Halecium pusillum Sars, 1856

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 : 32

Halecium pusillum Sars, 1856

Fig. 15F–H

Synonyms available from: Peña Cantero and Carrascosa (2002). Eudendrium pusillum M. Sars, 1857: 154 , pl. 1, figs 14-16.

Description: Colonies erect, up to 15 mm high, arising from a creeping hydrorhiza. Stem monosiphonic. Perisarc is moderately thick, with several annulations across it. Hydrocladia arise laterally just below the hydrothecae. Primary hydrothecae shallow, 257–543 µm high, 93–115 µm wide at the margin, with a ring of desmocytes above the diaphragm. Secondary hydrothecae arise directly from the primary ones, supported by a pedicel. One female gonotheca found, 877 µm high, 470 µm wide, completely annulated, with a lateral aperture, desmocytes present. Male gonothecae oval with transverse waves along their length, 437–642 µm high, 231–313 µm wide. Nematocysts microbasic euryteles discharged (8.6–10 × 4.02–4.8 µm).

Material examined: PCS – few colonies with and without gonothecae (male and female) from the dry and rainy seasons. CZUFS CNI-00148; CNI-00324.

Stations: PCS – 5, 6, 16, 17.

Bottom: mud.

Distribution: Brazil – This is the first record from the Brazilian coast. World distribution – Peña Cantero and Carrracosa (2002) and Gravili et al. (2015) considered the species circumglobal distributed, mainly in the Mediterranean and Atlantic portions of Europe and also in the South Atlantic (Franch Guiana, Leloup 1960) and Pacific ( Ecuador, Calder et al. 2003). Additionally, there is a record from the Caribbean Sea ( Cuba, Castellanos-Iglesias 2017).

Taxonomic remarks: The intensity of the waves found on the perisarc of material from Sergipe is similar to that described by Peña Cantero and Carrracosa (2002) and, quite different from that described by Gravili et al. (2015) that mentions the perisarcal waves in pedicel as extremely intense. The intensity of the waves seems to be a variable character, including between colonies in the same place, as in the PCS. Halecium pusillum resembles H. corrugatissimum Trebilcock, 1928 but is differentiated from this species because H. corrugatissimum has hydrothecae with everted margin ( Schuchert 2005, p. 635).

Remarks: Zooxanthellae found on the peduncle, ramifications, and gonangia. Colonies found on algae.

Nemalecium lighti (Hargitt, 1924) Fig. 12C–F

Synonyms available from: Galea (2008). Halecium lighti Hargitt, 1924: 489 , pl. 4 fig. 13. Nemalecium lighti –Bouillon, 1986: 73, figs 1–4, pls. 1–3, – Calder,

1991d: 27, fig. 17, 18, – Migotto, 1996: 36, fig. 7H, I, –Gravier-Bonnet and Migotto, 2000: 207, fig. 1, 2.

Description: Colonies erect, up to 41.6 mm high, arising from a creeping hydrorhiza. Stem monosiphonic, branched alternately or irregularly. Perisarc is moderately thick with annulations at the stem base, each ramification and internode with hydrothecae. Each internode carries a primary hydrotheca. Secondary hydrothecae with pedicel, arising from inside the primary ones or laterally to those, just below the primary hydrothecae. All hydrothecae shallow, 99–111 µm high, 112–132 µm wide, with a ring of large desmocytes. Hydranths elongated, with a constriction just below the tentacle insertion, with a whorl of 15–17 filiform tentacles. Most of the hydranths with a pair of short round nematodactyls. Only female gonothecae found, 1–3 per colony, in the form of an inverted cone, 2–2.6 mm high, 0.56–1.16 mm in maximum width, perisarc thick and smooth, arising from pedicel in the stem and carrying eggs. Nematocysts (large pseudostenoteles) were seen on hydranths and nematodactyls (35–36 × 12 µm).

Material examined: VB – few colonies, one of them with female gonothecae, from the dry and rainy seasons. CZUFS CNI-00055; CNI-00150.

Stations: VB – C1P12, C2P12, C2P34, C2P56, C3P12, C3P34, C3P56.

Distribution: Brazil – Pernambuco ( Oliveira et al. 2009, abastract), Espírito Santo ( Grohmann et al. 1997), Rio de Janeiro ( Nogueira et al. 1997, Miranda et al. 2015), and São Paulo ( Marques et al. 2001, 2013, Silveira and Morandini 2011, Fernandez et al. 2015). World distribution – Atlantic, Indian and Pacific (western) Oceans ( Calder 1991).

Remarks: Colonizing the plates, and also on Bryozoa, Ostreidae, Ascidiacea , and the hydroids Corydendrium parasiticum and Pennaria disticha . One case of poisoning is recorded for this species to São Paulo ( Marques et al. 2002). Several stems were covered by algae and diatoms.

Figures

Figure 12. (A-B) Mitrocomium cirratum: (A) general view of a colony; (B) detail of the proximal region of a polyp showing some nematocysts; (C-F) Nemalecium lighti: (C) general view of a stem showing a gonotheca (red arrow); (D) detail of a colony highlighting a hydranth with a pair of nematodactyls (red arrows); (E) detail of a colony with hydranths; (F) detail of the stem showing a gonotheca.

Figure 15. (A-B) Haleciidae sp. 1: (A) detail of a polyp with a gonotheca; (B) detail of a polyp with an expanded hydranth; (C-E) Haleciidae sp. 2: (C) detail of a stem showing a hydranth; (D) detail of a stem ramification; (E) detail of the distal region of a stem; (F-H) Halecium pusillum: (F) general view of a stem; (G) detail of a stem with two male gonothecae; (H) detail of a stem with a female gonotheca.