Possible myrmecophagy in African Brevicipitidae (Breviceps) and Australian Limnodynastidae (Notaden)

Myrmecophagy (https://en.wikipedia.org/wiki/Myrmecophagy) occurs in certain species of Anura (https://en.wikipedia.org/wiki/Frog), particularly in the family Microhylidae (https://en.wikipedia.org/wiki/Microhylidae).

Whereas myrmecophagous mammals tend to have long, tubular faces, their anuran counterparts tend to have extremely short faces. However, this is not obvious in the small-mouthed microhylids, which also have narrow faces for frogs.

In southern Africa, some spp. of Breviceps (Brevicipitidae) are particularly associated with a diet of termites.

Several of the Breviceps spp. that occur in savannas seem to specialise on alate termites (https://en.wikipedia.org/wiki/Alate, http://frogmap.adu.org.za/Species_text.php?sp=220 and https://en.wikipedia.org/wiki/Breviceps_adspersus and http://frogmap.adu.org.za/Species_text.php?sp=165).

However, the genus as a whole is certainly not myrmecophagous (https://en.wikipedia.org/wiki/Myrmecophagy).

Even the spp. (e.g. B. adspersus, http://eol.org/pages/1019120/details) most likely to exploit alate termites are not myrmecophagous in the usual sense, because they seem not to eat workers and soldiers, and they have not been recorded eating ants.

Breviceps does not seem to be specialised on a particular type of food. Instead, it seems specialised on a particular strategy vs predators.

This strategy is to

  • hide underground for most of the year, in some cases even for part of the rainy season;
  • hatch and develop underground (subterranean direct development with parental guarding);
  • inflate and distress-call when confronted by a predator within the burrow or above ground;
  • ooze toxic substances from the skin; and
  • promote confusion if the head with the posterior, partly by having an extremely flat face (the flattest-faced of all frogs worldwide), and partly by having the position of the eyes disguised by markings on the skin behind and below the eyes.

The closest counterparts to Breviceps in Australia belong to the genus Notaden (Limnodynastidae).

Both Notaden and Breviceps are proficient burrowers. Both genera, despite their dumpy appearance, can run surprisingly fast, like comical little round mice, e.g. when seen crossing roads at night.

Among Australian frogs, one of the genera most strongly associated with a diet of ants (and termites) is Notaden (Limnodynastidae), the distribution of which covers much of the continent (https://en.wikipedia.org/wiki/Notaden#/media/File:Notaden_distribution.png and http://upload.wikimedia.org/wikipedia/commons/d/d4/Notaden_distribution.png).

The following study (https://www.researchgate.net/publication/292012797_Ecology_of_desert_frogs_a_study_from_southwestern_Queensland) shows that the diet of Notaden nichollsi consists only of termites (presumably not alates) and ants.

Like other frogs, it does not penetrate the Nullarbor Plain (https://en.wikipedia.org/wiki/Nullarbor_Plain). It is also notably absent from southern Western Australia, which I suspect to be too nutrient-poor for this genus. However, it spans a great range in rainfall, from the wet northern tip of Queensland (https://en.wikipedia.org/wiki/Queensland) to the driest part of the whole continent just north of Lake Eyre (https://en.wikipedia.org/wiki/Lake_Eyre).

No species of Notaden is morphologically as specialised as Breviceps, in the sense of having as extreme a body form and, particularly, head form.

However, some species of Notaden (in particular N. nichollsi, a species that nearly reaches the northern limit of the Nullarbor Plain) seem more specialised on a diet of termites and ants (probably in that order) than is B. adspersus.

See https://terrestrialecosystems.com/non-cocooning-desert-frogs/.

Both Breviceps adspersus and Notaden nichollsi seem to reach a snout-vent length of about 6 cm, and penetrate hot, dry environments.

There is a difference in body form, with Breviceps so short-legged that, when inflated, it becomes virtually spherical (https://www.reddit.com/r/NatureIsFuckingLit/comments/sjc7ut/bushveld_rain_frog_breviceps_adspersus/). However, I would explain this difference according to the greater pressure of predation in Africa than in Australia.
 
Please note, in particular, that the colouration of B. adspersus crosses out its eyes. This is in combination with the head being indistinct, and the eyes not protruding in the normal way for frogs.

I interpret this as an extreme anti-predation tactic: the predatory regime in the habitat of B. adspersus is so intense that, even when this frog is fully inflated, it still needs to disguise its head to delay lethal attack.

Breviceps is the more specialised genus reproductively. It has ‘direct development’, in contrast to Notaden, which has typical aquatic tadpoles.
 
The whole genus Notaden may possibly qualify as ‘myrmecophagous’, although the photo of the tongue, below, does not look particularly different from the normal tongue associated with frogs.

Notaden is unlikely to be as specialised on a diet of ants and termites as certain other genera of frogs around the world.

However, it is one of the most specialised genera in Australia, and more dietarily specialised than sympatric frogs, which also spend most of their lives dormant underground, and emerge to breed in seasonal rain pools, eating many ants and termites during their breeding activity.

Something I do not understand about Breviceps adspersus is its disjunct distribution in EASTERN CAPE THICKET (see maps below).

This species occurs mainly in typical savannas in southern Africa, and does not penetrate the Highveld (https://en.wikipedia.org/wiki/Highveld).

