Morphometric Response of Galaxias maculatus (Jenyns) to Lake Colonization in Chile

Body and head shape in fish responds to environmental factors such as
water flow rate, food sources, and niche availability. However, the way in
which fish respond to these environmental factors varies. In Central
Chile, multiple river and lake systems along the coast provide an ideal
study site to investigate these types of shape changes. We use geometric
morphometrics to characterize shape differences in Galaxias maculatus
(Jenyns) between river and lake populations. Lake fish converge on a shape
with a more fusiform body, narrower head, and larger eyes, while river
fish have a more robust body, rounder head, and smaller eyes. These shape
changes are consistent with a shift to zooplanktivorous foraging in lakes,
as evidenced in other systems. Unlike some fish species that develop
polymorphisms in body shape after colonization (e.g., benthic and limnetic
forms), G. maculatus in lakes exhibit a monomorphic limnetic form.