, gill-less profile as neatly.