Observation 213552: Amanita rhopalopus Bas

When: 2015-08-16

Collection location: Cheesequake State Park, Matawan, New Jersey, USA [Click for map]

Who: I. G. Safonov (IGSafonov)

Specimen available

A single specimen collected (not by me) at the NJMA foray presumably under hardwoods.
It smelled like decaying protein and dirty socks (pretty disgusting).

Amyloid in Melzer’s;
[20/1/1]: L x W = (9.1-) 9.3-13.5 (-14.9) x (5.6-) 5.8-7.9 (-9.1);
L x W = 10.6 × 6.7 μm;
Q = (1.39-) 1.43-1.77 (-1.79); Q = 1.58; Ellipsoid (11 spores) to elongate (9 spores).

Unlike the fairly tight range of spore dimensions (especially the width) that I usually observe in amanitas, this collection was marked by a very wide range, including two giant spores of essentially the same size, 14.9 × 9.1 μm. Only one of the giants was used for calculations. I wonder if this observation had to do with young age and condition of the fruiting body collected in hot and dry weather.
The “broadside”, side-on view used for measurements was reminiscent of apple seeds, while the ventral/dorsal view looked like a pear. Either way, the back end was wider and rounder relative to the apiculus-bearing end. The reported width of each spore is the maximum width.


Mounted in Melzer’s and viewed at x400
Giant spore #1; mounted in Melzer’s and viewed at x1000
Giant spore #2; mounted in Melzer’s and viewed at x1000
Typical spores #1; mounted in Melzer’s and viewed at x1000
Typical spores #2; mounted in Melzer’s and viewed at x1000

Proposed Names

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Used references: Suggested by RET — see his comment below

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Add Comment
The internal structure of the volva of rhopalopus is very disorderly.
By: R. E. Tulloss (ret)
2015-08-22 18:47:43 PDT (-0700)

The result is that warts tend to be somewhat formless.

Very best,


Thank you, Rod…
By: I. G. Safonov (IGSafonov)
2015-08-22 18:23:43 PDT (-0700)

… I understand. Yes, the tannish shiny areas on the cap are the cap “skin”. I was just expecting more pointy warts for rhopalopus at this stage of development as per the pix on your website.

The volval material on the cap…
By: R. E. Tulloss (ret)
2015-08-22 18:16:36 PDT (-0700)

is largely removed. Between the warts, I think I see the pileipellis without a covering of criss-crossing hyphae. This suggests that this is not ravenelii, which can be confused with you rhopalopus.

Very best,


By: I. G. Safonov (IGSafonov)
2015-08-22 14:05:41 PDT (-0700)

thank you for your suggestion. I am unfamiliar with A. rhopalopus even though it’s supposed to be fairly common (?) in NJ. I have briefly considered it before posting the obs, but didn’t think at the time that the UV on cap was in line with the photos posted on WAO and pertinent obss on MO. Also, the UV looked very different from that of A. ravenelii that we also happened to find at Cheesequake (see obs 212974). I understand that the two species are frequently confused due to being morphologically similar.

In another post in recent days, I talked about giant spores from…
By: R. E. Tulloss (ret)
2015-08-22 06:38:52 PDT (-0700)

2-spored basidia in amanitas in which sporulation is just beginning. I mentioned that dividing the length of a giant spore by the cube-root of 2 (1.25992105….) yields a number in the range of non-giant spore length, etc.

I think your suggestion that the large spores seen in this case are giant spores associated with early sporulation is plausible.

The photographs suggest that this might be A. rhopalopus.

Very best,


Created: 2015-08-21 21:39:01 PDT (-0700)
Last modified: 2017-12-29 17:16:25 PST (-0800)
Viewed: 86 times, last viewed: 2017-12-29 17:28:16 PST (-0800)
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