Oxygen consumption in offspring tawny owls Strix aluco is associated with colour morph of foster mother

In several colour polymorphic species, morphs differ in thermoregulation either because dark and pale surfaces absorb solar radiation to a different extent and/or because morphs differ in key metabolic processes. Morph-specific thermoregulation may potentially account for the observation that differently coloured individuals are frequently not randomly distributed among habitats, and differ in many respects, including behaviour, morphology, survival and reproductive success. In a wild population of the colour polymorphic tawny owl Strix aluco, a recent cross-fostering experiment showed that offspring raised and born from red mothers were heavier than those from grey mothers. In the present study, we tested in the same individuals whether these morph-specific offspring growth patterns were associated with a difference in metabolic rate between offspring of red and grey mothers. For this purpose, we measured nestling oxygen consumption under two different temperatures (laboratory measurements: 4 and 20°C), and examined the relationships between these data sets and the colour morph of foster and biological mothers. After controlling for nestling body mass, oxygen consumption at 20°C was greater in foster offspring raised by grey foster mothers. No relationship was found between nestling oxygen consumption and coloration of their biological mother. Therefore, our study indicates that in our experiment offspring raised by grey foster mothers showed not only a lower body mass than offspring raised by red foster mothers, but also consumed more oxygen under warm temperature. This further indicates that rearing conditions in nests of grey mothers were more stressful than in nests of red mothers.     

Variation of pecking rate with sward height in wild wigeon Anas penelope

We examined how pecking rate changed with sward height in wintering European wigeon Anas penelope in a nature reserve of the French Atlantic coast. Pecking rates were recorded as the time taken to perform 10 or 50 pecks. We found a negative correlation between pecking rate and sward height over a range of heights from 1.0 to 3.5 cm, but no sex effect. Equations based on the time taken to perform 10 or 50 pecks were slightly different, suggesting that scanning (scans of the surroundings) and moving (search for plant items of good quality) had an effect on pecking rate. However, these costs were lower (i.e. a decrease of 6–10% of pecking rate) than the effect of handling time, which remained the dominant foraging process constraining pecking rate (i.e. a decrease of 24% with each 1-cm increase in sward height).     

Orientation and foraging movements in a patchy environment by the ant Serrastruma lujae (formicidae-myrmicinae)

Serrastruma lujae ants individually search for collembolans in the leaf litter of humid tropical forests. During the dry season, collembolans aggregate in wet patches randomly scattered in the dry litter where numerous single workers come hunting from their nest. We simulated this situation in the laboratory, and observed that workers seem to be able to use the humidity gradient direction to efficiently orient themselves towards a wet patch. Once the patch has been reached, they exhibit area-concentrated searching,consisting, in particular, of adopting a high sinuosity and a low speed. After capturing a collembolan, the ants return to their nest along nearly straight paths. This ability may rely on a spatial memory of the nest location by means of a path-integration process. In the absence of prey, however, various behaviours were observed after an unsuccessful search. Comparisons between these data and the results obtained with a homogeneously wet environment simulating the rainy season situation showed that these ants do not simply respond to the humidity level but are also sensitive to the degree of patchiness of their environment. They can therefore be said to be able to adapt suitably to the considerable climatic changes they encounter during the year.     

Biomass seasonality of Caulerpa taxifolia in the Mediterranean Sea

The biomass of the introduced and invasive alga Caulerpa taxifolia was measured monthly over one year at four different sites along the French Mediterranean coast at depths of 5 and 20 m in a sheltered and an exposed area. At the 5 m depth, C. taxifolia mean biomass ranged from 203 to 518 g dry wt. m⁻², while at the 20 m depth, it ranged from 62 to 466 g dry wt. m⁻². The study clearly shows that a major characteristic of C. taxifolia is its perennial life cycle with relatively high biomass values throughout the year, in different biotopes. This could be a factor in the broad ecological impact of C. taxifolia.     

