Friday 24 April 2020

Stejneger’s Stonechat—in Hong Kong last week

From Hong Kong last week came this photograph of a male stonechat. Taxonomy of the stonechats of Eurasia is mighty complicated and this one is known at present as Stejneger’s Stonechat, Saxicola stejnegeri.

I say mighty complicated because to old Hong Kong birders this was called the Siberian Stonechat, S. maurus and sometimes as an eastern race of the Common Stonechat, S. torquatus. Since some of the evidence that recognises the form found in Hong Kong as a passage migrant and winter visitor from its breeding grounds in north-east China, is based on differences in mitochondrial and not nuclear DNA, I am not sure that the present taxonomy will hold sway for that long.

Stejneger was the Norwegian-born Leonhard Hess Stejneger (1851-1943) who made his name in the U.S.A. mainly as a herpetologist working at the Smithsonian. The pronunciation of Stejneger always offers a challenge to Brits. Here, apparently, is the way it should sound.

Beautiful bird.

Thursday 23 April 2020

How—and why—do tadpoles fill their lungs?

Those of us who have watched and kept tadpoles will have noticed that sometimes they come to the surface to take in air. A recent paper shows that very young and therefore very small tadpoles cannot break through the surface tension of the water in which they live. However, they still manage to take in air by a process the authors call ‘bubble-sucking’.

Even three days after hatching and only 3 mm long tadpoles have been found to fill their lungs. High-speed video showed what was happening. In five species of frog from North America and in the much-studied African Clawed Frog, Xenopus laevis the authors found: 

…mouth attachment to the water’s undersurface, the surface drawn into the mouth by suction, a bubble ‘pinched off’ within the mouth, then compressed and forced into the lungs. 

As tadpoles grow, they gain the size and strength to breach the surface of the water to take in air. However, larger tadpoles of one species studied (Grey Treefrog, Hyla versicolor) continued to use bubble-sucking exclusively while those of others used both methods until metamorphosis.

The authors recorded a similar of taking in air in salamander larvae which have external gills.

From Schwenk & Phillips 2020

It would be easy to assume that tadpoles take in air in order to extract the oxygen it contains. Tadpoles would normally be expected to respire through their gills and skin. With low concentrations of oxygen in the water, hot or fetid, for example, the selective advantage of being able to breathe air is obvious. However, the presence of air in the lungs is related to another function in these aquatic organisms—the control of buoyancy. I am surprised that the authors in their discursive account chose to concentrate on a presumed respiratory function when there has been a considerable amount published on air in the lungs in relation to the control of buoyancy. The authors themselves noted that in at least one of the species studied the lungs at 3 days after hatching are poorly vascularised and do not acquire a rich blood supply typical of a site of gaseous exchange until later in development. 

Tadpoles, by having the ability to fill their lungs with air using the newly discovered method of ‘bubble-sucking’ to overcome the surface tension of water, thus have the opportunity to use that air for the control of buoyancy and as a source of oxygen, depending on their stage of development and the degree of oxygenation of the water in which they live.

And I am still fascinated by tadpoles despite the strictures of my grandfather that I would never be able to make a living by studying them.

Schwenk K, Phillips JR. 2020. Circumventing surface tension: tadpoles suck bubbles to breathe air. Proceedings of the Royal Society B 287: 20192704. 

see also

Gee JH, Rondeau SL. 2012. Strategies used By tadpoles to optimize buoyancy in different habitats. Herpetologica 68, 3-13

Friday 3 April 2020

The Coronavirus War: A quotation from an ace scientific adviser to government

Quoting from Solly Zuckerman, who pioneered operational research in the Second World War and who later became Chief Scientific Adviser to the British Government, might be appropriate in the present war against a novel virus in which scientific advice plays an even greater rôle:

One simply cannot order up so many assorted scientists to do a job, or command them to make a ‘break-through’. Operational prob­lems, I discovered, savoured more of the characteristics of biological enquiry than of those encountered by chemists or physicists. I had a fear that scientists who were accustomed to the handling of only strictly controlled situations, and who had little taste for others—for example, ‘pure’ mathematicians, or mathematical physicists, or theoretical biolo­gists—would have little to contribute to the solution of the kind of issues that were of overriding importance to the good military leader or politician… War generated an inflexibility of outlook, and the more remote from the scene of action, the more inflexible the desk warriors became. 

Pity, as an afterthought, I cannot find a quote about vulpine but scientifically illiterate journalists who labour an unimportant matter to advance their own or their organisation’s political agenda.

