Spermatogenesis in the archaic hydrothermal vent bivalve,Bathypecten vulcani,and comparison of spermatozoon ultrastructure with littoral pectinids

Summary

Bathypecten vulcani is considered a relict species from the Paleozoic, based on shell characteristics such as the presence of calcite prisms. To date, it is the only pectinid species reported from hydrothermal ecosystems. Histological and ultrastructural studies show that spermatogenesis is identical to that of littoral pectinids. The spermatozoon has a 2.7 μm long pyriform head and a 40 μm flagellum. The four mitochondria of the mid-piece are about 1.2 μm in diameter. The nucleus contains dense chromatin fibres and possesses a wide, shallow (0.1 μm) anterior fossa and a narrow, deeper (0.2 μm) posterior nuclear fossa. Comparison of the ultrastructural characteristics of the spermatozoon of B. vulcani with those of littoral pectinids shows that they can be used as a diagnostic feature of this species. In particular, its acrosome characters will be a useful complement to the shell characters in the study of the phylogenetic position of this species in relation to other pectinids.     

Do digger wasps commit the concorde fallacy?

The Concorde fallacy is a notorious theoretical error which tempts economists and evolutionists alike. It amounts to investing further in a project simply because one has invested in it heavily in the past, rather than because of potential future return on investment. Digger waps, Sphex ichneumoneus, disconcertingly appear to behave as if following the Concorde fallacy. Pairs of females fight over jointly occupied nests, provisioned with paralysed katydids. The prior investment by each wasp in the nest is measured as the number of katydids that she has put into it. The true value of the nest is approximated by the total number of katydids there. The evidence suggests that the wasp with the least prior investment is the one most likely to surrender. In a post-hoc attempt at rationalizing this Concordian result, we uncover some of the pitfalls of naive optimality speculations, and recommend analysis in terms of evolutionarily stable strategies.     

Die Alkoholkomponente des Bacteriochlorophyll a aus Rhodospirillum rubrum

Summary The esterifying alcohol of the bacteriochlorophyll a from Rhodospirillum rubrum was shown to be trans-trans-geranylgeraniol. Mass spectra of the corresponding bacteriopheophytins are used to determine the content and ratio of bacteriochlorophyll a_P and bacteriochlorophyll a_Gg in various strains of phototrophic bacteria.     

Relationship between eutrophication reference conditions and boundary settings considering OSPAR recommendations and the Water Framework Directive—examples from the German Bight

In order to allow for natural variability, the original OSPAR assessment procedure for eutrophication (Comprehensive Procedure) sets the threshold between Non-Problem/Problem Area (elevated levels) at 50% above natural background concentrations, which is equivalent to the boundary setting good/moderate for the EU Water Framework Directive (WFD). The 50% level corresponds to the recent natural variability of nutrient gradients in coastal and estuarine waters in the German Bight. Based on this threshold, a proposal is given for the additional boundary settings required for the WFD assessments. Examples, based on concentrations of total nitrogen and other correlated eutrophication components, are presented. However, for eutrophication effects such as oxygen deficiency, reduced transparency and increased transboundary loads, especially for offshore regions, 50% exceedance of the natural background surpasses ‘slight differences’ as recommended by the boundary good/moderate for the WFD. For this reason, 15% is proposed as the boundary setting for good/moderate and discussed for different parameters. Overlapping between recent means and their standard deviations and the four boundary settings for the WFD cannot be avoided, thereby causing weak assessments. Since the part of the variability of recent data is caused by hydrodynamics, coupled with salinity variation, the variability could be reduced to some degree by relating the data to mean salinities. By doing this, the significance of classifications could be improved. The application of this procedure is discussed for examples from the German Bight.     

Diversity of mitochondrial DNA in three Arabian horse strains

Arabian horse registries classify Arabian horses based on their dam lineages into five main strains. To test the maternal origin of Syrian Arabian horses, 192 horses representing the three major strains Saglawi, Kahlawi, and Hamdani were sequenced for 353 bp of their mitochondrial displacement loop (D-loop) region. Sequencing revealed 28 haplotypes comprising 38 sequence variations. The haplotype diversity values were 0.95, 0.91, and 0.90 in Kahlawi, Hamdani, and Saglawi strains, respectively. The pair-wise population differentiation estimates (Fst) between strains were low, ranging between 0.098 and 0.205. The haplotype diversity and the pair-wise population differentiation estimates (F_st) between strains showed high diversity within individuals of each strain and low variation between the three strains. Mitochondrial haplotypes scattered all over the neighbor-joining tree without clear separation of the three strains. In the median-joining network, the Syrian horses were grouped into seven major haplogroups. These results suggest that more than five ancestors exist that share common maternal haplotypes with other horse breeds.