Mycodinium fucatum Averinzeff, 1916

Dovgal, Igor & Mayén-Estrada, Rosaura, 2015, A taxonomic revision of order Pilisuctorida (Ciliophora, Apostomatia) with keys to the subordinate taxa, Zootaxa 4040 (5), pp. 543-558 : 545-547

Genus Conidophrys Chatton et Lwoff, 1934

As discussed above, the first pilisuсtorid cilate was discovered and described of Averinzeff (1916) as Mycodinium fucatum ( Fig. 1 A). The species was found in the Adriatic Sea near Trieste ( Italy) (type locality) on antennae and legs setae of amphipod crustacean Caprella sp. (type host). Some characters as cylindrical shape of cells, elongated nucleus and reproduction by division, with 3 to 4 tomites produced, were emphasised by Averinzeff (1916). However no information of dimensions of described organisms was provided by the author.

Chatton and Lwoff (1934) found on the secretory setae of amphipod crustacean Corophium acherusicum Costa, 1853 , from the Mediterranean Sea near Sète and brackish lagoon L'etang de Thau ( France), to Conіdophrys pilisuctor Chatton et Lwoff, 1934 and also, recorded two ciliate individuals on isopod crustaceans from genus Sphaeroma Latreille, 1802 .

According to Chatton and Lwoff (1934) diagnosis, the trophont of C. pilisuctor is elongated and lacking of ciliature. The infraciliature is arranged in two fields almost symmetrical about the sagittal plane. There is one macronucleus and one micronucleus, but no morphology of the macronucleus was done.

The trophont stage by successive linear division produced 2 to 3 (rarely from 5 to 6) ciliated disk-shaped tomites ( Fig. 3 A–G), formed at the distal end of the cell body. They argumented that at this stage the ciliate resembles the conidia of parasitic fungi from the families Eccrinidae or Ellobiopsidae .

It was Jankowski (1989) the first who called attention to the synonymy between generic names Conidophrys and Mycodinium, and Aescht (2001) considered the generic name Mycodinium as a nomen dubium, but Averintzeff (1916) name was based on detailed diagnosis and drawings, then the type species of genus, M. fucatum can be fixed by monotypy.

Dovgal (2003a) in turn submited a proposal to the International Commission on Zoological Nomenclature to keeping the name Conіdophrys as nomen protectum, and the name Mycodinium must referred as nomen oblitum. The International Comission took a decision in accordance with this proposition (Opinion 2106, ..., 2005). Under mentioned decision the name Mycodinium Averinzeff, 1916 was hereby suppressed and placed on the Official Index of Rejected and Invalid Generic Names in Zoology whereas the name Conidophrys Chatton & Lwoff, 1934 with type species C. pilisuctor Chatton & Lwoff, 1934 , and the name Conidophryidae Kirby, 1942 with type genus Conidophrys were hereby placed on the Official Lists of Generic Names and Family-Group Names in Zoology.

Jankowski (2007) did not accept the recommendations of the International Commission on Zoological Nomenclature and continued using the generic name Mycodinium, and moreover, believed that both M. fucatum and M. pilisuctor are valid name combinations. Jankowski (2007) opinion is that representatives of Conidophryidae are species-specific parasites assigning specific names to conidophryid ciliates which can differ only by inhabiting on different host species.

However, in our opinion there are no enough morphological differences between M. fucatum and C. pilisuctor . The cell body and macronucleus shape are similar, the attachment mode to the host setae, and division process are also similar in both species, and differences in the swarmer morphology of two species have not been observed. Accordingly, C. pilisuctor Chatton et Lwoff, 1934 syn. n. is a junior synonym of C. fucatum ( Averinzeff, 1916) comb. n. This combination for C. fucatum already has been used ( Dovgal and Boshko 2007), as the senior synonym of C. pilisuctor but without discussion on synonymy ( Chatterjee et al. 2013).

We consider Conіdophrys Chatton et Lwoff, 1934 as a valid generic name, with type species of genus as C. pilisuctor (as a junior synonym of M. fucatum ).

Conidophrys fucatum is probably a widely distributed species, as it has been observed in different regions on representatives of various crustacean taxa ( Mohr and Leveque 1948; Moore 1981). Jankowski (2007) has recorded to Conidophrys individuals in the Atlantic and Pacific oceans, near Tierra del Fuego coast, and in the subantarctic waters attached to isopods, amphipods, decapods and mysids; Lynn (2008) reported to C. fucatum on soil mites, an unusual host taxon.

Other records for conidophryids corresponds to Ólafsdóttir and Svavarsson (2002) on deep-water isopod, and for amphipod Melita petronioi Senna et al., 2012 ( Chatterjee et al. 2013).

One further species, Conidophrys guttipotor Chatton et Lwoff, 1936 ( Fig. 1 E,F) from isopod crustacean Sphaeroma serratum (Fabricius, 1787) from lagoon L’etang de Thau ( France) was described ( Chatton and Lwoff, 1936), whose trophont stage differs from C. fucatum in size, has a thickened covering, and cell body is bent by ventral outward. According to Chatton and Lwoff (1936), Conidophrys guttipotor from S. serratum were attached to short host secretory setae, the bottom of ciliate envelope formed an elongated stalk-like structure with numerous folds which completely covered the seta, which resembles the attachment to the short setae observed in C. fucatum , in particular, from the amphipod crustacean J. falcata , but without special stalk-like structure ( Fig. 1 D).

Moreover, Chatton and Lwoff (1936) reported that some individuals of C. guttipotor were attached to any point along the length of non-secretory setae ( Fig. 1 F), concluding that conidophryid ciliates from isopods may have different mode of feeding than the species living on amphipods. However, we believed that its possible that some individuals were detached from host body accidentally and engaged to any host setae.

