Antennella incerta Galea, 2010

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 : 37-40

Antennella incerta Galea, 2010

Fig. 17A–C

Antennella incerta Galea, 2010: 25 , figs 6H1, J, K.

Antennella incerta Calder, 2013: 41 , fig. 11b, c.

Description: Colonies with unbranched hydrocladium, arising directly from a creeping hydrorhiza, up to 5.2 mm high. Hydrocladium composed of several internodes, divided alternately by transverse and oblique nodes. First segments of hydrocladia smooth, without hydrothecae and nematothecae, followed alternately by segments composed by one hydrotheca and four nematothecae, one median, a pair of laterals, and a superior axillar, and an intersegment with a single nematotheca. Hydrothecae cylindrical, 156–289 µm high, 179–189 µm wide at the margin. Adcaulinary wall adnate to the hydrocladium by halfway or less of their length. Abcaulinar wall straight, perisarc thick, one cusp in the initial portion turned to the hydrothecal interior. All nematothecae two-chambered. Median nematothecae sessile disposed at a certain distance to the hydrothecae. Lateral nematothecae conical, arising from a long apophysis that alone almost reaches the hydrothecal length, formed by a long pedicel adnate to the hydrothecae and a superior chamber. Lateral nematothecae with a chamber and a part of their pedicel surpassing the hydrothecal margin. Axillar nematothecae short, with chamber aperture, turned to the hydrothecae. Intersegment nematothecae mobile, with the segments almost of the same size. Gonothecae pear-shaped, 406–446 µm high, 125–200 µm in maximum width, arising from the hydrocladium in short pedicels, between the median nematotheca and the hydrotheca. Nematocysts microbasic mastigophores? discharged (14.5–15.2 × 5.1–6.9 µm).

Material examined: PCS – few colonies, three of them with gonothecae, from the dry and rainy seasons. CZUFS CNI-00172; CNI-00257; CNI-00259; CNI-00260.

Stations: PCS – 5, 12, 13, 15, 18.

Bottom: gravel, sand, and mud.

Distribution: This is the first record from the Brazilian coast. World distribution – Florida ( Calder 2013) and Guadeloupe ( Galea 2010).

Taxonomic remarks: The material found at Sergipe resembles the species Antennella incerta recently described from Guadeloupe (French Antilles) by Galea (2010), matching all characteristics described for it, such as the presence of one nematotheca in the intersegment and an axillar nematotheca, lateral nematotheca surpassing the hydrothecal margin in at least the superior chamber length, and the presence of internal cusps in the abcaulinar hydrothecal portion. Both the description of A. incerta made by Galea (2010) and the second record for this species made by Calder (2013) were based on sterile material, so gonothecal morphology could not be compared. However, the sum of the characteristics mentioned above leads to the identification of specimens from Sergipe as Antennella incerta .

Remarks: Colonizing algae, Bryozoa, and the hydroids Sertularelloides cylindritheca , Synthecium tubithecum , and Thyroscyphus ramosus .

Antennella secundaria (Gmelin, 1791) Fig. 17F–G

Synonyms available from: Schuchert (1997).

Sertularia secundaria Gmelin, 1791: 3856 .

Description: Colonies with an unbranched hydrocladium arising directly from a creeping hydrorhiza, up to 15.2 mm high. Hydrocladia is composed of several intersegments, separated alternately by transverse and oblique nodes. First segments of hydrocladia smooth, ahydrothecate, and with zero, one or two nematothecae, followed alternately by segments formed by one hydrotheca and four nematothecae, one median, a pair of laterals and a superior axillar; and one intersegment with two nematothecae or, less frequent, with one or none. Intersegment regions sometimes do not present a distinct node, leaving the impression of nonseparation between the hydrothecal segments and the immediately superior segment. Hydrothecae cylindrical, 147–174 µm high, 185–239 µm wide at the margin, adnate to the hydrocladia by half or less of its length. All nematothecae two-chambered. Median inferior nematothecae sessile, short and curved, reaching the hydrothecal base. Lateral nematothecae conical, formed by a short pedicel and chamber, reaching half of the hydrothecae. Intersegmental nematothecae similar to the median inferior one, sessile, inferior and superior chambers of the same size or the inferior a little higher. Some intersegment regions without nematothecae. Gonothecae 387–434 µm high, 233–235 µm wide, arising in short pedicels between the hydrothecae and the median inferior nematothecae, pear-shaped, larger laterally, slightly curved towards the hydrothecae, with one pair of opposite nematothecae in the basal portion. Nematocysts microbasic mastigophores? undischarged (10.7–11.1 × 4.4–4.5 µm) and discharged (10.2–10.3 × 4.1–4.3 µm).

Material examined: PCS – few colonies, two with gonothecae, from the dry and rainy seasons. CZUFS CNI-00174; CNI-00175; CNI-00176.

Stations: PCS – 5, 6, 7, 11, 12, 15, 18.

Bottom: gravel, sand, and mud.

