Human Pregnancy: Gestation Period Variation Compared with Nanny Goats

One of the stories running during this year’s ‘silly season’, when news media are desperately trying to fill newspapers, radio, television and websites, was one highlighting research¹ which showed, in the words of the BBC News website, Pregnancy length “varies naturally by up to five weeks”.

Great surprise was expressed about this range of variation (14% of the mean ovulation to delivery period of 268 days). In practical terms the sheer stupidity of giving expectant mothers a ‘due date’ (with the implication that being ‘overdue’ is abnormal) was highlighted. In these days where education in biological systems has declined to the extent that the public expect certainty in all things biological and medical, the reports helped to highlight that variation and uncertainty are to be expected.

Reading of the extent of the variation, I tried to remember the variation I had found in the goat. In 1978 I collected all the data from the then goat herd at what is now the Babraham Institute that had been recorded between 1954 and 1977, a total of 374 cases². The mean time between mating and delivery was 150 days (as also found by Sydney Arthur Asdell in 1929). Although 90% of births occurred between 146 and 154 days, the full range was 135-159 days (24 days). The percentage variation (24/150) of 16 is very similar to the latest human data.

So, if we have 14% variation for the human gestation period and 16% for the caprine, what about other mammals? A quick look through a UFAW Handbook and elsewhere suggests a similar level of variation (cat 14%, dog 13%, rabbit 22%, guinea pig 11%, rat 14%). Somebody must have noted this before somewhere but if they have I cannot remember it nor can find reference to it.

Is the variation in the length of pregnancy the simple result in differences in the rate of development of the fetus? Or adaptive in that the time of parturition can be controlled? Or both?

As work on the initiation of parturition by activation of the fetal adrenal developed during the 1970s, the talk in the coffee room was that fetal control of the onset could not be the whole story since some herd animals clearly synchronised parturition in addition to synchronising oestrus. Wildebeest were the prime example. The extent of the control is illustrated by Berger’s studies on American Bison³. Gestation was shorter by approximately 6 days in those females that mated after the seasonal peak, thereby ensuring that births were synchronised with the females that had mated at the peak. There was a difference in whether or not the females were in good body condition. Gestation was earlier in those in good condition but not in those in poor condition. Clearly though there is an advantage in ensuring that births are synchronised since delivering early came with a cost. The tradeoff was that the offspring of those females that delivered early were approximately 20 kg lighter when 6 months old. Achieving synchrony, presumably to lessen the chances of predation, is clearly an important reproductive tactic. But are we any the wiser now as to the physiological mechanism of this control than we were in the mid-1970s?

Finally, is there any evidence of adaptive control of the onset of parturition in human mothers? I know of no evidence, only of all sorts of attempts to get things moving. I have seen the exertion of ascending the Peak in Hong Kong along Hatton Road as one try; the eating of a very large roast-beef dinner as another. Did they work? Well, the babies appeared eventually.

¹ Jukic, A.M., Baird, D.D., Weinberg, C.R., McConnhaughey, D.R. & Wilcox, A.J. 2013. Length of human pregnancy and contributors to its natural variation. Human Reproduction doi:10.1093/humrep/det297

² Peaker, M. 1978. Gestation period and litter size in the goat. British Veterinary Journal 134, 379-383.

³ Berger, J. 1992. Facilitation of Reproductive Synchrony by Gestation Adjustment in Gregarious Mammals: A New Hypothesis. Ecology 73, 323-329.

The Eponym Dictionary of Amphibians: Where’s Conrau?

Starting in 2003 with Whose Bird?, the Eponym Dictionary series (mammals following birds, then reptiles and, this year amphibians^†) has provided interest and amusement in epi-zoology. As the series has gone on, information from earlier volumes is often repeated, as a necessity since collectors, benefactors and museum workers often have birds, mammals, reptiles and amphibians named after them. There is particular overlap with reptiles and amphibians and I was often miffed to find I had already read an entry in one of the other volumes. I took three double pages at random and found that a third of entries were repeats from earlier volumes.

