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Summer Mortality (summer + mortality)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

QTL for resistance to summer mortality and OsHV-1 load in the Pacific oyster (Crassostrea gigas)

ANIMAL GENETICS, Issue 4 2010
C. Sauvage
Summary Summer mortality is a phenomenon severely affecting the aquaculture production of the Pacific oyster (Crassostrea gigas). Although its causal factors are complex, resistance to mortality has been described as a highly heritable trait, and several pathogens including the virus Ostreid Herpes virus type 1 (OsHV-1) have been associated with this phenomenon. A QTL analysis for survival of summer mortality and OsHV-1 load, estimated using real-time PCR, was performed using five F2 full-sib families resulting from a divergent selection experiment for resistance to summer mortality. A consensus linkage map was built using 29 SNPs and 51 microsatellite markers. Five significant QTL were identified and assigned to linkage groups V, VI, VII and IX. Analysis of single full-sib families revealed differential QTL segregation between families. QTL for the two-recorded traits presented very similar locations, highlighting the interest of further study of their respective genetic controls. These QTL show substantial genetic variation in resistance to summer mortality, and present new opportunities for selection for resistance to OsHV-1. [source]

Raptor predation and population limitation in red grouse

JOURNAL OF ANIMAL ECOLOGY, Issue 3 2000
Simon J. Thirgood
Summary 1.,We assessed the impact of predation by hen harriers and peregrine falcons on a red grouse population in southern Scotland during 1992,98. Grouse density in April, July and October declined during this time, coincident with an increase in the numbers of breeding harriers and peregrines. 2.,Winter losses of grouse between October and April averaged 33% and were density-dependent. Raptors were the cause of about 70% of winter mortality and they killed about 30% of the grouse present in October. We were unable to determine whether winter mortality in raptors was additive to other losses. 3.,Summer losses of adult grouse between April and July averaged 30% and were density-dependent. Raptors were the cause of more than 90% of the early summer mortality of adult grouse. Summer losses of grouse chicks between May and July averaged 45% and were not density-dependent. Harriers killed about 28% of grouse chicks by late July and about 37% by the end of August. Summer raptor predation on adult grouse and chicks appeared to be largely additive to other losses and we estimated that it reduced autumn grouse densities by about 50%. 4.,A model combining the estimated reduction in autumn grouse density caused by raptors with the observed density dependence in winter loss predicted that, in the absence of raptors for 2 years, grouse density in spring would be 1·9 times greater, and grouse density in autumn 3·9 times greater, than in the presence of raptors. The model suggested that raptor predation prevented the grouse population from increasing and was thus a limiting factor. [source]

Use of Shrubs as Nurse Plants: A New Technique for Reforestation in Mediterranean Mountains

RESTORATION ECOLOGY, Issue 2 2002
Jorge Castro
Abstract Common techniques currently used for afforestation in the Mediterranean basin consider the pre-existing vegetation (mainly shrubs) as a source of competition for trees, and consequently it is generally eliminated before planting. Nevertheless, it has been demonstrated that woody plants can facilitate the establishment of understory seedlings in environments that, like the Mediterranean area, are characterized by a pronounced dry season. In this study, we experimentally analyze the usefulness of shrubs as nurse plants for afforestation of two native conifers, Pinus sylvestris L. (Scots pine) and Pinus nigra Arnold (black pine). Two-year-old seedlings were planted in four microhabitats: (1) open interspaces without vegetation (which is the usual method used in afforestation programs), (2) under individuals of Salvia lavandulifolia, (3) under the north side of spiny shrubs, and (4) under the south side of spiny shrubs. Pine survival was remarkably higher when planted under individuals of the shrub S. lavandulifolia (54.8% for Scots pine, 81.9% for black pine) compared with open areas (21.5% for Scots pine, 56.8% for black pine; chi square, p < 0.05). The survival of both pines was also higher when planted on the north side of spiny shrubs, although the survival on the south side was similar to that found in open areas. In addition, pine growth was not inhibited when planted in association with shrubs. This pattern appears to result from the combination of abiotic conditions imposed by the presence of a nurse shrub, which leads to improvement in seedling water status and therefore reduced summer mortality by drought. The results show that the use of shrubs as nurse plants is a technique that offers both economic and ecological advantages, in terms of savings in labor and plant material and reduced and even negligible impact on the pre-existing vegetation. [source]

QTL for resistance to summer mortality and OsHV-1 load in the Pacific oyster (Crassostrea gigas)

Assessment of metabolic and immune changes in postspawning Pacific oyster Crassostrea gigas: identification of a critical period of vulnerability after spawning

AQUACULTURE RESEARCH, Issue 9 2010
Yan Li
Abstract This study investigates the vulnerable period in postspawning Pacific oysters (Crassostrea gigas) through physiological and immunological assessments. After spawning, the oyster condition index reduced by 50% and required 70 days to recover to the prespawning level. The mantle glycogen reduced quickly while the reduction in tissue protein occurred slowly. The mantle tissue also lost more protein than gills. The analysis of adenylate energy charge indicated that oysters were stressed in the first 8 days after spawning. As a result of spawning, haemocyte phagocytosis was reduced and remained at a low level for 3 days. In contrast, the reduction of haemolymph antimicrobial activity did not occur until 3 days after spawning and continued to decline until day 8. This immunesuppression was not directly correlated to the changes in haemocyte density. Our study suggests that the first 8 days after spawning are a critical period for oyster survival due to the loss of energy and low immunity. This study further improves our understanding of the coincidence between spawning and summer mortality in oyster aquaculture. [source]