| 1. |
- Arzel, Céline, et al.
(författare)
-
Individual strategies of dabbling ducks : a circum-annual perspectice
- 2003
-
Ingår i: Third North American duck symposium. ; , s. 73-
-
Konferensbidrag (refereegranskat)abstract
- Very little is still known about the ecology of dabbling ducks on staging areas in spring, despite the fact that this is a crucial period of the year when birds refuel during migration and prepare for subsequent reproduction. This lack of knowledge translates into the current inability to predict the consequences of changes in the environment and harvesting for the population dynamics of ducks. We have launched a joint project to study dabbling ducks in the flyway connecting wintering grounds in France with breeding areas in Sweden. The aim is to study individual dabbling ducks in a circumannual perspective. We are assessing food resource limitation, density-dependent effects and the role of competition by estimating available food, by using a reference functional response curve and by recording the foraging behaviour of wild individual dabbling ducks. We also study survival probability and breeding success, and we will assess inter-individual variation. Birds are captured, weighed, marked and subsequently observed in order to study foraging behaviour and potentially measure the changes in body mass across time through recaptures. Ducks are fitted with nasal marks for individual recognition. Eventually, we will provide a model to predict the number of young that a female duck will produce after simple measurements such as its date of arrival on the breeding grounds and its body-mass at this date. Duckling foraging efficiency and survival will be measured and the relationship with corresponding estimates for their mother will be explored.
|
|
| 2. |
- Bertolani, Roberto, et al.
(författare)
-
Experiences with dormancy in tardigrades
- 2004
-
Ingår i: Journal of limnology. - 1129-5767 .- 1723-8633. ; 63:Suppl. 1, s. 16-25
-
Tidskriftsartikel (refereegranskat)abstract
- Tardigrades often colonise extreme habitats, in which they survive using both types of dormancy: quiescence and diapause. Together with nematodes and bdelloid rotifers, tardigrades are known to enter quiescence (with several forms of cryptobiosis: anhydrobiosis, cryobiosis, anoxybiosis, osmobiosis) at any stage of their life cycle, from egg to adult. Entering anhydrobiosis, tardigrades contract their body into a so-called tun, loosing most of their free and bound water (>95%), synthesizing cell protectants (e.g., trehalose, glycerol, heat shock proteins) and strongly reducing or suspending their metabolism. Our research on cryptobiosis focused on some ecological and evolutionary aspects. We evaluated: i) the long-term anhydrobiotic survival by comparing quantitative data on recovery from naturally induced desiccation in several species of tardigrades; ii) differences in survival patterns between species and populations by experimentally inducing anhydrobiosis and cryobiosis; iii) phenotypic factors affecting anhydrobiotic survival. As regards diapause, we considered encystment and eggs. Encystment involves at least the synthesis of new cuticular structures. Morphological changes during cyst formation are more complex than those involved in tun formation. We analyzed more in detail encystment processes, comparing a semiterrestrial with a limnic species. Several inter-specific differences have been identified, other than the production of two types of cysts in the semiterrestrial species. Our analysis of life history traits of a laboratory reared strain of a soil tardigrade revealed a particular hatching phenology that involved the production of both subitaneous and resting eggs. The latter need a cue to hatch (dehydration followed by re-hydration). In addition, the evolutionary meaning of dormancy in tardigrades is discussed
|
|
| 3. |
- Elmberg, Johan, et al.
(författare)
-
Andkonferens på prärien
- 2001
-
Ingår i: Vår fågelvärld. - 0042-2649. ; 60:8, s. 25-
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Elmberg, Johan, et al.
(författare)
-
Hur påverkas andstammarna av jakt?
- 2000
-
Ingår i: Jakt och jägare. - 1401-8306. ; 60:10, s. 44-45
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Elmberg, Johan
(författare)
-
Slätten tur och retur på 25 år
- 2001
-
Ingår i: Fåglar i Västerbotten. - 0348-1166. ; 26, s. 54-57
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
-
A model on the evolution of cryptobiosis
- 2003
-
Ingår i: Annales Zoologici Fennici. - 0003-455X .- 1797-2450. ; 40:4, s. 331-340
-
Tidskriftsartikel (refereegranskat)abstract
- Cryptobiosis is an ametabolic state of life entered by some lower organisms (among metazoans mainly rotifers, tardigrades and nematodes) in response to adverse environmental conditions. Despite a long recognition of cryptobiotic organisms, the evolutionary origin and life history consequences of this biological phenomenon have remained unexplored. We present one of the first theoretical models on the evolution of cryptobiosis, using a hypothetical population of marine tardigrades that migrates between open sea and the tidal zone as the model framework. Our model analyses the conditions under which investments into anhydrobiotic (cryptobiosis induced by desiccation) functions will evolve, and which factors affect the optimal level Of Such investments. In particular, we evaluate how the probability of being exposed to adverse conditions (getting stranded) and the consequences for survival Of Such exposure (getting desiccated) affects the option for cryptobiosis to evolve. The optimal level of investment into anhydrobiotic traits increases with increasing probability of being stranded as well as with increasing negative survival effects of being stranded. However, our analysis shows that the effect on survival of being stranded is a more important parameter than the probability of stranding for the evolution of anhydrobiosis. The existing, although limited, evidence from empirical studies seems to support some of these predictions.
