Dentitheca bidentata (Jäderholm, 1905)

Castro Mendonça, Luana M., Parisotto Guimarães, Carmen R. & Haddad, Maria A., 2022, Taxonomy and diversity of hydroids (Cnidaria: Hydrozoa) of Sergipe, Northeast Brazil, Zoologia (e 21032) 39, pp. 1-65 : 43-46

Dentitheca bidentata (Jäderholm, 1905)

Fig. 20A

Synonyms available from: Migotto and Marques (1999). Plumularia bidentata Jäderholm, 1920: 7 , pl. 2, fig. 5, 6. Dentitheca crosslandi – Vannucci, 1949: 250–251, pl. 3, fig. 49, 50. Dentitheca bidentata –Migotto, 1997: 170–171.

Description: Colonies erect, up to 22 mm high, arising from a creeping hydrorhiza. Perisarc thick in the stem, moderately thick in the hydrocladia, and thin in the hydrothecae. Stem monosiphonic, unbranched, divided into one initial portion without hydrocladia, with or without nematothecae or internodes, followed by two or three short internodes, also without hydrocladia, separated by oblique nodes with one frontal nematotheca and, distally, by internodes carrying hydrocladia, those separated by oblique nodes and carrying apophysis and few nematothecae. Hydrocladia 1049–1651 µm high, arising alternately in angles of 124–146° from long apophysis positioned laterally to the stem, directed upward, build of several internodes with hydrothecae, separated from each other by oblique nodes. Each internode from the hydrocladia with one hydrotheca and four nematothecae, one median inferior, a pair of laterals, and one median superior. Hydrothecae 110–132 µm high, 58–98 µm in maximum width, adnate to the hydrocladium almost along all their length, tubular in shape, becoming larger distally. Hydrothecal margin everted, with two large and triangular lateral cusps and a shorter one in the median adcaulinar portion. Usually one internodal septum just below the insertion of lateral nematothecae and another just above insertion of medial inferior nematothecae. All nematothecae two-chambered, conical in shape, and mobile. Median inferior nematothecae with a long pedicel and a short superior chamber positioned at the base of the hydrothecae and curved in their direction. Lateral nematothecae with a pedicel shorter than the median inferior one, with the superior chamber surpassing the hydrothecal margin. Median superior nematothecae similar to the lateral ones, positioned at a distance from the hydrothecae. Gonothecae 675–2990 µm high, 510–2706 µm wide, arising from a short pedicel positioned next to the cauline apophysis, in the form of an inverted cone, larger distally, aperture round, with a thin operculum and a male medusoide inside, does not fill the gonothecal space. Gonothecal wall with a thick perisarc.

Material examined: PCS – few colonies, one of them with gonotheca, from dry and rainy seasons. CZUFS CNI-00188; CNI-00304; CNI-00305; CNI-00306; CNI-00308.

Stations: PCS – 4, 5, 6, 8, 18.

Bottom: gravel, sand, and mud.

Distribution: Brazil – Pernambuco ( Migotto and Marques 1999), Alagoas (Maximiliano M. Maronna unpub. data), Bahia ( Grohmann et al. 2003), Espírito Santo ( Vannucci 1949, 1951a, Grohmann et al. 1997, 2003), Rio de Janeiro ( Nogueira et al. 1997, Grohmann et al. 2003), and São Paulo ( Migotto and Marques 1999, Cunha and Jacobucci 2010, Silveira and Morandini 2011). World distribution – records from tropical regions of the Indian Ocean (western) and South Africa ( Millard 1975).

Remarks: Found on algae.

Monotheca margaretta Nutting, 1900 Fig. 20C

Synonyms available from: Calder (1997) and Galea (2010).

Monotheca margaretta Nutting, 1900: 72 , pl. 11, figs 1–3, – Silveira and Morandini, 2011, – Oliveira et al., 2016: 109.

Monotheca margaretta f. typica Vannucci Mendes, 1946, – Vannucci, 1949, 1950, 1951a, 1951b [polyp];

Monotheca margaretta f. curta Vannucci Mendes, 1946, – Vannucci, 1951a [polyp];

Description: Colonies erect, up to 11 mm high, arising from a tubular and creeping hydrorhiza. Perisarc thin in the entire colony. Hydrorhiza with several internal perisarc projections and nematothecae. Stem monosiphonic, unbranched, divided into regular internodes separated by transverse nodes. The first internode without hydrocladia or nematothecae, short and square-shaped. Other internodes formed by an apophysis in the distal portion and three nematothecae, two in the axis between the apophysis and the stem and the third one between the proximal transverse node and the apophysis. Apophysis carries one hydrocladium and one hydrotheca. Hydrocladia carries two internodes separated by transverse nodes, the first internode without hydrothecae or nematothecae and the second one with one hydrotheca and three nematothecae, a medial inferior and a pair or laterals. All nematothecae two-chambered and conical. Medial inferior nematothecae long, reaching half the hydrothecal length. Lateral nematothecae long, with an initial portion forming a Y projected to the internode, positioned behind the hydrothecae and surpassing the hydrothecal margin. Hydrothecae cylindrical, deep, 98–138 µm high, 84–119 µm wide, adnate to the internode along almost their length. Internodes and hydrorhizal nematothecae are similar to the medial inferior ones. Gonothecae 2446–2620 µm high, 1535–1566 µm wide, barrel-shaped, one per stem, arising from a short pedicel on the stem at the axis between the internode and a hydrotheca. Gonothecae with several longitudinal pleats in the perisarc.

