How to define a diatom genus? Notes on the creation and recognition of taxa, and a call for revisionary studies of diatoms

© by John Patrick Kociolek. This work is an open access paper licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. (CC BY-NC-ND 4.0). The attached file is the published version of the article

The genus <i>Nitzschia</i> on the South Shetland Islands and James Ross Island

The purpose of this study was to present LM and SEM observations of Nitzschia taxa encountered on the South Shetland Islands and James Ross Island. During the ongoing taxonomical revision of the freshwater and limno-terrestrial diatom flora on the South Shetland Islands and James Ross Island (Maritime Antarctic Region) eight unknown taxa belonging to the genus Nitzschia were found. These taxa were previously force-fitted into European names such as N. commutata or N. perminuta, but detailed light and scanning electron microscopical observations allowed their separation from the already known taxa and resulted in the description of eight new species. The paper discusses all twelve Nitzschia taxa found in the Maritime Antarctic Region. New taxa are compared to the morphologically most similar taxa and their ecology and biogeography are discussed. Although the genus Nitzschia is present worldwide, a large number of Nitzschia taxa have a restricted distribution within the Antarctic Region, showing a clear bioregionalism

Search for new synthetic immunosuppressants II. Tetrazole analogues of hymenistatin I

Linear and cyclic hymenistatin I (HS I) analogues with dipeptide segments Ile2-Pro3, Pro3-Pro4 and Val6-Pro7 replaced by their tetrazole analogues Ile-Ψ[CN4]-Ala3, Pro3-Ψ[CN4]-Ala4 and Val6-Ψ[CN4]-Alawere synthesized by the solid phase peptide synthesis method and cyclized with the TBTU and/or HATU reagent. The peptides were examined for their immunosuppressive activity in the lymphocyte proliferation test (LPT)

Hantzschia subandina Frenguelli (Bacillariophyceae): Morfología, status y tipificación, asi como la descripción de una nueva especie de Nitzschia.

Backgrounds and aims: Hantzschia Grunow is a genus characterized by having valves asymmetric to the apical axis, markedly dorsiventral, with an eccentric raphe on the ventral side supported by fibulae and ‘hantzschioid’ symmetry of the frustules. In 1942 J. Frenguelli published the flora of diatoms of Neuquén province (Argentina), work in which he erected Hantzschia subandina as a new species for science. This work investigates the identity and taxonomic status of this taxon.  M&amp;M: Original material of Hantzschia subandina of the Frenguelli Collection was analysed with light and scanning electron microscopy. Results &amp; Conclusions: Observations on the material suggested two different species were included in the concept of this species assigned originally to the genus Hantzschia. Furthermore, neither of the two species present are assignable to the genus Hantzschia. Nitzschia subandina (Frenguelli) comb. nov. has a large central nodule and a slight asymmetry about the apical axis; it also produces frustules with nitzschioid and hantzschioid symmetry. We designate a lectotype for this taxon. In addition, another diatom in the same material with slight asymmetry about the apical axis has distinctive ornamentation on the mantle of the valve and produces nitzschioid and hantzschioid frustules. For this taxon we tentatively assign it to the non-monophyletic genus Nitzschia, describing it as N. araucana sp. nov. We discuss the possible phylogenetic position of this new taxon, and suggest that the genus Nitzschia is “the next Navicula” ready to be further subdivided into distinct genera.Introducción y objetivos: Hantzschia Grunow es un género de diatomeas caracterizado por la asimetría dorsiventral de sus valvas, rafe soportado por fíbulas sobre el margen ventral, y simetría hatzschioide de los frústulos. En 1942 J. Frenguelli publicó la flora de diatomeas de la provincia de Neuquén (Argentina), obra en la que erigió a Hantzschia subandina como una nueva especie para la ciencia. El objetivo de este trabajo es analizar la identidad de este taxón y su status taxonómico.  M&amp;M: El material original de Hantzschia subandina, presente en la Colección Frenguelli depositada en el Herbario de la División Ficología del Museo de La Plata, fue analizado con microscopías óptica y electrónica de barrido. Resultados &amp; Conclusiones: la observación del material original de Hantzschia subandina sugiere que dos entidades distintas fueron incluidas en el concepto de esta especie. Ambas producen frústulos tanto con simetría nitzschiode como hantzschioide, por lo que ninguna de ellas pertenece al género Hantzschia. La primera presenta un nódulo central conspicuo y leve asimetría según el eje apical; consideramos que estos ejemplares corresponden a Nitzschia subandina (Frenguelli) comb. nov., y realizamos la enmienda y lectotipificación del taxón. La segunda entidad presente en el mismo material, posee una leve asimetría según el eje apical, y una distintiva ornamentación en el manto valvar; hemos asignado este taxón al género Nitzschia, describiendo N. araucana sp. nov. Discutimos la posible posición filogenética de este nuevo taxón dentro de Nitzschia, género polifilético que requiere de una profunda revisión y subdivisión en géneros, tal como ocurrió con el género Navicula

Simonsenia aveniformis sp nov (Bacillariophyceae), molecular phylogeny and systematics of the genus, and a new type of canal raphe system

