4
Xenopus
his untimely death, Daudin is credited with the description of dozens of new species of animals, working in many
cases from preserved specimens in collections around Paris
( Bour, 2011 ).
Among these is the frst description of the genus now
called Xenopus, though exactly which species seems unclear.
Working from a single preserved specimen in the Museum
d’Histoire Naturelle in Paris, Daudin succinctly described
the smooth body, the dorsally set eyes, and the “longitudinal
rows of small prickles” along the back (Daudin, 1803), an
anatomical landmark that even the newest student injecting
hormones to induce egg laying will recognize immediately.
Daudin’s book also includes the f rst scientif c illustration
of Xenopus (Figure 1.1). As it happens, his wife Adélaïde
was a talented artist, and she provided many illustrations
for his work, though the image of the smooth toad is attributed instead to an artist named Prévost. In a further tragedy,
Adélaïde also died of tuberculosis, a few days before her
husband (Bour, 2011).
Surprisingly, neither Daudin’s description nor the accompanying illustration makes note of the claws on what would
later come to be known as the African clawed frog. Thus,
when the great French naturalist Georges Cuvier assembled
his magnum opus Le Règne Animal in 1829, he chided
Daudin for his omission of the claws, and indeed, it does
seem like quite the blunder. However, in the f rst focused
and comprehensive description of our frog in 1864, J.E.
Gray notes that the animals’ claws are “deciduous in spirits”
(Gray, 1864), suggesting the possibility that the claws on
Daudin’s preserved specimen had dissolved before he made
his observations. Regardless, Cuvier renamed the genus
Dactylethra, a rendering of “fnger sheath” or “thimble”
( Cuvier, 1829 ).
The genus name Dactylethra was commonly used by
19th-century writers, including the frst description and
images of tadpoles of the species (Gray, 1864). The name
Xenopus only became fashionable in the 1890s, which
is curious, since it was actually frst suggested in 1827.
Even more curious is the forum in which that name was
frst bestowed: a footnote appended to a letter written by
Heinrich Boie and published in Lorenz Oken’s journal,
Isis (Wagler, 1827). Previous authors have attributed this
footnote to “Wagler, H.,” but thanks to the digitized archives
available from the Biodiversity Heritage Library ( www.
biodiversitylibrary.org/), I have been able to learn a bit more
about this important fgure in the history of Xenopus.
As it happens, the footnote proposing the genus name
“Xenopus” has no frst initial indicated; it is signed simply:
“Wagler” (Figure 1.2). This almost certainly refers to Johann
Georg Wagler, a noteworthy German naturalist, who in 1830
and 1831 published two monographs on the Amphibia. In
fact, in his Natürliches System der Amphibien of 1830, he
cites the earlier footnote in Isis, and moreover makes frequent
mention of Xenopus, making a special note of its clawed toes
(Wagler, 1830). Moreover, in his original footnote, Wagler
even lets Daudin off the hook for missing the claws, suggesting that he must have observed a decayed specimen (Wagler,
1827). In an unsettling coincidence, Wagler, like Daudin,
died tragically, in this case at 32 years old from an accidental,
self-inficted gunshot wound (Hess, 1896 ).
Wagler’s naming of the genus is the one that f nally stuck,
but not until long after his death. Dactylethra was used in
several important 19th-century studies of the animal. Just
the same, text searches of the Biodiversity Heritage Library
revealed that Wagler’s naming of Xenopus had been translated into French by 1829 (Boie and Wagler, 1829), and
even as early as 1831, an English synopsis of Cuvier’s book
acknowledges Wagler and includes Xenopus as a synonym
for Dactylethra ( Griffth, 1831). Though my survey was in
no way systematic, the earliest instance I found of Xenopus
being used as the primary name (with Dactylethra as a
junior synonym) was in a Handbook of Zoology from 1858
(van der Hoeven, 1858).