Alexandrium catenella and Alexandrium minutum blooms in the Mediterranean Sea: Toward the identification of ecological niches

Annual recurrent blooms of the toxic dinoflagellates Alexandrium catenella and Alexandrium minutum were detected from 2000 to 2003 in harbours along the Catalan coast. The interrelation study between the occurrence of the blooms and specific external conditions at the study sites demonstrated that different factors are required for the bloom of each Alexandrium species. Concentrations higher than 10⁵ cells l⁻¹ of A. catenella were only detected in Tarragona harbour. These blooms were associated with water surface temperature between 21 and 25 °C and salinities of around 34 psu or higher than 37 psu. A. minutum appeared widely spread along the Catalan coast, though the most intensive and recurrent blooms of this species were observed in Arenys de Mar harbour. Concentrations of millions of cells per litre of A. minutum were associated with water temperatures below 14 °C and salinities of around 34–36 psu. A. minutum cell densities showed a positive significant correlation with NO₃ but a negative correlation with NH₄. On the other hand, A. catenella blooms dominated when both NO₃ and NH₄ levels were high. The prevailing inorganic nitrogen form (NO₃ vs. NH₄) could explain why these two species rarely coincide in the same harbours. Accumulation of cysts in the sediment was found to be an important potential factor for the recurrence of these species. The 4.3 × 10³ A. catenella cysts cm⁻³ of wet sediment in Tarragona harbour and the 3.02 × 10³ A. minutum cysts cm⁻³ of wet sediment in Vilanova harbour were the highest concentrations observed from the cyst study. Confined waters such as harbours play an important role as reservoirs for the accumulation of cysts and vegetative cells, which contributes to the expansion of these dinoflagellates in the region. However, the particular environmental conditions are also decisive factors of bloom intensity.     

Photosynthesis and photoprotection responses to water stress in the wild-extinct plant Lysimachia minoricensis

Lysimachia minoricensis is an endemic species of the Balearic Islands that has become extinct in the wild, but persists in botanical gardens. Attempts of re-introducing the species into its natural habitat, which consisted in temporary dry streams, have failed. Low genetic variability has been reported for the garden individuals, suggesting that a reduced potential to adapt to environmental changes could be among the reasons for its extinction. In the present study, we particularly test whether photosynthesis and photoprotection responses of this species to water stress could help explaining the lack of success of this species in its natural habitat.

Plants of L. minoricensis were grown in pots in a growth chamber. Soil water depletion was imposed over 20 days by stopping irrigation. Early stomata closure was observed in response to soil water depletion while leaves desiccated progressively. Although net photosynthesis was low in irrigated plants, due to a remarkably low mesophyll conductance to CO₂, substantial photosynthetic activity was kept at severe drought, where leaf relative water content was as low as 50%, suggesting that L. minoricensis is a very drought-tolerant species. In parallel with decreased photosynthesis, thermal dissipation of the excess light and photorespiration progressively increased. The former was linearly related to increased de-epoxidation of the xanthophylls cycle. Photoprotection was effective, as pre-dawn maximum photochemical efficiency was maintained higher than 0.75 through the entire experiment. Moreover, photosynthetic capacity was largely (80%) recovered only 24 h after re-watering. These results show that stomatal regulation, photosynthetic metabolism and photoprotection in L. minoricensis are well adapted to water stress, suggesting that additional factors may be responsible for its status as a wild-extinct plant.     

Variation of within-day foraging costs in the striped mouse (Rhabdomys pumilio)

Foraging behavior is influenced by spatial and temporal habitat heterogeniety. Here we report on within-day foraging and perceived risk of predation by the striped mouse (Rhabdomys pumilio) in a grassland savannah with wooded “islands” using giving-up densities (GUD, amount of food left behind in depletable food patches). Higher GUDs correspond to higher forging costs. GUDs were measured six times per day at 2-h intervals from paired stations along fern–grass habitat boundaries at 3 and 6 m distances from 10 wooded islands. R. pumilio's GUDs varied significantly over the course of the day with highest GUDs during the afternoon hours of 1–3 pm, and lowest between 7 and 9 am in the morning. The same pattern was consistent for both habitats (fern and grass) and distances from the wooded islands. GUDs decreased with distance from the woody islands in both fern and grass habitats and were significantly lower in the fern habitat. This activity pattern suggests that R. pumilio responds to a spectrum of spatially and temporally varying risks from a variety of predators including aerial predators that increase risk as they make use of mid-day thermals.     