Solly Zuckerman
Tobruk, 1943

Zuckerman S. 1978. From Apes to Warlords. London: Hamish Hamilton, p 363

Thursday 2 April 2020

Frogs of China. Alice Boring’s Life and Work. 3. Herklots and Hong Kong Amphibians

As I mentioned in Parts 1 and 2 of this series Geoffrey Herklots sent specimens of Hong Kong amphibians to Peking for Alice Boring to identify. In the first of those papers all of which were published in Hong Kong Naturalist she wrote that the material was collected under the supervision of Dr Herklots for a period of a little over one year, from December 1930 to January 1932…Herklots had arrived at the University of Hong Kong in 1928 to teach biology, just like Boring in Peking, to medical students. Further specimens were sent in 1933 and possibly later but of these only one had not been represented previously. The specimens, number unknown, were collected on Hong Kong Island, on Lantau as well as in Kowloon and the New Territories.

Alice Boring identified 16 species (a 17th Herklots realised had been collected elsewhere and I have omitted any reference to it). To date 24 species of amphibians have been recorded in Hong Kong. Of the ones recorded before 1930 the Herklots collection missed only one.

The following is a checklist of Hong Kong amphibians, using the current scientific name. The ones marked § are those identified by Boring.

§Hong Kong Newt Paramesotriton hongkongensis
Leaf-litter Toad Leptolalax laui. First recorded in Hong Kong 1979
§Short-legged Toad Megophrys brachykolos (from tadpole as M. boettgeri and an adult tentatively as M. longipes )
§Asian Common Toad Duttaphrynus melanostictus
Hong Kong Cascade Frog Amolops hongkongensis. First recorded in Hong Kong 1950
South China Cascade Frog Amolops ricketti. First recorded in Hong Kong 2004
§Paddy Frog Fejervarya limnocharis
§Chinese Bullfrog Hoplobatrachus rugulosus
§Günther’s Frog Sylvirana (Hylarana) guentheri
Brown Wood Frog Hylarana latouchii. First recorded in Hong Kong 1984
§Three-striped Grass Frog Hylarana macrodactyla
§Two-striped Grass Frog Hylarana taipehensis
Big-headed Frog Limnonectes fujianensis (not recorded in Hong Kong between 1917 and 1987)
§Rough-skinned Floating Frog Occidozyga lima
§Green Cascade Frog Odorrana chloronata
§Lesser Spiny Frog Quasipaa exilispinosa (as Q. spinosa). Identified as species in 1975 (see below)
Giant Spiny Frog Quasipaa spinosa. Adults first discovered in Hong Kong 1978 (see below)
Romer’s Tree Frog Liuixalus romeri. Discovered in Hong Kong 1952
§Brown Tree Frog Polypedates megacephalus
§Spotted Narrow-mouthed Frog Kalophrynus interlineatus
§Asiatic Painted Frog Kaloula pulchra
Butler’s Pigmy Frog Microhyla butleri. First recorded in Hong Kong 1964
§Ornate Pigmy Frog Microhyla fissipes
§Marbled Pigmy Frog Microhyla pulchra

G.A.C. Herklots
As I read Boring’s papers I became intrigued about the two species of Quasipaa, exilispinosa and spinosa, now known to occur in hill and mountain streams. One, Q. spinosa is much larger than the other, reaching 14 cm—the largest anuran in Hong Kong. Although the drawing used to illustrate Boring’s paper is clearly of Q. exilispinosa (the webbing of the hind limbs does not reach the tip of the toes whereas in Q. spinosa it does) she wrote: ‘My material from Hong Kong includes two very large specimens and 7 medium-sized ones…’ Unfortunately, she provided no quantitative information but there remains the possibility that the collection sent by Herklots did contain the two species of spiny stream frogs rather than just the one.

This collaborative effort between Alice Boring and Geoffrey Herklots was the first organised survey of the amphibians of Hong Kong. It provided the basis on which others have built, starting, of course, with John Romer who began his activities soon after his arrival in the late 1940s.

I do not know if Boring and Herklots ever met. There was one opportunity in Hong Kong in 1937 when Boring, caught away from Yenching during the Japanese advance, made her way back to the university by first travelling south.

Paddy Frog (Fejervarya limnocharis)

Boring AM. 1934. The amphibia of Hong Kong Part I. Hong Kong Naturalist 5, 8-22

Boring AM. 1934. The amphibia of Hong Kong Part II. Hong Kong Naturalist 5, 95-107

Boring AM. 1936. The amphibia of Hong Kong Part III. Hong Kong Naturalist 7, 11-14

Karsen SJ, Lau M W-N, Bogadek A. 1998. Hong Kong Amphibians and Reptiles. Second Edition. Hong Kong: Provisional Urban Council