Biologists of today must, one sup­poses, be much cleverer than those of for­mer generations. At any rate there are no simple topics or uncomplicated organisms or situations to deal with anymore. Nowhere is this more apparent than in re­cent discoveries concerning cubozoans or box jellyfish.

It does not take a specialist to realize that jellyfish are not dainty delights of the deep. Although they may be beautiful in appearance, jellyfish are predators armed with uniquely nasty stinging cells. Apart from these special cells however, jellyfish initially were considered to be simple in structure. The textbook story was that these organisms were "primitive" animals with few kinds of cells organized merely into tissues. The cells of these tissues appeared to cope so well with multitasking that there was no need for specialized organs.

More than brainless blobs⤒🔗

Believe it or not, but jellyfish are said to be composed basically of two layers of skin cells with a jellylike layer separating the inner and outer tissues. The most com­mon type of cell in these skin layers are those equipped with muscle-like fibres. These muscle-like cell parts, when acting together with those from other cells, enable the organism to move. In addition, some cells are shed from the outer skin layer into the jelly material. These cells then or­ganize themselves loosely into a net of nerve cells. Transmission of signals pro­ceeds in two directions, unlike our nerves which send messages in one direction only. There is no brain.

Despite this apparently simple struc­ture, these organisms are not simple blobs. Jellyfish consist mainly of a bell or umbrella shaped body with tentacles hanging down from the bell. On the underside there is an opening into an interior digestive cavity. The mouth serves both to take in food and to eject the waste. Once the food is some­what broken up in the gravity, individual cells in the skin engulf particles for further digestion. Most jellyfish catch their food by chance encounters with suitable speci­mens. It is the case of wrong place and wrong time for the victims.

All jellyfish are armed with unique stinging cells called nematocysts. Inside each one of these amazingly specialized skin cells, a hollow sac forms. Each microscopic sac contains a lengthy hollow tube which is turned inside out (see simplified dia­gram). Inside this tube, along a spirally pleated wall, are fearsome hooks. The tube is also armed with a potent poison, always a protein and usually a paralyzing nerve toxin. When a tiny trigger on the cell is stimulated, the lid of the sac pops off and the tube emerges at fantastically high ve­locity. As the tube turns itself right side out, it revolves as the spiral pleats unfold.

At each turn, a new ring of hooks springs forward and then flicks backward. So strong and so fast is the process that the tube is able to penetrate such surfaces as crustacean exoskeletons, fish scales and human skin. Normally many nematocysts release at the same time.

Fearsome man-of-war←⤒🔗

Jellyfish have long received a bad press as far as humans are concerned, initially because of the Portuguese man-of-war. This fearsome creature has a large float visible above water level. The tentacles however can extend up to 9 meters from a tiny 12 cm long central body. With so small a semi­transparent floating structure, so far away, most victims are entirely ignorant of the ^-presence of this predator. After catching even a relatively large fish, the tentacles quickly contract to a mere fraction of their original length. This is a most remarkable capability which most organisms cannot even begin to match.

One expert com­mented, "Obviously the neuromuscular arrangements of tentacles capable of a hun­dredfold contraction must be peculiar."

It is evident that the mechanism by which this happens is not as yet understood.

Cubic killers←⤒🔗

In Australia, since the late 1800s, records have been kept of human deaths from jellyfish. Until 1943, all were attrib­uted to the Portuguese man-of-war. It was then that biologists began to turn their at­tention to cubozoans or box jellyfish. The first confirmed death from a cubozoan was in 1955 at Cardwell, about 150 km south of Cairns on the Queensland coast. During the next 45 years 59 more deaths were attrib­uted to these jellyfish. So potent is the toxin, that victims often die within five minutes. Such notoriety has certainly fo­cused attention on these organisms, but biologists have also become interested in other amazing features of these organisms.

Cubozoans or box jellyfish derive their name from their unusual shape. Unlike most jellyfish which have a round bell shape, cubozoans are square when viewed from above. There are about twenty species to be found in tropical seas around the world, but the sea wasp Chironex fleckeri of northern Australian waters is among the deadliest creatures known. During late Oc­tober to early June each year, it infests the shallow coastal area from Gladstone in Queensland to Exmouth in Western Aus­tralia. A large adult may reach 35 cm in di­ameter with as many as 15 tentacles, each 3 m long, extending from each corner of the bell. The shape is not the only noticeable thing about cubozoans. Unlike most jelly­fish which merely happen upon their vic­tims, cubozoans actively pursue their prey.

How they do that is something that experts have wondered about. Recently some scientists set out to find the answer. What they found has astonished everyone.

Box jellyfish are somewhat more com­plicated than other similar organisms. The tentacles at the corners are attached to special muscular pads. These push a victim toward the mouth once the tentacles have carried out their contracting feat to reel in the victim. This process may take only a minute. Once the food approaches the bell, a tube on the underside reaches out to­ward the victim. The mouth at the end of the tube expands and the food is then shoved up the tube into the stomach. This is the end result of the hunt.

