When we call someone “spineless” it's considered an insult that implies weakness and lack of courage. We’re suggesting the person has no backbone. But invertebrates – spineless creatures – are actually strong and awesome. Because life evolved in the oceans marine invertebrates are the backbone of life on earth. They make up more than 98 percent of all beings.
Beneath the ocean waves, hidden from view, there's a spectacular variety of invertebrates. These spineless creatures have exceptional shapes, patterns, textures, and colors — each tailored to its own special function. Quirky, quivery, spindly, spiky, sticky, stretchy, squishy, slithery, squirmy, prickly, bumpy, bubbly, and fluttery, marine invertebrates appear surreal. The more I learn about them, the more fascinated I become.
Some invertebrates are anchored to one spot. San Juan Stalked Jellyfish live attached to seaweed or grass. Eight arms radiate from a central mouth, each arm bearing an explosion of tentacles. Loaded with stinging cells, the pinhead tips of the tentacles capture tiny crustaceans for food.
Invertebrates that move have varied ways of getting around. These glassy orbs belong to a group of animals called Comb Jellies, similar to jellyfish. Unlike most jellyfish, which swim by the muscular pulsing of their bells, Comb Jellies get around with hundreds of little paddles called combs. Eight rows of the iridescent combs run from one pole to the other. The combs work together to create a unique form of movement.
We can thank invertebrates for our sense perception. What do Nudibranchs experience when they extend their rhinophores — that pair of finely grooved antennae protruding from their heads? Rhinophores can sniff, touch, and taste. Their sense organs detect chemical molecules dissolved in seawater. They depend on these appendages to find food. In one species, the rhinophores can even detect pheromones.
Lest you think all marine invertebrates are tiny, the Pacific Giant Octopus is a member of one of the largest octopus species in the world growing to weigh up to 99 pounds or more during its three-to-five year life span. Its long arms and excellent crawling ability make it a force to be reckoned with on the ocean floor. The eyes of octopuses are a wonder to scientists and evolutionary biologists. They have "camera-type eyes" meaning that cephalopods (another name for octopuses) can use physical tricks like: changing the depth of their eyeballs, or altering the distance between the lens and the retina to focus different wavelengths of light on the retina. Just this year scientists learned that their U-shaped pupils may allow them to distinguish colors differently from any other animals we know.
Hermit crabs recycle! They are a good example of evolutionary adaptation. Shells can last centuries after their owners have died. Hermit Crabs borrow the dead skeletons of snails and carry them around as protection. When a shell becomes too small for the growing crab, it moves to a larger one. Competition can be quite fierce for shells just the right shape and size and it’s not unusual for a hermit crab to attack another crab whose shell it covets.
We evolved from invertebrates. We can thank them for a central nervous system that gives us our sensory relationship to the world — the ability to see, hear, smell, and feel. Spineless creatures are also responsible for developing a broad variety of capabilities essential to our survival — ways of feeding, moving, breeding, and exchanging gases.
All this to say that if anyone calls you spineless it's a compliment!
Source: Susan Middleton, author of Portraits of Marine Invertebrates.