Arsenic Bioaccumulation in Freshwater Fishes

The arsenic ambient water quality criterion (AWQC) for protection of human health via ingestion of aquatic organisms is currently 0.14 μ g/L. This AWQC is derived using a bioconcentration factor (BCF) of 44, which is a consumption-weighted average based on two data points for oysters and fish that was proposed by the U.S. Environmental Protection Agency in 1980 for broad application to freshwater and marine environments. This BCF is based on the assumption that bioaccumulation is a simple linear function of the exposure concentration. In the nearly quarter of a century since this BCF was promulgated, there have been additions to the arsenic bioaccumulation database and a broader scientific understanding of bioaccumulation mechanisms and how they can be applied to estimating tissue concentrations in aquatic organisms. From this database, we identified 12 studies of arsenic bioaccumulation in freshwater fishes in order to explore differences in laboratory-generated BCFs and field-generated bioaccumulation factors (BAFs) and to assess their relationship to arsenic concentrations in water. Our analysis indicates that arsenic concentrations in tissue and arsenic BAFs may be power functions of arsenic concentration in water. A power function indicates that the highest BCF values may occur at low background levels and may decrease as environmental concentrations increase above the ambient range.     

The Ordovician-Silurian boundary stratotype: consequences of its approval by the IUGS

Lespérance, Pierre J., Barnes, Christopher R., Berry, William B. N., Boucot, Arthur J. & Mu En-zhi 1987 07 15: The Ordovician-Silurian boundary stratotype: consequences of its approval by the IUGS.
The Ordovician-Silurian stratotype at Dob's Linn, Scotland is the second systemic boundary approved by the International Union of Geological Sciences (IUGS). A review of the internationally accepted criteria required of a stratotype shows that few of these are possessed by the Dob's Linn section. The strongest attribute of the section is the presence of zonal graptolites, although the boundary is recognized primarily on a single biological event (base of acuminatus Zone) for which the evolutionary relationships of the taxa are not established. In approving this boundary proposal in 1985, which received only simple majority support within the Ordovician-Silurian Boundary Working Group (OSBWG) and which fails to meet most of the accepted prerequisites for a stratotype, the International Commission on Stratigraphy (ICS) and the IUGS have established an unfortunate precedent. It follows that future systemic boundaries need not meet the accepted standards. It raises serious questions on the assessment and voting procedures of the International Commission on Stratigraphy and on the credence accorded the recommendations developed by the International Subcommission on Stratigraphic Classification of IUGS.     

Assessing the impact of episodic pollution

The increased tightening of controls on industrial and municipal wastewater discharges has resulted in steady improvements in the quality of many important rivers over recent years. However, episodic pollution, particularly from farm wastes and combined sewer overflows continues to pose a major problem, and is one of the main causes of poor quality rivers today. Despite our acknowledgement of this continuing problem, very little is known of the mechanistic basis of responses and recovery of aquatic organisms and communities exposed to intermittent pulses of common pollutants. The majority of ecotoxicological studies to date have been concerned with the effects of continuous exposure. Although such studies may provide a means of predicting the impact of episodic pollution events, a more appropriate test design would be to assess toxicity under pulsed and fluctuating exposure. Studies should also include a post-exposure observation period and should consider recovery of individuals and communities. This paper reviews the results of reported studies relevant to the investigation of episodic pollution and pays particular attention to the effects of magnitude, duration and frequency of exposure. Results of field investigations using an in situ bioassay technique are also presented to emphasize the importance of field validation of proposed water quality criteria for intermittent pollution events.     

Multi-criteria clustering in genotype-environment interaction problems

Summary Significant genotype-environment interactions in an ANOVA can be found for a number of reasons: one is the differences in the among-environments variances for each genotype, another is the differences in the ordering of the environments by each genotype. Using conditional clustering, groups may be formed in which the means, variances and patterns are used simultaneously but separately to decide on group homogeneity. Contribution No. I-685 from the Engineering and Statistical Research Institute     

腐霉属分类性状评价及其中国的种

本文对腐霉属Pythium Pringsheim的研究历史作了简单的回顾,对该属的分类性状和系统进行了论述和评价,最后对中国已发现的55种腐霉,以检索表的方式进行了分类、检索。     

The empirical question of thresholds and mechanisms of mate choice

Summary Theoretical discussions concerning how animals might best sample and select mates have suggested that individuals could base decisions either on a sample of mates (sampled-based decisions) or on a threshold of comparison (threshold-based decisions). Recent theoretical work demonstrates that threshold-based mating decisions generate higher expected fitness than sample-based mating decisions when search costs exist. Empirical results from most unmanipulated systems, however, either conclude that females make sample-based decisions or are inconclusive. A few experimental studies designed to detect mating thresholds purport to demonstrate threshold-based choice but an examination of these studies indicates such conclusions were premature. We believe that few examples of threshold-based choice exist because protocols designed to identify mating thresholds were often inconsistent with models of threshold choice. We suggest that future empirical work strive not to document mating thresholdsper se. Rather, future work might best reveal decision rules by manipulating the distribution of quality among potential mates; such manipulations predict uniquely how females using sample-based and threshold-based decision rules should behave.     