|
|
| 19. |
- Jönsson, K. Ingemar, 1959-
(författare)
-
Björndjur
- 2001
-
Ingår i: Biologen. - 0345-1127. ; :1, s. 43-47
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
| 20. |
|
|
| 21. |
- Jönsson, K. Ingemar, 1959-
(författare)
-
Inget liv utan vatten
- 2001
-
Ingår i: Forskning och framsteg. - 0015-7937. ; :6, s. 59-
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
| 22. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
-
On the disparate terminological use of the concept cryptobiosis
- 2004
-
Ingår i: Journal of Fish Diseases. - : Wiley-Blackwell. - 0140-7775 .- 1365-2761. ; 27:3, s. 175-176
-
Tidskriftsartikel (refereegranskat)abstract
- Conceptual and terminological consistency is an important component of science, promoting clarity and preventing confusion. Scientists should therefore always try to avoid giving different meanings to the same term. Apart from this general aspect, multiple definitions of a single term also give rise to practical problems, particularly in connection with literature search. In this note, I will bring attention to a term, cryptobiosis, that has relatively recently appeared in the field of fish disease research, but which has a much longer history and use in a completely different area.The concept of cryptobiosis was introduced by Keilin (1959) and defined as ‘the state of an organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill’ (Keilin 1959, p. 166). Cryptobiosis replaced the earlier term anabiosis, and is today generally accepted as the common term for different ametabolic life forms (e.g. Clegg 2001; Wright 2001). Cryptobiosis means ‘hidden life’, an appropriate name for a state in which all traditional attributes of life (metabolism, reproduction, DNA replication) are absent. Cryptobiotic life forms have been documented in a variety of organisms, including both plants and animals, but in the latter category mainly among invertebrates (Wright, Westh & Ramløv 1992). Cryptobiosis is commonly induced by desiccation (so-called anhydrobiosis; e.g. Keilin 1959; Jönsson 2001), and aquatic invertebrates such as rotifers, nematodes and tardigrades living in microhabitats exposed to rapid desiccation frequently enter a cryptobiotic state. The research field dealing with cryptobiotic, sensu ametabolic, life forms has expanded considerably during the last 30 years, to a large extent fuelled by the detection of the ability of the disaccharide trehalose to protect dry and frozen biological cells (Crowe 2002).More recently, a completely different use of the term cryptobiosis has appeared in the literature on fish disease. In this literature, the term refers to infections of fish by biflagellated protozoa of the genus Cryptobia. Because of the economic importance of salmonid fish, much of the Cryptobia research has focused on Cryptobia salmositica (Katz) that infects salmonids (Woo 2001). The origin of the term cryptobiosis within fish pathology and studies of Cryptobia is unclear, but the earliest record of the term that I have found is Obradovic & Fijan (1979) who used it in a paper on chemotherapeutic treatment against Cryptobia in carp. From 1987 onwards, Woo et al. have used the term frequently (e.g. Woo, Leatherland & Lee 1987; Woo 1987, 1998, 2001), but apparently without any comments on the original proposal of the term. Curiously, few other researchers on Cryptobia seem to have adopted the cryptobiosis terminology, at least as judged from an examination of published titles. Other authors have instead used the expression ‘infections by Cryptobia’. Although using cryptobiosis as a term for infections by Cryptobia is consistent with the rule of creating names for infectious diseases by putting -osis as a post-fix to the name of the infecting organism, in the current case it creates terminological confusion.The problems of using the term cryptobiosis in several unrelated fields are obvious. A title such as ‘The biology of cryptobiosis’ would attract the attention of many students interested in ametabolic life forms. They would be disappointed, however, if the paper turned out to be about Cryptobia infection biology. Similarly, fish biologists would find the publication irrelevant to their research if it were properly confined to ametabolic life forms.Because ‘cryptobiosis’ as a term for ametabolic life forms is well established and has been used for more than 40 years, it should have priority over the more recent and limited use within fish pathology. I therefore hope that fish pathologists will avoid using the term cryptobiosis and instead use ‘infections by Cryptobia’, ‘cryptobiasis’ or some other term that does not interfere with already established terminology.
|
|
| 23. |
- Nudds, Thomas D., et al.
