Lamtopyxis callistoma Bonnet, 1974

Todorov, Milcho, 2015, On the morphology, biometry and biogeography of Lamtopyxiscallistoma (Amoebozoa: Arcellinida), Biodiversity Data Journal 3, pp. 4297-4297 : 4297

Lamtopyxis callistoma Bonnet, 1974

Materials

Type status: Other material. Occurrence: recordedBy: Milcho T. Todorov; individualCount: 75; Location: country: Madagascar; stateProvince: Maromizaha Protected Area; verbatimLocality: Central Madagascar, east of the capital Antananarivo and south of the village Anevoka, on the eastern slopes of the Central Highlands; verbatimElevation: 950 m; verbatimLatitude: 18°57'S; verbatimLongitude: 48°27'E; Record Level: collectionID: col:ta;prep.24,25,26/2014; institutionCode: IBER; collectionCode: Testate amoebae

Description

The shell is yellowish or light brown, circular in oral and dorsal views, and hemispherical in lateral view (Figs 1, 2). The apertural surface is smooth, composed of small to medium flattish mineral particles, bound together by a thick layer of porous and fibrous organic cement, which extends over the teeth (Figs 2a, b, c, 3a). The dorsal surface is rough and composed of bigger and angular pieces of quartz, bound together by considerably less amount of organic cement (Figs 2d, e, f, 3c). The shell wall has a thickness of about 5-6 µm and is composed of three layers: an outer layer of organic cement (300-500 nm) with a smooth outer lining, an intermediate layer of porous and fibrous organic cement (2-4 µm) with incorporated mineral particles and an inner layer of organic cement (1-1.5 µm) with a rough inner lining (Fig. 3e, f). Small single pores with a varying diameter of about 50-350 nm are often seen in the cement, in both on the apertural and dorsal shell surface (Fig. 3b). The aperture is central, deeply invaginated (about 40% of the shell depth), with pronounced apertural tube and two openings - external and internal (Figs 1c, d, 3d, e). The external opening is more often four-, less often three-lobed, bordered by 3-4 large and smooth teeth (Figs 1a, b, 2a, b, c). The internal opening is at the bottom of the apertural tube. It varies in shape from oval to almost circular and is surrounded by a small collar (Figs 1a, 3a). The apertural tube is reinforced at its base by a characteristic dark-brown coloured organic frame (visible by LM, but not by SEM) (Fig. 1a). The apertural tube is rough, composed of a mixture of medium to large mineral particles, bound together by a small amount of organic cement (Fig. 3a, d, e).

Biometry

The basic morphometric characters of 75 individuals from the Maromizaha Protected Area in Madagascar were measured and the results are given in Table 1. The analysis of the variation coefficients shows that the studied population of L. callistoma is comparatively homogeneous and almost all measured characters are weakly to moderately variable (CV less than 10%). The only exception is the length of the teeth, which varies in a wider range (CV = 12.12%). The parameters with minimal variability are depth of apertural tube (3.37%), depth of shell (3.59%), diameter of shell (4.15%) and diameter at the base of apertural tube (5.32%). The large and small axes of the internal opening are moderate variables (9.20% and 9.13%, respectively). These conclusions are also confirmed by the box plots, showing the variability of the shell’s characters in L. callistoma (Fig. 4).

Analysis of the size frequency distribution of the main characters indicates that L. callistoma is size-monomorphic species. The presence of comparatively well-expressed main-size class for the basic characters and the lack of the subsidiary peaks (bell-shaped curves) indicate a normal distribution (Fig. 5a, b, c). For example, 93% of all the individuals have a shell diameter of 166-190 µm and only 7% are smaller than 165 µm (Fig. 5a). Almost all measured individuals range in close limits, regarding the shell’s depth and diameter at the base of apertural tube (Fig. 5b, c). 98% of them have a diameter at the base of apertural tube between 54-64 µm, and in more than three quarters of the individuals (82%), shell depth varies between 122-134 µm. The average values (Mean ± SD) for these three shell characters are respectively 175.8 ± 7.30 (n=75), 128.1 ± 4.60 (n=43) and 59.8 ± 3.19 (n=75). These arithmetical means correlate with the main-size classes of the characters, and testify for monomorphism of the species.