D. tenebrosus MM post-ultimate molt

[Sergic]

I found this MM D. tenebrosus and brought him home intending to show him to a couple friends and then release him. Yesterday, he had a post-ultimate molt. He survived, but has fairly mangled legs and is very weak.

Below are images of just him, and him next to his molt. I've put him in a makeshift ICU, but things don't look good for him.

 

[Ungoliant]

I found this MM D. tenebrosus and brought him home intending to show him to a couple friends and then release him. Yesterday, he had a post-ultimate molt. He survived, but has fairly mangled legs and is very weak.

Are you sure that's really a post-ultimate molt? The palps on the exuviae look penultimate (swollen but undeveloped).

 

[spotropaicsav]

Perhaps the moisture in the ICU set up is not helping him?

 

[Sergic]

Are you sure that's really a post-ultimate molt? The palps on the exuviae look penultimate (swollen but undeveloped).

That could definitely be the case. When I caught him, I used an identification book to verify he was D. tenebrosus. His palps looked nearly identical to the palps on the male image in the book, which I assumed was a mature male. Could very well have been a bad assumption, though.

 

[Sergic]

Perhaps the moisture in the ICU set up is not helping him?

His condition has improved since moving him to the ICU, but he's hanging out on the side, so it's likely time to take him out of the ICU.

 

[Richard McJimsey]

Doesn't look like a post ultimate molt, IMO. Many species of true spiders will have significant amounts of palpal swelling prior to becoming mature, and based on the exuviae, I think that's the case here.

 

[Sergic]

Doesn't look like a post ultimate molt, IMO. Many species of true spiders will have significant amounts of palpal swelling prior to becoming mature, and based on the exuviae, I think that's the case here.

Good to know. Most of my experience with ultimate males has been with tarantulas, and they are quite obvious.

 

[Ungoliant]

That could definitely be the case. When I caught him, I used an identification book to verify he was D. tenebrosus. His palps looked nearly identical to the palps on the male image in the book, which I assumed was a mature male. Could very well have been a bad assumption, though.

Many male true spiders have swollen palps during their penultimate instar (one molt before sexual maturity). These palps look swollen and translucent, without the sclerotized details you see in mature palps.

Here is the palp of a mature male Dolomedes tenebrosus (click thumbnail for link to original):



I couldn't find a good image of a penultimate male Dolomedes on BugGuide, but here is a photo I took of a penultimate male Eriophora ravilla. You can see how his palps look swollen and translucent, lacking definition.


For comparison, here is the palp of a mature male Eriophora ravilla (click thumbnail for link to original):

 

[Sergic]

Many male true spiders have swollen palps during their penultimate instar (one molt before sexual maturity). These palps look swollen and translucent, without the sclerotized details you see in mature palps.

Here is the palp of a mature male Dolomedes tenebrosus (click thumbnail for link to original):



I couldn't find a good image of a penultimate male Dolomedes on BugGuide, but here is a photo I took of a penultimate male Eriophora ravilla. You can see how his palps look swollen and translucent, lacking definition.


For comparison, here is the palp of a mature male Eriophora ravilla (click thumbnail for link to original):

Thanks! Now I wonder how many "mature male" spiders I've encountered that were not quite mature.

 

[Ungoliant]

I couldn't find a good image of a penultimate male Dolomedes on BugGuide

As luck would have it, I found a penultimate male whitebanded fishing spider (Dolomedes albineus) in my yard tonight.

Penultimate Male Dolomedes albineus

• Ungoliant
• Jul 15, 2017
• albineus dolomedes dolomedes albineus fishing spider penultimate male pisauridae whitebanded fishing spider

I found this immature male whitebanded fishing spider (Dolomedes albineus) on top of one of our...

 

[Sergic]

As luck would have it, I found a penultimate male whitebanded fishing spider (Dolomedes albineus) in my yard tonight.

Penultimate Male Dolomedes albineus

• Ungoliant
• Jul 15, 2017
• albineus dolomedes dolomedes albineus fishing spider penultimate male pisauridae whitebanded fishing spider

I found this immature male whitebanded fishing spider (Dolomedes albineus) on top of one of our...

The palps on that albineus look very similar to the tenebrosus I caught. I'm fairly certain you're correct about it being penultimate, and the reason it had trouble molting was my mistake, not it attempting a post-ultimate molt.

I just had it in a deli cup to show a couple people before I released and didn't think I needed to give it anything to climb on before I released it. I'm pretty sure the lack of furniture to molt on is what did it in, actually.