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Acid water = stunted tadpoles?: |
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Donny Senior Member Joined: 11 May 2004 No. of posts: 53  View other posts by Donny |
Posted: 11 May 2004 Hi! At the weekend, I was out walking and I crossed over a piece of land that until three or four years ago, was a pine forest plantation. It has since been cleared, and I saw that many of the wheel ruts and depressions created by the vehicles during clearance have filled with water and are now teeming with wildlife, including tadpoles, which I assume are Common Frog, given pool size and my location (Eastern Scotland)...only thing is, all of the tadpoles are absolutely tiny, like newly hatched size, only much more lively. I even found some intact, obviously infertile spawn, and this is early May! Tadpoles in ponds just a short distance away are big and fat already. There is no remaining shade and the pools are all shallow and warm. Could this be due to the acidity in the soil? These taddies are seriously stunted compared to their neighbours, and if this is the case, I wonder why frogs would choose to breed in such a location at all..I worry about them growing enough to metamorphose this year. So are these taddies getting pickled or what's going on? |
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GemmaJF Admin Group Joined: 25 Jan 2003 No. of posts: 2090  View other posts by GemmaJF |
Posted: 12 May 2004 Hi Donny, Common frogs will lay spawn in hopelessly ephemeral water bodies, from ruts to puddles. It's thought to be a tactic to avoid predation of the tadpoles by fish and possibly newts, which they have little protection against. (Fish not living for very long in puddles). Smaller water bodies may also benefit the tadpole development as they heat up much more quickly. It's interesting to compare common toads that have a preference for fishponds, where they benefit from the common frog tadpoles being eaten by fish and the reduced competition, but they themselves are protected because they are so distasteful (not that I've ever tried one). I would guess that the stunting of your tadpoles is largely due to overcrowding and lack of invertebrate food in the small water bodies you found them in and it is likely they will perish before metamorphosis, but this is the chance that common frogs take to gain advantage in other ways. last year I was called out to look at some 'bullfrog' tadpoles in London. It turned out that they were huge common frog tadpoles close to metamophosis, this was in a pond little more than 2ft square. The reason for this massive growth seemed to be an abundance of tubifex worms in the tiny pond - in this case the common frogs tactics had paid off! Gemma Fairchild, Independent Ecological Consultant |
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Ewan Member Joined: 14 Jul 2003 No. of posts: 21 View other posts by Ewan |
Posted: 13 May 2004 Hi Donny A quick literature search would seem to suggest that if your ponds are indeed fairly acid then that would go some way towards explaining any impaired tadpole development. Ewan. 1. Author(s): Glos J; Grafe TU; Rodel MO; Linsenmair KE Title: Geographic variation in pH tolerance of two populations of the European common frog, Rana temporaria Source: COPEIA 2003, Iss 3, pp 650-656 Abstract: In a laboratory experiment, we investigated the effects of low pH environment, a key parameter of acidity, on mortality, growth, and development in two populations of Rana temporaria that differ in the pH of their breeding ponds. In a population with pH neutral breeding sites, low pH treatment caused a prolongation in embryogenesis and an increased embryonic mortality, a higher proportion of deformed hatchlings and an increased larval time. Embryos and larvae from a population that was exposed naturally to low pond pH were more pH tolerant, as the only effect of low pH was increased larval time. 2. Author(s): Pakkasmaa S; Merila J; O'Hara RB Title: Genetic and maternal effect influences on viability of common frog tadpoles under different environmental conditions Source: HEREDITY 2003, Vol 91, Iss 2, pp 117-124 Abstract: The influence of environmental stress on the expression of genetic and maternal effects on the viability traits has seldom been assessed in wild vertebrates. We have estimated genetic and maternal effects on the viability (viz probability of survival, probability of being deformed, and body size and shape) of common frog, Rana temporaria, tadpoles under stressful (low pH) and nonstressful (neutral pH) environmental conditions. A Bayesian analysis using generalized linear mixed models was applied to data from a factorial laboratory experiment. The expression of additive genetic variance was independent of pH treatments, and all traits were significantly heritable (survival: h(2) approximate to 0.08; deformities: h(2) approximate to 0.26; body size: h(2) approximate to 0.12; body shape: h(2) approximate to 0.14). Likewise, nonadditive genetic contributions to variation in all traits were significant, independent of pH treatments and typically of magnitude similar to the additive genetic effects. Maternal effects were large for all traits, especially for viability itself, and their expression was partly dependent on the environment. In the case of body size, the maternal effects were mediated largely through egg size. In general, the results give little evidence for the conjecture that environmental stress created by low pH would impact strongly on the genetic architecture of fitness-related traits in frogs, and hamper adaptation to stress caused by acidification. The low heritabilities and high dominance contributions conform to the pattern typical for traits subject to relatively strong directional selection. 