Salient Batrachians

Salient Batrachians on the Llano Estacado

Published Oct 19th 2000 in Wildlife

Salient batrachians (SB) lay their eggs in water, where they remain throughout their larvalhood. As adults they develop lungs. At this point, some will stay in or near water, while others may only return there for mating. The larval forms have tails. In some species, eggs are laid singly. Others may lay ribbons of eggs or leave behind large masses of eggs. Some species lay up to 12,000 eggs at each mating. The largest SB does not lay the largest eggs.

After hatching, some SBs cling to any surface they can get close to for several days. Others are active and begin to feed from the moment of birth. Some larvae do not metamorphose for two years -- others change into adult form within 2 weeks of birth. The left front leg appears before the right front because of the breathing spiraculum on the left side of the larvae -- it needs the spiraculum because its gills are covered with skin. Water enters the mouth, passes through the gills and exits through the spiraculum.

Long-lived larvae are able to regrow parts of their tails that may be lost before they reach adulthood. The larval form has a circular mouth with horny, rasp-like edges. The adult does not.

Metamorphosis is hastened by hunger, and delayed by cold or plenty of food. The larvae have lateral line sense organs, like fish, which are not confined to a single row as a fish’s is. The larval head has a network of papilla -- pores at the end of tubules. The adult's internal ears appear to develop from the organs of the lateral line network.

Salient Batrachians are, of course, cold-blooded. They can endure astonishingly cold temperatures -- even freezing does not necessarily cause death. Blood circulation and life processes may stop, but if the blood and protoplasm temperature of the heart does not drop below freezing, the frozen parts recover. Heat and dryness kill SBs quickly.

When handled, many adult SBs urinate a harmless fluid, but it often gets in a predator's eyes and slows them down. Some SBs secrete poison from skin glands when handled. They also have slime glands, which aid the skin’s respiration. Yes, SBs can breathe and drink through their skin.

All male SBs sing. Females make alarm noises, but do not sing. The males possess internal vocal sacs in the throat or at the side of the shoulder. When filled with air, the sacs act as resonators, increasing the volume of sound. Most SBs only have one note, but each species has different rhythms and periods of sounds. Almost all species sing as a chorus.

SBs can change the color of their skin. Pigment cells expand and contract. Bright light, heat and activity contract the cells, while darkness and cold expand them.

Adult SBs only recognize food when it moves. Their vision is clear to a distance of about four feet, but large moving objects further away will stimulate them to flee. Many SBs are positively phototactic, heading toward brightness when the temperatures are between 10 and 30 degrees Celsius. At 30 degrees Celsius, they become negatively phototactic.

Many SBs puff up when scared, and some even play dead. SBs are tamable. They will line up for food at a given time, and take it from the hand. They will also become used to the types of movements that people make and cease to flee. Since they eat only moving prey, however, they can be hard to keep in captivity.

It is as if SBs see only movement, and only certain movements, at that. To humans, this type of sensory system may be difficult to imagine. A simplified explanation for how it works is that there are more nerve cells in the retina than there are fibers leading to the brain. The nerve cells are either excitatory or inhibitory, sort of a yes/no switch like a computer. Each succeeding cell makes a decision whether to fire or not based on different factors. The firing occurs in a dendritic pattern, which constitutes an ever-enlarging field of the total "view."

These fields identify certain shapes -- straight lines, change of contrast, rapid darkening, moving convex forms -- or whatever is most important to the creature. If the shapes do not match, then this set of cells does not fire, and the SB sees nothing.

It seems that an SB sees only abstract shapes, and only when they are moving. I wonder if they learn mazes, and if they do, do they learn them "blind?"

Such eyes do not provide the animal with photographic, true to life images. Only the moving object is seen -- not in its natural shape. If the moving object is approaching the SB, the movement registers. If the object is moving away from the SB, it makes no "sense" and he does not see it. He does not see what does not concern him.

He does not see grass waving in the wind -- for there is no change in contrast. But when a large object moves toward him, the convex forms and changes of contrast register and he flees.

Salient Batrachians can sit still for hours. Does nothing stimulate them? Do they purposefully move -- hoping to find a place where something else is moving? After a rain they move into a pasture. How do the senses of touch and smell work to cause them to leave their proper habitat?

Scent plays at least some role in the lives of SBs. If one large larva is placed with several small ones, the small ones stop feeding, and die. The large larva can be swished around in the water and removed, but the smaller ones will still die.

Salient Batrachians, otherwise known as amphibians, are truly alien.