Topic: Amphibians and Reptiles

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πŸ”— Boiling Frog

πŸ”— Skepticism πŸ”— Amphibians and Reptiles

The boiling frog is a fable describing a frog being slowly boiled alive. The premise is that if a frog is put suddenly into boiling water, it will jump out, but if the frog is put in tepid water which is then brought to a boil slowly, it will not perceive the danger and will be cooked to death. The story is often used as a metaphor for the inability or unwillingness of people to react to or be aware of sinister threats that arise gradually rather than suddenly.

While some 19th-century experiments suggested that the underlying premise is true if the heating is sufficiently gradual, according to contemporary biologists the premise is false: a frog that is gradually heated will jump out. Indeed, thermoregulation by changing location is a fundamentally necessary survival strategy for frogs and other ectotherms.

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πŸ”— Dimetrodon

πŸ”— Palaeontology πŸ”— Amphibians and Reptiles πŸ”— Mammals

Dimetrodon ( (listen) or , meaning "two measures of teeth") is an extinct genus of non-mammalian synapsids that lived during the Cisuralian (Early Permian), around 295–272Β million years ago (Ma). It is a member of the family Sphenacodontidae. The most prominent feature of Dimetrodon is the large neural spine sail on its back formed by elongated spines extending from the vertebrae. It walked on four legs and had a tall, curved skull with large teeth of different sizes set along the jaws. Most fossils have been found in the southwestern United States, the majority coming from a geological deposit called the Red Beds of Texas and Oklahoma. More recently, fossils have been found in Germany. Over a dozen species have been named since the genus was first described in 1878.

Dimetrodon is often mistaken for a dinosaur or as a contemporary of dinosaurs in popular culture, but it became extinct some 40Β million years before the first appearance of dinosaurs. Reptile-like in appearance and physiology, Dimetrodon is nevertheless more closely related to mammals than to modern reptiles, though it is not a direct ancestor of mammals. Dimetrodon is assigned to the "non-mammalian synapsids", a group traditionally called "mammal-like reptiles". This groups Dimetrodon together with mammals in a clade (evolutionary group) called Synapsida, while placing dinosaurs, reptiles and birds in a separate clade, Sauropsida. Single openings in the skull behind each eye, known as temporal fenestrae, and other skull features distinguish Dimetrodon and mammals from most of the earliest sauropsids.

Dimetrodon was probably one of the apex predators of the Cisuralian ecosystems, feeding on fish and tetrapods, including reptiles and amphibians. Smaller Dimetrodon species may have had different ecological roles. The sail of Dimetrodon may have been used to stabilize its spine or to heat and cool its body as a form of thermoregulation. Some recent studies argue that the sail would have been ineffective at removing heat from the body due to large species being discovered with small sails and small species being discovered with large sails, essentially ruling out heat regulation as its main purpose. The sail was most likely used in courtship display with methods such as threatening rivals or showing off to potential mates.

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πŸ”— Hybridogenesis in water frogs

πŸ”— Genetics πŸ”— Amphibians and Reptiles

The fertile hybrids of European water frogs (genus Pelophylax) reproduce by hybridogenesis (hemiclonally). This means that during gametogenesis, they discard the genome of one of the parental species and produce gametes of the other parental species (containing a genome not recombined with the genome of the first parental species). The first parental genome is restored by fertilization of these gametes with gametes from the first species (sexual host). In all-hybrid populations of the edible frog Pelophylax kl. esculentus, however, triploid hybrids provide this missing genome.

Because half of the genome is transmitted to the next generation clonally (not excluded unrecombined intact genome), and only the other half sexually (recombined genome of the sexual host), the hybridogenesis is a hemiclonal mode of reproduction.

For example, the edible frog Pelophylax kl. esculentus (mostly RL genome), which is a hybridogenetic hybrid of the marsh frog P. ridibundus (RR) and the pool frog P. lessonae (LL), usually excludes the lessonae genome (L) and generates gametes of the P. ridibundus (R). In other words, edible frogs produce gametes of marsh frogs.

The hybrid populations are propagated, however, not by the above primary hybridisations, but predominantly by backcrosses with one of the parental species they coexist (live in sympatry) with (see below in the middle).

Since the hybridogenetic hybrids require another taxon as sexual host to reproduce, usually one of the parental species, they are called kleptons (with "kl." in scientific names).

There are three known hybridogenetic hybrids of the European water frogs:

  • edible frog Pelophylax kl. esculentus (usually genotype RL):
    pool frog P. lessonae (LL) Γ— P. ridibundus (RR)
  • Graf's hybrid frog Pelophylax kl. grafi (PR):
    Perez's frog P. perezi (PP) Γ— P. ridibundus (RR) or
    Perez's frog P. perezi (PP) Γ— edible frog P. kl. esculentus (RE)
    (it is unclear which one crossing was the primary hybridisation)
  • Italian edible frog Pelophylax kl. hispanicus (RB):
    Italian pool frog P. bergeri (BB) Γ— P. ridibundus (RR)

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πŸ”— Wells and Wellington Affair

πŸ”— Australia πŸ”— Amphibians and Reptiles πŸ”— Academic Journals

The Wells and Wellington affair was a dispute about the publication of three papers in the Australian Journal of Herpetology in 1983 and 1985. The publication was established in 1981 as a peer-reviewed scientific journal focusing on the study of amphibians and reptiles (herpetology). Its first two issues were published under the editorship of Richard W. Wells, a first-year biology student at Australia's University of New England. Wells then ceased communicating with the journal's editorial board for two years before suddenly publishing three papers without peer review in the journal in 1983 and 1985. Coauthored by himself and high school teacher Cliff Ross Wellington, the papers reorganized the taxonomy of all of Australia's and New Zealand's amphibians and reptiles and proposed over 700 changes to the binomial nomenclature of the region's herpetofauna.

Members of the herpetological community reacted strongly to the pair's actions and eventually brought a case to the International Commission on Zoological Nomenclature to suppress the scientific names they had proposed. After four years of arguments, the commission opted not to vote on the case because it hinged largely on taxonomic arguments rather than nomenclatural ones, leaving some of Wells and Wellington's names available. The case's outcome highlighted the vulnerability to the established rules of biological nomenclature that desktop publishing presented. As of 2020, 24 of the specific names assigned by Wells and Wellington remained valid senior synonyms.

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