3. Author(s): Pahkala M; Rasanen K; Laurila A; Johanson U; Bjorn LO; Merila J Title: Lethal and sublethal effects of UV-B/pH synergism on common frog embryos Source: CONSERVATION BIOLOGY 2002, Vol 16, Iss 4, pp 1063-1073 Abstract: Although the negative effects of ultraviolet-B (UV-B) radiation on the development of many amphibian species have been demonstrated, some species-such as the common frog (Rana temporaria)-seem to be tolerant of UV-B radiation. The amount of UV-B radiation received is likely to vary among populations of the same species, but little is known about geographic variation in UV-B tolerance. Similarly, although UV-B radiation can have synergistic effects with other stressors, no studies have focused on geographic variation of these effects on amphibians. We investigated the synergistic effects of UV-B radiation and low pH on hatchability and early development of R. temporaria embryos in a factorial laboratory experiment with animals originating from southern and northern Sweden. Newly fertilized eggs were exposed to three different UV-B treatments (no UV-B [control], 1.254 k/J/m(2) [normal] and 1.584 k/J/m(2) [26% enhanced]) and two pH treatments (4.5 [low] and 7.6 [neutral]). Ultraviolet-B radiation in combination with low pH lead to markedly (approximately 50%) reduced survival rates and increased (approximately 30%) frequency of developmental anomalies in the northern but not in the southern population. The UV-B- exposed embryos hatched at smaller size in the southern population, whereas low pH reduced hatchling size in both populations. In both populations and pH treatments, embryos in the normal UV-B treatment developed significantly faster than embryos in the enhanced or control UV-B treatments. No interaction between pH and UV-B on developmental rates or hatchling size was detected. The results demonstrate-contrary to earlier belief-that R. temporaria embryos are not insensitive to increased levels of UV-B radiation. The lethal effects of UV-B radiation may, however, become manifested only in combination with other stressors, such as low pH, and the effects of this synergism may differ among different populations of the same species. 4. Author(s): Surova GS Title: Effects of acid environmental conditions on viability of the common frog (Rana temporaria) eggs Source: ZOOLOGICHESKY ZHURNAL 2002, Vol 81, Iss 5, pp 608-616 Abstract: The influence of high water acidity on the viability of large and small eggs of Rana temporaria L. were studied in two geographical polulations: in the northern (Solovki Islands) and central (Moscow region) parts of its range. There is intra- and interpopulation variability of egg sizes. In Moscow region, the frog clutches with large (1.8 +/- 0.05 mm diameter) and small (1.5 +/- 0.03 mm. diameter) eggs differ to a greater extent. On the Solovki Islands, eggs are of larger size (2 0.03 mm). The role of acid marsh water (pH 4.5 in Moscow region and 4.9 on Solovki Islands) on the viability of different-sized eggs was estimated experimentally. At the same time, relationhsips between the egg mortality in natural spawning areas and pH of water were studied. The egg mortality was estimated by the percentage of died eggs just before hatching. The initial size of eggs is shown to affect their survival neither in acid nor neutral environmental conditions. The egg mortality in acid water increases to 5%. Inspection of 14 natural ponds (pH from 4.5 to 7.0) has revealed the distinct correlation between the mortality level and water pH value (r = -0.96). A high dispersion of clutches according to the viability of eggs (from 0 to 100%) was found. It was independent of water pH and geographical position of spawning grounds. The large sizes of clutches and egg aggregations protect embryos against acid water, especially in the central pails of the clutches. 5. Author(s): Rasanen K; Laurila A; Merila J Title: Carry-over effects of embryonic acid conditions on development and growth of Rana temporaria tadpoles Source: FRESHWATER BIOLOGY 2002, Vol 47, Iss 1, pp 19-30 Abstract: 1. Conditions experienced during the early stages of development may have carry-over effects on performance during later life. The egg laying period and embryonic development of temperate and boreal zone amphibians often coincides with peak acidity resulting from spring snow-melt, but the effects of acid conditions during embryonic stage on subsequent performance are unknown. 2. We investigated the potential carry-over effects of acidity during the embryonic stage on performance up to metamorphosis in the common frog (Rana temporaria) tadpoles. There were four combinations of acid (4.5) and neutral (7.5) pH treatments applied to the egg and larval stages in a factorial laboratory experiment. In addition, we studied the difference in embryonic and larval tolerance of acidity between two populations originating from circumneutral (pH 6.6) and acidic conditions (pH 4.8). 3. The effects of acid conditions during the embryonic stage were sublethal, as indicated by delayed development and reduced size. Under acid conditions, tadpoles that had been raised in neutral water as embryos at first grew more slowly than tadpoles raised under acid conditions as embryos. At metamorphosis, no effects of embryonic acidity were detectable indicating that tadpoles were able to compensate fully for the initial reduction in growth. 4. Acid conditions during the larval period had a strongly negative effect on survival, size and age at metamorphosis. The amount of food consumed was lower under acid conditions, suggesting that reduced food consumption was at least partly responsible for the negative effects. 5. Although the two populations differed in the length of larval period, there was no indication of a differential response to the treatments in any of the metamorphic traits studied. 6. These results suggest that, although moderate acid conditions during embryonic development affect growth and development negatively, this influence does not persist after conditions have returned to normal. However, even moderately acid conditions during the larval period may have a strong negative influence on survival and performance of the tadpoles. Ewan Shilland Contract Research Scientist Environmental Change Research Centre University College London |
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Donny Senior Member Joined: 11 May 2004 No. of posts: 53 View other posts by Donny |
Posted: 15 May 2004 Thanks for the replies...I thought maybe the years of pine needle build up might have made the soil too acid, but i suppose there are several factors to coinsider. Your story about the alleged 'Bullfrog' tadpoles reminds me of some HUGE Common Frog tadpoles and froglets i saw once in and around a drainage ditch that had also used as a dump for horse stable sweepings and dung...I think they must have been benefiting from the extra 'nutrition'! |
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GemmaJF Admin Group Joined: 25 Jan 2003 No. of posts: 2090 View other posts by GemmaJF |
Posted: 16 May 2004 Much like an A-Level biology field trip I went on. We had to do a project and I got lumbered with 'proving' the field center sewage outlet into a local river damaged the invert population. All it showed was massively high concentrations of inverts around the outlet tailing off as you moved downstream away from it :0) (I hope by now they are little more ecologically friendly with their sewage treatment) Gemma Fairchild, Independent Ecological Consultant |
- Acid water = stunted tadpoles? |