Apofrontonia dohrni sp. n. and the phylogenetic relationships within Peniculia (Protista, Ciliophora, Oligohymenophorea)

Abstract

Apofrontonia dohrni, a new peniculine ciliate, was discovered in a slightly brackish water sample from Mediterranean coastline puddle in Naples, Italy. Its morphology was studied in vivo, in silver‐ and Feulgen‐stained preparations, as well as at the scanning electron microscope; 18S rRNA gene sequence was also determined. The species is characterized by a medium cell size (118 × 61 µm — fixed cell) and an oval‐extended body, flattened dorsoventrally; a very long sausage‐like macronucleus rolled up into almost a ring; a comparatively large compact micronucleus; relatively small number of vestibular kineties (4) and a peculiar structure of 3 peniculi, consisting of 5‐6, 4‐5 and 3 ciliary rows, respectively. The ciliate always has about 20 contractile vacuoles distributed beneath its entire body surface. Using these features, A. dohrni, definitely, can be easily discriminated from the two other species of the genus: Apofrontonia lametschwandtneri and Apofrontonia obtusa. The general re‐analysis of morphological characters of Apofrontonia spp. allowed us to remove this genus from family Frontoniidae, where it was put in the first description (Foissner & Song 2002). We provisionally consider genus Apofrontonia as incertae sedis within the order Peniculida due to (i) the limited number of morphological characters joining Apofrontonia to already described Peniculida families and (ii) the absence of molecular data for most representatives of Peniculida families. Frontonia leucas 18S rRNA gene was also characterized to increase the balance among represented taxa. According to the present analysis, Apofrontonia so far appears more closely related to Paramecium than to Frontonia.