I found a few omissions. The most remarkable I noted was the absence of Gustav Conrau who collected in the Cameroons in the closing years of the 19th century. He does appear in the volume on reptiles for the gecko, Lygodactylus conraui. Conrau should appear in the volume on amphibians for the genus Conraua, now comprising six species including that famous amphibian, the Goliath Frog, Conraua goliath. The genus was erected by Fritz Nieden in 1908 for G. robusta (Die Amphibienfauna von Kamerun. Mitteilungen des zoologischen Museums Berlin 3, 489-518) and the Goliath Frog, described by Boulenger in 1906 as Rana goliath, was moved into it by Nieden.

The story of Conrau, a German trader and labour recruiter in Cameroon is told in the Eponym Dictionary of Reptiles. He had recruited labour from the Bangwa people for a plantation to the south. When he returned, the Bangwa thought their labourers must have died since they were not with him. The Bangwa held him hostage against their men’s return. He was wounded while trying to escape. He probably killed himself to avoid being captured although he may have been shot by his pursuers. The Germans sent two punitive expeditions as a consequence.

Fritz Nieden (1883-1942), incidentally, does appear – for the caecilian Boulengerula niedeni described in 2005.

^†The Eponym Dictionary of Amphibians. 2013. Beolens, B., Watkins, M., Grayson, M. Exeter: Pelagic Publishing

Donors of Reptiles to London Zoo 1914/15: 9. C.R. Walker and Mons. de Southoff

I reach the end of this series of posts with failure. I have been unable to find any more information on two donors. This is what Clin Keeling wrote in A Short History of British Reptile Keeping:

First there was one C.R. Walker, F.Z.S., of The Vivarium, West Bromwich, near Birmingham, who during the early days of the war sent, and received on an exchange basis, quite a lot of material to Regent's Park; for example one consignment of his consisted of twenty-five assorted Skinks, Geckos (including the New Zealand species) and Tree Frogs, while during research in another direction I made the fascinating discovery that on 15th October 1913 London's first Soft-shelled Turtles (Trionyx) came from him. As far as we're concerned just who and/or what he was must, pro tem, remain a mystery, although it sounds very much to me as though The Vivarium was a shop that specialised in animals of this kind – in which case it must have been one of the very first in the country and possibly indicative that even at that period there was more demand for them than wenow realise  – or it could even have been some kind of reptile display, or both. As things stand, though, we must leave it there in the shadowy land of speculation.

The only thing I do know is that C.R. Walker was not a Fellow of the Zoological Society in 1910 or 1913. There is a speculative geographical connexion with Herbert Tomlin Pollitt (23 June 1013 post) but that is all I have been able to find. This one needs more work in the Zoo Library because it would be very interesting to shed more light, for the reasons Clin explained, on just who Walker was and what The Vivarium did.

Finally, I have also been unable to find anything about the Mons. de Southoff who donated European salamanders and snakes.

ITV’s The Zoo: An Own Goal for The Zoo?

ITV’s three-part television series on London and Whipsnade Zoos has just ended. It was, of course, as dumbed down and as superficial as one would expect of ITV at 8.00 pm. However, what the Zoological Society of London (why was it 'Zedessell' with every breath?) clearly saw as an exercise in free publicity seemed to me to backfire.

Nearly every sequence (ignoring the endless repeated cutaways and fill-in shots) involved some kind interventions by vets or the hand-rearing of mammals and birds by keepers. Notwithstanding the fact that advances in veterinary practice have had an enormous impact on our ability to care for wild animals in captivity and the Zoo itself has been in part responsible for the impressive array of technology now available, the truth is that just about every veterinary intervention that is necessary in a zoo reflects a failure of animal husbandry of some kind. In the same way, hand-rearing reflects a failure to provide the physiological or psychological requirements of the mother. Calling in the vet or having to hand rear are indicative of failure — not success — in zoo practice.

I presume that so much emphasis was placed on the team of vets because operations on animals provide ‘good’ television for the great British public to gawp at, but some of the ‘health checks’ seemed more likely to prevent breeding (through the physiological axis that links stress with reproductive success) than enable it. Cute hand-reared mammals and stroppy, fluffy penguins fall into the same category of ‘good’ television but failed husbandry. I really do hope that the emphasis the producers of the programmes chose does not reflect the balance of activity at the two zoos in the 2010s. Surely, wild animal husbandry has advanced more than that in the past thirty years even if some of the housing at the Zoo hasn’t. We in this house may not be alone in thinking that we saw more interventions by the vets at the Zoo than interventions by the Blair-Brown government.

