Amphibian

• TUSTIN, Calif., Feb. 19, 2024 /PRNewswire/ -- MiDOG Animal Diagnostics LLC, a prominent leader in microbiome-based veterinary diagnostic solutions employing Next Generation DNA Sequencing analysis, has unveiled a revamped branding strategy in 2024.
• The updated branding emphasizes the adaptability of MiDOG's technology across all animal species, departing from its previous emphasis on canine diagnostics.
• By extending its diagnostic capabilities to encompass a diverse range of animal species, MiDOG aims to equip veterinarians with the tools needed to address acute, chronic, and non-responsive infections effectively.
• The innovation at MiDOG Animal Diagnostics LLC is its microbiome-based comprehensive test, covering bacterial, fungal, and antimicrobial resistance (AMR) analysis.

• More than 380 million years ago, a sleek, air-breathing predatory fish patrolled the rivers of central Australia.
• Known from at least 17 fossil specimens, Harajicadectes is the first reasonably complete bony fish found from Devonian rocks in central Australia.

Meet the biter

• This group had strongly built paired fins and usually only a single pair of external nostrils.
• Tetrapodomorph fish from the Devonian period (359–419 million years ago) have long been of great interest to science.
• They include the forerunners of modern tetrapods – animals with backbones and limbs such as amphibians, reptiles, birds and mammals.

A long road to discovery

• Packed within red sandstone blocks on a remote hilltop were hundreds of fossil fishes.
• The vast majority of them were small Bothriolepis – a type of widespread prehistoric fish known as a placoderm, covered in box-like armour.
• These included a lungfish known as Harajicadipterus youngi, named in honour of Gavin Young and his years of work on material from Harajica.

• There were early attempts at figuring out the species, but this proved troublesome.
• Then, our Flinders University expedition to the site in 2016 yielded the first almost complete fossil of this animal.

A strange apex predator

• Likely the top predator of those ancient rivers, its big mouth was lined with closely-packed sharp teeth alongside larger, widely spaced triangular fangs.
• It seems to have combined anatomical traits from different tetrapodomorph lineages via convergent evolution (when different creatures evolve similar features independently).

• Similar giant spiracles also appear in Gogonasus, a marine tetrapodomorph from the famous Late Devonian Gogo Formation of Western Australia.
• They are also seen in the unrelated Pickeringius, an early ray-finned fish that was also at Gogo.

The earliest air-breathers?

Other Devonian animals that sported such spiracles were the famous elpistostegalians – freshwater tetrapodomorphs from the Northern Hemisphere such as Elpistostege and Tiktaalik. These animals were extremely close to the ancestry of limbed vertebrates. So, enlarged spiracles seem to have arisen independently in at least four separate lineages of Devonian fishes.

• The only living fishes with similar structures are bichirs, African ray-finned fishes that live in shallow floodplains and estuaries.
• It was recently confirmed they draw surface air through their spiracles to aid survival in oxygen-poor waters.

Brian Choo receives funding from the Australian Research Council and is employed by Flinders University. Alice Clement receives funding from the Australian Research Council and is employed by Flinders University. John Long receives funding from The Australian Research Council.

• Our research, published today in the journal Global Change Biology, attempts to pin down why certain tetrapod species are rediscovered but others not.
• It also reveals that the number of lost tetrapod species is increasing decade-on-decade.
• This means that despite many searches, we are losing tetrapod species at a faster rate than we are rediscovering them.

Rediscoveries lead to conservation action

• Thus, rediscoveries are important: they provide evidence of the continued existence of highly threatened species, prompting funding for conservation action.
• The results or our study may help to prioritise searches for lost species.
• In the image below, we mapped their global distribution, identifying regions with many lost and few rediscovered species.

What factors influence rediscovery?

• Are there specific factors that influence rediscovery?
• We then proposed three broad hypotheses about factors that might influence rediscovery: characteristics of (i) tetrapod species, and (ii) the environment influence rediscovery, and (iii) human activities influence rediscovery.
• For example, body mass (a species characteristic) may positively influence rediscovery, as larger lost species should be easier to find.
• Based on these hypotheses, we collected data on a series of variables associated with each lost and rediscovered species (for example, their body mass), which we then analysed for their influence on rediscovery.

Hard to find + neglected = rediscovered

• In fact, since the completion of our study, De Winton’s Golden Mole (Cryptochloris wintoni) has been rediscovered in South Africa.
• Our results also suggest some species are neglected by conservation scientists, particularly those that are not considered to be charismatic, such as reptiles, small species and rodents.
• Voeltzkow’s chameleon (Furcifer voeltzkowi), a small reptile species, was rediscovered in Madagascar in 2018.

Lost or extinct?

• For example, remaining lost mammal species are, on average, three times larger than rediscovered mammal species.
• Furthermore, one third of remaining lost mammal species are endemic to islands, where tetrapod species are particularly vulnerable to extinction.
• Perhaps the limited resources available for biodiversity conservation would be better used to search for lost species likely to still exist.

Thomas Evans received funding from The Alexander von Humboldt Foundation.

• Across the vast Australian continent, feral pigs, feral deer and European rabbits roam in their millions.
• By different names – wild boar, venison and lapin – these could all be served in a Michelin star restaurant.
• Feral and invasive species are becoming popular meals for native wildlife too.

Of crocs and pigs

• This seems like a much-needed good news story for the environment – a natural way to limit feral pigs, one of Australia’s most widespread and damaging invasive species.
• At present, though, we don’t know for sure that crocs keep pig numbers down.
• Together, this means feral pigs can endure relatively high predation rates and still persist in ecosystems in large numbers.

Of quolls and rabbits

• Unfortunately, quolls are now absent or still declining in many places, due likely to competition or predation with the bigger, heavier predators Europeans introduced: feral cats and foxes.
• As quolls have disappeared, rabbits may have taken advantage of the predatory void and expanded.
• Fast-breeding rabbits are now arguably Australia’s worst invasive alien species.

Dangerous dinners

• Cane toads have devastated some native species such as northern quolls, which naturally prey on native amphibians but cannot survive toad toxin.
• Regrettably, a recent attempt to train quolls not to eat cane toads appears to have failed.
• European house mice and introduced rats can be easy prey for owls, snakes, and many other native predators.

Invasive prey aren’t going away

• As time goes on, invasive prey species can become regular meals for native predators – and part of the food web.
• When we try to remove invasive prey species from ecosystems, we must take a big picture view and proceed with great caution.
• When feral cats were killed off on New Zealand’s Little Barrier island, it was done with the best intentions: protect the seabirds nesting there.
• But with the cats gone, invasive rat populations surged and soon began killing the seabird chicks.

Euan Ritchie receives funding from the Australian Research Council and the Department of Energy, Environment, and Climate Action. Euan is a Councillor within the Biodiversity Council, and a member of the Ecological Society of Australia and the Australian Mammal Society.