Yet it pops up again, for some strange reason, in the coastal Eastern Cape (https://en.wikipedia.org/wiki/Eastern_Cape), where I cannot imagine there are many termites.

It would be interesting to know what it eats in vegetation dominated by Portulacaria afra (https://en.wikipedia.org/wiki/Portulacaria_afra).

Anyway, this is part of an overall picture that indicates to me that Breviceps is not generally myrmecophagous, despite being extremely specialised morphologically.

Notaden seems more consistently dependent on a diet of ants (and termites) than is Breviceps.
 
The bottom line, pending further studies, is that Notaden qualifies as a truly myrmecophagous lineage of frogs.

Because it spends most of its life dormant, it can specialise on this diet in environments too drought-prone or infertile to support mammalian myrmecophages.

I do not know of any mammal in Australia that is as strongly associated with a diet of ants as Notaden is, and that includes the echidna, Tachyglossus aculeatus (https://en.wikipedia.org/wiki/Short-beaked_echidna).

SOUTH AFRICA:

Brevicepitidae:

Breviceps adspersus:

Of dozens of photos of this species on the web, this is one of the few not showing some degree of inflation of the body. Breviceps adspersus, judging from photos, seems to feel so insecure at the surface that it is almost permanently inflated when viewed by photographers.
http://www.sareptiles.co.za/gallery/albums/userpics/21147/Bushveld_Rain_Frog_(Breviceps_adspersus).JPG

The following photo shows how extremely short the face is in Breviceps, more so than in any Australian frog, and probably more than in any frog worldwide.
http://www.sabisabi.com/images/21Feb12-Bushveld-Rain-Frog---Wim-Vorster.jpg

The following shows B. adspersus inflated as an anti-predator tactic.
https://40.media.tumblr.com/tumblr_lvuuwxDpw91qdxr59o1_500.jpg

The following show that, in full inflation, B. adspersus is almost spherical. Note the toxic secretions on the skin. No frog in Australia can inflate itself to this degree. Note the crossing out of the eyes, which seems to matter most in full inflation.
https://www.flickr.com/photos/cowyeow/4885007478
http://40.media.tumblr.com/tumblr_lrovd89x1w1qi3ps8o1_1280.jpg

Breviceps adspersus:
https://kidadl.com/facts/animals/bushveld-rain-frog-facts
https://www.alamy.com/stock-image-bushveld-rain-frog-breviceps-adspersus-marakele-national-park-limpopo-165827685.html?imageid=BDF60A55-A18A-4B4A-85DA-A0ECD9ECA81D&p=361566&pn=3&searchId=71fb4c324a4421ca52815d76cc56a0fa&searchtype=0
https://alchetron.com/Breviceps-adspersus

The following show the distribution of Breviceps adspersus, particularly its disjunct occurrence in the Eastern Cape.
http://en.wikipedia.org/wiki/Breviceps_adspersus#/media/File:Breviceps_adspersus_map-fr.svghttp://maps.iucnredlist.org/map.html?id=57712

AUSTRALIA:

Limnodynastidae:

Notaden nichollsi:

The following shows this species, apparently somewhat inflated as an anti-predator tactic. This is not as extreme as in Breviceps. Note that the face is extremely foreshortened for an Australian frog, but the head still protrudes.
https://www.gettyimages.ae/detail/news-photo/desert-spadefoot-toad-spends-most-of-its-life-underground-news-photo/157890412?adppopup=true
http://wetlandinfo.ehp.qld.gov.au/wetlands/species/photo/notaden-nichollsi.desert-shovelfoot.cd-notanich.jpg

Notaden melanoscaphus, the smallest member of the genus, with SV up to 4.9cm:
https://c1.staticflickr.com/3/2198/3538470612_e22c7f1e2a.jpg

Notaden weigeli, the largest member of the genus, with SV up to 7.1cm:
http://museum.wa.gov.au/sites/default/files/imagecache/wam_v2_page_full_gallery/photo-galleries/578.jpeg

Notaden weigeli, showing tongue as it eats an ant:
http://www.fieldherpforum.com/forum/viewtopic.php?f=2&t=645

Publicado el 14 de agosto de 2022 por milewski milewski

Comentarios

Dexterity in Breviceps:
http://www.jacobsjungle.com/frogs/bushveld-rain-frog-breviceps-adspersus/ . The frog disappears underground with consummate ease, which is remarkable because the hind foot is small and that it digs only with the metatarsal tubercle, a tiny proximal ‘claw’ that seems completely inadequate to shift earth as easily as one sees happening here. This is why I think considerable dexterity is involved: it is only by sophisticated, subtle movements that Breviceps could possible sink into the ground with so few strokes of the hind feet, particularly considering the defensively inflated shape, which must impede submersion. The digging action seen in this video clip, which is typical of all the ant-eating, burrowing frogs, warrants serious thought.

Dexterity of a different kind in Notaden bennettii: https://www.theanimalfacts.com/amphibians/crucifix-toad/.

Publicado por milewski hace más de 1 año
Publicado por milewski hace más de 1 año

See https://www.rswa.org.au/publications/Journal/86(3)/v86(3)Thompsonetal.pdf. Neobatrachus sutor (https://en.wikipedia.org/wiki/Shoemaker_frog) may possibly qualify as myrmecophagous, if its main diet is termites.

Publicado por milewski hace más de 1 año

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