Monotheca posidoniae Picard, 1952

Gravili, Cinzia, Vito, Doris De, Camillo, Cristina Gioia Di, Martell, Luis, Piraino, Stefano & Boero, Ferdinando, 2015, The non-Siphonophoran Hydrozoa (Cnidaria) of Salento, Italy with notes on their life-cycles: an illustrated guide, Zootaxa 3908 (1), pp. 1-187 : 123-124

Monotheca posidoniae Picard, 1952

Fig. 87 A–C

See below References for a complete synonymy.

Material examined. HCUS-S 123 (Hydrozoa Collection, University of Salento—fauna of the Salento Peninsula)—polyp stage.

Description (based on our own observations; Picard 1952):

Hydroid. Hydrorhiza straight, unbranched to slightly branched; colonies erect, up to 45 mm; hydrocaulus zigzag, with distinct internal ribs, internodes slightly curved, each bearing a latero-distal apophysis, with 2 nematothecae at the level of the apophysis insertion and another nematotheca on the segment; hydrocladia borne on the apophyses, each comprising a basal athecate internode and another with one hydrotheca surrounded by 3 nematothecae, one median inferior reaching the base of the hydrotheca and 2 immediately above and behind hydrotheca; hydrothecal compartments much swollen distally; hydrothecae cup-shaped, entire adnate, rim even but sinuous, not flared, aperture at right angle with the internode; nematothecae 2-chambered, basal chamber narrow, tubular, distal chamber cup-shaped.

Gonothecae. Gonothecae imperfectly known, said to be identical to that of Monotheca obliqua .

Cnidome. Microbasic mastigophores.

Habitat type. Posidonia oceanica ( Picard 1952) .

Substrate. Epibiontic on Posidonia .

Seasonality. August–September ( Picard 1952) in the French coast of the Mediterranean Sea; August–September ( Bianchi et al. 1993a) in the Tyrrhenian Sea; August (this study) in Salento waters.

Reproductive period. August–September ( Picard 1952) in the Mediterranean Sea.

Distribution. Mediterranean endemic.

Records in Salento. Rare in Otranto (this study). Other Apulian records: coast of Bari ( Marano & Vaccarella 1970).

Remarks. Boero (1981a) indicated that the colonies of M. posidoniae have considerable morphological variability and that the strong perisarc thickening of the hydrothecate internodes decreases with increasing depth.

References. Stechow (1919, 1923) as Monotheca obliqua ; Broch (1933), Leloup (1934), and Billard (1936) all as Plumularia obliqua ; Picard & Roch (1949) as M. obliqua ; Rossi (1950) as P. ob l i q ua; Picard (1951b as M. posidoniae, 1952 as M. obliqua ); Riedl (1966) as Monotheca heteronoma and M. obliqua ; Marano & Vaccarella (1970), Relini et al. (1977), and Repetto et al. (1977) all as M. posidoniae ; García Corrales et al. (1978) as P. obliqua ; Marinpoulos (1979) as M. posidoniae ; Boero (1981a, b), Fresi et al. (1982), Boero et al. (1985), Boero & Fresi (1986), Gili (1986) as Plumularia obliqua posidoniae ; García-Rubies (1987, 1992) all as P. obliqua ; Piraino & Morri (1990) as Plumularia obliqua f. posidoniae ; Morri et al. (1991) as P. obliqua ; Roca et al. (1991), Bianchi et al. (1993), Galea (2007), all as P. obliqua ; Giovannetti et al. (2010) as M. obliqua .

Figures

FIGURE 87. Monotheca posidoniae: A, general aspect of a colony; B, hydrotheca and associated nematothecae; C, gonotheca (A, C drawn by F. Boero; B drawn by C. G. Di Camillo). Scale bars: A, 1 mm; B, 250 µm; C, 200 µm.