Porosia paracarinata Bobrov

Anatoly BOBROV & Anush KOSAKYAN, 2015, A New Species from Mountain Forest Soils in Japan: Porosia paracarinata sp. nov., and Taxonomic Concept of the Genus Porosia Jung, 1942, Acta-Protozoologica 54, pp. 289-294 : 290-293

Porosia paracarinata Bobrov et Kosakyan ( Figs

2, 3, 4)

Diagnosis: Test large, pyriform, laterally compressed, with rounded posterior part, narrow elliptical in profile. At approximately 1 / 3 of test length starting from aperture, two distinct lateral depressions with two large invaginated pores are situated on each side, which are connected by internal tubes as in Porosia bigibbosa . In profile, small lateral pores can be observed, just anterior to the large pores. At approximately after 1 / 2 of the length of the test counted from aperture, a lateral keel emerges such as in Nebela carinata , the width of which can vary between individuals (see Table 1, Figs 3, 4). Test is colorless, composed of circular or elliptic or irregular plates, often covered by the thin layer of organic cement. Length = 202–236 µm, Breadth = 142–157 µm. Aperture is oval, 56–67 µm wide, curved, surrounded with a thick organic lip.

Morphometry and morphological variability: Morphometric analyses of Porosia paracarinata show that species is characterized by low variability ( Table 1). The largest standard deviation ( SD) was observed in test length. The most stable morphological character is the thickness of the organic lip surrounding the aperture. The width of the lateral keel can also be variable among the individuals starting from very narrow (3.75 µm, see Fig. 4) to very wide (13.13 μm, see Fig. 3).

Ecology: Porosia paracarinata inhabits wet leaves (forest litter layer A 0 or L-layer) in the mixed forest of Fagus sp. and Cider japonica.

Type locality: Japan, Honshu island, mountains of Tateyama , Bijodaira , 36 34 ′ 58.93 N, 137 27 ′ 39.49 E, alt 997 m.

Etymology: The species name is emphasizing a morphological distinct character such as lateral keel which can be comparable with Nebela carinata .

Haplotype: The type specimen is located in Dr. A. Bobrov’s collection (Preparation B- 1 / 2015 ), Department of Soil Sciences, Moscow State University named after M. V. Lomonosov .

List of the associated testate amoebae: Porosia paracarinata was found in associations with the following species: Arcella arenaria compressa , A. arctocrea aplanata , A. rotundata aplanata, Centropyxis aculeata, C. elongata , C. spinosa , C. sylvatica, Cyclopyxis eurystoma , C. eurystoma parvula, Plagiopyxis bathystoma, Heleopera lata, H. petricola, H. petricola amethystea, Hyalosphenia subflava, Padaungiella lageniformis, P. marginata , P. wailesi, Argynnia dentistoma, A. caudata, Physochilla griseola, Schoenbornia humicola, Phryganella hemisphaerica, Assulina muscorum, Quadrulella symmetrica, Tracheleuglypha acolla, Euglypha cristata decora, Sphenoderia fissirostris, Trinema complanatum, T. enchelys, T. lineare, T. lineare terricola, Cryptodifflugia oviformis fusca.

Related species – similarities and differences: Porosia paracarinata shares interesting morphological features with other hyalospheniid genera such as Ne- * For average morphometric characteristics of species the following literature data are used – Porosia bigibbosa (Penard 1890, Cash et al. 1919, Wailes and Penard 1911, Deflandre 1936, Hoogenraad 1940, Ogden and Hedley 1980, Todorov 2002, Tsukii 2005); Nebela carinata (Cash et al. 1909, Ogden and Hedley 1980).

bela, particularly Nebela carinata , N. marginata because of the distinct lateral keel; Certesella because of two distinct lateral depressions with two large invaginated pores, situated on each side. Porosia paracarinata can be easily distinguished from the Nebela species, which do not have lateral depressions with large invaginated pores. However, there can be some confusion between certain Certesella species for which these kind of pores are typical. Certesella australis can be especially tricky because, like Porosia paracarinata , it also has a lateral keel. However, it is a much more elongated species with a distinct neck. With close and detailed observation, it is possible to see little pores situated in a parallel line to the aperture, which are the result of internal indentations typical for Certesella species. It could be possible that Porosia paracarinata is an intermediate species between those of Nebela , Certesella and Porosia . This new species differs from Porosia bigibbosa by larger dimensions and the presence of the lateral keel. Fig. 5 schematically shows the relationship of P. paracarinata with two possible closely related species such as P. bigibbosa and Nebela carinata .

Tables

Table 1. Biometric characterization of Porosia paracarinata sp. nov. based on 30 measured specimens. SD – standard deviation; Min – minimum; Max – maximum. Measurements of characters (in μm) shown on Fig. 2: 1 – test length; 2 – test breadth; 3 – aperture diameter; 4 – distance from posterior end of the test to the keel starting point; 5 – distance from aperture to large pores; 6 – breadth of the test in the area of the large pores; 7 – keel breadth.

N = 30	1	2	3	4	5	6	7
Mean	223,15	151,13	62,42	94,13	85,50	98,98	8,25
Median	225,00	150,00	62,69	91,88	86,25	97,50	7,88
SD	9,27	5,60	3,55	8,19	5,81	5,60	2,94
Min	202,50	142,50	56,25	82,50	75,00	93,75	3,75
Max	236,50	157,50	67,60	112,50	93,75	112,25	13,13