Distribution: Brazil – São Paulo ( Fernandez et al. 2015) and Santa Catarina ( Bouzon et al. 2012, Miranda et al. 2015). World distribution – cosmopolitan with a preference from warm temperate regions ( Schuchert 1997).

Remarks: Colonizing algae and Bryozoa.

Halopteris alternata ( Nutting, 1900) Fig. 18E–F

Synonyms available from: Schuchert (1997) and Galea (2008).

Plumularia alternata Nutting, 1900: 62 , pl. 4 fig. 1, 2.

Thecocaulus diaphanus –Vannucci-Mendes, 1946: 576, pl. 5, fig. 46, 47 [not Halopteris diaphana (Heller, 1868) ]

Schizotricha billardi Vannucci, 1951: 88 , pl. 3 fig. 19, 20 (in part, Brazilian material only).

Halopteris diaphana – Migotto, 1996: 45, fig. 9D, E [not H. diaphana (Heller, 1868) ].

Description: Colonies erect, up to 20 mm high, arising from a creeping hydrorhiza. Stem monosiphonic, unbranched, separated in three regions, a first basal one, with variable length, similar to a pedicel, larger than the second region and separated from it by constrictions and annulus. A second region without hydrothecae or hydrocladia, higher or of the same high as the first region and separated from the third one by an oblique node. The third region carrying hydrocladium and cauline hydrothecae, separated by internodes, each internode with one hydrotheca, four nematothecae, a median inferior, a pair of laterals and a short axillar superior to the hydrothecae; and one hydrocladium inserted in a lateral apophysis. Axillar nematothecae generally not found in the distal portion of the stem. Stem intersegment carrying one nematotheca. Hydrocladia also segmented, arising alternately from the stem. The first segment of each hydrocladium short, square-shaped, without nematothecae, separated from the next segment by a transverse node. The second segment long, with one nematotheca at the distal portion and an oblique node also at this portion. Other hydrocladial segments followed by regions with one hydrotheca and three nematothecae, one median and a pair of laterals, and intersegments ahydrothecate with a single nematotheca. Hydrothecae cylindrical, 178–234 µm high, 160–169 µm wide, adnate to the hydrocladium along almost half of their length. All nematothecae two-chambered. Median inferior nematothecae placed far from the hydrothecae, conical and immovable. Lateral nematothecae mobile, conical, formed by short pedicel and a superior chamber. Intersegment nematothecae are similar to the median inferior ones but mobile. Axillar nematothecae from cauline hydrothecae mobile. Cauline hydrothecae and nematothecae are similar to the hydrocladial ones. A single colony with gonothecae, those inserted in a single pedicel in the main stem. Gonothecae pear-shaped, 748–774 µm high, 418–431 µm wide, with a pair of opposite nematothecae near the base. Gonothecae aperture rounded to oval with one operculum.

Material examined: PCS – few colonies, one of them with gonothecae, from the dry and rainy seasons. CZUFS CNI-00177; CNI-00178; CNI-00327; CNI-00328.

Stations: PCS – 5, 11, 15, 18.

Bottom: gravel, sand, and mud.

Distribution: Brazil – Arquipélago de São Pedro e São Paulo ( Amaral et al. 2000), Alagoas (Maximiliano M. Maronna unpub. data), and São Paulo ( Migotto 1996, Oliveira et al. 2006, Shimabukuro 2007, Silveira and Morandini 2011, Fernandez et al. 2014, 2015). World distribution – records to Florida, Caribbean, and Brazil ( Schuchert 1997).

Taxonomic remarks: Halopteris alternata belongs to a group designated by Schuchert (1997) as H. diaphana group, also including H. billardi (Vannucci, 1951) , H. diaphana , H. tenella (Verrill, 1874) , and H. platygonotheca Schuchert, 1997 . Halopteris alternata differs from H. billardi by having a monosiphonic stem and also axillar nematothecae in the hydrothecae; differs from H. tenella by having unbranched hydrocladium; and, from H. diaphana and H. platygonotheca by the form of the female gonothecae, that in H. diaphana is distinct, in the form of cornucopia and, in H. playgonothecaca the gonothecae is flattened like an oar ( Schuchert 1997, Calder et al. 2019). A comparative table of the species from H. diaphana group is available in Schuchert (1997, p. 42).

Remarks: Found on algae.

Figures

Figure 17. (A-C) Antennella incerta: (A) general view of a colony on algae; (B) detail of a hydrocladium showing few hydrothecae, nematothecae and a gonotheca (Go - red arrow); (C) detail of an internode with one hydrotheca and nematothecae; (D-E) Antennella curvitheca: (D) detail of a colony on algae; (E) detail of a hydrocladium showing one hydrotheca and nematothecae; (F-G) Antennella secundaria: (F) general view of a colony on algae: (G) detail of a hydrocladium showing one hydrotheca and nematothecae. Details on the images: a – lateral nematotheca, b – medial nematotheca, c – upper axillar nematotheca, d – intersegmental nematotheca, e – upper non-axillar nematotheca, f – intrathecal cusp.

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).