Do positive interactions between marine invaders increase likelihood of invasion into natural and artificial habitats?

Positive species interactions such as facilitation are important for enabling species to persist, especially in stressful conditions, and the nature and strength of facilitation varies along physical and biological gradients. Expansion of coastal infrastructure is creating hotspots of invasive species which can spillover into natural habitats, but the role of positive species interactions associated with biological invasions remains understudied. Theory suggests that stronger biotic pressure in natural habitats inhibits invasion success. In space-limited marine systems, sessile organisms can overcome this limiting resource by settling as an epibiont on a substrate organism – basibiont. Using a series of spatially extensive surveys, we explored the role of invasive and native basibionts in providing habitat for other invasive and native epibionts, and tested whether environmental context (i.e. if the receiving habitat was natural or artificial), altered ecological outcomes. Overall, provision of space by basibionts was more important for invasive epibionts than for native epibionts but was dependent on the environmental context. Invasive basibionts facilitated invasive epibionts in natural habitats, and appeared to be more important for native epibionts in artificial habitats respectively. Native basibionts facilitated invasive, but not native epibionts in both natural and artificial habitats. These results advance our understanding of facilitation and highlight the idiosyncratic nature of biofouling and epibiosis, and the potentially important influence of environmental context. The degree to which native habitat-forming species versus invasive habitat-forming species either do or do not facilitate other native or non-native species is a rich area for investigation. Experimental work is required to disentangle the processes underpinning these patterns.     

Aspects of reproduction and their implications for the conservation of the endangered limpet,Patella ferruginea

Summary

The protandric limpet, Patella ferruginea G., is the most endangered marine species in the Western Mediterranean and is at serious risk of extinction. Nevertheless, its biology and ecology are little known. In the present work, several reproductive aspects are studied. Recruitment take place in June and the largest individuals are the most scarce. The sex ratio is slanted towards the largest sizes, and the species seems to show sex change at sizes from 60 mm upwards, although males can be observed up to 80 mm. There is no correlation between size of oocytes and shell length; however, the larger females contribute greatly to the reproductive event, with high fecundity and GSI values. The mean diameter of oocytes was observed to be 149.78 μm, whereas the heads of spermatozoa were 3.78 μm long. The results of the present study increase the maximum length for males by double that cited in previous literature and highlight the importance of strictly protecting females (i.e., most of the largest individuals, >60 mm), since their population percentage is very low, in order to develop adequate strategies to preserve the species.     

New polymorphic microsatellite markers for the limpet Patella rustica and cross-priming testing in four Patella species

Eighteen microsatellite markers have been characterized from the Patella rustica genome. An average of 10 alleles per locus and an expected heterozygosity ranging from 0.054 to 0.937 were observed in a sample of 32 wild individuals from Viana do Castelo, Portugal. Distinct cross-priming amplification rates were recovered on four additional Patella species. Three monomorphic P. rustica loci were polymorphic in other Patella species. The microsatellites developed herein could be a useful intraspecific genetic tool to undertake fine population studies in the genus Patella.     

The lmx1b gene is pivotal in glomus development in Xenopus laevis

We have previously shown that lmx1b, a LIM homeodomain protein, is expressed in the pronephric glomus. We now show temporal and spatial expression patterns of lmx1b and its potential binding partners in both dissected pronephric anlagen and in individual dissected components of stage 42 pronephroi. Morpholino oligonucleotide knock-down of lmx1b establishes a role for lmx1b in the development of the pronephric components. Depletion of lmx1b results in the formation of a glomus with reduced size. Pronephric tubules were also shown to be reduced in structure and/or coiling whereas more distal tubule structure was unaffected. Over-expression of lmx1b mRNA resulted in no significant phenotype. Given that lmx1b protein is known to function as a heterodimer, we have over-expressed lmx1b mRNA alone or in combination with potential interacting molecules and analysed the effects on kidney structures. Phenotypes observed by over-expression of lim1 and ldb1 are partially rescued by co-injection with lmx1b mRNA. Animal cap experiments confirm that co-injection of lmx1b with potential binding partners can up-regulate pronephric molecular markers suggesting that lmx1b lies upstream of wt1 in the gene network controlling glomus differentiation. This places lmx1b in a genetic hierarchy involved in pronephros development and suggests that it is the balance in levels of binding partners together with restricted expression domains of lmx1b and lim1 which influences differentiation into glomus or tubule derivatives in vivo.     

Gonad development and fatty acid composition of Patella depressa Pennant (Gastropoda: Prosobranchia) populations with different patterns of spatial distribution, in exposed and sheltered sites

