Mitochondrial plasticity in brachiopod (Liothyrella spp.) smooth adductor muscle as a result of season and latitude

Habitat temperature and mitochondrial volume
density (Vv(mt,mf)) are negatively correlated in fishes, while seasonal acclimatization may increase Vv(mt,mf) or the
surface density of the mitochondrial cristae (Sv(im,mt)). The effect of temperature on invertebrate mitochondria is
essentially unknown. A comparison of two articulate brachiopod species, Liothyrella uva collected from Rothera
Station, Antarctica in summer 2007, and Liothyrella
neozelanica collected from Fiordland, New Zealand in
winter 2007 and summer 2008, revealed a higher Vv(mt,mf)
in the Antarctic brachiopod. The Sv(im,mt) was, however,
significantly lower, indicating the Antarctic brachiopods
have more, less reactive mitochondria. L. uva, from the
colder environment, had larger adductor muscles in both
absolute and relative terms than the temperate L. neozelanica.
Furthermore, a seasonal comparison (winter vs.
summer) in L. neozelanica showed that the absolute and
relative size of the adductor increased in winter, Vv(mt,mf)
was unchanged, and Sv(im,mt) was significantly increased.
Thus, seasonal acclimatization to the cold resulted in the
same number of more reactive mitochondria. L. neozelanica
was clearly able to adapt to seasonal changes using a
different mechanism, i.e. primarily through regulation of
cristae surface area as opposed to mitochondrial volume
density. Furthermore, given the evolutionary age of these
living fossils (i.e. approximately 550 million years), this
suggests that mitochondrial plasticity has roots extending
far back into evolutionary history.