Kauhala, K., Viranta, S., Kishimoto, M., Helle, E. & Obara, I. 1998: Skull and tooth morphology of Finnish and Japanese raccoon dogs. — Ann. Zool. Fennici 35: 1–16.
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Laurila, A., Peuhkuri, N., Seppä, T., Piironen, J., Hirvonen, H. & Ranta, E. 1998: Differentially directed startle response in alevins of three salmonid species. — Ann. Zool. Fennici 35: 17–19.
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Peuhkuri, N. & Seppä, P. 1998: Do three-spined sticklebacks group with kin? — Ann. Zool. Fennici 35: 21–27.
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Pasanen, S., Laitinen, M. & Alhonen, T. 1998: Effects of pH on the wintering of the common frog (Rana temporaria L.). — Ann. Zool. Fennici 35: 29–36.
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Kilpi, M. & Öst, M.1998: Reduced availability of refuse and breeding output in a herring gull (Larus argentatus) colony. — Ann. Zool. Fennici 35: 37–42.
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Vennerström, P., Söderhäll, K. & Cerenius, L. 1998: The origin of two crayfish plague (Aphanomyces astaci) epizootics in Finland on noble crayfish, Astacus astacus. — Ann. Zool. Fennici 35: 43–46.
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Mönkkönen, M. & Aspi, J. 1998: Sampling error in measuring temporal density variability in animal populations and communities. — Ann. Zool. Fennici 35: 47–57.
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Laitinen, M. & Pasanen, S. 1998: Wintering site selection by the common frog (Rana temporaria) and common toad (Bufo bufo) in Finland: A behavioural experiment. — Ann. Zool. Fennici 35: 59–62.
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Mikola, J. 1998: On the role of varying species combinations in microcosm experiments: how to test ecological theories with soil food webs? — Ann. Zool. Fennici 35: 63–66.
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Kauhala, K., Viranta, S., Kishimoto, M., Helle, E. & Obara, I. 1998: Skull and tooth morphology of Finnish and Japanese raccoon dogs. — Ann. Zool. Fennici 35: 1–16.
The skull and tooth morphometrics of Finnish and Japanese raccoon dogs (Nyctereutes procyonoides ussuriensis and N. p. viverrinus, respectively) were examined and compared. The skulls of Finnish raccoon dogs were larger overall than those of Japanese raccoon dogs (tanukis) and were also larger relative to occipital condyle breadth, i.e. body size. Almost all measurements differed among samples in relation to skull size, indicating differences in skull shape. Mandible width and jaw height were the best measurements for discriminating among populations; the mandible is both absolutely and relatively more robust and the jaws more powerful among Finnish than among Japanese raccoon dogs. Japanese raccoon dogs have a relatively longer rostrum and longer tooth rows than Finnish raccoon dogs. Although the absolute measurements of most teeth of Finnish raccoon dogs were larger than those of Japanese raccoon dogs, the relative measurements of molars in particular were larger in Japan than in Finland, indicating a larger grinding surface among Japanese raccoon dogs. We suggest that viverrinus has adapted to a milder climate and less carnivorous diet than ussuriensis. The Japanese raccoon dog is smaller and, due to its less carnivorous diet, its head has become decreased in size and the jaws less powerful; however, since its diet consists largely of invertebrates and coarse plant material, its molars have increased relative to skull size.
Laurila, A., Peuhkuri, N., Seppä, T., Piironen, J., Hirvonen, H. & Ranta, E. 1998: Differentially directed startle response in alevins of three salmonid species. — Ann. Zool. Fennici 35: 17–19.
We studied responses of yolk-sac fry of three salmonid species to simulated predator attacks. Remaining motionless after tactile stimulation was more common in arctic charr alevins than in brown trout or Atlantic salmon. When stimulation was followed by a startle response, arctic charr predominantly responded with an upward swimming burst, whereas fry of brown trout and Atlantic salmon mainly performed a short swimming burst near the aquarium bottom. We suggest that differences between species in flow and predator regime may explain the differential behaviour between the three salmonids.
Peuhkuri, N. & Seppä, P. 1998: Do three-spined sticklebacks group with kin? — Ann. Zool. Fennici 35: 21–27.
We studied the kin structure in schools of juvenile three-spined sticklebacks (Gasterosteus aculeatus) using allozymes as genetic markers. Young of the three-spined stickleback stay in their natal nest for several days after hatching. They thus have an opportunity to associate with kin when leaving the nest for independent life. Juveniles have also been shown to preferentially associate with kin in laboratory conditions, and furthermore, schools of free-ranging juveniles are size-assorted, all suggesting that schools might consist of relatives in the wild. However, our data show no close relatedness among individuals within the schools, indicating that school members are a random sample from the genetic pool of the population. The result therefore suggests that, despite young sticklebacks' apparent opportunity to group with kin, their school formation in the wild is not tightly linked with genetic relatedness.