The present study examines the effect of shore exposure on the feeding performance (assessed by fatty acid analyses of the whole body) and gonad condition (stage of development and gonad somatic index, GSI) of Patella depressa populations. Male and female limpets were collected at exposed and sheltered sites, during winter and summer. The population at the exposed site was at a more advanced stage of gonad development, with a higher dispersion of gonad stages, both in winter and summer. Additionally, limpets from the exposed site, particularly the males, presented a higher GSI than the corresponding stage in the sheltered site. The quantitatively most important fatty acids were the saturated fatty acids (SFA) 16:0, 14:0, and 18:0, the monounsaturated fatty acids (MUFA) 18:1(n−7), 18:1(n−9), 16:1(n−7) and 20:1(n−9) and the polyunsaturated fatty acids (PUFA) 20:5(n−3) and 20:4(n−6). Females had a significantly higher fatty acid methyl esters (FAME) content (in summer and winter) and higher amounts of SFA and MUFA (in summer), which points to a higher degree of storage of neutral lipids in this sex. Male and female limpets at the exposed site had a significantly higher FAME, SFA, MUFA, PUFA and highly unsaturated fatty acids (HUFA) content than the corresponding sex in the sheltered site in summer. In addition, an inversion in the eicosapentaenoic acid (EPA)/arachidonic acid (ARA) and (n−3)/(n−6) ratios was observed in the sheltered site, as a result of the significantly higher levels of ARA and (n−6) fatty acids and lower amounts of EPA and (n−3) fatty acids found in the sheltered limpets. A high variability among patches in the fatty acid composition in the exposed site was found in winter, possibly related to the aggregation of limpets at this time. The differences found between limpets from the exposed and sheltered sites suggest qualitative and quantitative differences in their diets. Additionally, the results show that the spatial aggregation strategy adopted by limpets in sites of great wave and wind exposure does not affect their feeding and reproductive success, at least in the site examined here. In fact, more developed gonads, a higher GSI and an elevated FAME content was found in the exposed population. Possible factors are suggested and discussed to explain these observations.     

Equatorial range limits of an intertidal ectotherm are more linked to water than air temperature

As climate change is expected to impose increasing thermal stress on intertidal organisms, understanding the mechanisms by which body temperatures translate into major biogeographic patterns is of paramount importance. We exposed individuals of the limpet Patella vulgata Linnaeus, 1758, to realistic experimental treatments aimed at disentangling the contribution of water and air temperature for the buildup of thermal stress. Treatments were designed based on temperature data collected at the microhabitat level, from 15 shores along the Atlantic European coast spanning nearly 20° of latitude. Cardiac activity data indicated that thermal stress levels in P. vulgata are directly linked to elevated water temperature, while high air temperature is only stressful if water temperature is also high. In addition, the analysis of the link between population densities and thermal regimes at the studied locations suggests that the occurrence of elevated water temperature may represent a threshold P. vulgata is unable to tolerate. By combining projected temperatures with the temperature threshold identified, we show that climate change will likely result in the westward expansion of the historical distribution gap in the Bay of Biscay (southwest France), and northward contraction of the southern range limit in south Portugal. These findings suggest that even a minor relaxing of the upwelling off northwest Iberia could lead to a dramatic increase in thermal stress, with major consequences for the structure and functioning of the intertidal communities along Iberian rocky shores.     

关节置换前后髌骨高度对膝关节功能的影响

目的:研究全膝关节置换术前、术后Insall-Salvati指数和改良Insall-Salvati指数与术后膝关节活动度的关系。方法:采用HSS评分系统对患者全膝关节置换术后半年至一年的关节功能、活动度、肌力、屈曲畸形、稳定性等进行评价。测量81例(106膝)患者术前、术后X线片Insall-salvati指数及改良Insall-salvati指数。结果:术后HSS评分为(89±10)分,术前Insall-salvati指数及改良Insall-salvati指数分别为(1.00±0.13)、(1.61±0.21),术后Insall-salvati指数及改良Insall-salvati指数分别为(0.94±0.19)、(1.67±0.34)。关节置换术后Insall-salvati指数较置换前显著降低(P0.05),改良Insall-salvati指数显著提高(P0.05)。术后低位髌骨组(Insall-salvati指数0.8)HSS评分、活动度和屈曲畸形分值均较正常髌骨组(0.8Insall-salvati指数1.5)显著降低(P0.05)(P0.05)。高位髌骨组(Insall-salvati指数1.5)和正常髌骨组各项评分均无显著差异(P0.05)。术前改良Insall-salvati指数小于1.8的患者术后膝关节HSS评分、功能、活动度、肌力、屈曲畸形、稳定性显著高于大于1.8的患者(P0.05)。结论:术前改良Insall-salvati指数和术后Insall-salvati指数可作为评价术后膝关节功能的参考指标。术前、术后的膝关节高度均会影响术后关节功能,全膝关节置换术中精确截骨对术后关节功能十分重要。     

Comparison of patella bone strain between females with and without patellofemoral pain: A finite element analysis study

Elevated bone principal strain (an indicator of potential bone injury) resulting from reduced cartilage thickness has been suggested to contribute to patellofemoral symptoms. However, research linking patella bone strain, articular cartilage thickness, and patellofemoral pain (PFP) remains limited. The primary purpose was to determine whether females with PFP exhibit elevated patella bone strain when compared to pain-free controls. A secondary objective was to determine the influence of patella cartilage thickness on patella bone strain. Ten females with PFP and 10 gender, age, and activity-matched pain-free controls participated. Patella bone strain fields were quantified utilizing subject-specific finite element (FE) models of the patellofemoral joint (PFJ). Input parameters for the FE model included (1) PFJ geometry, (2) elastic moduli of the patella bone, (3) weight-bearing PFJ kinematics, and (4) quadriceps muscle forces. Using quasi-static simulations, peak and average minimum principal strains as well as peak and average maximum principal strains were quantified. Cartilage thickness was quantified by computing the perpendicular distance between opposing voxels defining the cartilage edges on axial plane magnetic resonance images. Compared to the pain-free controls, individuals with PFP exhibited increased peak and average minimum and maximum principal strain magnitudes in the patella. Additionally, patella cartilage thickness was negatively associated with peak minimum principal patella strain and peak maximum principal patella strain. The elevated bone strain magnitudes resulting from reduced cartilage thickness may contribute to patellofemoral symptoms and bone injury in persons with PFP.