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Comment by willis936 | Hacker News Reader

I suspect crustacean allergies are actually arthropod allergies. I haven't seen much research on this though.

I suspect arthropods are way too diverse to fall under a single umbrella of "is_allergic". Millions of years of evolution can produce very radically different things for our bodies to worry about. Just the fact that there are no marine insects (completing their lifecycle within an ocean) tells us something about how different their biologies, and therefor allergenic "surface" are. Poison pathways from venom can target completely different systems in a humans.

Almost no marine insects. https://en.wikipedia.org/wiki/Halobates

Re lifecycle:

> The coastal species lay their eggs close to the water surface on rocks, plants, and other structures near the shore, while the oceanic species attach their egg masses on floating objects such as cuttlebone and feathers.

I know of Halobates, they live on top the ocean, not in the ocean. I.e. they have no adaptations to breathe in salt water. There are many other species like this that are restricted to tidal (flies, parasitic wasps, etc.) or costal areas and nowhere else, but again, not under water.

Even their nymphs?

Right, they are not underwater. Hemimetaboulous insects like Holobates look like baby adults when they are born, and undergo multiple "partial" metamorphosis. In this case their wings are almost non-existent. They will go through multiple molts, gradually looking more like the adult. Holometabolous insects (e.g. beetles, wasps, butterflies, flies) are the ones with radically different body plans, often exploiting different niches, the larva could be aquatic, the pupa and adult terrestrial. Some more "basal" insects (dragonflies, mayflies) also have different body-plans at different stages, though instead of "larva" we say "imago", and things like that, for those lineages.

Okay but they both have exoskeletons that have many shared proteins. Allergies are just a protein check.

It's an allergic reaction to tropomyosin, which is found in shellfish and cockroaches.

I recall an anecdote of an entomologist who studied cockroaches in particular claiming to have developed a shellfish allergy from her work.

https://en.wikipedia.org/wiki/Tropomyosin

If this were a sci-fi movie, it would be because the cockroaches were sentient and trying to protect themselves.

People with shellfish allergies are generally advised to avoid eating crickets for this reason.

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