New record of Thecacineta calix (Ciliophora, Suctorea) from Florida coast, Gulf of Mexico

The suctorian ciliate Thecacineta calix is reported off the coast of Panama, Florida (USA) 
epibiont on meiobenthic harpacticoid copepod. This is the first report of T. calix from Florida coast. The length of stalk in the present specimens, epibiont on harpacticoids, ranged from one seventh to one eighth of the lorica length.


Introduction
Suctorian ciliate Thecacineta calix (Schröder, 1907), the type species of genus Thecacineta Collin, 1909, was firstly described as epibiont on marine nematodes from Kerguelen Islands, Antarctica (Schröder, 1907). After first description, the species was not observed during a long time. Matthes (1956) was the first after Schröder who found and reinvestigated the T. calix in Rovinj, Croatia, the Adriatic Sea. He described the peculiarities of morphology and reproduction of T. calix and some its congeners in details and erected the new suctorian family Thecacinetidae Matthes, 1956 for loricate suctorians with apical bundle of tentacles and vermigemmic budding.
Detailed remarks on the systematics and nomenclature of this species are provided in Dovgal et al. (2008).
Several recent investigations of suctorian ciliates distribution demonstrated that T. calix is wide spread in marine and brackish waters. The species has been reported as an epibiont on nematodes, copepods, and halacarid mites from the Atlantic, Pacific, Antarctic and Indian Oceans, from the intertidal region to the deep sea. Details of distribution and host specificity of this species is given in Chatterjee et al. (2019). However, further findings of thecacinetid suctorians are important to clarify the ecology and distribution of sessile ciliates.
This paper reports the epibiont Thecacineta calix collected off Panama city, Florida, USA (Gulf of Mexico).  Meiobenthic samples were initially fixed in formalin Rosebengal and latter sieved in the laboratory using a 45 µm mesh size sieve. Infested meiofauna were hand sorted, mounted on a 50% glycerine slide and sealed with DPX.

Specimens of suctorian ciliate
Measurements were carried out on six specimens using the program Toup View 3.7 for digital camera.
Specimens are kept in the collection of the first author (BI). Diagnosis: Marine loricate suctorian. Cell body entirely fills the lorica and attach to its base. Loricais ribbed with a series of transverse annular ridges that become progressively closer toward the base. Apical part of body protrudes beyond lorica aperture. Clavate tentacles (up to 30) arise from apical surface of body. Curved stalk with apical widening. The macronucleus ovoid and located in the basal region of the cell body. Large contractile vacuole located usually near macronucleus in the basal region of body.

Discussion
Thecacineta calix has been reported as an epibiont on nematodes, copepods, and halacarid mites from the Atlantic, Pacific, Antarctic and Indian Oceans, from the intertidal region to the deep sea (Chatterjee et al., 2019).
This ciliate species was recorded on harpacticoid copepod from East St. John, U.S. Virgin Islands, 53 m depth; Caja de Muertos Island near Ponce, Puerto Rico, 52 m depth; Buoy, La Parguera, Puerto Rico, 46 m depth, Caribbean Sea (Chatterjee et al., 2014); on harpacticoid copepod from Bajo de Sico, a mesophotic reef formation located in Mona Passage of Puerto Rico, 70 m depth, Caribbean Sea (Chatterjee et al., 2020). It was also reported among algae Enteromorpha flexuosa from Tamiahua lagoon (near Tampache), Veracruz, Mexico (Martínez-Murillo, 1997). This is the first record of this species from the Florida coast.
It should be mentioned that the stalk of T. calix from Florida, epibiont on harpacticoids in present observation is short, the stalk length ranged from one seventh to one eighth of the lorica length.