Material examined: PCS – abundant colonies, several with gonothecae, from the dry and rainy seasons; VB – two infertile colonies from the dry season. CZUFS CNI-00020; CNI-00060; CNI-00193; CNI-00194; CNI-00195; CNI-00198.

Stations: PCS – 1, 4, 5, 6, 9, 10, 11, 12, 13, 15, 16, 18; VB – C2P34, C3P56.

Bottom: gravel, sand, and mud.

Distribution: Brazil – Ceará ( Marques et al. 2006, Shimabukuro 2007), Fernando de Noronha ( Shimabukuro 2007), Paraíba (Felipe F. Campos unpub. data), Pernambuco ( Calder and Maÿal 1998), Alagoas (Maximiliano M. Maronna unpub. data), Bahia ( Grohmann et al. 2003, Kelmo et al. 2003), Espírito Santo ( Vannucci 1949, 1951a, Grohmann et al. 1997, 2003), Rio de Janeiro ( Vannucci Mendes 1946, Vannucci 1949, 1950, 1951a, Nogueira et al. 1997, Miranda et al. 2015), São Paulo ( Vannucci Mendes 1946, Vannucci 1949, 1951a, Migotto 1996, Oliveira et al. 2006, Shimabukuro 2007, Cunha and Jacobucci 2010, Oliveira and Marques 2011, Silveira and Morandini 2011, Fernandez et al. 2014, Miranda et al. 2015), Paraná ( Vannucci 1951a, Miranda et al. 2015, Maria A. Haddad unpub. data), and Santa Catarina ( Miranda et al. 2011, 2015, Bouzon et al. 2012). World distribution – considered circumglobal, with records from Western and Eastern Atlantic and Pacific Oceans ( Calder 1997).

Taxonomic remarks: The recognition of Monotheca as distinct from Plumularia Lamarck, 1816 has been made elsewhere based on evidence of both morphology ( Calder 1997) and genetics (Moura et al. 2018).

Remarks: The PCS colonies were colonizing algae, Bryozoa, Gastropoda ( Xenophora sp. ), Polychaeta tubes, rocks, Brachyura (Majoidea), and the hydroid Hincksella formosa . Estuarine colonies were colonizing the plates.

Monotheca obliqua (Johnston, 1847) Fig. 20D–E

Synonyms available from: Watson (2011).

Plumularia obliqua Johnston, 1847: 106 , pl. 28, fig. 1.

Description: Colonies erect, up to 12.5 mm high, arising from a tubular and creeping hydrorhiza. Stem monosiphonic, sympodial, divided into internodes moderately long, separated by transverse nodes. Initial internodes short, without hydrothecae or nematothecae. Posterior internodes alternately, carrying one apophysis in the distal portion and two nematothecae, one in the axis between the apophysis and the stem and the other in the middle of the internode. Apophysis carrying one hydrocladium with one hydrotheca. Hydrocladia with two internodes separated by transverse nodes, the first one without hydrothecae or nematothecae and the second one with one hydrotheca and three nematothecae, one medial inferior and a pair or lateral. Hydrothecal internode is almost entirely occupied by the hydrotheca, larger distally and with one or two internal septa behind the hydrotheca. Hydrothecae cylindrical, 133–150 µm high, 137–151 µm wide, abcaulinar and adcaulinar wall slightly convex. All nematothecae two-chambered and mobile. Medial inferior nematothecae short, reaching almost the hydrothecal base. Lateral nematothecae directed outward, inserted in the final portion of the intersegment with hydrothecae, surpassing completely the hydrothecal rim.

Material examined: PCS – few infertile colonies from the dry and rainy seasons. CZUFS CNI-00021; CNI-00197.

Stations: PCS – 5, 6, 12, 13, 15, 18.

Bottom: gravel and mud.

Distribution: Brazil – Rio de Janeiro ( Nogueira et al. 1997). World distribution – considered cosmopolitan ( Watson 2011).

Taxonomic remarks: As mentioned above, the recognition of Monotheca as distinct from Plumularia Lamarck, 1816 has been made elsewhere based on evidence of both morphology ( Calder 1997) and genetics (Moura et al. 2018).

Remarks: Found on algae.

Figures

Figure 20. (A) Dentitheca bidentata: detail of a stem with few hydrocladia and one male gonotheca; (B) Plumularia floridana: detail of a stem showing several hydrothecae and mature gonangia (red arrows); (C) Monotheca margaretta: detail of a stem with few hydrothecae and one gonotheca; (D-E) Monotheca obliqua: (D) general view of a stem; (E) detail of a hydrotheca; (F) Plumularia sp.: (F) detail of a stem showing several hydrocladia and hydrothecae.