A gland new to Science, hiding in plain sight on the steenbok (Raphicerus campestris)?

@dejong

There seems to be a gland in the steenbok (Raphicerus campestris), plainly visible in hundreds of photos (e.g. https://stock.adobe.com/search?k=steenbok&asset_id=404356409), that has not been recorded by any zoologist - until now.

This apparently glandular feature is noteworthy, because

• its location seems unique among ungulates, and possibly among all animals, and
• no trace of this dark vertical streak is visible in the other two spp. of the same genus, namely Raphicerus melanotis and R. sharpei.

I will call this feature the radial gland, because it is situated on the outer surface of the upper foreleg, where the main bone is the radius (https://www.inaturalist.org/observations/6316536).

This location is near the carpal joint. However, it differs from that of a gland long-recognised in other genera. I refer to the carpal gland, located on the anterior surface of the carpal joint.

Estes (1991, page 45) states that the scent glands of R. campestris comprise "smallish preorbital glands, larger in male, pedal glands in all feet, no inguinal glands, and possibly a throat gland (Smithers 1983)". He apparently overlooked research by Cohen, showing an intermandibular gland in both sexes (https://journals.co.za/doi/pdf/10.10520/AJA00382809_3949).

The following show the intermandibular gland in the form of a swelling under the lower jaw (https://www.canstockphoto.com/close-up-of-steenbok-ram-head-with-18371818.html and https://www.canstockphoto.com/close-up-of-steenbok-ram-head-with-18303890.html).

However, no author has mentioned any gland on the upper foreleg of any species of Raphicerus.

For comparison, Estes (1991, page 57) states that the scent glands of Ourebia ourebi comprise "very large preorbital glands in males (unused and possibly undeveloped in females); black spot below ear underlain by apocrine glands which diffuse scent into air (Kingdon 1982); deep inguinal pouches; carpal glands beneath brushes of long hair on front legs (as in gazelles), shorter brushes below hocks; well-developed glands between all hooves".

The carpal glands of Gazella and Ourebia presumably function by means of kneeling (https://blog.londolozi.com/2022/01/04/the-secret-life-of-a-steenbok/), which the animals perform every time they lie down or get up from the resting posture adopted for rumination. This would leave scent on the earth or herbage.

In the corresponding position on the front of the carpal joint, R. campestris simply has a small callus (https://en.wikipedia.org/wiki/Callus).

The hair-tufts covering the carpal glands are clearly visible in the following, because of their pigmentation:

• Gazella subgutturosa https://animalia.bio/goitered-gazelle
• Gazella bennetti https://www.gettyimages.com.au/detail/photo/photographic-image-royalty-free-image/1141952662?adppopup=true
• Ourebia montana cottoni https://www.alamy.com/stock-photo-female-oribi-in-the-northern-serengeti-125863317.html?imageid=7E57F6A1-9093-405A-97DE-830F18C9C806&p=149870&pn=1&searchId=3066f7aee4fda0c5aa30eb635704b2fc&searchtype=0
• Ourebia ourebi ourebi https://www.alamy.com/female-oribi-gorge-nature-reserve-kwazulu-natal-south-africa-image360755992.html?imageid=6DE2BF8C-90E5-4307-BDF0-B46358254D86&p=311300&pn=1&searchId=3066f7aee4fda0c5aa30eb635704b2fc&searchtype=0

The location of the radial gland in R. campestris is different enough from that of the carpal glands to make a similar function unlikely.

Furthermore, the radial gland seems bare of pelage, the dark appearance being that of bare but callus-free skin.

The following (https://stock.adobe.com/search?k=dikdik&asset_id=493868805) shows that the radial gland is at least as large as the preorbital gland (https://en.wikipedia.org/wiki/Preorbital_gland), which is the main gland associated with masculinity in R. campestris.

