Answer:
Large surface area
Explanation:
Animals that have gills for respiration generally have large surface area as compared to the animals with in the same species respiring though lungs.
To absorb maximum oxygen from water, the gill size must be large and in order to accommodate large gills the surface area of animals possessing gill must be large too.
Hence, marine annelids without gills will be smaller than the lungworm species that possesses gils.
