Phenotypic effects of antibiotic‐induced axenity and egg disinfection in early larval European seabass (Dicentrarchus labrax L.)

In the present study, the hypothesis that the difference in axenic conditions in the incubation and rearing environment of European seabass larvae induces size and shape effects on the specimens is tested. This difference is studied between xenic and axenic seabass larvae of DAH (day after hatching) 0, 5, 11 and 15. The axenic rearing protocol involves an egg disinfection with glutaraldehyde after the primary one with iodine in the hatchery, and the hypothesis that this secondary disinfection induces size and shape effects is also tested. In order to accomplish this, three egg and larvae treatments are included: “DA” (disinfected axenic), “DX” (disinfected xenic) and “NX” (nondisinfected xenic). Regarding the effect of antibiotic‐induced axenity, DA larvae exhibited larger bodies than both DX and NX on DAH 5 and 11. They also had a smaller yolk sac than DX at hatching, but consumed it slower. Towards the end of the experiment, DA larvae were thicker, but slightly more curved than DX and NX, which may be an abnormal shape, or a slightly more advanced ontogenetic stage. As far as egg disinfection, it had significant but very moderate shape effects on DAH 5 and 11, and disinfected larvae consumed their yolk sac faster. To the best of our knowledge, this study is one of the first to illustrate the subtle but significant size and shape effects caused by antibiotic‐induced axenity and secondary egg disinfection in the early larval stages, which suggest the existence of bacterial mechanisms that play a phenotypic role.     

The large‐scale removal of mammalian invasive alien species in Northern Europe

Numerous examples exist of successful mammalian invasive alien species (IAS) eradications from small islands (<10 km²), but few from more extensive areas. We review 15 large‐scale removals (mean area 2627 km²) from Northern Europe since 1900, including edible dormouse, muskrat, coypu, Himalayan porcupine, Pallas' and grey squirrels and American mink, each primarily based on daily checking of static traps. Objectives included true eradication or complete removal to a buffer zone, as distinct from other programmes that involved local control to limit damage or spread. Twelve eradication/removal programmes (80%) were successful. Cost increased with and was best predicted by area, while the cost per unit area decreased; the number of individual animals removed did not add significantly to the model. Doubling the area controlled reduced cost per unit area by 10%, but there was no evidence that cost effectiveness had increased through time. Compared with small islands, larger‐scale programmes followed similar patterns of effort in relation to area. However, they brought challenges when defining boundaries and consequent uncertainties around costs, the definition of their objectives, confirmation of success and different considerations for managing recolonisation. Novel technologies or increased use of volunteers may reduce costs. Rapid response to new incursions is recommended as best practice rather than large‐scale control to reduce the environmental, financial and welfare costs. © 2016 Crown copyright. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Distribution and ecology of the Belgian Campodea species (Diplura: Campodeidae)

From 2004 till 2008, Diplura were sampled at 96 localities in Belgium. Nine different species of Campodea were collected: Campodea fragilis Meinert 1865, Campodea lankesteri Silvestri 1912, Campodea lubbocki Silvestri 1912, Campodea meinerti Bagnall 1918, Campodea plusiochaeta Silvestri 1912, Campodea remyi Denis 1930, Campodea rhopalota Denis 1930, Campodea staphylinus Westwood 1842 and Campodea wallacei Bagnall 1918. The ordination technique non-metric multidimensional scaling indicated that pH and temperature/humidity were probably the most important variables determining species composition. However, it was remarkable that almost all combinations of species were encountered in the field, often even under the same stone. As no temporal segregations seem to take place, it remains unknown how these very similar species can occur together.     

No evidence of a plant extinction debt in highly fragmented calcareous grasslands in Belgium

Long transient times in response to decreasing habitat area and increasing isolation may cause the present plant species distribution to reflect the historical rather than the present landscape configuration, resulting in a so-called extinction debt. To investigate how plant species richness is shaped by both present and historical landscape configuration and local environmental conditions in fragmented calcareous grasslands, 64 sites in Southern Belgium were surveyed for their total species richness and environmental characteristics. Species were subdivided in specialist and generalist groups and the former were clustered into emergent groups (EGs) according to 16 relevant life-history traits. Four specialist emergent groups were derived: orchids, rosette species, annuals and half-rosette species. Both specialist and generalist species richness increased with present fragment area, while present fragment connectivity only affected the number of specialist species. This trend was maintained for most EGs, although habitat area was mostly more important than connectivity. All species groups responded to an insolation gradient, except EGs of rosette and annual species. Differential response to fragmentation among emergent groups could be interpreted in terms of dispersal and persistence traits. No relation between species richness and historical area or connectivity was found, making an extinction debt unlikely. Hence, present-day variation in plant species diversity seems to be no legacy of past landscape configuration. Our results clearly indicate that plant species may be quickly lost in response to new fragmentation events. To restore plant diversity, management should focus both on mitigating landscape fragmentation and restoring habitat quality.     

Scale-dependent effects of terrestrial habitat on genetic variation in the great crested newt (Triturus cristatus)

Landscape Ecology - Terrestrial landscapes surrounding aquatic habitat influence the persistence of amphibian spatially structured populations (SSPs) via their crucial role in providing estivation...     

