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Leptogromia operculata
Leptogromia operculata, notice the very large granular nucleus

Leptogromia operculata Valkanov, 1970

Diagonosis: Shell pyrifom, organic, thin, hyaline and colorless, in cross-section broad elliptical; aperture rounded triangular, invaginated, with a small but distinct tube; cytoplasm doesn’t fill the membrane completely; a globule, not a vacuole, is always present just above the aperture in the narrowing cytoplasm which moves through the aperture; nucleus large, ovoid, granular; filopodia branching and anastomosing, with bidirectional streaming of small granules; cytoplasm filled with food in the region of the aperture and with globules around the nucleus; vacuoles present near the aperture. The aperture is bordered by three flexible ‘membranes’ by which the aperture can be closed or opened.

Dimensions: 56-70 µm (n=18)

Ecology: Brackish and marine. Valkanov reported it from the Black Sea (salinity of 15-20 ). I sampled it from sediment in a small stream (2011) and a pond (2018), both with brackish water (salinity 13 ‰) on the island of Schiermonnikoog, in the northern part of the Netherlands.

Remarks: The most remarkable key characteristic is the globule which is always present in the cytoplasm just above the aperture. Also remarkable is the triangular shape of the aperture. However, Valkanov (1970) describes this as circular, but probably he has overlooked this small trait.

Leptogromia Schiermonnikoog
Leptogromia schiermonnikoog
Leptogromia operculata
Leptogromia operculata
Leptogromia operculata, with branching and anastomosing filopodia
Leptogromia operculata
Leptogromia operculata, structure of the pseudostome; notice the structure inside the globule
Leptogromia operculata
Leptogromia operculata. with branching and anastomosing filopodia
Leptogromia operculata
Leptogromia operculata, showing in side view the valves that close the pseudostome.
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Four different specimens, but all with a globule above the pseudostome
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
Different specimens, showing their pseudostome. The pseudostome is often surrounded by a ring of undefined material.
Leptogromia operculata
Leptogromia operculata. with branching and anastomosing filopodia
Leptogromia operculata schiermonnikoog
This specimen is probably encysting; note also the distinct globule.
Leptogromia operculata
Leptogromia operculata, note the remarkable globule.
Leptogromia operculata
Leptogromia operculata, theca with striae. This was also noted by Valkanov, 1970.
Leptogromia Schiermonnikoog
Leptogromia schiermonnikoog
Leptogromia operculata
Leptogromia
Leptogromia operculata, from Schiermonnikoog, cross-section
Leptogromia
Leptogromia operculata, with typical triangular aperture
Leptogromia
Leptogromia operculata
Leptogromia operculata schiermonnikoog
Leptogromia operculata schiermonnikoog
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