Caecitellus parvulus D.J.Patt. et al.

Caecitellus parvulus (Figs 2e, 3b)

Cells are 3–4 μm long and somewhat triangular or rounded. The mouth is protruding ventrally on the left side of the cell. The cell is two flagella of unequal length. The acronematic anterior flagellum is beating slowly while inserting apically. It is slightly longer than the cell length. The non-acronematic posterior flagellum is about 2.5 times the cell length, and is merging from the ventral face of the cell and trailing posteriorly. The cells are gliding slowly by the anterior flagellum in close contact with the substrate. Description is based on the observations of 30 cells. Occurance: every month at Acı Lake, temperature 1–23.5 °C, salinity 24–67.5 psu, dissolved oxygen 3.75–13.2 mg /L.

Remarks: Generally, the observations are consistent with the findings of Griessmann (1913) and Larsen and Patterson (1990) under the name Bodo parvulus which was transferred to Caecitellus parvulus by Patterson et al. (1993). Later, Hausmann et al. (2006) carried out an ultrastructural, molecular study and established two new species – Caecitellus paraparvulus and C. pseudoparvulus – that can only be distinguished from Caecitellus parvulus by ultrastructural and molecular characters (Hausmann et al. 2006 for more details). Thus, in this study, we prefer to follow the criteria described by the previous works (Larsen and Patterson 1990, Lee and Patterson 2000, Al-Qassab et al. 2002) for this morphospecies. Caecitellus parvulus is characterized by the protruding mouth on the ventral side of the cell, the beating pattern of the anterior flagellum and the flagellar insertion (Larsen and Patterson 1990, Lee and Patterson 2000). This species is similar to Glissandra innurende Patterson and Simpson 1996 with the protruding mouth on the ventral side, but can be distinguished by its anterior flagellum’s beating pattern and the insertion of the flagella. Caecitellus parvulus has been reported in Australia, North Atlantic, Brazil, Danish Wadden Sea, England, equatorial Pacific and Turkey, with the reported size range 2 to 7 μm (Larsen and Patterson 1990, Patterson et al. 1993, Ekebom et al. 1996, Patterson and Simpson 1996, Tong 1997b, Tong et al. 1998, Lee and Patterson 2000, Aydin and Lee 2012; Lee 2015, 2019).