However, the pursuit of the victim is the really exciting event. By contracting muscles in the bell, as well as by contract­ing the rim of the bell to force water out faster, Chironex has been observed to cruise as fast as 2 m per second! More typically they move at 1 m per five to ten seconds. These creatures avoid crashing into objects like mangrove roots in their favorite habi­tat. They can avoid capture and they pursue their victims much the way predatory fish do. It is apparent to everyone that these jellyfish must be able to see. Recent studies have shown that this is indeed the case, but the fresh insights have led to even more puzzling questions.

Seeing without a brain←⤒🔗

Biologists have long known about spe­cial sense organs near the margins of ordi­nary jellyfish. Each organ contains two sensory pits to perceive chemical stimuli (like our sense of smell), one spot sensitive to light, two structures sensitive to touch, and one body which indicates orientation (upside down, sideways etc.) Biologists have long known that ordinary jellyfish only swim when they have at least one of these organs functioning. If all are de­stroyed, the jellyfish stops swimming and dies. Similarly box jellyfish have sensory or­gans, but theirs are much fancier

Box jellyfish have four sensory organs, each in a niche near the bottom of the bell. The organ is a small club like structure at­tached by a stalk to the bell proper. Inside the club there are four pigment filled pits to perceive light. Two of the pits face out­ward (horizontally) from the organism and two face upward (vertically). In addi­tion there are two much larger eyes. The interesting thing about the two larger eyes, one of which faces upward and the other outward, is that these are camera style eyes like our eyes. The questions that arise from this fact are: why do these jelly fish have eyes like animals with backbones (vertebrates), what do these jellyfish see, and how are they able to respond without a brain?

The tiny eyes of box jellyfish are in­deed real camera-type eyes and they have all the appropriate components: cornea, lens, retina, a pigment layer and an iris. All parts function too. In the lower eye, even the pupil contracts in response to bright light. This choice of eye design re­veals quite a paradox.

As Simon Conway Morris says in his book Life's Solution: "at first sight the sophistication of the cubozoan eyes, which typically total eight around the margin of the swimming bell, is quite surprising."

p. 154

One might re­mark that this is typical British under­statement. The surprise is that supposedly simple organisms possess such fancy eyes.

Most animals without backbones (inverte­brates) have compound eyes (as in insects, for example). However there are a few in­vertebrates such as squid and octopus, fa­mous for their intelligence, which enjoy camera style eyes.

Dr Morris thus declares that "It is beginning to look as if active, fast moving, and at least in some cases in­telligent animals opt for the camera-eye."

p. 158

How does any creature opt for any feature of its anatomy, one wonders. At any rate Dr. Morris concludes that "cam­era eyes are not only different from com­pound eyes; they are better" (p. 160). So we have a supposedly primitive organism with the best type of eye. The wonder of it is that cubozoans have no obvious brain to in­terpret messages from their eyes.

The question still arises as to precisely what the box jellyfish eyes perceive. The May 12, 2005 issue of the scientific journal Nature, published a report on such a study. A team of scientists studied the optics of the lens from the cubozoan eye. They al­ready knew that the protein which forms transparent crystals in the lens of the jelly­fish, is unlike the proteins which make up lenses in other eyes of similar design. With a unique composition, the jellyfish lens could not be evolutionarily related to or­ganisms with similar type eyes. Thus the jellyfish eye had a separate origin. On this issue the scientists muse:

Making good lenses seems to be a demanding task, because only a few animal phyla have ac­complished it.

Nature p. 202

Great eyes, but they need glasses?←⤒🔗

How is it then, that the jellyfish man­aged it? That issue, however, was just the beginning of the paradoxes. What the team discovered is that the jellyfish lenses are so well constructed that the focus is very sharp. Thus they declare, "Fresh isolated lenses are able to form good images irrespective of lens orientation" (p. 202). A commentator, in the same issue of Nature, points out that the lens design involves highly sophisticated optics, conforming exactly to optical theory. It is amazing how clever those jellyfish must be.

There is however another remarkable feature of the cubozoan eye. The retina, which receives the image from the lens, is much too close to receive a sharp image. These jellyfish are like humans who need glasses. The commentator points out that this situation leads to "a loss of fine visual detail that the lens is able to provide." (p. 159) Now the questions become really pressing the commentator asks "But what are the jellyfish's eyes designed for?"

The scientists conclude that the jelly­fish may manage better with a blurry focus or large objects rather than precise images of irrelevant small objects in the environ­ment. From an evolutionary point of view, it seems incredible that so fancy a lens would arise when something less precise would be adequate. How would natural selection se­lect for a sharp focus when that wasn't be­ing used or needed. Surely in this case it is obvious that we are dealing here with in­telligent choice rather than evolutionary processes. To the Christian, it is apparent that God conferred sophisticated eyesight on a "simple" organism just because it pleased Him to do so.

Since these creatures lack a brain, sci­entists wonder how they see. After all, it is obvious that cubozoans do perceive and they do respond, we just don't know how. In actual fact, the idea that these creatures are primitive, is no doubt an outmoded idea. They live as they were designed to live, with talents and design features beyond our understanding. Indeed, there are no simple stories in biology any more. We should feel humble at the creative finesse, which we can never hope to duplicate, that we see displayed in nature.