Potential gain from selection for yield stability in two grain sorghum populations

Summary Maximum yield under highly unpredictable environments should be associated with selection of genotypes with superior performance across good and poor environments. Several stability parameters have been proposed to identify superior genotypes over a wide range of environments. None of these has been used as selection criteria, however, because of their low heritability. The objective of the study presented here was to compare the relative efficiency of predicted gain from indirect selection among three stability parameters: the coefficient of regression (b), deviation from regression (S _d ² ), and principal components scores (PC) from the AMMI model; two indices including mean yield and a stability parameter; and three indices involving yield at the best, the worst, and an intermediate environment. Two hundred S₁ families from each of two sorghum populations (TP24D and KP9B) were evaluated at four dry-land evironments over 2 years. The low heritability estimates and the low genetic correlation between the various stability parameters and mean yield resulted in their low relative efficiency as indirect selection criteria for high yield across environments. However, when the parameters were combined with mean yield over all to create indices, the relative efficiency increased for all the environments. In terms of resource allocation, these indices were not as efficient as mean productivity, rank summation, and selection index that involved fewer environments in their estimation.Contribution no. 9820 of Agricultural Research Division, Univ. of Neb. and no. 92-203-J of Kansas Exp. Stn.     

Homologies of the stapedial artery in humans, with a reconstruction of the primitive stapedial artery configuration of Euprimates

Data drawn from the perspectives of paleontology, comparative anatomy, embryology, teratology, and normal adult variation were analyzed with nine homology criteria in order to determine the homologues of the stapedial artery in adult humans. It was determined that 1) the stem of the stapedial artery does not persist within the cranial cavity; 2) the stem of the ramus inferior is retained in its entirety and forms the upper portion of the stem of the middle meningeal artery; 3) the proximal part of the ramus infraorbitalis is normally absent and is replaced by a collateral shunt arising from the ramus mandibularis; 4) the ramus mandibularis is retained and forms the lower portion of the middle meningeal stem and the inferior alveolar artery; 5) the most proximal portion of the maxillary artery is formed by an anastomotic shunt connecting the external carotid artery to the ramus mandibularis; 6) the anterior division of the ramus superior is normally present and well developed; 7) the posterior division of the ramus superior is present in many individuals; and 8) the junction of the two divisions of the ramus superior with the ramus inferior usually migrates to the floor of the middle cranial fossa. The range of human arterial patterns, and those of all other euprimates, can be derived from a hypothetical primitive pattern that is very similar to that of primitive rodents. In this pattern, the stapedial artery stem enters the middle cranial fossa and trifurcates into the anterior and posterior divisions of the ramus superior and the ramus inferior. In their evolution, strepsirhines initially lose the ramus inferior and haplorhines initially reduce the stapedial artery stem.     

Strategic Habitat Conservation for Beach Mice: Estimating Management Scenario Efficiencies

The Perdido Key beach mouse (Peromyscus polionotus trissyllepsis), Choctawhatchee beach mouse (P. p. allophrys), and St. Andrew beach mouse (P. p. peninsularis) are 3 federally endangered subspecies that inhabit coastal dunes of Alabama and Florida, USA. Conservation opportunities for these subspecies are limited and costly. Consequently, well-targeted efforts are required to achieve their downlisting criteria. To aid the development of targeted management scenarios that are designed to achieve downlisting criteria, we developed a Bayesian network model that uses habitat characteristics to predict the probability of beach mouse presence at a 30-m resolution across a portion of the Florida Panhandle. We then designed alternative management scenarios for a variety of habitat conditions for coastal dunes. Finally, we estimated how much area is needed to achieve the established downlisting criterion (i.e., habitat objective) and the amount of effort needed to achieve the habitat objective (i.e., management efficiency). The results suggest that after 7 years of post-storm recolonization, habitat objectives were met for Perdido Key (within its Florida critical habitat) and Choctawhatchee beach mice. The St. Andrew beach mouse required 5.14 km² of additional critical habitat to be protected and occupied. The St. Andrew beach mouse habitat objective might be achieved by first restoring protected critical habitat to good dune conditions and then protecting or restoring the unprotected critical habitat with the highest predicted probability of beach mouse presence. This scenario provided a 28% increase in management efficiency compared to a scenario that randomly protected or restored undeveloped unprotected critical habitat. In total, when coupled with established downlisting criteria, these quantitative and spatial decision support tools could provide insight into how much habitat is available, how much more is needed, and targeted conservation or restoration efforts that might efficiently achieve habitat objectives. © 2020 The Wildlife Society.     

Evaluation of the standards compliance of the queen bees reared in the Mediterranean region in Turkey

The influence of different commercial queen producers on the quality of Apis mellifera queens was assessed. It was aimed to determine the quality characteristics of queens reared by commercial queen producers located in the province of Antalya, which is an important region in queens production due to its climatic characteristics. For this purpose, the quality characteristics of a total of 105 queen bees obtained from 21 enterprises were determined. Differences between the enterprises in terms of the number of spermatozoa (P < 0.01) were determined. In terms of the diameter of spermatheca, spermatheca volume and live weight, statistical differences between the enterprises were also observed (P < 0.05). When the relationships between the measured characteristics were examined, significant values were obtained statistically between live weight and diameter of spermathecae (0.268) and spermatheca volume (0.258). It was also determined that there is a significant correlation between spermatheca diameter and spermatheca volume (0.995). The spermatheca diameter of a good quality queen bee should not be <1.2 mm, spermatheca volume 0.90 mm³ and live weight not <200 mg. Only live weight was found to be within the normal quality standard values when the average results of the quality criteria are taken into consideration. Other characters such as spermathecae diameter, spermathecae volume and number of spermatozoa in spermathecae seem to be below quality standard values.