Bresslaua vorax Kahl, 1931
In an attempt to find tardigrades in the abundant lichen growing on my untreated deck, I instead grew out from the lichens soaking in water lots of colpodiids. First there were a lot of small colpodids and soon larger carnivorous Colpodidae, Bresslaua vorax, appeared and began feasting on their smaller cousins. It is amazing how the vestibule has evolved to capture and consume their preferred meal, the much smaller bacteriovore colpodids.
Bresslaua exhibits dimorphism, ie the species occurs in 2 morphological forms depending upon nature of food supply. The smaller (microstome) form grows when micro-algae and bacteria are the food source; this transforms into the larger (macrostome) form when fed upon ciliates. The shape of the huge cytopharyngeal vestibule fits the contours of the smaller colpodid population like a glove. The small colpodids almost seem to volunteer to be eaten by their much larger cousins. I show here two different individuals of different sizes enjoying their meals. I think the larger one first depicted is a large trophont. As Bruce Taylor writes: "The species is common, and notoriously gluttonous known to cannibalize its microstome brothers, which might even raise the possibility that you have one species here!.
Imaged in Nomarski DIC using Olympus BH2S under SPlan 40x objective plus variable phone cropping on Samsung S9+.
Bresslaua Kahl, 1931
Class Kinetofragminophora: Subclass Vestibulifera: Order Colpodida
Suborder Colpodina Foissner, 1978: Family Colpodidae Ehrenberg, 1838
Bresslaua vorax Kahl, 1931
Dimorphic; microstome form, pyriform to reniform, plastic, with a latero-ventral invagination, 35-100 um by 16-50 um; macrostome form, oval in dorsal view; rigid with convex dorsal and flattened ventral surface, up to 250 um long; the prominent cleft in the anterior quarter forms the anterior margin of vestibular opening; one macronucleus and one micronucleus; encystment.
Key to the Colpodidae From: Biol Fertil Soils (1990) 9:110-118 Kuehneltiella terricola gen. nov., sp. nov. a carnivorous ciliate (Protozoa, Ciliophora) from a sandy soil in Australia * W. Foissner. http://www.wfoissner.at/data_prot/Foissner_1990_110-118.pdf
Foissner writes: The most common soil ciliates belong to the class Colpodea, and Foissner (1987a) has designated the soil ciliate community as "Colpodetea". The evolutionary success of the Colpodea in terrestrial biotopes depends on their r-selected survival strategy, especially on their capability to produce four or more offspring in reproductive cysts. Within the family Colpodidae, two feeding strategies have been evolved. Members of the large genus Colpoda (about 30 reliable species) feed mainly on bacteria, and are comparatively small-sized species with a funnel-shaped mouth. These species obviously profit from the high number of microbes present in terrestrial biotopes. The three other genera of this family, Bresslaua, Krassniggia, and Kuehneltiella gen. nov., each consisting of only a few large species, have a huge oral apparatus occupying the anterior half of the cell. These species are rapacious carnivores, consuming the production of bacteria-feeding ciliates and flagellates. Lynn (1979) suggested that carnivorous colpodids evolved from bacteria-feeding ones".
