How to use live sampling tissues and archived specimens in cetacean stable isotope research

Cetaceans are unique ecological engineers,and their restoration may have a crucial impact on the future structure of aquatic ecosystems,which calls for more investigations into their trophic ecology.Among current techniques,stable isotope analysis(SIA)has the advantages of non-invasive sampling and long timescales.However,the full benefits of SIA in cetacean research may not be achieved due to issues like different types of tissue between sampling methods and use of chemical preservation solutions in historical specimens.To address these challenges,we conducted a study on Narrow-ridged Finless Porpoises(Neophocaena asiaeorientalis).Multiple tissues from freshwater and marine subspecies,as well as tissues preserved using different solutions such as ethanol and formalin were collected for SIA.Linear mixed effects models were used for data analysis.Our results showed that,except for blubber,kidney,and stomach,differences between other tissues were correctable.In tissues from live sampling,we found no significant difference between blood and muscle,and skin could also be used for isotope analysis after proper correction.Ethanol preservation caused significant positive changes in δ^(13)C and δ^(15)N values of muscle,while formalin preservation caused negative changes in δ^(13)C and δ^(15)N.Our findings provide valuable insight into unifying data from stranded carcasses and live sampling,as well as correcting for the effect of chemical preservation on museum specimens.Findings from this research support further application of stable isotope analysis in the conservation of endangered finless porpoises,offer a reference for other similar cetaceans,and also provide guidance for chemical preservation when freezing conditions are not available.

Thresholds of population persistence for the Yangtze finless porpoise:implications for conservation managements

The Yangtze finless porpoise(Neophocaena asiaeorientalis asiaeorientalis),a critically endangered species,is the only cetacean species in the Yangtze River following the functional extinction of baiji(Lipotes vexillifer).To inform conservation actions,two important questions need to be addressed:what is the threshold value of survival rate,and what is the threshold value of population size?We calculate the instantaneous rate of population increase(¯r)for the Yangtze finless porpoise for various combinations of the calf and the non-calf survival rates.We also test the probability of extinction for different minimum carrying capacities for 100 and 500 years using a stable population model.The threshold value of the non-calf survival rate is never lower than 0.869,but current estimates from field data have been far below this threshold.Our model based on extinction probability and carrying capacity suggests that the threshold for the population size to persist 100 years required 113 animals,and 472 animals are required to persist 500 years.Therefore,we recommend establishing an ex situ reserve network to guarantee the minimum 100-year carrying capacity.To ensure the long-term population viability,we suggest establishing two in situ reserve zones in two lakes and their surrounding reserves to meet a minimum 500-year carrying capacity.In addition,measures to avoid further habitat fragmentation should be priority.

The intestinal microbiome of an Indo-Pacific humpback dolphin(Sousa chinensis)stranded near the Pearl River Estuary,China

The mammalian intestinal microbiome is critical for host health and disease resistance.However,the cetacean intestinal microbiota remains relatively unexplored.By using high-throughput 16S rRNA gene sequencing,we analyzed intestinal bacterial samples from an Indo-pacific humpback dolphin(Sousa chinensis)stranded near the Pearl River Estuary in China.The samples included 3 anatomical regions(foregut,midgut,and rectum)and 2 anatomical locations(content and mucus).Our analyses revealed that the dolphin intestinal bacteria contained 139 operational taxonomic units(OTUs),dominated at the phyla level by Firmicutes(47.05%in the content;94.77%in the mucus),followed by Bacteroidetes(23.63%in the content;1.58%in the mucus)and Gammaproteobacteria(14.82%in the content;2.05%in the mucus).The intestinal bacteria had a small core community(15 OTUs,accounting for 99.74%of the reads),some of which could be potentially pathogenic to both human and dolphins.As an alternative to sampling the dolphin intestinal bacteria,fecal sampling could be used.Additionally,function potentials such as,xenobiotics biodegradation,beta-lactam resistance,and human disease-related pathways,were detected in the dolphin intestinal bacteria.These findings provide the first baseline knowledge of the intestinal microbiome of the Indo-Pacific humpback dolphin,which may offer new insights into cetacean conservation by using microbial surveillance.

3D multiphysic simulations of energy field and material process in radial ultrasonic rolling electrochemical micromachining

The radial ultrasonic rolling electrochemical micromachining(RUR-EMM)combined rolling electrochemical micromachining(R-EMM)and ultrasonic vibration was studied in this paper.The fundamental understanding of the machining process especially the interaction between multiphysics in the interelectrode gap(IEG)was investigated and discussed by the finite element method.The multiphysics coupling model including flow field model,Joule heating model,material dissolution model and vibration model was built.3D multiphysics simulation based on micro dimples process in RUR-EMM and R-EMM was proposed.Simulation results showed that the electrolyte flowed into and out IEG periodically,gas bubbles were easy to squeeze out and the gas void fraction deceased about 16%to 54%,the maximum current density increased by 1.36 times in RUR-EMM than in R-EMM in one vibration period of time.And application of the ultrasonic vibration increased the electrolyte temperature about 1.3–4.4%in IEG.Verification experiments of the micro dimple process denoted better corrosion consistency of array dimples in RUR-EMM,there was no island at the micro dimple bottom which always formed in R-EMM,and an aggregated deviation of less than 8.7%for the micro dimple depth and 4%for the material removal amount between theory and experiment was obtained.

Blubber fatty acid compositions in different geographic populations of finless porpoise in Chinese waters:implications for thermal adaptation

The stratification of blubber fatty acids(FAs)is a widely used strategy in marine mammals and can be influenced by many factors,including their diet,environmental temperature,and physiological status.There are 3 distinct finless porpoise species/subspecies in Chinese coastal and inland waters in a wide range from 20°N to 40°N.The biochemical stratification of the blubbers of finless porpoises in different regions may provide valuable information for understanding their environmental adaptations.The FA compositions of 4 geographic populations of finless porpoise(FP)collected from the Bohai Gulf,East China Sea,South China Sea,and Yangtze River were therefore analyzed and compared.The blubber FA compositions of finless porpoises were dominated by∑MUFAs,followed by∑SFAs and∑PUFAs,and were generally consistent with those of other cetaceans.The blubber of finless porpoises was significantly stratified with increasing levels of∑MUFAs and decreasing levels of∑SFAs and∑PUFAs from the inner to the outer layers.The 3 marine populations shared more similarities in their FA compositions and stratifications compared to the freshwater porpoises,particularly regarding the PUFAs in the inner layers,which might have been mainly influenced by the diet compositions of marine and freshwater porpoises.Contrary to what was expected,in the 3 marine populations,the SFA and MUFA levels showed opposite correlations(negative and positive,respectively)with habitat temperatures,possibly indicating an adaptation mechanism in finless porpoises characterized by a trade-off between the insulation and fluidity properties of the blubber through the adjustment of the compositions and gradients of MUFAs and SFAs across the blubber depth in response to environmental temperature/latitude changes.

Record of a juvenile Omura's whale live stranded in Hainan Island:Evidence of a potential breeding ground in the South China Sea?

On January 12,2011,a very young juvenile Bryde's-like baleen whale was found stranded alive on the east coast of Hainan Island,in the South China Sea.Unfortunately,it died the next morning.This baleen whale showed some unique external morphology and skull features of the Omura's whale(Balaenoptera omurai).Subsequently,it was genetically identified as an Omura's whale using two different mitochondrial DNA markers.This study documents the first confirmed live stranding of a juvenile Omura's whale on Hainan Island,China.Our findings expand the known distribution range of this species in Chinese waters and may indicate that waters around Hainan Island in the South China Sea could be a potential breeding ground for the Omura's whale.