Ageing does not significantly affect performance in a spatial learning task in the domestic cat (Felis silvestris catus)

A spatial learning task was used to examine cognitive function in 36 cats (1.0–15.1 years of age), with a control for motor function. No significant age-related decline in cognitive function was found. Initial selection of 75 cats showed no significant age differences between young (0–3 years), adult (3.1–8 years), senior (8.1–12 years) and geriatric cats (12.1–15.1 years) locating food rewards in a holeboard box. Consequently, the senior and geriatric groups were combined because of a concern that age effects may not be seen in the 8–12-year-old cats. Differences between these three age groups of cats to learn the position of three food rewards in an array of 30 otherwise empty (food-scented) positions were non-significant. Differences between age groups remained non-significant for retrieval of rewards from these three positions even when masked with a tissue paper cover. There was no significant effect of age on speed of reaching each criterion. Although the total number of errors was similar, there was a significantly increased proportion of working memory errors (when the cat returned to a previously baited position) and decreased proportion of reference memory errors (when the cat put a nose or paw in an empty position) with increasing age. There was no effect of age on motor function, with success in a plank-crossing test related only to plank width. These findings support previous work suggesting that the cat differs from other species in the way in which it demonstrates age-related declines in cognitive function. Further studies using different testing methodologies are required to assess other cognitive functions that may decline with age.     

The population dynamics of Orthopyxis crenata (Hartlaub, 1901) (Hydroza, Cnidaria), an epiphyte of Halimeda tuna in the northwestern Mediterranean

O. crenata on the alga Halimeda tuna were sampled every 2 wk for a year off Tossa de Mar, northeastern Spain. The hydroids were most abundant from November to April when three cohorts, identified by size frequency, were present. From April to October the population consisted of two cohorts, except in June and July when the population density was low and only one cohort, of young hydroids, was identifiable. The paucity of O. crenata in summer was attributed to the high rate of turnover of host thalli, interspecifuc competition with other epiphytes, and a possible shortage of suitable planktonic prey. Recruitment was predominantly asexual, by stolons, and occurred throughout the year. Gonozoids were found only from late October to early December when recruitment by planula larvae also occurred. In winter, when the cohorts lived for the maximum of ≈6 wk, colony sizes quintuplicated and triplicated in successive 15-day periods. Although colonies (ramets) of O. cretana on H. tuna have a short life span reproduction and dispersal to other thalli by stolons means that the genets can survive beyond the life of a host, and perhaps indefinitely.     

Life stage-related differences in hardening and acclimation of thermal tolerance traits in the kelp fly, Paractora dreuxi (Diptera, Helcomyzidae)

It is widely appreciated that physiological tolerances differ between life stages. However, few studies have examined stage-related differences in acclimation and hardening. In addition, the behavioural responses involved in determining the form and extent of the short-term phenotypic response are rarely considered. Here, we investigate life stage differences in the acclimation and hardening responses of the survival of a standard heat shock (SHS) and standard low temperature (or cold) shock (SCS), and the crystallization temperature (or supercooling point, SCP) of adults and larvae of the sub-Antarctic kelp fly, Paractora dreuxi. These stages live in the same habitat, but differ substantially in their mobility and thus environmental temperatures experienced. Results showed that neither acclimation nor hardening affected the lower lethal limits in larvae or adults. Adults showed an increase in survival of upper lethal limits after low temperature acclimation, whilst larvae showed a consistent lack of response. The acclimation × hardening interaction significantly affected the SCP in adults, but no response to either acclimation or hardening was found in the larvae. This study further demonstrates the complexities of thermal tolerance responses in P. dreuxi.     

The presence of the potentially toxic genera Ostreopsis and Coolia (Dinophyceae) in the North Aegean Sea, Greece

The examination of macrophyte, water and sediment samples, collected at depths less than 1.5 m from 50 different sites along the North Aegean coasts, has revealed, for the first time in Greek coastal waters, the presence of two Ostreopsis species (O. ovata and O. cf. siamensis) and Coolia monotis in the majority of the sampling sites (94% and 100%, respectively). Other epiphytic dinoflagellates of the genera Prorocentrum and Amphidinium and diatoms were accompanying species in this epiphytic community. Morphometric features, plate formula and thecal ornamentation were used for species identification. O. ovata cells were smaller in dorsoventral (DV) diameter and width (W) (26.18–61.88 μm and 13.09–47.60 μm, respectively) in comparison with O. cf. siamensis (35.70–65.45 μm and 23.80–49.98 μm, respectively). In contrast, the anterioposterior (AP) diameter of O. cf. siamensis was smaller (14.28–26.18 μm) resulting in DV/AP ≈ 3, whereas the above ratio for O. ovata was less than 2 (AP ranging between 14.28–35.70 μm). Moreover, the theca of O. ovata cells was ornamented with scattered pores, which fluctuated in a wider range (0.07–0.32 μm) than those of O. cf. siamensis (0.23–0.29 μm). Coolia monotis cells were almost round with average DV diameter 26.88 μm, AP 25.66 μm and width 26.76 μm. Small and large cells were recorded in both field and culture populations of Ostreopsis spp. and C. monotis, while hyaline cysts were observed for O. ovata. The presence of O. ovata and O. cf. siamensis exhibited a clear seasonal pattern dominating (maximum abundance up to 4.05 × 10⁵ cells gr⁻¹ fwm) the period from midsummer to late autumn in years 2003 and 2004, while C. monotis was found also in winter and spring months.     

