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Epibiosis is a common phenomenon in marine systems. In marine environments, ciliates are among the most common organisms adopting an epibiotic habitus and nematodes have been frequently reported as their basibionts. In the present study, we report several new records of peritrich and suctorian ciliates-nematode association worldwide: from a deep-sea pockmark field in the NW Madagascar margin (Indian Ocean), from a shallow vent area in the Gulf of Naples (Mediterranean, Tyrrhenian Sea), in a MPA area in the Gulf of Trieste (Mediterranean, Adriatic Sea), from a mangrove system in French Guiana (South America, Atlantic Ocean), and from the Maldivian Archipelago. In addition, three new species of Suctorea from the Secca delle Fumose shallow vent area (Gulf of Naples) were described: Loricophrya susannae n. sp., Thecacineta fumosae n. sp. and Acinetopsis lynni n. sp. In the light of these new records and data from the existing literature, we discuss the suctorian–nematode epibiosis relationship as a lever to biodiversity.

The spermatozoon of an undescribed species of Dolichodasys (Cephalodasyidae) from the Pacific coast of Panama was studied at structural and ultrastructural levels. Under optical microscopy, it appears as a short and wide cell with pointed extremities but without a flagellum. The cell body is made up of two well distinct regions: an anterior region with a homogeneous appearance, and a posterior region containing an evident rod-like nucleus. Under TEM, a peripheral layer of microtubules densely arranged extends for the whole cell length. In the anterior cell region, microtubules surround many tubular cisternae of smooth endoplasmic reticulum (SER), and a thin layer of vesicles with a probable acrosomal function lies just beneath the plasma membrane. The rod-shaped nucleus fills up the posterior cell region and forms a pouch that hosts a single large, irregular mitochondrial mass. A hypothesis about the motility of this aflagellate cell is advanced, on the basis of the coexistence of singlet microtubules and SER. The general architecture of Dolichodasys sp. spermatozoon departs from the Macrodasyida sperm basic model, consisting of a filiform cell with a corkscrew-shaped acrosome, a spring-shaped nucleus surrounding a mitochondrial axis and an ordinary flagellum. The unusual morphology of the Dolichodasys sperm seems to be unique in the family Cephalodasyidae: the data available for 6 species belonging to the other 4 genera of the family report spermatozoa perfectly matching the basic sperm plan of the Macrodasyida. A sister-taxon relationship between Dolichodasys and Cephalodasys, two genera drastically different in sperm shape, emerged from recent phylogenetic molecular studies, but it needs confirmation due to the still limited number of molecular data and the likely polyphyletic nature of the family Cephalodasyidae

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The aim of this work was to test and analyse the bioeffects of Prunus spinosa L. (Rosacaee) fruit ethanol extract on Trichoplax adhaerens Schulze, 1883 (Placozoa) laboratory cultures which—for the first time—were employed as in vivo biological model to assess the bioactivity of a natural extract. The ethanol extract of P. spinosa was administrated during a 46 day experimental period; ultrastructural (by optical, confocal, TEM and SEM microscopy) and morphometric analyses indicated that treated Trichoplax adhaerens showed significant differences in viability, reproductive modalities, body shape and colour with respect to the control group. Finally, P. spinosa bioactive compounds seem to exert profound protective effects on T. adhaerens reproduction and phenotype. Our results may support additional investigations related to other bioactive compounds properties useful for nutraceutical preparations to be used as food supplements.