Fish
Shortnose Gar
Lepisosteus platostomus · also called shortnose gars
In a stagnant backwater too low in oxygen for most fish to survive, a shortnose gar rises to the surface, gulps a breath of air directly into a swim bladder that works almost like a lung, and sinks back down as if nothing unusual had happened at all.
Overview
The shortnose gar, Lepisosteus platostomus, is a compact, ancient-lineage fish native to large rivers, lakes, and backwater habitat across central North America. Its air-breathing capability and armour-like ganoid scales connect it to a fish lineage that has changed remarkably little over tens of millions of years.
A fish still using a backup breathing system
Long after most fish evolved to rely on gills alone, the shortnose gar has kept an ancient air-breathing option in reserve, a trait that turns water most other species would abandon into perfectly survivable habitat.
Status
Least Concern — widespread across suitable large river and lake habitat throughout central North America.
Shortnose Gar: common questions
How does the shortnose gar breathe air at the surface?
A shortnose gar has a modified, highly vascularised swim bladder that functions much like a primitive lung, allowing it to gulp air directly at the water's surface and extract oxygen from it, an adaptation that lets the species survive in stagnant or low-oxygen water where most other fish would be unable to persist.
How is the shortnose gar different from the longnose gar?
The shortnose gar has a distinctly shorter, less elongated snout compared with the longnose gar, along with a generally more compact overall body shape, differences reflected directly in each species' common name and useful for telling the two closely related gar species apart at a glance.
Why are gars sometimes called living fossils?
Gars, including the shortnose gar, belong to an ancient fish lineage that has remained relatively unchanged in overall body plan for tens of millions of years, a remarkable degree of evolutionary stability that has earned the group an informal reputation as living fossils among ichthyologists.
What kind of scales does a shortnose gar have?
A shortnose gar is covered in hard, diamond-shaped, non-overlapping scales called ganoid scales, a notably tougher, more armour-like covering than the thin, overlapping scales typical of most other fish species, offering the gar additional physical protection.