Halopteris tenella (Verrill, 1874)

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 : 42-43

Halopteris tenella (Verrill, 1874)

Fig. 18 H-I

Synonyms available from: Schuchert (1997), Galea (2013) and

Oliveira et al. (2016). Plumularia tenella Verrill, 1874: 731 . Halopteris diaphana – Galea, 2008: 42, fig. 8E, – Calder, 2013: 43,

fig. 13B–D [not H. diaphana (Heller, 1868) ]. Halopteris constricta – Migotto, 1996: 44, fig. 9A–C (not H. constricta Totton, 1930 ), Oliveira, 2003; Oliveira et al., 2006 [polyp]. Schizotricha tenella – Calder & Maÿal, 1998 [polyp].

Description: Colonies up to 9.3 mm high, arising from a creeping hydrorhiza. Stem monosiphonic, unbranched, divided into two regions, first one basal of variable length, similar to a pedicel, separated from the second one by an oblique node. The first region ahydrothecate with zero to five nematothecae. The second region is composed of internodes, separated alternately by oblique and transverse nodes, all of them with hydrothecae, five to six nematothecae (one median inferior, a pair of laterals, and two or three superior ones), and one hydrocladium, arising laterally above the cauline hydrothecae. Hydrocladia arises alternately from the stem in short apophysis, distant from each other, and also divided into internodes alternately by transverse and oblique nodes. The first segments of each hydrocladium are short, square-shaped, without hydrothecae or nematothecae, separated from the next segment by a transverse node. The second segment is elongated, ahydrothecate, with one or two nematothecae in the medial-superior portion, with an oblique node at the distal end. The remaining hydrocladial segments are followed by intersegment with one hydrotheca and three nematothecae, one median and a pair of laterals, and by short intersegments, ahydrothecate, and with one nematotheca. Hydrothecae cylindrical, 0.12–0.26 mm high, 0.14–0.19 mm in maximum width, adnate to the hydrocladium along almost half of their length. All nematothecae mobile and two-chambered. Median inferior nematothecae distant to the hydrothecae, conical, with the two chambers of similar size or the inferior one a little bigger. Lateral nematothecae conical, formed by a short pedicel and a superior chamber. Intersegment nematothecae are similar to the median ones. Female gonothecae 427–731 µm high, 252–400µm wide, cornucopia-shaped, up to 18 per stem, arising from the stem and/or hydrocladium in pedicels with two segments. Gonothecal margin turned inside, aperture rounded, with an operculum. Gonothecae with a pair of opposite nematothecae near the base. Nematocysts microbasic euryteles (only one measured, 14.5 × 6.7 µm).

Material examined: VB – several colonies, few with gonothecae, all of them from the rainy season. CZUFS CNI-00058.

Station: VB – C3P56.

Distribution: Brazil – Penambuco ( Calder and Maÿal 1998) and São Paulo ( Migotto 1996, as H. constricta Totton, 1930 , Oliveira et al. 2006). World distribution – from Massachusetts to the Caribbean Sea ( Calder 1983) and from southern California to Panama ( Galea 2013).

Taxonomic remarks: As mentioned in the observations to H. alternata , H. tenella belongs to the H. diaphana group, but can be distinguished from the others by the female gonotheca with cornucopia shape and by having homomerous cauline segmentations.

Remarks: Colonizing the plate.

Monostaechas quadridens (McCrady, 1859) Fig. 18C, G

Synonyms available from: Schuchert (1997).

Plumularia quadridens McCrady, 1859: 199 .

Monostaechas fisheri – Vannucci 1949, 1950, 1951a [non Monostaechas fisheri Nutting, 1905 ] [polyp].

Description: Colonies up to 23 mm high, arising from a creeping hydrorhiza formed by branched hydrocladia and ramifications, which arise immediately at the superior portion of the anterior part of hydrocladium, forming a scorpioid sympodium. Few stems with the initial part divided into two and, each ramification carrying the hydrocladia structured as scorpioid sympodia. First hydrocladium of each stem formed by an initial portion, similar to a pedicel, with variable length, with two segments, a short and a large one, both ahydrothecate, and generally with three nematothecae. Hydrocladia segmented, divided by transverse nodes. The first segment of each hydrocladium ahydrothecate, with three or more nematothecae, with one transverse node in the proximal region and an oblique one in the distal end. Subsequent segments alternating between ones with hydrothecae and four nematothecae (a median inferior, a pair of laterals, and an axillar one), and ones with ahydrothecate intersegment, and one or two nematothecae, those segments are separated by transverse and oblique nodes alternately. Hydrothecae cylindrical, 197–205 µm high, 251–282 µm wide, abcaulinar margin straight. All nematothecae two-chambered. Median inferior nematothecae mobile, inserted next to the hydrothecae. Lateral nematothecae are formed by a pedicel, parallel to the hydrothecae, and a conical chamber, directed towards the back. Axillar nematothecae small, with the superior chamber aperture directed towards the hydrocladium. Intersegment nematothecae are similar to the median inferior one but smaller. Gonothecae pear-shaped, larger distally, 436–504 µm high, 245–473 µm wide, arising in short pedicels divided into two segments at the hydrocladia in the basal portion of hydrothecae; a pair of nematothecae in the gonothecal basal part, just above the pedicel.

Material examined: PCS – few colonies, one of them with gonothecae, from the dry and rainy seasons. CZUFS CNI-00016; CNI-00182; CNI-00183; CNI-00184.

Station: PCS – 4, 5, 9, 12.

Bottom: gravel, sand, and mud.

Distribution: Brazil – Bahia (Kelmo et al. 2003, Shimabukuro 2007), Espírito Santo ( Vannucci 1951a, Grohmann et al. 2003), Rio de Janeiro ( Vannucci 1950, Grohmann et al. 2003, Miranda et al. 2015), São Paulo ( Migotto 1996, Silveira and Morandini 2011, Miranda et al. 2015), and Santa Caratina ( Miranda et al. 2015). World distribution – considered circumglobal from temperate and tropical regions ( Schuchert 1997).

Remarks: Colonizing algae, Bryozoa, and Sertularelloides cylindritheca .

Figures

Figure 18. (A-B, D) Halopteris carinata: (A) detail of a stem showing few hydrocladia and hydrothecae; (B) detail of stem with two female gonotheca; (D) detail of few hydrocladia with three male gonothecae (red arrows); (C, G) Monostaechas quadridens: (C) general view of a colony; (G) detail of a hydrocladium ramification with two gonothecae (red arrows); (E-F) Halopteris alternata: (E) detail of a stem showing hydrocladia and hydrothecae; (F) detail of a stem ramification with three gonothecae (red arrows); (H-I) Halopteris tenella: (H) detail of a stem with hydrocladia, hydrothecae and gonothecae; (I) detail of a stem with gonothecae (red arrows).