Fitzpatrick, S. 1998: Colour schemes for birds: structural coloration and signals of quality in feathers. — Ann. Zool. Fennici 35: 67–77.
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Van Dongen, S. 1998: The distribution of individual fluctuating asymmetry: Why are the coefficients of variation of the unsigned FA so high? — Ann. Zool. Fennici 35: 79–85.
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Pertoldi, C., Madsen, A. B., Randi, E., Braun, A. & Loeschcke, V. 1998: Variation of skull morphometry of Eurasian otters (Lutra lutra) in Denmark and Germany. — Ann. Zool. Fennici 35: 87–94.
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Ranta, E. & Lindström, K. 1998: Fish yield versus variation in water quality in the lakes of Kuusamo, northern Finland. — Ann. Zool. Fennici 35: 95–106.
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Rahkonen, R. & Valtonen, E. T. 1998: Role of water temperature on the size, migration activity and pathogenity of Diphyllobothrium dendriticum (Cestoda) plerocercoids in brown trout Salmo trutta m. lacustris (L.). — Ann. Zool. Fennici 35: 107–113.
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Berg, L. & Berg, Å. 1998: Nest site selection by the dormouse Muscardinus avellanarius in two different landscapes. — Ann. Zool. Fennici 35: 115–122.
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Voipio, P. 1998: Strict statements and their consequences — a story around cycles. — Ann. Zool. Fennici 35: 123–128.
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Henttonen, H. 1998: A story around cycles — a commentary. — Ann. Zool. Fennici 35: 129–130.
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Fitzpatrick, S. 1998: Colour schemes for birds: structural coloration and signals of quality in feathers. — Ann. Zool. Fennici 35: 67–77.
Plumage coloration may signal individual quality through carotenoid and melanin colour patterns; novel mechanisms by which structural coloration in feathers could signal individual quality are proposed here. Uniformity of structural colour is suggested to signal developmental stability during feather growth, the colour constituting an amplifier. For structural coloration produced by coloured portions of barbules which are susceptible to loss by abrasion, the intensity of colour is suggested to signal feather quality and abrasion-resistance, the structural colour constituting an amplifying handicap. In both cases, large areas of structural coloured plumage may be more revealing of quality than small areas. Predictions as to the extent, position and combinations of these structural colours relative to carotenoid and melanin coloration were derived from these mechanisms and supported by comparative tests. Structural coloration may thus be a component in multiple messages of individual quality in plumage coloration.
Van Dongen, S. 1998: The distribution of individual fluctuating asymmetry: Why are the coefficients of variation of the unsigned FA so high? — Ann. Zool. Fennici 35: 79–85.
It has been established for a long time that rigorous statistical analyses of fluctuating asymmetry (FA) requires great caution. The reason for this is twofold. Firstly, the magnitude of FA is often small and measurement error (ME) may substantially bias asymmetry estimates, and secondly, there are other forms of asymmetry that are sometimes difficult to distinguish from real FA. To avoid bias due to ME, within-subject repeats and mixed model analysis are required. The model assumptions, however, are that both FA and ME are normally distributed. In this paper I show that in many cases these assumptions are not met. In particular, available data in the literature and these presented here suggests that FA (signed) often has a leptokurtic distribution, as indicated by relative high coefficients of variation of the absolute value of the signed FA. This may be due to patterns of antisymmetry and/or heterogeneity of FA within the sample.
Pertoldi, C., Madsen, A. B., Randi, E., Braun, A. & Loeschcke, V. 1998: Variation of skull morphometry of Eurasian otters (Lutra lutra) in Denmark and Germany. — Ann. Zool. Fennici 35: 87–94.
The distance between opistokranion and zygomatic process of frontal bone (A), the condylobasal length (X), and the total length of the mandible (M) were measured in skulls of the Eurasian otter collected in Denmark and in the east of Germany (Lausitz). The Danish population showed a strong reduction in size of the traits in males, and an increase with time in the variances of the traits in females, whereas in the Lausitzian population, no significant changes in the same traits over the same time period were observed. The skulls were also investigated for fluctuating asymmetry (FA) and a negative correlation was found between the size of a skull and FA in the males from both populations, whereas no correlations were found in the females.
Ranta, E. & Lindström, K. 1998: Fish yield versus variation in water quality in the lakes of Kuusamo, northern Finland. — Ann. Zool. Fennici 35: 95–106.
Our goal was to ascertain whether fish yield differences (0.2–43 kg ha–1 yr–1) among 166 Northern Finnish lakes could be attributed to level and variability of 14 limnological variables. Water quality variables were assessed at shallow and deep water in winter and summer. For most of them, the greatest share of the variation (65%) was due to the season, while that of the water depth averaged 28%. Fish yield tends to increase with increasing levels of oxygen saturation, conductivity, Na and K concentrations. A decreasing fish yield was observed with an increasing chemical oxygen demand of lake water and with increasing N. Intermediate levels of water colour were associated with the highest fish yield. A variable variability accounted for a fair proportion of the total variance in the fish yield together with a variable level only in the chemical oxygen demand of the lake water. For most of the variables examined for variability, no clear covariation with the fish yield could be shown. We selected 25 lakes with the lowest fish yield (mean 0.4 kg), and 25 lakes with the highest yield (20 kg). The 14 variables were compared in the two groups of lakes. We found that the oxygen saturation, conductivity and pH were significantly higher in the high-yield lakes than in the low-yield lakes, whilst Fe levels were much lower in the high-yield lakes. We conclude that water quality affects the lake-specific fish yield. The relationship in Finnish lakes is, however, too weak to enable the usage of water quality as a lake-specific fish yield prediction tool.
Rahkonen, R. & Valtonen, E. T. 1998: Role of water temperature on the size, migration activity and pathogenity of Diphyllobothrium dendriticum (Cestoda) plerocercoids in brown trout Salmo trutta m. lacustris (L.). — Ann. Zool. Fennici 35: 107–113.
The size, migration activity and pathogenity of Diphyllobothrium dendriticum (Cestoda) plerocercoids in the intermediate host were studied experimentally in age 1+ brown trout Salmo trutta m. lacustris (L.). In the first experiment (A) which lasted 12 weeks, two water temperatures were used: heated water at about 15°C and non-heated at about 10°C. In the second experiment (B) which lasted 7 weeks, the water temperature was raised gradually to 24–26°C. Increased water temperature did not promote D. dendriticum-induced mortality in either of the experimental conditions. Experiment A revealed, however, that the worms were longer and migrated more actively outside the body cavity of fish in heated aquaria.
Berg, L. & Berg, Å. 1998: Nest site selection by the dormouse Muscardinus avellanarius in two different landscapes. — Ann. Zool. Fennici 35: 115–122.
Nest site selection of dormice was studied in two different landscapes in southern Sweden: a forest-dominated landscape and an open landscape dominated by farmland, pastures and apple orchards. Randomly selected plots (10 x 10 m) were searched for dormouse nests and habitat characteristics of plots with and without nests were compared with logistic regression. Number of shrub species, cover of different shrub species and distance to closest forest edge were the main factors that were related to occurrence of dormice. Dormice have earlier been shown to nest in tree hollows, and thus such nests could be overlooked with our method. However, natural cavities are scarce in the habitats investigated here, and it is argued that the observed preferences for shrubby areas close to forests are real, and different shrub species are suggested to be important as sheltered and predator-safe nest sites and as food sources.