Pituitary response to thyrotropin, corticotropin, and gonadotropin-releasing hormones in lactating cows treated with sometribove for a fourth consecutive lactation

The effect of chronic treatment with recombinant methionyl bovine somatotropin (USAN, sometribove) on anterior pituitary secretions and its target organs was investigated in six control and six sometribove-treated British Friesian cows. Cows averaged 112 and 119 d postpartum in their fourth lactation of treatment and, except for one control, had active corpora lutea. During each lactation, treated cows received sometribove injections (500 mg) every 2 wk (injection cycle) starting 60 ± 3 d postpartum. On Day 9 of one injection cycle, blood was sampled for 390 min, starting 30 min before an intravenous injection of thyrotropin (TRH, 0.33 μg/kg), corticotropin (100 μg), and gonadotropin (GnRH, 200 μg)-releasing hormones. Baseline somatotropin (bST) and adrenocorticotropin (ACTH) were higher in sometribove-treated cows vs. controls (3.27 vs. 1.03 ng/ml and 35.24 vs. 19.28 pg/ml, respectively). Baseline total thyroxine, free thyroxine, triiodothyronine, prolactin, follicle stimulating and luteinizing hormones, estradiol, and progesterone (P4) were similar across treatments. Circulating cortisol levels did not differ between control and sometribove cows, indicating a reduced adrenal ACTH responsiveness in the latter. Releasing factors induced similar changes across treatments in hormones studied with the following exceptions: a bST spike was seen in control cows only, cortisol response to ACTH was reduced in treated cows, and a significantly higher P4 concentration was detected in the plasma of sometribove-treated cows, suggesting increased ovarian responsiveness to GnRH-stimulated P4 output. The study demonstrated reduced bST response to TRH, consistent with physiologic feedback mechanisms, whereas the release profiles of the other pituitary hormones were unaffected. Target tissue responses affected by chronic sometribove treatment appear to be adrenal cortisol and ovarian P4 output.     

Low impact of present and historical landscape configuration on the genetics of fragmented Anthyllis vulneraria populations

Decreasing habitat fragment area and increasing isolation may cause loss of plant population genetic diversity and increased genetic differentiation between populations. We studied the relation between the historical and the present landscape configuration (i.e., patch area and patch connectivity), and the present management of calcareous grassland fragments on the one hand, and the within and between population genetic structure of 18 Anthyllis vulneraria populations on the other hand. Despite the long-time fragmentation history and the mainly selfing breeding system of the species, we detected very low genetic differentiation (Φ_st = 0.056) among habitat fragments and no significant isolation-by-distance relation. Average within fragment genetic diversity measured as molecular variance and expected heterozygosity, were relatively high (16.46 and 0.28, respectively), and weakly positively correlated with the current fragment area, most likely because larger fragments contained larger populations. We found no effects of the historical landscape configuration on the genetic diversity of the populations. Our data suggest that the consequences of habitat fragmentation for genetic differentiation and genetic diversity of A. vulneraria are relatively minor which is very likely due to the historical high levels of seed exchange among fragments through grazing and roaming livestock. This study provides indirect evidence that nature management by grazing not only positively affects habitat quality but that it might also mitigate the genetic consequences of habitat fragmentation. From the conservation point of view, this study illustrates the importance of grazing and of the regular transport of livestock between fragments to prevent the long-term effects of fragmentation on the genetic diversity of the populations studied.     

Saddleback syndrome in European sea bass Dicentrarchus labrax (Linnaeus, 1758): anatomy,ontogeny and correlation with lateral‐line,anal and pelvic fin abnormalities

This study focused on the anatomy and ontogeny of saddleback syndrome (SBS) in reared European sea bass. The abnormality was detected at an unusually high frequency (12–94%) during a routine quality control in a commercial hatchery. Anatomically the abnormality was mainly characterized by the loss of 1–5 hard spines and severe abnormalities of the proximal pterygiophores (anterior dorsal fin), size reduction of a few lepidotrichia, missing lepidotrichia and/or lepidotrichia of poor ossification (posterior dorsal fin). SBS was significantly correlated with abnormalities of the anal and pelvic fins in all the examined populations. Moreover, in juvenile fish, SBS was significantly correlated with an abnormal lack of sectors of the lateral line. The examination of early larval samples revealed that SBS was ontogenetically associated with severe abnormalities of the primordial marginal finfold, which developed at the flexion stage (ca 8.5–11.0 mm SL). Histologically, these abnormalities were associated with extensive epidermal erosion. The results are discussed in respect of the critical ontogenetic period and the possible causative factors of SBS in European sea bass. It is suggested that causative factors acted during a wide ontogenetic period including flexion and metamorphosis phases.     

Effects of antibiotic‐induced differences in bacterial load on growth and shape of early larval European seabass (Dicentrarchus labrax L.)

The aim of the present study was to quantify the effects of antibiotic‐induced differences in bacterial load on the size and shape of fish larvae, using Dicentrarchus labrax of day after hatching (DAH) 3 as a case study. They were split in two treatment groups and reared in 50 ml vials until DAH 14, with the control treatment (“NA”) including larvae reared in filtered autoclaved seawater without antibiotics, while the second (“A”) included larvae reared in filtered autoclaved seawater with rifampicin, ampicillin, kanamycin, trimethoprim and gentamicin, with a concentration of 10 mg/L each. They were sampled for bacterial presence on DAH 4, 7 and 14, and had their mortalities recorded, their total lengths, gut lengths, anal body depths, eye diameters, head depths, yolk sac lengths and yolk sac depths measured, and their outlines analysed on DAH 7 and 14. Treatment NA exhibited the highest mortalities on DAH 14. The antibiotics had a significant size effect, yielding larvae with larger total length on DAH 7 and 14, larger bodies on DAH 7, and on DAH 14 larger anal body depth and greater variance in body size. Their effect on outline shape was also significant in both age classes, with increasing differences from DAH 7 to DAH 14. On DAH 7, “A” specimens were more uniform in their dorso‐ventral development, and on DAH 14 “NA” had more slender shapes. The beneficial total length and size effects and the witnessed shape effects might be associated with the low bacterial presence.