Casting some doubt on the glandular nature of this feature is the occurrence, in a few individuals of R. campestris, of a corresponding dark feature - where the hairs seem to have been worn off - on the hindleg:

https://www.gettyimages.com.au/detail/news-photo/female-steenbok-in-the-jao-concession-okavango-delta-in-news-photo/1200531573?adppopup=true

https://www.gettyimages.com.au/detail/news-photo/female-steenbok-in-the-jao-concession-okavango-delta-in-news-photo/1200531605?adppopup=true

https://www.gettyimages.com.au/detail/news-photo/close-up-of-a-female-steenbok-feeding-in-the-jao-concession-news-photo/1200531612?adppopup=true

https://www.gettyimages.com.au/detail/photo/female-steenbok-royalty-free-image/628346620?adppopup=true).

Intriguingly, the available photographic evidence suggests that there is subspecific variation in the incidence of the radial gland.

This feature seems to be particularly poorly-developed in R. campestris campestris, which is also the most distinctive subspecies in general colouration.

The following show the presence of the radial gland in various subspecies and both sexes of R. campestris.

campestris, female:

https://www.alamy.com/stock-photo-steenbok-raphicerus-campestris-nursing-karoo-national-park-south-africa-20458147.html?imageid=6D8944F6-61A5-46A2-AC95-2E9833E4259A&p=40779&pn=1&searchId=81afea0714a7b7094a750bf43216e26d&searchtype=0

https://www.inaturalist.org/observations/98392799

https://www.inaturalist.org/observations/41908928

https://www.alamy.com/weibliches-steinbckchen-hlt-ausschau-female-steenbok-looking-out-raphicerus-campestris-namaqualand-sdafrika-image333121951.html?imageid=BE16C88D-4083-4926-ACBC-3FDF6B393BAC&p=1151839&pn=1&searchId=c9304c518b7bb098e6083b00691cb84a&searchtype=0

campestris, male:

(many photos are available on the Web, but none show the feature in question)

capricornis, female:

https://www.istockphoto.com/photo/steenbuck-gm583977962-99962993?phrase=steenbok

https://www.istockphoto.com/photo/steenbok-ewe-kruger-national-park-gm1401423583-454646848?phrase=steenbok

https://www.istockphoto.com/photo/steenbok-standing-alert-gm524396756-92197869?phrase=steenbok

https://www.gettyimages.com.au/detail/photo/the-steenbok-royalty-free-image/636770832?adppopup=true

https://www.inaturalist.org/observations/94425108

https://www.alamy.com/stock-photo-steenbok-raphicerus-campestris-pup-in-evening-light-grazing-south-76132026.html?imageid=8D8D4245-9F6E-4BD8-8429-6E27576B9C46&p=68577&pn=1&searchId=c9304c518b7bb098e6083b00691cb84a&searchtype=0

capricornis, male:

https://www.istockphoto.com/photo/capricorn-in-green-savanna-gm1184254719-333285629?phrase=steenbok

https://www.istockphoto.com/photo/steenbuck-gm583977682-99962713?phrase=steenbok

https://www.istockphoto.com/photo/steinbuck-in-kruger-national-park-in-south-africa-gm1313842690-402234870?phrase=steenbok

https://www.istockphoto.com/photo/steenbok-raphicerus-campestris-gm495952922-78292089?phrase=steenbok

https://www.istockphoto.com/photo/steenbok-gazelle-gm1077769610-288723218?phrase=steenbok

https://www.istockphoto.com/photo/capricorn-gm1286648370-383087965?phrase=steenbok

https://www.istockphoto.com/photo/steenbok-antelope-gm487464396-72932291?phrase=steenbok

https://www.tripadvisor.co.uk/LocationPhotoDirectLink-g312618-i1689945-Kruger_National_Park.html

https://www.gettyimages.com.au/detail/photo/steenbok-adult-male-feeding-kruger-nationalpark-royalty-free-image/1209482706?adppopup=true

https://www.gettyimages.com.au/detail/photo/kruger-national-park-royalty-free-image/592939385?adppopup=true

https://www.inaturalist.org/observations/62689596

steinhardti, female:

https://www.inaturalist.org/observations/26661297

https://en.wikipedia.org/wiki/Steenbok#/media/File:Raphicerus_campestris_female_(Etosha,_2012).jpg

https://www.istockphoto.com/photo/steenbok-in-kgalagadi-transfrontier-park-south-africa-gm1392343427-448616170?phrase=steenbok

https://www.inaturalist.org/observations/100241068

https://www.gettyimages.com.au/detail/photo/steenbok-royalty-free-image/148697094?adppopup=true