On one redeeming note, the baby Malay Tapir and its mother did appear in the final episode without an anaesthetic dart in sight. But The Zoo was not The Ark and Molly Dineen it was not.

Biological Systems: Is Redundancy Redundant?

The term redundancy is often used to describe two or more processes in biological systems that appear to do the same job. The term has been borrowed from Information Theory. The definition in Wikipedia is as useful as any:

Redundancy in information theory is the number of bits used to transmit a message minus the number of bits of actual information in the message. Informally, it is the amount of wasted "space" used to transmit certain data.

I have never been comfortable with the term in biological systems except in discussions on signalling systems (endocrine, autocrine, paracrine, intracrine) where it can be used in its proper, Information Theory, sense^‡. My qualms on using it for biochemical pathways and membrane transport systems, for example, are that it has implications of a mechanism being present but not needed. I have argued in the past that parallel pathways and different transport mechanisms carrying the same substrate are better described as safety mechanisms (belt-and-braces adaptations) or as systems that may be used in some circumstances and not others.

The other problem in using the term is that it can be confused with redundancy in the evolutionary sense, a vestigial character for example. I sometimes think we should leave the term in its more usual English meaning of superfluous in the hands of human resource departments, those parasitic forms of life, to apply to themselves. Auto-redundancy in these anti-personnel departments^† would do more than a little to aid economic recovery — and benefit science, technology and engineering.

The twitching of my ears and muscular contractions in other parts of my anatomy at hearing the term (along with ‘model organism’, ‘model system’ and the like) appear more and more to be justified as mechanisms are investigated in greater depth than the appearance of blots on gels.

A recent paper in Proceedings of the Royal Society* by Zoe Dumas, Adin Ross-Gillespie and Rolf Kümmerli sums up in its title the dangers of using the term willy-nilly: Switching between apparently redundant iron-uptake mechanisms benefit bacteria in changeable environments. I can do no better than to quote from the abstract:

Bacteria often possess multiple siderophore-based iron uptake systems for scavenging this vital resource from their environment. However, some siderophores seem redundant, because they have limited iron-binding efficiency and are seldom expressed under iron limitation. Here, we investigate the conundrum of why selection does not eliminate this apparent redundancy. We focus on Pseudomonas aeruginosa, a bacterium that can produce two siderophores—the highly efficient but metabolically expensive pyoverdine, and the inefficient but metabolically cheap pyochelin. We found that the bacteria possess molecular mechanisms to phenotypically switch from mainly producing pyoverdine under severe iron limitation to mainly producing pyochelin when iron is only moderately limited. We further show that strains exclusively producing pyochelin grew significantly better than strains exclusively producing pyoverdine under moderate iron limitation, whereas the inverse was seen under severe iron limitation. This suggests that pyochelin is not redundant, but that switching between siderophore strategies might be beneficial to trade off efficiencies versus costs of siderophores…

So, how many apparently redundant mechanisms can really be described as such? Perhaps we really should confine it to its proper use in signalling systems where redundancy in the message decreases the error in transmission.

^‡ Peaker, M. 1992. Chemical signalling systems: the rules of the game. Journal of Endocrinology 135 1-4
* Proceedings of the Royal Society B 7 August 2013 vol. 280 no. 1764 20131055
^† Sir Barry Cross’s loudly whispered description in the early 1980s of the personnel department of the old Agricultural Research Council (later AFRC, now BBSRC)

Donors of Reptiles to London Zoo 1914/15: 8. Herbert Tomlin Pollitt

Again, and nearing the end of this series of posts, this is what Clin Keeling wrote in A Short History of British Reptile Keeping:

H. Pollit of 7 Grosvenor Road, Handsworth, Birmingham, gave an Alligator, an Eyed Lizard and a European Pond Tortoise…

Thanks to a search of the 1911 Census, a family history on ancestry.co.uk and the keeper of that history, Any Pollitt, I have identified this ‘H. Pollit’ as Herbert Tomlin Pollitt. He was born in 1897 in Irlam, Lancashire. In 1911, aged 13, he was living at the address shown in the Zoo’s records. His father, a chemist, was manager of a soap works; he worked for Lever Brothers (now Unilever).

