Three New “Biological” Species of Tetrahymena (T. hegewischi n. sp., T. sonneborni n. sp., T. nipissingi n. sp.) and Temperature Tolerance of Members of the “pyriformis” Complex1

Stocks of the Tetrahymena pyriformis complex have been collected in North America and their mating reactivity has been studied. In addition to stocks mating with Tetrahymena americanis, T. borealis, T. pigmentosa, T. hyperangularis, and T. australis, stocks belonging to old syngen 5 and three new mating groups, numbers 13, 14, and 15, were discovered. Syngen 5 and groups 13 and 14 are distinct “biological” species, based on their reproductive isolation from other groups and on the ability of withingroup crosses to produce immature progeny. These species have been named T. hegewischi n. sp., T. sonneborni n. sp., and T. nipissingi n. sp., respectively. The cross between the two group 15 stocks did not produce immature progeny, and there is not sufficient evidence to conclude that this pair of stocks represents a separate species. Temperature tolerance measurements have been made on stocks representing all known micronucleate members of “pyriformis” complex. Within each species, the range of temperature tolerances is narrow; the average within-species standard deviation is 0.63°C. The species averages range from 32.7 to 40.7°C. Using syngen numbers, the order from lowest to highest temperature tolerance is 9, 8, 10, 7, 6, 4, 13, 14, 12, 11, 5, 3, 2, 1. The large differences among species make temperature tolerance a useful aid in identification, but the origins of the differences among species are unknown.     

Sphenophyllum miravallis Vetter and Bowmanites cupulatus sp.n. from the “Illinger Flözzone” (“Heusweiler Schichten”, Lower Stephanian, Saar Basin, German Federal Republic)

This paper deals with a detailed study of Sphenophyllum miravallis Vetter, a member of the “Sphenophyllum thonii group”. New material from the Reisbach colliery, working the “Illinger Flözzone” of the “Heusweiler Schichten” (Lower Stephanian, Saar Basin, German Federal Republic), is described morphologically and anatomically, and the species is discussed. The new material enlarges the known range of variability of the normal aspect of the foliage, i.e. the foliage of the thinner branches. Thicker stems with their aberrant polymorphous foliage, and cellular details, are described for the first time. An emended diagnosis is given. Comparisons with other species are made.

The new species Bowmanites cupulatus is introduced to accommodate fructufications most probably belonging to Sphenophyllum miravallis.

S. crenulatum Knight ex Wagner is considered to be a heterotypic synonym of S. miravallis, the latter name having priority.     

Morphology,Morphogenesis, and Molecular Phylogeny of Paraparentocirrus sibillinensis n. gen., n. sp., a “Stylonychine Oxytrichidae” (Ciliophora,Hypotrichida) Without Transverse Cirri

A terrestrial oxytrichid ciliate Paraparentocirrus sibillinensis n. gen., n. sp., which was found in soil samples of a beech forest stand within the National Park of Sibillini Mountains, Italy, was investigated using live observation and protargol impregnation. The morphology of interphase, morphogenesis, and molecular phylogeny inferred from SSU rDNA sequences of this ciliate were studied. Paraparentocirrus n. gen., is mainly characterized by a semirigid body, an undulating membrane in the Oxytricha pattern, six fronto‐ventral (FV) rows, the absence of transverse cirri, one right and one left row of marginal cirri, four dorsal kineties, two dorsomarginal rows, and caudal cirri at the end of dorsal kinety 4. During morphogenesis, oral primordia develop through the proliferation of basal bodies from some cirri of FV rows 4 and 5, and FV row 6 takes part in the anlagen formation of the proter. The dorsal morphogenesis was typical of oxytrichids, with simple fragmentation of dorsal kinety 3, and the dorsomarginal rows developed from the right marginal row. Phylogenetic analyses based on the SSU rDNA sequences support the classification of this new genus in the stylonychines.     

Heterogeneous Single Atom Electrocatalysis,Where “Singles” Are “Married”

There is an intensive search for heterogeneous single atom catalysts (SACs) of high activity, efficiency, durability, and selectivity for a wide variety of electrocatalytic conversion and chemical reactions, such as the hydrogen evolution reaction (HER), oxygen evolution/reduction reaction (OER and ORR), CO₂ reduction reaction (CO₂ RR), and nitrogen reduction reaction (NRR). With the downsizing from nanoparticles and clusters to single atoms, there are steady changes in the bond and coordination environment for each and every atom involved. Indeed, the single atoms in these electrocatalysts are not “singles”; they are “married” to the supporting surfaces, and their performance is controlled by the bonding and coordination with the substrate surfaces. Herein, an overview is presented on the brief history leading to the rapid development of SACs and their current status, by focusing on their synthesis, control of composition, strategies to realize single atoms with the desired bonds and coordination, and targeted performance in selected reactions. Their applications in the selected spectrum of energy conversion and chemical reactions are discussed, in relation to their structures at varying length scales down to the atomic level. A particular emphasis is placed on on‐going research activities, together with the future perspectives and particular challenges for SACs.     

Hydrology of winter–spring “red tides” in Bahía de Mazatlán, Sinaloa, México

“Red tide” events are frequent and periodical in Bahía de Mazatlán, Sinaloa, México. Yet, the ones observed from 4 February to 4 June 2000, showed some distinctive features: First, the dinoflagellates Prorocentrum balticum (85%), P. mexicanum (5%), and Ceratium furca (5%), dominated the composition of the blooms; Second, the average cell abundance by date was 1.3×10⁶ cells l⁻¹, with a range of 3.5×10³ to 24,500 × 10³ cells l⁻¹, well above previous records; Third, the temperature registered at 10–20 m deep was unusually cold (19 °C), below the normal average of 21.5 °C observed over the last 10 years. Salinity was high (35.9 psu) and showed very little influence on the water density gradient. A mean thermal stratification index (TSI), of 3.4, with a maximum of 7 °C, was observed throughout the period, in spite of a weak upwelling activity and intermittent strong NW winds which were unable to break up water column stratification. Temperature fluctuations at the surface and at the bottom layers showed a 30-day periodicity, suggesting some association with the lunar cycle. To explain the characteristics of the “red tides” registered in Bahía de Mazatlán during the winter–spring period of year 2000, it is proposed that the temperature and density stratification, stabilized further by internal waves that compensated for the weak upwelling activity and provided the necessary nutrients to the surface layer, favored the persistence and intensity of the harmful algal bloom events then observed.     

A merciful death for the “earliest bilaterian,” Vernanimalcula

Fossils described as Vernanimalcula guizhouena, from the nearly 600 million‐year‐old Doushantuo Formation in South China, have been interpreted as the remains of bilaterian animals. As such they would represent the oldest putative record of bilaterian animals in Earth history, and they have been invoked in debate over this formative episode of early animal evolution. However, this interpretation is fallacious. We review the evidential basis of the biological interpretation of Vernanimalcula, concluding that the structures key to animal identity are effects of mineralization that do not represent biological tissues, and, furthermore, that it is not possible to derive its anatomical reconstruction on the basis of the available evidence. There is no evidential basis for interpreting Vernanimalcula as an animal, let alone a bilaterian. The conclusions of evolutionary studies that have relied upon the bilaterian interpretation of Vernanimalcula must be called into question.