Most of us think that all creepy-crawlies we find in our surroundings are insects.
Even if such creatures got wings and technically don’t belong to the insect class, we still generalize them under the same category.
With that idea in mind, let’s take a look at a curious group of creatures known as isopods. To some of us, this name sounds novel.
But, what exactly are they? And, are isopods part of the insect family?
If you’re curious enough to find out, better continue reading the article below to find out more about them.
Is an Isopod an Insect?
An Isopod is not an insect. It is a crustacean. Isopods have 14 legs while insects have only 6. Insects belong to a different class called Insecta while isopods are in the class Crustacea. Technically, isopods are marine crustaceans and members of the Order Isopoda. Isopods include several families including Aegidae, Amphisopodidae, Ancinidae, Antarcturidae, Antheluridae, Anthuridae, Anuropidae, Arcturidae, Arcturididae, Armadilloidae, Aselloidea, Atlantasellidae, etc. Some famous examples of isopods include lobsters, krill, crabs, and shrimps. Lesser-known examples include pill bugs, woodlice, and sowbugs. Most isopods are tiny animals.
Isopod Anatomy
Isopods, like insects, have a three-part body. They have a head, a thorax, and an abdomen.
The first segment of the isopod’s thorax is bonded to its head. The other sections, called pereon, each have a pair of pereopods (legs).
Pereopods make it easy for isopods to move and capture their prey.
As for an isopod’s abdomen, it comprises five pleonites or parts. The fifth pleonite is then fused with a telson.
Other than that, pleonites also have pleopods, or limbs attached to them. These limbs are useful for breathing and swimming.
Like insects, isopods too have compound eyes and antennae as well as jaws. The first pair of jaws on an isopod’s body is called mandibles. The second, third, and fourth are called maxillae 1 &2 and maxillipeds respectively.
Here are some of the characteristics that all isopods have in common:
- Compound eyes
- Their eyes aren’t raised on a stalk
- Two antenna pairs
- Four jaw pairs
- Seven body segments
- A pair of limbs for each body segment, or pereon
- All are aquatic or semi-aquatic
- Biphasic molting
Isopod Habitats
Isopods comprise thousands of species and they are the most ubiquitous crustaceans. You will find them nearly everywhere – even in the desert.
As long as they can find some moisture, they can survive.
Isopods breathe through special gill-like organs. This means that they always need moisture, even when they are not necessarily in water.
Not only that, they are also found in cool, damp places like under rocks, under wet leaves, beneath rotting wood, around water ponds, in moist or muddy soil, and decaying vegetation.
They only come out to forage at night as it is cooler and not too dry.
You are most likely to come across a marine isopod along the bottom of the sea, in shallow waters, or along the shoreline.
But, with those said, you’ll find that freshwater isopods are a minority. Aside from that, freshwater isopods also tend to be smaller than their marine counterparts.
What Isopods Feed On
Isopods subsist as detritivores, micro-grazers, parasites, and micro predators. Isopod mandibles look different depending on their diet.
Herbivore mandibles are designed to grind. Carnivorous isopods have mandibles that function as blades.
Many sea isopods are scavengers who consume dead fish, whales, and squid. Some catch slower sea animals like sea sponges, nematodes, and cucumbers.
Some sea isopods are also parasitic, attaching themselves to larger fish. Watch out for them in aquariums. Some are opportunistic, attacking fish caught in trawls.
On land, isopods help to break down the soil by feeding on dead wood, linches, leaves, and moss.
They even break down dead insects and stones because their bodies need so much calcium for nourishment. The majority of land isopods feed on plants.
Some land isopods will consume dead animal matter. Larger sea isopods have an incredible survival skill – they can last a long time in between meals.
Differences between Isopods and Insects
As mentioned earlier, isopods are crustaceans. They are a class under the phylum Arthropoda. The other classes are the Arachnida, Myriapoda, and Insecta or insects.
Since they’re crustaceans, they are entirely different from insects.
More scientifically speaking, crustaceans belong to the phylum Arthropoda and subphylum Crustacea.
You probably already know that lobsters, crabs, and shrimps belong under the subphylum Crustacea.
But, aside from these popular names, there are thousands of lesser-known crustaceans out there that you still need to discover.
With that said, take a look at American lobsters.
American lobsters make up some of the largest crustaceans. They are part of an order that includes 10,000 species. These lobsters can weigh up to 20 kilograms or 44 pounds.
Another creature that belongs to this diverse subphylum are the water fleas. Probably unknow to you, water fleas are considered the smallest crustaceans in the world, measuring only about 0.25 mm long.
But, one thing you’ve probably noticed with most crustaceans is that they love to live in seawater, inland brines, and freshwater.
While other crustaceans prefer living in aquatic environments, others prefer to stay in sand, mud, and rock;.
Some even take refuge in seaweed fronds. They can even live in the icy environment of the Arctic.
So, technically, crustaceans can live both in land and in water. Take for example the crabs.
Crabs can occupy both land and water. Hence, they’re known as amphibious isopods. Some crustaceans even run and climb trees.
But even the crabs that spend most of their lives on land still go to the water to hatch their larvae.
On the other hand, insects have three defining features that crustaceans don’t have: an exoskeleton, three or more pairs of legs, and segmented bodies.
Unlike isopods, insects live everywhere on earth. But, of course, you’d probably least find insects living on active volcanoes or the frozen poles due to the temperature extremes in those areas.
Frequently Asked Questions about Isopods
What is the largest land isopod?
Porcellio Magnificus is the largest if you judge by length. It grows up to two inches long and digests fecal matter as well as decaying leaves.
Is a cockroach an isopod?
It may not seem like it, but cockroaches have more in common with termites than the deep-sea crustaceans they so resemble. However, cockroaches are insects in the same order as termites, Blattodea. But, the so-called “sea cockroaches” are part of the crustacean family.
How do isopods reproduce?
Isopods are similar to other crustaceans in the way they reproduce. They lay eggs which are smaller replicas of adult isopods. They molt twice, one half first and then the other. Mature female isopods have pouches where the young spend their early days in safety.