Volume 39, Number 1,
October 1992:
Springtails

Text-only version

ABOUT THIS ISSUE
- about KSN
- about the author

IN THIS ISSUE
- part 1
- part 2
- part 3
- part 4
- part 5
- part 6
- part 7
- part 8
- part 9
- part 10

SLIDESHOW
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Springtails
by Kenneth Christiansen

Many species of Collembola can only live in the intertidal zone at the seashore. During high tide they hide under stones, in rock crevices or any other place, enclosed in air droplets formed as their water repellent cuticle contacts the water. During low tide they come out to feed. If you saw specimens on the east coast of the United States or in Europe, they were probably members of the genus Anurida (Figure 4) since these are among the most abundant sea shore Collembola. Because they lack the ability to move on water, they are frequently temporarily trapped on small tide pools. Many other species occur in the same habitat or in the interstitial space in shoreline or littoral sand. This unique habitat, formed in the shore line sand where the freshwater seeping down form land meets the salt water seeping in from the ocean, is inhabited by many species of Collembola. The fact that most of these species are restricted to this zone suggests a high degree of physiological specialization.

Springtails are all wingless arthropods which, similar to insects, have six legs but are not closely related to them. Even the unspecialized types show a variety of body shapes and three basic unspecialized types are shown on the cover. While Collembola vary greatly in most features, all are wingless and the primitive forms generally have most of the characteristic features shown in Figure 5. One of the most remarkable of these is the peculiar jumping apparatus, called the furcula, near the end of the abdomen. It is this structure which gives Collembola their common name of "Springtails." This structure is normally kept tucked under the body, held in place by a sort of latch mechanism called the tenaculum.When the latch is released, the furcula snaps back with great force, driving the animal up to 100 times its body length. This usually allows the animal to escape any attacker, but there is a problem. The Collembolan has absolutely no control over which way it goes or where it is going to come down. Imagine that you are jumping the height of a two story house and up to a half a block in distance but have no control over where you will land! Fortunately Collembola are probably not given to anxiety attacks. Many specialized types of Collembola such as the Anurida (Figure 4) have, through evolution, lost the furcula and all jumping ability with it.

An even more unusual feature is the ventral tube. This structure is present on all Collembola and in no other animals. Its bottom is always wet and usually sticky and this in some forms allows the animals to stick to any smooth or wet surface, even when upside down. Its thin wet surface also serves as a respiratory organ since Collembola generally lack any other specialized organs for this purpose and largely obtain oxygen through their thin cuticle or skin. Probably the most important function of the ventral tube is drinking. A very tiny capillary tube is drinking. A very tiny capillary tube runs from the bottom of the ventral tube to the mouth and when the animals which to drink, they stick the tube into a drop of water and suck the water off the tope of this tube - sort of like carrying your own soda-straw with you everywhere.

Springtails are more or less well covered by simple to very complicated hairs or setae of many sorts and, in some groups, scales. A variety of these setae is shown in Figure 6. In addition some groups have heavy spines; when they occur at the end of the abdomen they are called anal horns (see in Figure 5).