1) Mosquitofish, freshwater fish with a taste for mosquito larvae, are highly social.

2) When a mosquitofish finds itself alone, its top priority becomes finding others.

3) Agrillo's team also found that mosquitofish can discriminate between numbers up to 16, but only if the ratio between the fish in each shoal was greater than 2:1.

4) He is now testing whether mosquitofish can also distinguish 3 geometric objects from 4, without volumetric cues.

5) To consider this possibility, Agrillo repeated his mosquitofish tests, this time using geometrical shapes of varying size and brightness in place of their shoal-mates.

6) "They fly low over the water and catch surface-feeding fish, such as the mosquitofish, with their claws," Aihartza said.