Two new species and a phylogenetic analysis of the genus Tectidrilus (0Iigochaeta, Tubifcidae)

Tectidrilus probus sp.n. and Tectidrilus profusus sp.n. are described from offshore localities in southern California. Both species appear closely related to T. diversus Ersëus, 1982, which occurs in the same area, but they differ from the latter by possessing small oesophageal diverticula; T. probus differs also by its very small spermathecal vestibules. Tectidrilus profusus is a highly apomorphic form with elaborate, partly muscular, male ducts and spermathecae. Monophyly of Tectidrilus is supported by the short clitellum and the unisetal 'bundles' in postclitellar segments. Patterns of apomorphic character states within the genus are analyzed under the principle of Camin-Sokal parsimony (irreversibility of character states), giving three equally parsimonious cladograms. In the strict consensus tree of these cladograms, eight of the twelve members of Tectidrilus form an apomorphic group defined by the papillated body wall, but the individual species within this group cannot be unequivocally resolved from each other.     

The relative importance of lethal and non-lethal effects of fish on insect colonisation of ponds

1. We hypothesised that adult insects actively monitor potential habitats for the presence of fish by means of chemical cues and avoid sites that pose significant risks. This was examined by quantifying colonisation of insects in outdoor pools with no fish (controls), fish (direct predation effect) or caged fish (chemical predator cues).
2. A significant direct effect of predation was found, but no indirect effect (avoidance of chemical cue pools), on the total biomass of colonising insects. However, predatory insects avoided fish-cue pools, thus releasing non-predatory insects from predation. This resulted in significantly greater biomass of non-predatory insects in fish-cue pools than control pools.
3. Fish reduced the number of species of colonising insects in pools through predation. This negative influence of fish implies that caution is necessary when stocking wetlands and ponds with fish if the goal is to maximise biodiversity.
4. Our data suggest that although predatory aquatic insects may use chemical signals to assess the quality of potential habitats with respect to predation risk, direct predation is the main method by which fish affect insect assemblages in ponds. Because fish and invertebrate predators may both have strong effects on prey mortality, behavioural adjustment by insects to the actual predator regime within a habitat should be more important than avoiding colonisation of habitats with fish.     

Marine Oligochaeta from the Koster Area, West Coast of Sweden, with Descriptions of Two New Enchytraeid Species

A total of 28 species of marine Oligochaeta (belonging to the families Naididae, Tubificidae and Enchytraeidae) are reported from eulittoral and sublittoral sediment samples taken in the Koster area on the Swedish West Coast. Lumbricillus algensis sp.n. and Grania ovitheca sp.n. are described and their morphological and taxonomical relations to other enchytraeids are discussed. L. algensis is characterized mainly by its spermathecae, which project into segment VI, and by its very large penial bulbs. G. ovitheca possesses no dorsal setae, the ventral setae being present posterior to the clitellum only, and its spermathecae consist of a narrow duct and a large egg-shaped to oval ampulla, filling most of the coelom of segment V. Four sublittoral species, Limnodriloides barnardi (Tubificidae), Lumbricillus semifuscus, Marionina sublitoralis and Grania roscoffensis (all Enchytraeidae) are reported as new to the Swedish fauna.     

Taxonomic Studies on the Marine Genera Aktedrilus Knöllner and Bacescuella Hrabe' (Oligochaeta, Tubificidae), with Descriptions of Seven New Species

The taxonomy and morphology of Aktedrilus Knöllner, 1935 and Bacescuella Hrabe' 1973 (subfamily Phallodrilinae), both common genera of the marine, littoral meiofauna, were studied on the basis of material from various geographical areas. A. monospermathecus Knöllner, 1935 is redescribed from France and Scotland. A. magnus sp.n., A. hrevis sp.n., A. curvipenis sp.n. and A. floridensis sp.n. are described from Italy, Brazil, France and Florida, respectively. Two very closely related forms are described from the Pacific: A. locyi sp.n. (California) and A. parviprostatus sp.n. (Great Barrier Reef). B. mediterranea sp.n. is described from Italy, and new European records are given forB. arclica Erséus, 1978 andfi. parvithecata Erséus, 1978. Both genera are characterized by having two pairs of prostate glands, well developed penes, and unpaired, mid-dorsal spermatheca (if present). The species of Bacescuella transfer their sperm by means of external spermatophores, structures that are not developed in Aktedrilus. The eight species of Aktedrilus are largely distinguished by means of the morphology of the spermatheca, penes and prostates. The four species of Bacescuella differ principally from each other in the length of the vasa deferentia, and in the morphology of the prostates and copulatory organs. Most Bacescuella species lack spermatheca.     