Impact of active soil carbonate and burn size on the capacity of the rockrose Cistus laurifolius to produce Tuber melanosporum carpophores in truffle culture

There are very few studies on Tuber melanosporum associated with Cistus populations. In central Spain, we confirm that C. laurifolius shows carpophore production of Tuber melanosporum. This study demonstrates a correlation between T. melanosporum production and the size of the 41 burns, with burn size explaining 26 % of the variability in carpophore production. However, statistical analysis of the results indicates that average production of 21 burns with Cistus laurifolius is 73 % lower than the production of 20 burns associated with Quercus/Corylus without Cistus laurifolius in this zone, respectively. C. laurifolius develops small burns, which has an impact on their carpophore production, and their soils have 92 % less active carbonate than the burns associated with Quercus/Corylus in this zone, respectively. The low levels of active carbonate allow Cistus laurifolius to grow, but impair Tuber melanosporum production. We thus provide a mechanism, based on the inability of Cistus laurifolius to grow in highly carbonated soils, which contradicts the well-known fact that C. laurifolius might act as a transmitter of Tuber melanosporum mycorrhizae. These results indicate that this rockrose can not be considered a useful species for truffle culture. We thus recommend that particular attention should be given to the concentration of active carbonate present in the soil in future studies on the relationship between Cistus species and truffles.     

Trail following behaviour in relation to pedal mucus production in the intertidal gastropod Monodonta labio (Linnaeus)

Trail following behaviour and pedal mucus production were investigated in the mid-shore topshell, Monodonta labio (Linnaeus) in Hong Kong. On the shore, individuals exhibited both conspecific and self trail following while awash on ebb and flood tides, although fidelity to resting sites during emersion on successive days was low. In the laboratory, animals that encountered trails that had been aged on the shore for different periods showed similar patterns of movement (distance moved, speed and tortuosity) suggesting that degradation of cues in the mucus that animals responded to did not occur until > 3 days post-deposition. Animals moved faster, with a lower rate of radular rasping, on freshly laid mucus trails than on a biofilm-covered substratum and did not change their speed when moving over aged (biofilm-covered) mucus compared to fresh mucus. Mucus production rates were similar when animals were crawling on vertical or horizontal surfaces, but significantly more mucus was produced when animals were emersed than when submerged. Mucus trail profiles were of variable thickness, but ‘double’ mucus trails (marker + tracker trails) did not contain significantly more mucus than ‘single’ trails (marker mucus only) and were considerably thinner than single trails suggesting tracker snails utilized mucus laid by marker snails, reducing their own deposition of mucus. Thus, while M. labio do not appear to utilize trails for orientation or refuge location, snails that follow trails have the potential to save energy through reducing mucus production or to gain energy through mucus ingestion. Given the role of pedal mucus production in the overall energy balance of gastropods, such energetic benefits are considerable and may have implications for the life history of the snail.     

Colour and pattern in relation to sexual and aggressive behaviour in the bluehead wrasse Thalassoma bifasciatum

Terminal phase adult male bluehead wrasse show rapid and frequent changes of body colour from bright green to opalescent. Green body colour is associated with aggressive chases of other fish, opalescent with courting females and spawning and so the body colour gives an indication of the fish's ‘intention’ over the next few seconds. Pectoral fin spots appear during courtship and a hypothesis is suggested for their function.     

