Friday, February 17, 2012

Fire in the hole!

It's Crabday again! Hooray! This week I asked Courtney Lyons (from the sea lion attack story) which crab I should look into and she said the

Black-clawed Crab
Lophopanopeus bellus

a beautiful L. bellus from Peiser Island, AK

Courtney actually knew the scientific name and everything! And we all know how important (and impressive) that is. Black-clawed crabs range from the Aleutian Islands up here in Alaska all the way down to California. When researching them, I came across an amazing article about "the explosion of the spermatozoa" of this species! Can you picture it?

(original picture from here)

OK, so it really looks like this:

the top panel (A) shows normal spermatozoa
the bottom panel (B) shows exploding spermatozoa in
calcium chloride (the first one) and distilled water (the last two)

The "explosions" occur in different solutions that cause the spermatozoa to push out, or evert, the primary or secondary vesicles (labelled in panel A as v and v'). So they weren't really exploding on their own, just eviscerating themselves in when they were in solutions with lower osmotic pressures than seawater. And how did the scientist get all the spermatozoa for this experiment? Black-clawed crabs are pretty neat in that they only have one large spermatophore (unlike snow crabs who have many little spermatophores), so all the guy had to do was, "rupture the deferent ducts and the male gametes oozed out in tremendous numbers". Gotta love science from the 1920's!

"do I?"

Possible explosions and 1920's scientists are not the only things these guys have to deal with. Black-clawed crabs are parasitized by those nasty barnacles, rhizocephalans, that hijack the reproductive organs of crabs. Apparently up to 25% of the black-clawed crabs in Sitka are assaulted by them!

Yikes! It makes exploding spermatozoa sound pleasant!
(the rhizocephalan is
Loxothylacus panopaei)

Do you have a crab you'd like to learn about/celebrate in Crabday fashion? Let me know!

Explosive paper:
Fasten, N. 1921. The explosion of the spermatozoa of the crab Lophopanopeus bellus (Stimpson) Rathbun. Biological Bulletin 41: 288-300.

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