Taxonomy and diversity of hydroids (Cnidaria: Hydrozoa) of Sergipe, Northeast Brazil Author Castro Mendonça, Luana M. Instituto de Ciências Biológicas e da Saúde, Universidade Federal de Alagoas. Avenida Lourival Melo Mota, & Programa de Pós-Graduação em Zoologia, Departamento de Zoologia, Setor de Ciências Biológicas, Universidade Federal do Paraná. Caixa Postal 19020, 81531 - 980 Curitiba, PR, Brazil. mahaddad. 2014 @ gmail. com Author Parisotto Guimarães, Carmen R. Departamento de Biologia, Centro de Ciências Biológicas e da Saúde, Universidade Federal de Sergipe. Avenida carmenparisotto@gmail.com Author Haddad, Maria A. Instituto de Ciências Biológicas e da Saúde, Universidade Federal de Alagoas. Avenida Lourival Melo Mota, text Zoologia 2022 e 21032 2022-11-25 39 1 65 http://dx.doi.org/10.1590/s1984-4689.v39.e21032 journal article 10.1590/S1984-4689.v39.e21032 1984-4689 13176475 2B189EA2-803A-428C-AE26-C3669A5F3100 Halopteris carinata Allman, 1877 Fig. 18A–B, D Synonyms available from: Schuchert (1997) . Halopteris carinata Allman, 1877: 33 , pl. 19, figs 3–7. Description: Colonies fragmented, longest stem fragment with 8 cm . Stem erect, monosiphonic, straight, perisarc thick. Stem divided into two regions, the first with several internodes of variable length, separated by straight nodes, each internode with nematothecae. The second region with regular segments, separated by oblique nodes, composed by one cauline hydrotheca with three associated nematothecae, a median inferior and a pair of laterals, and four or more distal nematothecae, disposed in pairs after the hydrothecae and one hydrocladium inserted laterally to the hydrothecae at the stem. Hydrocladia unbranched, arising alternately from the stem, composed of segments separated by oblique nodes. First hydrocladial segment ahydrothecate, and with one nematotheca. Further hydrocladial segments generally with one hydrotheca and four nematothecae, positioned concerning the hydrothecae, one median inferior, a pair of laterals, and a superior one, not axillar. Hydrothecae cylindrical, 198–223 µm high, 193–206 µm wide at the margin, adnate to the hydrocladium for more than heaf of their length, abcaulinar margin straight, margin smooth with one sharp cusp in the distal end. All nematothecae two-chambered. Median inferior nematothecae, apparently immovable, in the form of a spoon. Lateral nematothecae is composed of a pedicel adnate to the hydrothecal wall and a superior concave free chamber that surpass the hydrothecal margin. Superior nematothecae reduced, mobile, with an aperture in the form of a spoon. Intersegment nematothecae similar to the superior ones but higher. Cauline hydrothecae shorter and shallower than the hydrocladial ones. Male and female gonothecae on the same stem. Female gonothecae barrel-shaped, longer than wider, 1533–1570 µm high, 1029–1103 µm in maximum width, flattened laterally with an oval aperture and an operculum, arising from a short pedicel from the stem, generally in groups of three. Up to 11 female gonothecae per colony, one or two per hydrocladium. Male gonothecae small, 420–477 µm high, 176–230 µm in maximum width, sac-shaped, arising from a short pedicel from the hydrocladium, laterally above the hydrothecae. The male and female gonothecae with nematothecae in the basal portion, one and two, respectively. Gonothecal nematothecae mobile, formed by a long pedicel and a conical superior chamber. Nematocysts microbasic mastigophores undischarged (31–35.4 × 10.2–11 µm) and discharged (27.5–30.4 × 10–11.4 µm). Material examined: PCS – few colonies, several of them with gonothecae, from dry and rainy seasons. CZUFS CNI-00014; CNI-00180; CNI-00329. Station: PCS – 5, 11, 12, 15, 17. Bottom: gravel, sand, and mud. Distribution: Brazil – Pernambuco ( Calder and Maÿal 1998 ), Alagoas (Maximiliano M. Maronna unpub. data), Espírito Santo , Rio de Janeiro ( Grohmann et al. 2003 ), and Santa Catarina ( Miranda et al. 2015 ). World distribution – recorded mainly from Western Atlantic with preferences for warm regions. Records from the Caribbean, Bermuda , Bahamas , and Florida ( Calder 1997 ). 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). Remarks: Unknown substrate.