A Novel Colonial Ciliate Zoothamnium ignavum sp. nov. (Ciliophora, Oligohymenophorea) and Its Ectosymbiont Candidatus Navis piranensis gen. nov., sp. nov. from Shallow-Water Wood Falls
2016
Symbiosesbetween
ciliatehosts and prokaryote or unicellular eukaryote symbionts are widespread. Here, we report on a novel
ciliatespecies within the genus Zoothamnium Bory de St. Vincent, 1824, isolated from shallow-water sunken wood in the North Adriatic Sea (Mediterranean Sea), proposed as Zoothamnium ignavum sp. nov. We found this
ciliatespecies to be associated with a novel genus of bacteria, here proposed as “
CandidatusNavis piranensis” gen. nov., sp. nov. The descriptions of host and symbiont species are based on morphological and ultrastructural studies, the
SSU rRNAsequences, and in situ hybridization with symbiont-specific probes. The host is characterized by alternate microzooids on alternate branches arising from a long, common stalk with an
adhesive disc. Three different types of
zooidsare present: microzooids with a bulgy oral side, roundish to ellipsoid macrozooids, and terminal
zooidsellipsoid when dividing or bulgy when undividing. The oral ciliature of the microzooids runs 1¼ turns in a clockwise direction around the peristomial disc when viewed from inside the cell and runs into the
infundibulum, where it makes another ¾ turn. The ciliature consists of a paroral membrane (haplokinety), three
adoral
membranelles(polykineties), and one stomatogenic kinety (germinal kinety). One circular row of barren kinetosomes is present aborally (trochal band). Phylogenetic analyses placed Z. ignavum sp. nov. within the clade II of the polyphyletic family Zoothamniidae (
Oligohymenophorea). The ectosymbiont was found to occur in two different morphotypes, as rods with pointed ends and coccoid rods. It forms a monophyletic group with two uncultured
Gammaproteobacteriawithin an unclassified group of
Gammaproteobacteria, and is only distantly related to the ectosymbiont of the closely related
peritrichZ. niveum (Hemprich and Ehrenberg, 1831) Ehrenberg, 1838.
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