The genus Simonsenia is reviewed and S. aveniformis described as new for science by light and electron microscopy. The new species originated from estuarine environments in southern Iberia (Atlantic coast) and was isolated into culture. In LM, Simonsenia resembles Nitzschia, with bridges (fibulae) beneath the raphe, which is marginal. It is only electron microscope (EM) examination that reveals the true structure of the raphe system, which consists of a raphe canal raised on a keel (wing), supported by rib like braces (fenestral bars) and tube-like portulae; between the portulae the keel is perforated by open windows (fenestrae). Based on the presence of portulae and a fenestrated keel, Simonsenia has been proposed to be intermediate between Bacillariaceae and Surirellaceae. However, an rbcL phylogeny revealed that Simonsenia belongs firmly in the Bacillariaceae, with which it shares a similar chloroplast arrangement, rather than in the Surirellaceae. Lack of homology between the surirelloid and simonsenioid keels is reflected in subtle differences in the morphology and ontogeny of the portulae and fenestrae. The diversity of Simonsenia has probably been underestimated, particularly in the marine environment.Polish National Science Centre in Cracow within the Maestro program [N 2012/04/A/ST10/00544]; Sciences and Technologies Foundation-FCT (Portugal) [SFRH/BD/62405/2009]info:eu-repo/semantics/publishedVersio

Part I Synthesis and study of cyclic sulfamates Part II Investigation of endocyclic nucleophilic substitution at tetracoordinate sulfur(VI)

Part I. 5-Nitro-N-(p-toluenesulfonyl)-1,2,3-benzoxathiazole-2,2-dioxide was synthesized and reacted with various nucleophiles. Nitrogen nucleophiles attacked the exocyclic sulfur atom resulting in cleavage of the tosyl group. This is due in part to the acidity of the parent benzoxathiazole ring. A series of substituted N-H-1,2,3-benzoxathiazole-2,2-dioxides were synthesized and their pK\sb{\rm a} values were determined. An ab initio study was also undertaken on a simple sulfamate model in order to determine the origin of the increased acidity of the cyclic sulfamates, compared to their acyclic analogues. It was determined that the increased acidity was directly affected by the conformation of the neighboring heteroatoms. This is primarily due to heteratom-sulfur delocalization. Investigations of the role of d-orbitals on the stabilization of the system were inconclusive. An ab initio study of the increased acidity of the cyclic compounds compared to their acyclic analogues of sulfamide, methyl sulfonamide and vinyl sulfonamide was undertaken. The sulfamide and methyl sulfonamide models gave results consistent with experimental results, the former showing an increased acidity, the latter showing no change in acidity. Vinyl sulfonamide gave results contrary to those observed experimentally. The calculation suggested no increase in acidity, although one is observed experimentally. Part II. The synthesis was undertaken of several compounds capable of endocyclic nucleophilic substitution through a five-membered intermediate or transition state. The synthesis of two amino alcohols was unsuccessful. N-methyl-N-p-toluenesulfonyl-2-phenyl-ethylenediamine was synthesized and treated with n-butyllithium and lithium diisopropylamide. In each case, the anticipated rearrangement product was not observed. N-p-toluenesulfonyl-1,8-naphthosultam was also synthesized and treated with n-butyllithium and lithium diisopropylamide. The former resulted in nucleophilic attack of the base and ring opening. The latter resulted in an elimination-addition reaction yielding an undesired sultam. N-2-bromobenzyl-1,8-naphthosultam was also synthesized and treated with n-butyllithium. The sultam rearranged to a thiazocine through an endocyclic nucleophilic substitution, presumably by way of a five-membered intermediate or transition state, thus providing the first example of a rearrangement through this intermediate

Modelling the Extrinsic Finger Flexors: Tendon Excursions and Moment Arms

A musculoskeletal model of the hand is needed to investigate the pathomechanics of tendon-related disorders and carpal tunnel syndrome. The purpose of this thesis was to develop a model with realistic extrinsic finger flexor tendon excursions and moment arms. An existing upper extremity model served as a starting point, which had programmed movement for the index finger. Movement capabilities were added to the middle, ring and little fingers. Metacarpophalangeal linkages were modelled as universal joints to simulate flexion/extension and abduction/adduction. Interphalangeal linkages were modelled as hinge joints to simulate flexion/extension. Extrinsic finger flexor tendon paths were modelled using two different approaches. The first method used control points fixed in the metacarpal and phalangeal coordinate systems to represent the annular and cruciate pulleys. The second method used wrapping surfaces at the metacarpophalangeal and interphalangeal joints to model constant moment arms with finger movement. Extrinsic finger flexor tendon excursions and moment arms in both the control point and joint wrapping models were iteratively adjusted to match the anthropometric regression model developed by Armstrong and Chaffin (1978) for a 50th percentile male. Musculoskeletal scaling algorithms were also used to further evaluate the control point and joint wrapping models. More specifically, metacarpal and phalangeal segments were adjusted to determine the effects of length and thickness scaling on tendon kinematics. Tendon excursions and moment anns in the joint wrapping model best matched the anthropometric regression model. However, anatomical features of the tendons paths at the finger joints were not preserved in the joint wrapping model as noted by ultrasound imaging. Depending on user needs, both anatomic fidelity and model outcomes should be considered as compromises may be necessary in the modelling process.Master of Science (MS