debor042

by Luca Marazzi* Nitzschia amphibia belongs to the nitzschioid group : its v alves are symmetrical to both apical and transapical axes, and taper to bluntly rounded apices ; the raphe is well developed near the valve margin, and enclosed within a canal 1 . The original description was made by Albert Grunow in 1852, when the US President was Millard Fillmore, the  last one not to be affiliated with either the Democratic   or   Republican party . This is how ‘old’ are some of the species names of algae and other organisms that persist to this day, while new species are continuously described at an increasing rate. Grunow was one of the eight most ‘profilic’ algal taxonomists who described more than 1,000 species during their career, the others being Kützing, Gottfried, Hustedt, Agardh, Harvey, who worked in the 1800s, and Lange-Bertalot (the only one still alive and active ) and Skvortsov in the 1900s 2 . Fig. 1.   a)  Nitzschia amphibia  in valve view and ...

by Luca Marazzi* This month’s diatom comes from quite far, some 5,000 miles or 8,100 km North-East of Florida: Northern Italy. Its name is Eunotia cisalpina (on this side of the  Alps , the  south ern   side) , and it was described a few years ago 1 by Marco Cantonati, the Science Museum of Trento ’s (MUSE) Head Limnologist and Phycologist whom I am visiting this week. We are at the foot of the famous and wonderful Dolomites mountains , one of over 50 UNESCO World Heritage sites in Italy, comprising some of the highest limestone walls in the world. North-west from here, small mountain lakes, springs, and mire pools dot the landscape of the Adamello and Cevedale mountain ranges; their waters have lower mineral content than the calcareous Dolomites due to the prevalence of siliceous rocks, such as granites. These oligotrophic, acidic, low conductivity habitats are perfect for E. cisalpina (and for E. fallacoides and E. insubrica , other new taxa to science described in ...

by Luca Marazzi* Rhopalodia gibba belongs to the epithemioid group , that is to say it has v alves symmetric about a line (bilateral symmetry), but asymmetrical to the apical (longitudinal) axis, the raphe system is well developed, enclosed within a canal, and positioned near the valve margin 1 . It is longer and more slender than other species such as the lunate R. gibberula , and the more arched R. musculus ; it is found in the benthos, attached to substrata such as plant (epiphytic), or gliding more freely and opportunistically 2 . Interestingly, R. gibba seems to have declined significantly in the United Kingdom due to agricultural intensification and associated large use of nitrogen fertilizers. In fact, t his pennate ( bilaterally symmetric) diatom species lives in nitrogen poor habitats, but it has evolved an endosymbiosis with cyanobacteria that fix nitrogen 3 . So it does not like when there is too much nitrogen around, and loses its competitive edge against other fellow di...

by Luca Marazzi* ‘Who’ is it and where does it live? This diatom is monoraphid, that is to say it has a raphe only on one valve, as shown in the figures. Monoraphid species are one of 9 major morphological types of diatoms - the other ones are: centric (like Cyclotella meneghiniana ) , araphid (e.g. Asterionella formosa , which forms star-shaped colonies !), eunotioid (e.g. the beautifully ornamented Eunotia diadema ), symmetrical biraphid (e.g. the slender Navicula lanceolata ), asymmetrical biraphid (e.g. Gomphonema parvulum ), epithemioid (e.g. Rhopalodia gibba , which hosts nitrogen-fixing bacteria as symbionts), nitzschioid (e.g. the organic pollution-loving Nitzschia palea ), and surirelloid (the big Surirella ovalis ) 1 . Like in many other cases, the taxonomy is far from settled though; following recent research, numerous specimens usually named C. placentula should be more accurately named Cocconeis lineata and C. euglypta 2 .             ...

by Luca Marazzi* ‘Who’ is it and where does it live? This diatom is a symmetric biraphid species, i.e. it has a raphe on either valve allowing it to move sliding on substrata. Mastogloia calcarea was ‘discovered’ / described by Sylvia Lee during her PhD research at Evelyn Gaiser’s lab at FIU; it is similar to M. smithii and M. lacustris , common freshwater species in this predominantly marine genus. This new species typically lives in karstic wetlands of the Caribbean region (Mexico, Jamaica and Belize) and in the Florida Everglades, as compared to the temperate zones where M. smithii and M. lacustris live and are found 1 .                                       Mastogloia calcarea in valve (top) and girdle (bottom) view ( http://westerndiatoms.colorado.edu/ ) 1 ; scalebar = 10  µ m .                           ...