New discovery: Plaice are spotted (on the inside)

Have you seen a spotted plaice? Probably. However, marine biologist
Helen Nilsson Sköld at the University of Gothenburg is the first
person to research the spotted insides of plaice.

Many species of animal have skin or fur with intricate pigmentation
patterns, which they use for camouflage, communication, regulation of
body heat and protection against the sun. A study conducted by
researchers at the Department of Marine Ecology at the University of
Gothenburg has found that several species of fish also have
highly-coloured internal pigmentation.

Adapts to its surroundings

In a study published in Pigment Cell & Melanoma Research, marine
biologist Helen Nilsson Sköld and her colleagues show that the number
of internal pigment cells has a direct link to the degree of transparency of the fish.
Transparent fish can change colour using their internal pigment cells,
thus enhancing external skin pigmentation and their ability to adapt
to the background colours of their surroundings.

Bewildering display of colour

Mysteriously, plaice also have a high number of internal pigment cells
in, for instance, the ear and brain and around their internal organs.
Plaice however are not particularly transparent. The internal pigment
cells of
this fish
cannot be seen easily from the outside, which makes its internal
display of colour somewhat bewildering.

Unknown functions

According to Helen Nilsson Sköld and her colleagues, the fact that
less transparent fish also have this internal pigmentation indicates
that the pigment cells may have other, as yet unknown, functions.

“We believe that the internal pigment cells either function as vessels
for excess pigment or perhaps provide various forms of protection or
contribute to the immune system. We hope to investigate this subject
further,” says Helen Nilsson Sköld.