The name Xenopus became increasingly common in
the 1890s, starting with a description of Xenopus breeding in the wild (Leslie, 1890), and shortly thereafter, with
the frst description of Xenopus breeding in captivity by
Frank Beddard, working with animals at the London Zoo
(Beddard, 1894). Beddard included some quite nice illustrations of the tadpole, but he laments that the “intervening Sunday prevented me from examining the early stages”
(Beddard, 1894). His account is flled with other rich details,
including that the tadpoles he observed had been deposited
on Saturday May 27th. Such details may also be his undoing, however, as he also reports that the frogs he studied
were collected by a Mr. Finn in Zanzibar, the home not
of X. laevis but of X. mulleri. These and other interesting
minutiae of early Xenopus research were the subject of a
fun series of blog posts by Malcolm Peaker in his Zoology
Jottings ( https://zoologyweblog.blogspot.com/ ).
Xenopus may be said to have formally entered the realm
of developmental biology with a sprawling and impressive paper on their early development from Edward Bles in
1905. He was a noted naturalist, though “for the shackles of
departmental teaching and organization, Bles had some distaste” (Hopkins, 1926 ). Lucky for him, he also had tremendous personal wealth. After several efforts as a traditional
academic, he decided that independent, entirely self-funded
science was best and pursued that course for over 20
years (Hopkins, 1926 ) While working at the University of
Glasgow, Bles set about to breed and raise Xenopus frogs.
Of course, work with tropical frogs in the cold of Glasgow
required new apparatus, and a tropical aquarium devised by
Samuel Budgett (of the now-popular Budgett’s frog [Amin et al.,
2015]) provided just the thing (Bles, 1905).
With this apparatus, Bles was able to provide a remarkably
comprehensive description of the early development of
Xenopus laevis, and moreover, the work was accompanied
by a gorgeous series of illustrations by A.K. Maxwell (Bles,
1905). These images of Xenopus would launch Maxwell’s
decades-long career as a scientifc illustrator of the f rst
order, with work ranging from medical illustration of wounds
during WWI, to updating the illustrations in Gray’s Anatomy,
to rendering Max Perutz’s frst model of hemoglobin (De
Xenopus
his untimely death, Daudin is credited with the description of dozens of new species of animals, working in many
cases from preserved specimens in collections around Paris
( Bour, 2011 ).
Among these is the frst description of the genus now
called Xenopus, though exactly which species seems unclear.
Working from a single preserved specimen in the Museum
d’Histoire Naturelle in Paris, Daudin succinctly described
the smooth body, the dorsally set eyes, and the “longitudinal
rows of small prickles” along the back (Daudin, 1803), an
anatomical landmark that even the newest student injecting
hormones to induce egg laying will recognize immediately.
Daudin’s book also includes the f rst scientif c illustration
of Xenopus (Figure 1.1). As it happens, his wife Adélaïde
was a talented artist, and she provided many illustrations
for his work, though the image of the smooth toad is attributed instead to an artist named Prévost. In a further tragedy,
Adélaïde also died of tuberculosis, a few days before her
husband (Bour, 2011).
Surprisingly, neither Daudin’s description nor the accompanying illustration makes note of the claws on what would
later come to be known as the African clawed frog. Thus,
when the great French naturalist Georges Cuvier assembled
his magnum opus Le Règne Animal in 1829, he chided
Daudin for his omission of the claws, and indeed, it does
seem like quite the blunder. However, in the f rst focused
and comprehensive description of our frog in 1864, J.E.
Gray notes that the animals’ claws are “deciduous in spirits”
(Gray, 1864), suggesting the possibility that the claws on
Daudin’s preserved specimen had dissolved before he made
his observations. Regardless, Cuvier renamed the genus
Dactylethra, a rendering of “fnger sheath” or “thimble”
( Cuvier, 1829 ).
The genus name Dactylethra was commonly used by
19th-century writers, including the frst description and
images of tadpoles of the species (Gray, 1864). The name
Xenopus only became fashionable in the 1890s, which
is curious, since it was actually frst suggested in 1827.
