Hyalosphenia papilio (Leidy, 1874)
Diagnosis: shell colorless to light yellow or brown, transparent, completely organic; in shape resembling a pouch or the blade of an axe, smooth and laterally flattened; usually with two lateral pores, one on each side, in the upper part of the shell; depending upon environmental conditions, up to 13 pores may be present in the borders of the fundus; aperture terminal, a narrow slit, surrounded by a small collar; protoplasm not filling the shell but attached to the inner surface by epipodia, always containing zoochlorellae; pseudopods often numerous active.
Dimensions: According to Leidy (1879): Shell length 108–140 μm; width 68–84 μm; depth 32–40 μm; aperture 32–40 μm x 8 μm; including subsequent observations: Length 90–175 μm; width 60–155 μm; aperture 30–40 μm.
Habitat: Sphagnum; common in swamps.
Geographical distribution: Africa, Europe, Iceland, South and North America, Asia, Japan, China, Australasia: New Guinea.
Remarks: Booth and Mayers (2010) assessed whether variability in pore number was related to substrate moisture by comparing the abundance of individuals with different numbers of pores to measured water-table depths at 67 sites in North America. Their results indicated that the abundance of individuals with higher numbers of pores increased in wetter conditions. Individuals with 2 pores were relatively widespread, although they dominated drier habitats.
Both investigators also suggest that H. papilio is identical to H. ovalis: Although early descriptions separated H. ovalis from H. papilio by its larger size, more oval shape, and rounded keel, some recent peatland work has focused more on the pronounced convex tapering of the aperture in H. ovalis (Charman et al. 2000). However, using this criterion, tests identified as H. ovalis are generally smaller than H. papilio, which is inconsistent with early descriptions. In fact, even specimens of H. ovalis in Penard’s slides at the British museum would be classified as H. papilio if the convex tapering of the aperture were used as the primary diagnostic feature (Charman et al. 2000). To add to the confusion, individuals of Nebela tincta sometimes lack plates, as is common in some modern samples and most fossil samples, yet these would be identified as H. ovalis using the approach of Charman et al. (2000). N. tincta is generally smaller than H. papilio, and confusion between these taxa may help explain the smaller size of tests identified as H. ovalis in recent studies (Charman et al. 2000).
References: Robert K. Booth and Blaze Meyers, Environmental Controls on Pore Number in Hyalosphenia papilio: Implications for Paleoenvironmental Reconstruction, Acta Protozool. (2010) 49: 29-35
Hyalosphenia papilio – broad form from Wales
Diagnosis: shell transparent, yellowish, with two lateral pores; shell slightly broader than high.
Dimensions: Shell height c. 104-110 µm; breadth c. 110-126 µm.
Habitat: Peat bog, Wales.
Remarks: This form was collected by Richard Payne in 2011 from a marsh in Wales, along the coast. It was first thought to be a new species, but sequences matched for 100% with those of H. papilio (Angela O’Donnell, who did the PCR, Clément Duckert and Quentin Blandenier, pers. comm.).