Jankowski (2007) considered C. guttipotor as a valid species name, but he cited the figure of C. guttipotor after Chatton and Lwoff (1936), denoting the species as Mycodinium sp.

It should be noted that the mode of trophont attachment to host body in C. guttipotor as well as some peculiarities of the morphology of species, are very similar to Conidophrys sp. found by Jones and Khan (1970) on isopod Jaera albifrons Leach, 1814 from Pembrokeshire (Black Tar Beach, Milford Haven, South Wales) ( Fig. 1 G–I), but spite to some differences such as the different mode of attachment to the host, and the presence of a trophont stage with a permanent funnel-shaped opening ( Jones and Khan 1970), we believe this species can be previously identified as a C. guttipotor , despite the trophont and tomite dimensions are missing, based on size of the macronucleus (and proportion to the cell), and well-defined longitudinal folds of stalk.

Jones and Khan (1970) also emphasized that Chatton and Lwoff (1936) described that some representatives of genus Conidophrys attach to the host body with stalk-like structure, and argumenting that the stalk of the studied species (without any setae inside of stalk), is more similar to the stalks of suctorian and chonotrich ciliates, but C. guttipotor was not considered.

Jankowski (2007) (only in figure 373 on page 880) assigned the new name combination Mycodinium (= Conidophrys ) jaerae to conidophryid ciliate found by Jones and Khan (1970). However both the diagnosis or labeling "sp. n." were not provided. Hence the name M. jaerae Jankowski, 2007 is an unavailable in accordance with Article 16.1 of the International Code of Zoological Nomenclature (International ..., 1999).

Jankowski (1966a) reported the discovery of three new species of genus Conidophrys on intertidal crustaceans ( Gammarus oceanicus Segerstråle, 1947 , Marinogammarus obtusatus (Dahl, 1938) and hermit crab Pagurus bernhardus Linnaeus, 1758 ) from the Barents Sea near village Dalnie Zelentsy. However, only the diagnosis of C. enkystotrophos Jankowski, 1966 from G. oceanicus was published, but trophont figures were included later ( Jankowski 1972, 2007) ( Fig. 1 J). Jankowski (2007) also recorded to G. setosus Dementieva, 1931 from the same locality, as a host for C. enkystotrophos .

According to Jankowski (1966a), C. enkystotrophos differs from other species of the genus by its attaching mode to the setae and its crimped band-like macronucleus. The ciliate is clamped parallel to the seta, whose tip is bent 180 degrees with respect its longitudinal axis.

Bradbury (1975) described to C. pіtelkae Bradbury, 1975 from shrimps ( Fig. 1 K–N), collected near Roscoff (type locality) and Penpoull ( France). The trophonts of the species vary from tiny tear-drop-shaped to long, slender forms. However, unlike to other representatives of the genus, C. pitelkae produces only a single tomite; a long, serpentine, with fun-shaped distal widening macronucleus is characteristic for the species.

Bradbury and Tyson (1982) emphasize the ability of cyst in C. pіtelkae to grow with the ciliate cell body, due to the presence of short folds in the cyst walls formed during its secretion through tomite metamorphosis. Thereupon these folds are straightened during cell growth. As the growth of cyst and cell body has been reported in various pilisuctorid taxa ( Chatton and Lwoff 1936; Deroux et al. 1975), we consider is a common process to all cystte Pilisuctorida.

The new species name C. marinogammari Jankowski (in press) for Conidophrys from Marinogammarus obtusatus was done by Jankowski (2007, p. 887). However this name is nomen dubium because was not accompanied by species diagnosis or figure.

Figures

FIGURE 1. Ciliates of genus Conidophrys described by different authors. A— Mycodinium fucatum; B—trophont of Conidophrys pilisuctor; C—tomite of C. pilisuctor (lateral view); D—individual at the short seta of Jassa falcata; Eindividual of C. guttipotor at the short seta of Sphaeroma serratum; F—individual at the host non-secretory seta; G—trophont of Conidophrys sp. from Jaera albifrons with developing tomites (Mac—macronucleus; Mic—micronucleus; Cytcytopharynx): H—cucurbitoid stage of developing trophont from J. albifrons; I—the stalk and its base; J— Conidophrys enkystotrophos; K—trophont of C. pіtelkae, left lateral view; L—trophont of C. pіtelkae, right lateral view; M—young trophont of C. pіtelkae; N—ventral view of C. pіtelkae tomite (X—tube; Cy—cytostome). (A—modified from Averinzeff 1916: B-F—modified from Chatton and Lwoff 1936; G-I—modified from Jones and Khan 1970; J—modified from Jankowski 1972; K-N—modified from Bradbury 1975).

FIGURE 3. The life cycles of ciliates from genera Conidophrys and Ascophrys after different authors. A—trophont of Conidophrys with two tomites; B—emerged tomite of Conidophrys; C— Conidophrys’ tomite attached to seta; D—lacrymoid stage of Conidophrys’ trophont development; E—spheroid stage of Conidophrys; F, G—cucurbitoid stages of Conidophrys; H—frontal view of Ascophrys rodor zenithal tomite; I—frontal view of nadiral tomite (m—macronucleus; o. f. — adhesive organelle); J—phoront stage in circular cyst; K—the early stage of trophont development; L—trophont stage; M—the development of trophont to tomont (propagative trophont) stage; N—tomitogenesis; O—the hatching of tomites; P—the field of trophont primordial ciliature; Q—the primary anlage of infraciliature in young tomont; R—multiplication of infraciliature anlages before tomitogenesis (stage M); S and T—two sequential phases of tomite infraciliature morphogenesis (a— “ narrowed field; b— “ ampliate field). (A – G—modified from Chatton and Lwoff 1936; H – T—modified from Campillo and Deroux 1974).