A telemetry study on the diurnal distribution and activity of adult pikeperch, Sander lucioperca (L.), in a riverine environment

The diurnal movements and spatial distribution of adult pikeperch, Sander lucioperca, in the Elbe River, Czech Republic was observed using radio telemetry. The hypothesis that light intensity, within four different intervals (dawn, day, dusk, night), would determine the spatial distribution of pikeperch in a riverine environment were tested across a time span of 12 months. During the day, fish were located in deep water of the main channel, moving towards shallower waters during twilight and residing in the littoral zone, closest to the riverbanks, at night. Movement activity followed the behavioural pattern in a drainage canal with maximum at twilight and minimum at night. This suggests that nocturnal positions of adult pikeperch in the shallows were not associated with hunting but more likely with resting. Handling editor: J. Cambray     

The DcMaster Transposon Display maps polymorphic insertion sites in the carrot (Daucus carota L.) genome

DcMaster is a family of PIF/Harbinger-like class II transposable elements identified in carrot. We present a modified Transposon Display molecular marker system allowing amplification of genomic regions containing DcMaster elements. We scored 77 DcMaster Transposon Display (DcMTD) amplicons, of which 54 (70%) were segregating in the F₂ progeny from the cross between wild and cultivated carrot. Segregating amplicons were incorporated into a previously developed molecular linkage map of carrot. Twenty-eight markers were attributed to the wild parent, 23 originated from the cultivated parent, and three markers remained unlinked. The markers were evenly distributed among the nine linkage groups. However, differences in the distribution pattern of DcMaster insertion sites in the genomes of the wild and cultivated parent were observed. Specificity of the obtained amplicons was confirmed by sequencing and three putative DcMaster subfamilies, differing in the sequence of their terminal inverted repeats, were revealed.     

Male and female contributions to provisioning rates of thin-billed prions, Pachyptila belcheri , in the South Atlantic

We recorded individual provisioning patterns of male and female thin-billed prions in the largest known colony on New Island (Falkland Islands, South Atlantic Ocean), to determine male and female contributions to provisioning rates and to compare them with data from their other main breeding site, on Kerguelen, in the Southern Indian Ocean. Both male and female birds from New Island undertook trips of 1–8 days’ duration (median 3 days), similar to those on Kerguelen, although we did not observe a clear distinction between long and short trips. Meal sizes increased with longer trips but did not differ between male birds and female birds. Thus, as on Kerguelen, male and female thin-billed prions on New Island contributed equally to chick provisioning. The proportion of short trips was comparable to those observed in a more favourable year, and was higher than those in a poor year, on Kerguelen. In order to avoid potential disturbance to the birds in the colony by frequent capture and handling, we used miniature radio-tags to record the presence of individuals in the colony and to evaluate the influence of transmitter load on the birds. Despite generally deteriorating conditions towards the end of the breeding season, chicks of tagged adults were fed normally, indicating that the method is adequate.     

Lack of a genetic bottleneck in a recent Lessepsian bioinvader, the blue-barred parrotfish, Scarus ghobban

The present study investigates the genetic diversity of Scarus ghobban, a recently introduced parrotfish in the Mediterranean Sea via the Suez Canal. Two mitochondrial and one nuclear DNA regions were sequenced and phylogenetic relationships investigated, from samples collected from Lebanon and across its natural range. Scarus ghobban clustered in two major clades, Pacific Ocean and Indian Ocean, indicating strong population structure, or cryptic speciation. Expectedly, Mediterranean samples clustered with Indian Ocean-Red Sea individuals. However, unlike other recent Lessepsian invaders, S. ghobban displayed high genetic diversity. These results underscore that genetic diversity is a poor predictor of success of an invasive species.     

Spatial patterns in at-sea behaviour during spring migration by little gulls ( Larus minutus ) in the southeastern North Sea

At-sea distribution of seabirds has been studied on different scales and with different focus in many parts of the world. However, factors and/or processes causing certain patterns are often not easily explained. This also holds true for fast migrating species of international conservation concern, such as the little gull (Larus minutus) in the German Bight (southeastern North Sea). In this study, we used multiyear distributional data in combination with behavioural observations and food sampling to investigate spatial and temporal patterns and their possible causes during spring migration. The results show a highly focussed migration pattern during the last week of April and the first week of May. The river Eider seemed to play an important role as main migration route. Highest numbers were found either close to the mainland or close to the offshore islands. Little gulls used certain subareas for intense feeding (i.e. the region near Helgoland and the outlet of river Elbe) and others for migration. Hydrographic phenomena such as fronts and foam lines play an important role within the feeding sites and strongly influence behaviour and distribution. Feeding behaviour as well as samples of probable prey revealed different quality of feeding sites according to the energy density of the most abundant probable food items (drowned insects versus zooplankton and fish). In conclusion, the area utilisation of L. minutus during spring migration in the German Bight showed a clear pattern, and sites with main feeding action should be regarded as sensitive for little gulls, at least during spring migration.