https://www.inaturalist.org/observations/36941231

https://www.inaturalist.org/observations/36127710

steinhardti, male:

https://en.wikipedia.org/wiki/Steenbok#/media/File:Raphicerus_campestris_male_(Etosha,_2012).jpg

https://www.istockphoto.com/photo/steen-buck-walks-through-the-long-grass-in-the-kalahari-desert-south-africa-gm1351983424-427535947?phrase=steenbok

https://www.istockphoto.com/photo/steinbuck-antelope-looking-at-camera-in-etosha-national-park-namibia-gm540862142-96671299?phrase=steenbok

https://www.gettyimages.com.au/detail/photo/steenbok-etosha-pan-namibia-royalty-free-image/970408986?adppopup=true

https://www.inaturalist.org/observations/53130004

https://www.inaturalist.org/observations/50249368

https://www.inaturalist.org/observations/36127707

https://www.inaturalist.org/observations/34610708

https://www.istockphoto.com/photo/steenbok-raphicerus-campestris-small-shy-beautiful-antelope-from-african-savannah-gm1215318410-353932104?phrase=steinbok

neumanni, female:

https://www.alamy.com/steinbuck-raphicerus-campestris-tanzania-image6357425.html?imageid=4FC75135-114E-472E-ADBC-3951BA2051C7&p=2585&pn=1&searchId=30e86c64bd74ac276119489cea99aea1&searchtype=0

https://www.inaturalist.org/observations/18053713

https://www.inaturalist.org/observations/12006271

neumanni, male:

https://www.gettyimages.co.uk/detail/photo/dik-dik-in-the-serengeti-tanzania-east-africa-royalty-free-image/1203979753?adppopup=true

https://www.alamy.com/stock-photo-closeup-of-steenbok-scientific-name-raphicerus-campestris-or-funo-170650319.html?imageid=BC8588CB-D22B-4102-8E3C-A1BCE9BD9545&p=141090&pn=1&searchId=c9304c518b7bb098e6083b00691cb84a&searchtype=0

https://www.inaturalist.org/observations/32006732

FOOTNOTE:

The whole skin in Raphicerus campestris, apart from most of the anterior surface of the ear pinnae (https://stock.adobe.com/search?k=steenbok&asset_id=221530819), seems to be darkly pigmented.

This includes

• rhinarium,
• bare edges of the lips,
• perineum/anus (https://www.alamy.com/steenbok-raphicerus-campestris-female-namibia-image61805632.html and scroll in https://africawild-forum.com/viewtopic.php?p=234338#p234338),
• prepuce (https://www.istockphoto.com/photo/steenbok-raphicerus-campestris-gm495952950-78292117 and https://fineartamerica.com/featured/solitary-male-steenbok-antelope-cam-bornet.html),
• scrotum (https://www.alamy.com/steenbok-in-yellow-grass-image227670603.html?imageid=A505DDB3-255E-4003-8E22-67823FAA1EB0&p=95934&pn=1&searchId=30e86c64bd74ac276119489cea99aea1&searchtype=0 and https://stock.adobe.com/search?k=steenbok&asset_id=393358354),
• udder (https://www.inaturalist.org/observations/104420754), and
• a large bare area in the groin, extending to the junction of the hindleg with the flank (https://fineartamerica.com/featured/5-steenbok-raphicerus-campestris-roger-de-la-harpe.html).

The darkness of the skin shows through the pelage, around the eyes of R. melanotis and R. sharpei (but not R. campestris except for the antorbital gland), on the posterior surface of the ear pinnae in all three spp., and on the lower part of the buttocks of R. campestris when the pelage is matted.

Even the tongue is so dark-pigmented in R. campestris that it can be called black (https://www.mirror.co.uk/news/world-news/oh-deer-huge-python-spends-6367197 and https://www.alamy.com/stock-photo-a-steenbok-looking-camera-while-it-eats-leaves-off-tree-kgalagadi-40211532.html and https://fineartamerica.com/featured/portrait-of-a-steenbok-john-haldane.html).

Posted on Σεπτέμβριος 29, 2022 0432 ΠΜ by milewski