Are there insects in the sea?

[njtt]

I mean that live there, and have their full life cycle underwater.

It occurred to me that, although there are insects all over the place on land, and there are lots of other sorts or arthropods that live in the sea, I do not recall ever hearing of a submarine insect. I know there are some insects, like caddis flies, whose larvae live underwater, but even there, the adults fly in the air, and I think the water the larvae live in is fresh. There are also, I know, such things as water spiders, but, again, I think it is fresh water they live in, and they are not insects anyway.

Even if insects first evolved on land (I am not sure if that is true, but I assume so), you would think that by now some of them wold have recolonized the oceans, as mammals did with whales, seals, etc, and reptiles with icthyosaurs, turtles, saltwater crocodiles etc. I feel there must be submarine insects, but I have never heard of any.

[wevets]

There are indeed marine insects, but so very few that even many entomologists don’t know they exist.

There are tons and tons of marine arthropods, such as crustaceans, that probably fill many niches that would otherwise be available to insects.

[Shagnasty]

There aren’t any insects that live under water their whole lives. This short article gives the reasons why that is:

Friday 5: Five Reasons There Are Few Marine Insects

The closest that I know of are oceanic water striders (genus Halobates). They are some of the only insects that float on the surface of the ocean far from land. There are other insects that thrive in salt marshes and near the shore but very few that have a habitat in the open ocean.

Halobates

[njtt]

@wevets

There are indeed marine insects, but so very few that even many entomologists don’t know they exist.

There are tons and tons of marine arthropods, such as crustaceans, that probably fill many niches that would otherwise be available to insects.

Hmm, the “sea skaters” that that article talks about seem to live on the ocean surface, not under it. Interesting, but not quite what I had in mind.

It does seem to say there are some insects in the sea, but relatively few species compared to land insects. If that is so, the question arises as to why. Why so few insects in teh sea, but so many other types of arthropods, and why, by comparison, so many insects and types of insects on land, and by comparison, so few other arthropods. (I know there are lots of non-insect land arthropods, but compared to the vast numbers and diversity of actual insects the numbers - either of individuals or species - do not seen to be very impressive.)

[Shagnasty]

@njtt

Hmm, the “sea skaters” that that article talks about seem to live on the ocean surface, not under it. Interesting, but not quite what I had in mind.

It does seem to say there are some insects in the sea, but relatively few species compared to land insects. If that is so, the question arises as to why. Why so few insects in teh sea, but so many other types of arthropods, and why, by comparison, so many insects and types of insects on land, and by comparison, so few other arthropods. (I know there are lots of non-insect land arthropods, but compared to the vast numbers and diversity of actual insects the numbers - either of individuals or species - do not seen to be very impressive.)

The first article that I linked covers this. Insects developed on land and have many traits that make it hard for them to survive in deeper, unprotected water for any length of time (including a respiratory system that requires oxygen or they will eventually drown). The main reason that they have never been able to adapt to an underwater marine environment is that they have never had the chance to. Did you ever notice that bait stores sell live insects and even artificial ones as some of the most common fish bait? As soon as they start getting comfortable in the water, the fish and other marine animals introduce them to the concept of the food chain.

[njtt]

@Shagnasty

The first article that I linked covers this. Insects developed on land and have many traits that make it hard for them to survive in deeper, unprotected water for any length of time (including a respiratory system that requires oxygen or they will eventually drown). The main reason that they have never been able to adapt to an underwater marine environment is that they have never had the chance to. Did you ever notice that bait stores sell live insects and even artificial ones as some of the most common fish bait? As soon as they start getting comfortable in the water, the fish and other marine animals introduce them to the concept of the food chain.

Well, yes, you posted while I was composing my second post, and your link does address my follow-up question. The “predation” answer does not seem very satisfying to me, however. Surely that point applies to any type of creature attempting to colonize a new type of environment, but some of them clearly manage it. As I noted, reptiles and especially mammals seem to have managed to recolonize the sea fairly well (and they are like insects in having a respiratory system originally adapted to use in air).

[Shagnasty]

@njtt

Well, yes, you posted while I was composing my second post, and your link does address my follow-up question. The “predation” answer does not seem very satisfying to me, however. Surely that point applies to any type of creature attempting to colonize a new type of environment, but some of them clearly manage it. As I noted, reptiles and especially mammals seem to have managed to recolonize the sea fairly well (and they are like insects in having a respiratory system originally adapted to use in air).

I am not going to pretend to have all of the nuanced answers to these specific objections. However, I don’t think sea mammals and reptiles are directly analogous to insects. Both of those are much, much bigger for one so that automatically limits the number of potential predators. Insects are very small especially during some stages of their life cycle. It is very different when you are a proto-whale or walrus and just have to deal with say, sharks, than if you are a insect that can be eaten in a single gulp by even a small fish and your larvae can be wiped out by some wandering minnows.

Insects are going to be at the bottom of the food chain unlike reptiles and mammals. For them to be able to thrive in the open ocean, they would an extremely aggressive reproductive strategy like krill in order to keep a sustainable population.

[John_Mace]

So then you start out with the adult stage as marine, and the larval stage as terrestrial. Then you go “all in” at some point. Insect larvae or no less vulnerable than many fish eggs.

Or… they revert to something many of their crustacean cousins do (protect the eggs with their bodies). The fact that insects have not colonized the water does imply there is something making it very difficult to do so, but I doubt it’s because of the vulnerability of their larvae.

[Shagnasty]

@John_Mace

So then you start out with the adult stage as marine, and the larval stage as terrestrial. Then you go “all in” at some point. Insect larvae or no less vulnerable than many fish eggs.

Or… they revert to something many of their crustacean cousins do (protect the eggs with their bodies). The fact that insects have not colonized the water does imply there is something making it very difficult to do so, but I doubt it’s because of the vulnerability of their larvae.

Maybe it is just one of those overlooked ‘intelligent design’ features then :). Can you imagine what it would be like in a world where you hit the Caribbean on your paddle board but have to apply the aquatic equivalent of OFF along with sunscreen all over you first to keep the giant sea cockroaches and ocean mosquitos from attacking you as soon as you get into the water? :eek: No thanks, I will take the small risk of a Jaws attack over that any day. Thank goodness we have a safe refuge from those bastards.