(författare)
-
Ecomorphology and coexistance in breeding holarctic dabbling ducks
- 2000
-
Konferensbidrag (refereegranskat)abstract
- We have debated the effects of interspecific competition, especially in ecological time, on the distribution and abundance of dabbling ducks (Anas spp.), and the relative importance of bill morphology and body size in facilitating coexistence. Evidence from North American and Baltic coastal wetlands indicates that species with few lamellae (but longer bodies) tend to feed in shallow, vegetated microhabitats where invertebrate prey is large; species with dense lamellae (but shorter bodies) tend to feed offshore where prey is smaller. In northern Europe, however, the evidence is opposite, suggesting that differences in body length instead facilitate coexistence. Here, we present evidence that these views are compatible under a refined conceptual model. In both northern Europe and North America, microhabitat diversity within wetlands correlates with a-diversity (species per wetland). With increasing latitude, a-diversity decreases, coincident with changes in the shape of wetland basins from largely "saucer-" (prairie/steppe potholes) to "bowl-shaped" (nemoral/ boreal lakes and tarns). We propose that (1) there is less absolute microhabitat (water-depth/vegetation) gradient along which species can be accommodated in northern wetlands, owing to shoreline steepness, and (2) body length is more important in facilitating species co-existence among breeding dabbling ducks in "bowl-shaped" wetlands, whereas lamellar density is more important in "saucer-shaped" wetlands.
|
|
| 24. |
- Nummi, Petri, et al.
(författare)
-
Breeding success of boreal mallard and wigeon in relation to population density and food resources
- 2003
-
Ingår i: Third North American duck symposium. ; , s. 79-
-
Konferensbidrag (refereegranskat)abstract
- Breeding success of mallard and wigeon was studied for 12 years in a boreal lake area in southern Finland. Aquatic and surface-emerging prey were trapped to obtain annual indices of food abundance. The average density of mallards was 0.42 pairs per 1000 m shore line and that of wigeon 0.18. The mean brood production per pair was 0.24 in mallard and 0.41 in wigeon. We correlated brood:pair and duckling:pair ratios to pair density and per capita food availability to test whether per capita breeding success decreases in a density-dependent way when pair density or the number of nesting pairs per available food unit increases. No density-dependent pattern was found in mallards. In wigeon, in contrast, we found two independent patterns of density dependence. Per capita brood production correlated negatively with pair density, and brood:pair and especially duckling:pair ratio correlated negatively with per capita abundance of surfaceemerging prey.
|
|
| 25. |
- Nummi, Petri, et al.
(författare)
-
Gräsandungar tjänar forskningen
- 2000
-
Ingår i: Jägaren. - 0283-8109. ; 49:3, s. 26-28
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
| 26. |
- Pöysä, Hannu, et al.
(författare)
-
Habitat selection and distribution of breeding mallards : what do they reveal about population limitation?
- 2000
-
Konferensbidrag (refereegranskat)abstract
- The distribution of individuals among habitats and habitat-specific breeding output are basic elements for understanding population limitation and regulation. We studied the connection between habitat selection and population limitation in breeding mallards on boreal lakes in Sweden and Finland with experimental and long-term observational data. Wingclipped mallards were introduced on breeding lakes before migratory wild mallards arrived to test 2 alternative hypotheses of habitat selection, namely ideal preemption and conspecific attraction. The ideal preemptive rule was rejected while the conspecific attraction rule was to some extent supported. However, by combining the results of the introduction experiment with those from an experiment done with mallard ducklings to measure habitat quality, we found that only good-quality lakes attracted wild mallards, whereas poor-quality lakes did not. Long-term observational data from 35 lakes, classified into rich and poor based on shore vegetation, revealed that breeding pairs prefer rich lakes over poor, breeding success also being better there than on the poor lakes. In accordance with the experimental findings, density on the rich lakes increased with overall population density while that on the poor did not. However, breeding success did not show clear density dependence. Our results indicate habitat-specific limitation of breeding numbers, though this may not translate to limitation at the population level.
|
|
| 27. |
- Sjöberg, Kjell, et al.
(författare)
-
Andungar i forskningens tjänst
- 2000
-
Ingår i: Svensk jakt. - 0039-6583. ; 138:5, s. 80-82
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
|