Even more curious is the forum in which that name was
frst bestowed: a footnote appended to a letter written by
Heinrich Boie and published in Lorenz Oken’s journal,
Isis (Wagler, 1827). Previous authors have attributed this
footnote to “Wagler, H.,” but thanks to the digitized archives
available from the Biodiversity Heritage Library ( www.
biodiversitylibrary.org/), I have been able to learn a bit more
about this important fgure in the history of Xenopus.
As it happens, the footnote proposing the genus name
“Xenopus” has no frst initial indicated; it is signed simply:
“Wagler” (Figure 1.2). This almost certainly refers to Johann
Georg Wagler, a noteworthy German naturalist, who in 1830
and 1831 published two monographs on the Amphibia. In
fact, in his Natürliches System der Amphibien of 1830, he
cites the earlier footnote in Isis, and moreover makes frequent
mention of Xenopus, making a special note of its clawed toes
(Wagler, 1830). Moreover, in his original footnote, Wagler
even lets Daudin off the hook for missing the claws, suggesting that he must have observed a decayed specimen (Wagler,
1827). In an unsettling coincidence, Wagler, like Daudin,
died tragically, in this case at 32 years old from an accidental,
self-inficted gunshot wound (Hess, 1896 ).
Wagler’s naming of the genus is the one that f nally stuck,
but not until long after his death. Dactylethra was used in
several important 19th-century studies of the animal. Just
the same, text searches of the Biodiversity Heritage Library
revealed that Wagler’s naming of Xenopus had been translated into French by 1829 (Boie and Wagler, 1829), and
even as early as 1831, an English synopsis of Cuvier’s book
acknowledges Wagler and includes Xenopus as a synonym
for Dactylethra ( Griffth, 1831). Though my survey was in
no way systematic, the earliest instance I found of Xenopus
being used as the primary name (with Dactylethra as a
junior synonym) was in a Handbook of Zoology from 1858
(van der Hoeven, 1858).
The name Xenopus became increasingly common in
the 1890s, starting with a description of Xenopus breeding in the wild (Leslie, 1890), and shortly thereafter, with
the frst description of Xenopus breeding in captivity by
Frank Beddard, working with animals at the London Zoo
(Beddard, 1894). Beddard included some quite nice illustrations of the tadpole, but he laments that the “intervening Sunday prevented me from examining the early stages”
(Beddard, 1894). His account is flled with other rich details,
including that the tadpoles he observed had been deposited
on Saturday May 27th. Such details may also be his undoing, however, as he also reports that the frogs he studied
were collected by a Mr. Finn in Zanzibar, the home not
of X. laevis but of X. mulleri. These and other interesting
minutiae of early Xenopus research were the subject of a
fun series of blog posts by Malcolm Peaker in his Zoology
Jottings ( https://zoologyweblog.blogspot.com/ ).
Xenopus may be said to have formally entered the realm
of developmental biology with a sprawling and impressive paper on their early development from Edward Bles in
1905. He was a noted naturalist, though “for the shackles of
departmental teaching and organization, Bles had some distaste” (Hopkins, 1926 ). Lucky for him, he also had tremendous personal wealth. After several efforts as a traditional
academic, he decided that independent, entirely self-funded
science was best and pursued that course for over 20
years (Hopkins, 1926 ) While working at the University of
Glasgow, Bles set about to breed and raise Xenopus frogs.
Of course, work with tropical frogs in the cold of Glasgow
required new apparatus, and a tropical aquarium devised by
Samuel Budgett (of the now-popular Budgett’s frog [Amin et al.,
2015]) provided just the thing (Bles, 1905).
With this apparatus, Bles was able to provide a remarkably
comprehensive description of the early development of
Xenopus laevis, and moreover, the work was accompanied
by a gorgeous series of illustrations by A.K. Maxwell (Bles,
1905). These images of Xenopus would launch Maxwell’s
decades-long career as a scientifc illustrator of the f rst
order, with work ranging from medical illustration of wounds
during WWI, to updating the illustrations in Gray’s Anatomy,
to rendering Max Perutz’s frst model of hemoglobin (De