A Little Pike of Peculiar Habits
Say "pike" to Alaskans, and they're likely to think of a big swift fish easily found--but not so easily caught--in northern lakes. Say "pike" to Australians, and they're likely to think only of ancient weaponry--unless they pay keen attention to ichthyological developments Down Under. A member of the pike family of fishes has turned up in Australia's southwestern corner, according to "Geo," a quarterly journal reminiscent of "National Geographic" but devoted to the region extending from southeast Asia through the South Pacific islands.
The relationship isn't obvious. A good-sized northern pike may be the size of a big man's leg; the Australian variety wouldn't exceed his finger. It's slow moving, seems to lack its northern cousin's ferocity, and even appears to blush.
The fish has had plenty of time to develop some peculiarities. The last time the northern and southern branches of the pike clan, technically the Esocoidei, could have hung out together is earlier than 200 million years ago. By then the supercontinent of Pangaea had pretty well come apart, severing any connection that a protopike could traverse between what eventually would become Australia and North America-Eurasia.
Perhaps because no other member of the Esocoidei has been found in the Southern Hemisphere, this little fish was assigned to another group when it was first described in scientific literature. (That was only in 1961; Australia, like Alaska, has a lot of territory but few scientists.) Yet the more thoroughly researchers studied this fish, the more convinced they became that some of its structural features inescapably assigned it to the Esocoidei.
Pike kin it may be, but pikelike it isn't. It isn't even very fishlike. Its common name is salamander fish. It is roughly eel-shaped, but has a neck and can breathe air.
When their home creeks dry up in Western Australia's hot and rainless summers, salamander fish hunker down under streambed debris or rocks. If they can't find an adequate shelter, they dig one, burrowing straight down into the sandy bottoms of pools. When its tail is just below the surface, a salamander fish makes a sharp U-turn with the help of its flexible neck. It digs back upward, front half nearly parallel to back half, until its head is alongside its tail.
Hunkered down or dug in, a salamander fish surrounds itself with a mucus sheath that helps retain moisture. Its metabolism slows, and it goes into aestivation, the hot-weather parallel to hibernation. The scant energy it needs to stay alive for several weeks or even several months in this comatose condition comes from a keel of fat laid down along its belly during the good wet times.
The oxygen it needs comes from the atmosphere. Salamander fish have well-developed internal air sacs lying near their gills. These sacs are packed with a network of fine blood vessels that offer a large surface area for gas exchange. (That is, the air-sac structures
operate much like lungs, efficiently and quickly exchanging carbon dioxide in the bloodstream with oxygen from the outside air.) The blood vessels are what give the little fish its characteristic flushed-cheek look.
The rosy cheeks can be especially striking when the fish ends its aestivation and wriggles free of its burrow. That shift back to wakefulness may be nearly the fastest thing a normally slow-moving salamander fish does. It's up and swimming within a minute after water again covers its hiding place.
The "Geo" article said nothing about the edibility of salamander fish, and offered only oblique and rather negative comments about its fightin' style: "occupies its restricted habitat in a state of semi-torpor, generally lying low, propped on its elegant pelvic fins." Not what we expect here from northern pike. Ah well; every family has its misfits.