Pasanen, S., Laitinen, M. & Alhonen, T. 1998: Effects of pH on the wintering of the common frog (Rana temporaria L.). — Ann. Zool. Fennici 35: 29–36.
The aim of the present study was to establish whether acid water affects the behaviour and physiology of the wintering common frog. Frogs were caught from two biotopes (“neutral” and “low-pH” populations). Initially frogs were kept in containers in water with different pH where they could chose whether to be in or out of water. Then altogether 210 frogs were over-wintered at different pH and after winter the liver and muscle glycogen contents were determined from 106 frogs. In the biomonitoring experiments we tested if changes in water pH had had an effect on the total activity of wintering frogs. The same monitoring apparatus was also used to measure the heart rates of the frogs at pH 4 and pH 6.5. Following metamorphosis the common frog is very well adapted to cope with environmental acidity. It does not avoid water at pH 4 and wintering success occurs also in acid environment. In fact it is a matter of concern that mature frogs react so slightly to water acidity and therefore they obviously do not avoid acid habitats.
Kilpi, M. & Öst, M.1998: Reduced availability of refuse and breeding output in a herring gull (Larus argentatus) colony. — Ann. Zool. Fennici 35: 37–42.
We studied the reproductive performance of herring gulls (Larus argentatus) in an old stable colony in SW Finland. Over the period 1993–1997, the colony decreased, and the garbage dumps the birds may have utilised have all closed. This had an effect on the breeding performance of the colony when comparing the year prior to the closing of the last garbage dump available (1996), and the following season (1997). It is clear that the last-laid egg size decreased significantly between years, more eggs were lost due to predation, and fewer of the hatched young fledged. The quality (in terms of body weight) of hatching chicks (both first and last) was not reduced, but first chicks grew slower in 1997. These changes are in agreement with predictions from other studies, and are likely effects of diminishing food resources. However, overall production was still good, and the birds seem capable of successful breeding without the presence of nearby garbage dumps.
Vennerström, P., Söderhäll, K. & Cerenius, L. 1998: The origin of two crayfish plague (Aphanomyces astaci) epizootics in Finland on noble crayfish, Astacus astacus. — Ann. Zool. Fennici 35: 43–46.
A fungus identified as Aphanomyces astaci was isolated from two crayfish plague epizootics among noble crayfish, Astacus astacus, in Central Finland. The isolated fungal strains from Vaikkojoki, Kaavi and Iso-Suojärvi, Saarijärvi were able to kill healthy A. astacus crayfish in aquarium experiments and the fungus could be reisolated from the diseased animals. The genomic DNA of the isolated strains were characterized by applying a polymerase chain amplification technique with arbitrarily primed DNA. One strain was identical, i.e. showed an identical DNA band pattern, with an A. astaci strain earlier isolated from signal crayfish, Pacifastacus leniusculus. The latter strain has been the cause of several crayfish plague outbreaks in Sweden. These data suggest that the introduction of North American crayfish into Finland has resulted in the transmission of the disease to populations of the native crayfish, A. astacus.
Mönkkönen, M. & Aspi, J. 1998: Sampling error in measuring temporal density variability in animal populations and communities. — Ann. Zool. Fennici 35: 47–57.
Variation in animal numbers is an interesting ecological problem in both theoretical and applied research. Recent research has shown that there is a myriad of problems involved in measuring variability in animal populations, which have not been addressed in most empirical studies on fluctuations of animal densities. Therefore, we actually know less about variability in animal populations and communities than we think. It is rarely possible to accurately sample entire populations and our estimates of variability usually come from spatially restricted samples of counts drawn from local populations. The observed variability not only reflects variability in population density or size but also involves a sampling variance component. Sampling variance occurs principally due to inexactness of the counts (i.e. all individuals present in the sampling unit do not enter into samples) and spatial variance (the size of the sampling unit is inadequate to capture the dispersion pattern of individuals in the field). Many samples are affected by both of these sources of error and in most cases we are unable to separate their effects. Sampling variance usually affects the variability estimates and particularly besets small samples. When comparisons are to be made in temporal variability between communities, species, populations or sites, great care must be taken to mitigate the effects of sampling variance. If the counts are replicated in space or time then sampling error can fairly simply be estimated and removed. Even in the absence of replication, statistical methods exist allowing estimation of the sampling variance. These methods are only applicable if we are prepared to make assumptions about the distributions of the counts. We exemplify one of these methods by considering a classical case of latitudinal gradients in density variability in animal communities. We finally discuss recent studies, the results of which might be artefacts arising from sampling variance.