Responses of riparian trees and shrubs to flow regulation along a boreal stream in northern Sweden

1. Flow dynamics is a major determinant of riparian plant communities. Therefore, flow regulation may heavily affect riparian ecosystems. Despite the large number of dams worldwide, little specific information is available on the longitudinal impacts of dams on vegetation, for example how far downstream and at what degree of regulation a dam on a river can influence riparian woodlands. 2. We quantified the long‐term responses of riparian trees and shrubs to flow regulation by identifying their lateral distribution and habitat conditions along a boreal river in northern Sweden that has been regulated by a single dam since 1948. The regulation has reduced annual flow fluctuations, this effect being largest at the dam, downstream from which it progressively decreases following the entrance of free‐flowing tributaries. 3. We related changes in the distribution patterns, composition, abundance and richness of tree and shrub species to the degree of regulation along the river downstream from the dam. Regulation has triggered establishment of trees and shrubs closer to the channel, making it possible to measure ecological impacts of flow regulation as differences in vegetation attributes relative to the positions of tree and shrub communities established before and after regulation. 4. Trees and shrubs had migrated towards the mid‐channel along the entire study reach, but the changes were largest immediately downstream of the dam. Shrubs were most impacted by flow regulation in terms of lateral movement, but the effect on trees extended furthest downstream. 5. The species composition of trees progressively returned to its pre‐regulation state with distance downstream, but entrance of free‐flowing tributaries and variation in channel morphology and substratum caused local deviations. Species richness after regulation increased for trees but decreased for shrubs. The changes in species composition and richness of trees and shrubs showed no clear downstream patterns, suggesting that other factors than the degree of regulation were more important in governing life form.     

Population structure in an isolated Arctic fox, Vulpes lagopus, population: the impact of geographical barriers

The genetic composition of a population reflects several aspects of the organism and its environment. The Icelandic Arctic fox population exceeds 8000 individuals and is comprised of both coastal and inland foxes. Several factors may affect within-population movement and subsequent genetic population structure. A narrow isthmus and sheep-proof fences may prevent movement between the north-western and central part and glacial rivers may reduce movement between the eastern and central part of Iceland. Moreover, population density and habitat characteristics can influence movement behaviour further. Here, we investigate the genetic structure in the Icelandic Arctic fox population ( n  = 108) using 10 microsatellite loci. Despite large glacial rivers, we found low divergence between the central and eastern part, suggesting extensive movement between these areas. However, both model- and frequency-based analyses suggest that the north-western part is genetically differentiated from the rest of Iceland (F_ST = 0.04, D_S = 0.094), corresponding to 100–200 generations of complete isolation. This suggests that the fences cannot be the sole cause of divergence. Rather, the isthmus causes limited movement between the regions, implying that protection in the Hornstrandir Nature Reserve has a minimal impact on Arctic fox population size in the rest of Iceland.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 18–26.     

Multiple effects of temperature,photoperiod and food quality on the performance of a pine sawfly

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Spatial and temporal variation in the biomass and nutrient status of epilithic algae in Lake Erken, Sweden

1. The aim of this study was to estimate patchiness in biomass and in the internal nutrient status of benthic algae on hard substrata (epilithon) in Lake Erken, Sweden, over different levels of distance, depth and time. Knowledge of the sources and scale of patchiness should enable more precise estimation of epilithic biomass and nutrient status for the entire lake. We focused on the horizontal scale, about which little is known. 2. We sampled epilithon by SCUBA diving and used a hierarchical sampling design with different horizontal scales (cm, dm, 10 m, km) which were nested in two temporal scales (within and between seasons). We also compared two successive years and three sampling depths (0, 1 and 4 m). Biomass was measured as particulate carbon and chlorophyll a (Chl a) and internal nutrient status as carbon : nitrogen : phosphorus (C : N : P) ratios and as specific alkaline phosphatase activity (APA). 3. Horizontal variation accounted for 60–80 and 7–70% of the total variation in biomass and in nutrient status, respectively, at all depths and during both years. Both small and large scales accounted for significant variation. We also found variation with time and depth. Biomass increased in autumn after a summer minimum, and the within‐season variation was very high. The lowest biomass was found at 0 m depth. Both N and P limitation occurred, being higher in 1996 than in 1997 and decreased with depth. 4. As a consequence, any sampling design must address variation with distance, depth and time when estimating biomass or nutrient limitation of benthic algae for an entire lake. Based on this analysis, we calculated an optimal sampling design for detecting change in the epilithic biomass of Lake Erken between different sampling days. It is important to repeat the sampling as often as possible, but also the large scales (10 m and km) and the dm scale should be replicated. Using our calculations as an example, and after a pilot study, an optimal sampling design can be computed for various objectives and for any lake. 5. Short‐term impact of the wind, light and nutrient limitation, and grazing, might be important in regulating the biomass and nutrient status of epilithic algae in Lake Erken. Patchiness in the nutrient status of algae was not coupled to the patchiness of biomass, indicating that internal nutrients and biomass were regulated by different factors.     

Properties of Mg2+-Stimulated and (Na++K+)-Activated Adenosine-5'-Triphosphatase from Sugar Beet Cotyledons

Sugar beet leaf homogenate contains Mg²⁺-stimulated ATPase activity with the highest specific activity in the 25,000–30,000 ×g-fraction. This fraction also has (Na⁺+ K⁺)-activated ATPase activity. Both activities have two pH optima, one stable at pH 7.9 and one variable at lower pH. When optimal conditions of Na⁺ and K⁺ were tested with 64 combinations of these ions, at least two mountains of activity were revealed. The (Na⁺+ K⁺)-ATPase had a high specificity for ATP. It had lost about 50% of its original activity after 56 days of storage at ?85°C. The activity drop was most pronounced at high ionic concentrations in the test medium. The (Na⁺+ K⁺)-ATPase shows four peaks of activity when tested at constant ionic strength. The idea is put forward that the four peaks reflect two ATPases, one in the tonoplast and one in the plasmalemma, which undergo conformational changes in relation to the ionic milieu.