Herbert had ‘a very colourful life’. In 1917 he was commissioned 2nd Lieutenant from the Indian Army’s Cadet College at Quetta (now in Pakistan). The Cadet College occupied the buildings of the famous Staff College which was closed for the duration of the war. By the end of the war it appears he was with 20th Deccan Horse, an Indian Army cavalry regiment (renowned for its charge on the Somme in 1916) on the western front.

He became a garage owner (authorised Morris dealer) in Birmingham, and is shown as living on a farm near Droitwich. Thrice-married, he was killed, along with a son from his second marriage and a son from his third marriage, in November 1965, aged 68.

So here we do seem to have somebody who may have given his reptiles to London Zoo before joining the army. We do not know if he retained any interest in animals after the war or at the farm where he lived near Droitwich.

We also do not know where he got his reptiles in the first place. It seems unlikely that they come from his father’s travels For Lever Brothers since one was North American and the others European. However, I cannot help wondering if they came from a local source. Clin Keeling mentions C.R. Walker from “The Vivarium”, West Bromwich (I will deal with him in a later post) as a donor of reptiles to London Zoo over this period. Handsworth is adjacent to West Bromwich. Was there a connexion?

Blue Poison-Dart Frog: The Times Gets It All Wrong

The Times really should check its sources and material before publication. Today’s edition has a short article that states:

British scientists have successfully bred a rare species of frog that contains enough poison to kill up to ten adults. The blue poison dart frog, which is 2.5cm long, is found in the tropical forests of Costa Rica and Brazil. Experts at Walford and North Shropshire College have successfully bred one in their laboratory…

What a load of cock. Where did The Times get such an inaccurate story?

The blue poison dart frog was originally described as Dendrobates azureus. It was discovered in 1968 in mountainous island in the Sipaliwini savanna of Suriname. It was named by its discoverer (Hoogmoed) in 1969. He writes:

In 1970 I returned to the Sipaliwini savanna on another expedition and at that time I collected 10 specimens of D. azureus from the Vier Gebroeders forest island, and transported them alive to Holland, where they formed the basis of the first, and only legal, breeding colony of D. azureus. All other colonies were established with smuggled specimens, from which the present specimens in captivity are descendants¹.

Private breeders in the Netherlands and Germany soon began to breed these frogs and they entered the open market. Some zoos (Edinburgh was one) were also keen to breed them because of reports that their habitat was threatened by fire. In short, D. azureus was, for a short time, treated as an endangered species.

I bought adults and tadpoles from Dutch breeders in the early 1990s and the late Bob Davies and I bred them. They are now commonly kept and bred in captivity throughout the world and there is no justification whatsoever in the claim published in The Times. Indeed, an quick search shows them available at £60 each from a British dealer. As the IUCN website³ says:

This species breeds easily in captivity, and is found in zoos around the world.

Having seen these frogs alongside coloured forms of Dendrobates tinctorius, the thought of many of us was that they were a local form of D. tinctorius. Other than in colour they resembled D. tinctorius and there was no evidence that tinctorius and azureus were sympatric. This suspicion was confirmed in 2006: D. azureus was demoted to a junior synonym of D. tinctorius (summary in 2).

All the information anybody needs, from taxonomy to distribution, is readily available from the IUCN website where D.tinctorius rates ‘least concern’³.

So, here’s one we bred earlier:

The reason for my writing about this claim here is to highlight a common and growing problem. Zoos and wildlife collections are forever putting out press statements that they have bred such-and-such and that it is ‘endangered’. Such claims are rarely true and even when it is correct that the species in question is endangered, or in some other less than safe category in the wild, there are often so many in captivity that zoos do not know what to do with them. Not only do such silly or trivial claims play straight into the hands of members the anti-zoo lobby who know a false claim when they see one but detract from the hard-earned achievements of those involved in ex-situ conservation.

I now expect to see reports that such and such an organisation has bred axolotls — critically endangered in the wild. I shall probably read the report while drinking coffee in Dobbie’s Garden Centre, yards away from tanks containing axolotls at £22 each.

¹ http://www.sipaliwinisavanna.com/docs/discovery_of_the_blue_arrow_poison_frog.pdf

² http://research.amnh.org/vz/herpetology/amphibia/?action=references&id=9710
³ http://www.iucnredlist.org/details/summary/55204/0