Ian, please see the attached figure: the siphon (2) is partly covered by the mantle skirt (1); the hypobranchial gland (4) is seen directly (because the roof of the mantle cavity was apparently broken during shell removal) while the ctenidium (4) and the osphradium (3) are just seen by transparency. The testis (10) lies over the digestive gland and what you are labelling 9 is probably a part of the gut (to be sure you'll need to check it histologically)

Agreed. Not clear what is (9), may be better seen in other view. Prostate gland is usjually not seen thrpugh the mantle, so I am not sure about this labelling

Dear Alfredo and Yu, many thanks for your helpful comments. I shall remove 7 & relocate 9 as suggested by Alfredo's alteration to the image. This specimen had a penis, but I am aware that females with imposex have them too. I cannot see a sperm ingesting gland in the image, so have assumed it is a genuine male, but I may have missed it because of angle of view. Is the ginger colour of the testis another way of differentiating males from females with paler ovary? Or do the colours of ovary and testis vary and overlap?

Best wishes, Ian.

Hello Ian,

I do agree with Alfredo in respect of number 9. It seems to me that it might be the posterior oesophagus or part of the stomach. The prostate gland is less glandular than the capsule gland and has more or less a plae pink colour; 7 points to the position that should occupy the prostate gland, so it might be right.  I send you attached a file with further explanations. I added with Adobephotosho a few letterings. 14, is propodium or say simply foot (although the foot has three parts). 13 is the cephalic tentacle and the small black spot on the tentacle, the eye. 9 is either oesophagus or stomach, it is not clear but in any case surely not the digestive gland. 12 is the digestive gland and 11 the seminal vesicle. I could not make the letterings bigger, sorry.

The colour of the ovary and testis when they are ripe, as I see, are different depending on the species but may also be the same, at least in Muricidae. For example, in Coralliophila meyendorffii (a Mediterranean species of the subfamily Coralliophilinae) depending on whether the female feed on A. equina or A. sulcata (=A. viridis), the ovary is either pink or pale yellow while in males the testis is white, redish orange or golden brown. In Babelomurex cariniferus, another Coralliophilinae, the ovary and the testis has the same red colour when they are ripe. I see that in N. lapillus male and females can be distinguished by the colour of the gonads. I wonder only if the ovary has different colours depending on what the females feed.

Just one thing more; you can only see the penis of the male if you cut open the mantle skirt. Take a razor blade and make a longitudinal slit along the midline of the mantle skirt, that is more or less parallel to the hypobranchial gland. You will see at the right side of the muscular head-foot right behinf the right cephalic tentacle  the penis.

After looking at my micrographs of Trophon geversianus (Muricidae) I am afraid that Yu was right (and not me) when he expressed his doubts regarding the identity of the prostate in the original Ian's picture. I am attaching a composite section of the right pallial ridge in T. geversianus which shows that the prostate is below the hypobranchial gland and the rectum, and so, the prostate could not be discerned by transparency in an upper view of the snail as that of Ian.

I am sorry. I've uploaded the composite picture without the labellings. I'm now uploading the right one.

Dear All

I have held back from posting my opening up of a (male) mantle cavity as I am sure it is not of a good standard of presentation. It was opened by a cut along the siphon and mantle-fold/channel leading to it. I fear I may be trying your patience, but perhaps some of you would be willing to comment.

Numbers 1-10 are as on my previous images.

1: mantle edge, 2: siphon, 3: osphradium 4: ctenidium, 5: hypobranchial gland, 7: prostate gland 9: digestive gland, 10: testis

I hope 7 is correctly the prostate gland. I can see how it would be concealed, as Yu & Alfredo suggest, when the mantle and organs are undissected.

New features I have labelled are

15:penis 16: ?? 17: vas deferens?? 18: ??, 19: pink buccal mass within anterior of proboscis, 20: gland of Leiblein?? 21: ??, 22: whitish salivary gland? 23: posterior end of retracted proboscis that extends in a silvery horseshoe towards right of animal and then leftwards to pink buccal mass (19)??, 24: distinct robust white fold in mantle forming a channel from siphon to osphradium (suitable name?) 25: mantle skirt (= roof of mantle cavity).

I am unsure of 18 & 21 (are they two bits of the same organ, kidney perhaps) and 16?

As you say only the distal end (2) of feature 24 is the siphon, is there a name I can apply to the rest of the channel?

Thank you for any help you can give.

Best

Ian

Here is a live male displaying its penis. Quite different from when dead.

Dear Alfredo and Yu, I am most grateful for your time and advice, so I hope that you will not mind if I respectfully raise again the question about the prostate gland. Below is an image of another male tilted to bring the right side more into view. It clearly shows a structure in position 7 of my original image. I think if Alfredo's image of the pallial ridge is tilted to bring the animal's right side more into view from above, the part containing the prostate gland would be visible (the anal gland and hypobranchial gland would also be brought into view to resemble their positions in my photo).

Would you agree if I labelled the structure either as 'prostate gland' or 'pallial ridge containing prostate gland and rectum' ? Or could you suggest a better name for the structure?

I also attach an image of the same specimen opened to show the pink prostate gland.          Best wishes, Ian.

Dear Ian,

I don't have any experience with N. lapillus but with another muricid (T. geversianus). My impression is that the pink 'sausage' in your dissection of Nucella is indeed the prostate gland. It appears to me that the prostate is less developed in Trophon, while the hypobranchial gland of Trophon is more developed than in Nucella and it covers the prostate and rectum. However, I am not able to identify the rectum in your nice pictures. If you don't have access to histology, perhaps a razor blade cut, transversal to the prostate, may allow you to see where the rectum actually is. If you perform this cut in a fixed specimen, I believe you would be able to recognize the rectum better than in a fresh specimen. You should also notice that the anal gland in Trophon is only seen in histological sections: it is not bulky enough to see it in dissections.

I am wondering what for are you interested in these matters, and what for are you obtaining such nice photographs! 

Dear Alfredo, thank you again for responding. I have been a keen naturalist for 60 years and I find marine biology especially fascinating. I have no educational qualifications in biology (unless you count biogeography which was part of my geography degree). I am largely self-taught and very grateful to you and other professionals for helping me. I am editor of the marine slug section of the Conchological society of GB & Ireland's on-line encyclopedia at  http://www.conchsoc.net/groupbrowser/Marine%20slug . The information I am seeking about Nucella, and the images, are for an account I shall add to my collection of sea snails (and Cirripedia) at https://www.flickr.com/photos/56388191@N08/collections/ . It is only recently that I have started including anatomy that cannot be seen on live specimens, but I am enjoying greatly learning about it from books, my observations and the help of you and others. I hope to interest other naturalists in more than just identification, list compiling and putting dots on distribution maps. I have started making my accounts into pdfs so they can be printed off by users. So far I have only done them for https://www.flickr.com/photos/56388191@N08/13938163357/in/set-72157644559746634 (scroll down below the image) and https://www.flickr.com/photos/56388191@N08/14157433480/in/set-72157644597342439 You will see a link on the Flickr accounts to a Facebook Group where the pdfs can be downloaded without joining the group (but you need to be registered on Facebook). They are not peer reviewed articles, but if you or others think it appropriate, I would be pleased to make the pdfs available on Researchgate.

Best wishes

Ian