Abstract
The Psilotrichidae are a family of middle-sized hypotrichs with unique morphological and ontogenetic features (e.g. the oral primordium develops in a deep pouch) that, however, did not provide a definite phylogenetic signal. Thus, we studied the 18S rRNA gene of Urospinula succisa (Müller 1786) Esteban et al., 2001 as well as the morphology and ontogenesis of Psilotrichides hawaiiensis, a new genus and species from an ephemeral swamp on Oahu Island, Hawaii. The molecular data classify the psilotrichids into the oxytrichids but without clear branching position. A brief revision, using the structure of the oral apparatus, the location of the contractile vacuole, and three ontogenetic features, showed four distinct genera: Psilotricha Stein, 1859; Urospinula Corliss, 1960; Hemiholosticha Gelei, 1954; and Psilotrichides nov. gen., which differs from the confamilials mainly by the obliquely oriented buccal cavity and the shape of the undulating membranes as well as by a distinct ridge along the right buccal margin. The pyriform species, P. hawaiiensis, is about 65 × 45 μm in size and is easily recognized by the table tennis racket-shaped appearance due to the elongated last cirrus of the left marginal row. Refined diagnoses are provided for the family Psilotrichidae Bütschli, 1889 and the genera contained.
Highlights
The Psilotrichidae are a family of middle-sized hypotrichs with unique morphological and ontogenetic features that, did not provide a definite phylogenetic signal
Psilotrichides hawaiiensis was discovered in a sample of dry surface soil and litter (0–3 cm) from an ephemeral swamp grown with fern (Marsilea sp.) on Koko Head, Oahu Island, Hawaiian archipelago, W157°41044′′ N21°15052′′
An evolutionary distance tree using Neighbor Joining (NJ) algorithm was calculated in SeaView (Galtier et al 1996)
Summary
The Psilotrichidae are a family of middle-sized hypotrichs with unique morphological and ontogenetic features (e.g. the oral primordium develops in a deep pouch) that, did not provide a definite phylogenetic signal. Stiller (1974) classified Psilotricha into the Holostichidae Faure-Fremiet 1961; synonymized Urospinula with Psilotricha; and realized that P. acuminata sensu Dingfelder (1962) is U. bicaudata Gelei 1944 She accepted B. viridis Penard 1922 and H. viridis Gelei 1954; which resulted in secondary homonymy. A few years later, Foissner (1983) described the morphology and ontogenesis of Psilotricha succisa established by Mu€ller (1786) as Trichoda succisa He synonymized U. bicaudata (Gelei 1944) and P. acuminata sensu Dingfelder (1962) with P. succisa but accepted U. calcibia and U. sinistrocaudata because of the different dorsal infraciliature. Berger (2011) rejected the transfer of Urospinula to the Orthoamphisiellidae because the frontoventral cirral rows do not originate via primary primordia and the anlagen A1 and A2 of the opisthe originate from the oral primordium (Foissner 1983)
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