Specimen with a shell mutation.
Tenute Mazzoni e Pineta di Volano. Oltre 300 individui
Collected from a subtidal silicate sand sample in 6m depth close to a seagrass bed, during the 2010 BIOSAND workshop in Elba.
When Joseph Leidy found these in the late nineteenth century he considered them specimens of Arcella mitrata. In a later revision of the genus Arcella, George Deflandre gave the morphotype a named rank, calling them Arcella mitrata var. spectabilis, from the Latin "spectabil", meaning visible, or remarkable. When Ferry Siemensma discovered European populations of this variety, he judged it to be distinct from A. mitrata and raised it to species level. Siemensma's populations, like the ones Leidy found, have smaller shells than A. mitrata. However, the ones I find in Mer Bleue are somewat larger, with an average diameter around 125 um, and a height of about 120 um. This puts them within the range of A. mitrata, which often blooms alongside them in the same samples. I don't encounter "transitional" forms, and am inclined to think they really are a distinct species. However, it remains possible that spectabilis is a phenotype of mitrata, with identical genetics. I've collected specimens for DNA extraction, and hope to learn the answer to that question, eventually.
first waterbear! found in lichen/moss on rock wall in woods
Sample taken on 2024-07-20.
Slowing solution 0.5% Methyl cellulose.
Inside moss fallen from a roof. Sample taken a couple of months ago.
My first attempt at diatoms cleaning.
Three specimens observed, from the same sample of my previous observation https://www.inaturalist.org/observations/141202070 taken on 2022-11-05.
Stria density: 7-8 per 10 μm (center), 10-11 (extremities).
Puncta density: 11 per 10 μm.
Length 213-225 µm, width 41-44 µm.
Stigmata visible near the central nodule.
According to Diatoms of Europe vol.3 by Kurt Krammer, 2002, it looks like Cymbella peraspera:
“Valves moderately to distinctly dorsiventral, dorsal margin rather evenly arched, ventral margin with a slightly gibbous central portion. Valve ends not protracted and broadly rounded. Length (130)154-320 µm, breadth 44-52 µm, maximal length/breadth ratio about 6. Axial area moderately wide, linear, widening at mid-valve to form a shallow central area, about ¼ to nearly ⅓ of the valve breadth. Raphe slightly lateral, tape ring near proximal and distal ends, becoming filiform near the proximal and the distal ends. Proximal raphe ends with moderately large roundish central pores which are slightly ventrally deflected; terminal fissures sickle-shaped and dorsally bent. Striae throughout radiate. Puncta distinctly and more or less roundish in focus high and low. A large number of stigmata on the ventral side of the central nodule, in focus low differently shaped from the puncta, commonly distant from the middle ventral striae. Striae 5-8/10 µm, becoming up to 10/10 µm near the extremities. Puncta 7-10(11) in 10 µm.”
Stesso punto, stessa parete.
Le 2 foto sono state scattate a distanza di 7 anni.
La prima è del 2013 la seconda del 2020.
La terza è dell'8 agosto 2023
Il sito si trova a circa 18 metri di profondità