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 Eudendrium carneum Clarke, 1882 Fig. 5D–G Synonyms available from: Schuchert (2008b) . Eudendrium carneum Clarke, 1882: 137 , pl. 7 figs 10–17, Fraser, 1944: 64, pl. 8 fig. 36, Vervoort, 1968: 8, Millard, 1975: 82 , fig. 28, Watson, 1985: 202 , figs 59–62, Wedler and Larson, 1986: 84, fig. 6Ba, b, Calder, 1988: 43 , figs 33–35, Bavestrello and Piraino, 1991: 197 , fig. 1a–c, Marinopoulos, 1992: 57, fig. 2.3, Marques et al., 2000a: 90 , figs 35–41, Marques et al., 2000b: 206 . Eudendrium cunninghami Kirkpatrick, 1910: 127 , pl. 7 figs 1–3, Vannucci, 1954: 101 , synonym, Marques et al., 2000b: 207 , synonym. Description: The material was in poor condition, mostly fragmented, without hydranths or with much-degenerated hydranths. Colonies erect and bushy. Stem long, monosiphonic, up to 9 cm high, 0.16–0.2 mm wide, forming intercrossed aggregates. Hydrocladium divided into varying degrees, with terminal hydranths on pedicels of variable length. Perisarc thick, annulated at the base of branches and pedicels, less frequently annulated between pedicels and in their distal parts. Hydranths partially degenerated 0.2–0.34 mm high, 0.13–0.2 mm wide. One whorl of 10–16 filiform tentacles inserted just above the medial region of the hydranth. The form of the hypostome was not noticeable. Mature and spent gonophores surrounded by perisarc without traces of the hydranth, up to 1.3 mm high, 0.96 mm wide. Only female gonophores present, arising as sporosacs on short pedicels with some perisarcal annulations. One to six sporosacs per blastostyle, each with one egg . Spadices bifurcated and curved over the sporosac. Eggs are encased in a perisarc cover, typically with two fenestrations per egg. Nematocysts of two types : anisorhiza undischarged (7.4–7.9 × 3.4–3.9 µm); small eurytele undischarged (15.4–18.5 × 9.8–12.5 µm) and discharged (15.3–16.3 × 8.2–11.2 µm) and large undischarged (27.9–34.5 × 14.6–18.4 µm) and discharged (23.3–29. 9 × 16.2–17.2 µm). Material examined: PCS – abundant colonies, few with female gonophores, from dry and rainy seasons. CZUFS CNI-00086. Stations: PCS – 1, 2, 5, 7, 9, 10, 12, 14, 15, 16. Bottom: gravel, sand, and mud. Distribution: Brazil – Ceará ( Marques et al. 2006 , Shimabukuro et al. 2006), Fernando de Noronha ( Pires et al. 1992 , Amaral et al. 2009 ), Bahia ( Kelmo and Santa-Isabel 1998 ), Pernambuco ( Calder and Maÿal 1998 ), Espírito Santo ( Grohmann et al. 1997 , 2003 ), Rio de Janeiro ( Nogueira et al. 1997 ), São Paulo ( Marques et al. 2001 , Silveira and Morandini 2011 , Marques et al. 2013 , Fernandez et al. 2014 , 2015 , Alaja-Batista 2020 ), Paraná ( Cangussu et al. 2010 ), and Santa Catarina ( Miranda et al. 2011 , Bouzon et al. 2012 ) (see other records in Oliveira et al. 2016 ). World distribution – Mediterranean ( Bavestrello and Piraino 1991 , Marques et al. 2000b ), from New England to Florida ( Marques et al. 2000a ), South Africa ( Millard 1975 ), and Australia ( Watson 1985 ) (see specific records in Marques 2001 and Schuchert 2008b ). Taxonomic remarks: Despite the poor conditions of the colonies, the morphology of the female blastostyles and gonophores, and the cnidome agree with the diagnostic characteristics of E . carneum , namely: “ Eudendrium with large hererotrichous anisorhizal nematocysts... Spadix of the female gonophore bifurcated... The oocytes, together with the blastostyle, are encased in a perisarc forming a capsule, in which there are typically two fenestrations per oocyte.” ( Marques 2001 , 355–356). Although Marques (2001) mentions the large hererotrichous anisorhizal type as a character of E . carneum , Schuchert (2008b) mentions that these are also reported as isorhiza, and differentiating isorhiza from anisorhiza is not simple. Remarks: Few colonies found associated with a substratum; those are on Bryozoa, algae, and a thyroscyphid hydroid. Eudendrium merulum Watson, 1985 Fig. 5A–C Eudendrium merulum Watson, 1985: 200 , figs 53-58, – Bavestrello and Piraino, 1991: 200 , figs 2–4, – Marques et al., 2000a: 100 , figs 64–66, – Marques et al., 2000b: 203 , – Peña Cantero and García Carrascosa, 2002: 30 , fig. 5a, b, –Bouillon et al., 2004: 59, fig. 35A–G, – Schuchert, 2008b: 717–719 , fig. 19, 20. Description: Male and female colonies, up to 8.3 cm high. Some colonies form aggregates with stems intertwined. Stem monosiphonic, 0.12–0.17 mm in diameter, divided into more than one order, arising from a creeping hydrorhiza. Perisarc thick, smooth, with annulations at the base of pedicels and at the main stem above the insertion of the hydrocladia. Hydranths thin, 0.31–0.92 mm high, 0.29–0.54 mm wide, with a trumpet-shaped hypostome. Hydranths with one whorl of 16–22 filiform tentacles, inserted just below the hypostome. Fixed gonophores with wrinkled perisarc emerging from long pedicels in the male colonies and short ones in the female colonies. Hypostomes and tentacles in male blastostyles were completely reduced. One to three sporosacs per blastostyles, with 3–4 chambers each, connected by sporosac constraints. First chamber 90–114 × 74–76 µm and the last 122–174 × 115–159 µm. Hydranth partially or completely reduced in the female blastostyle, without hypostome. Female blastostyle up to 4.44 mm high and up to 3.01 mm wide. Female sporosac with a simple curved spadix over it. A single egg per sporosac and 4 to 7 sporosacs per blastostyle. Macrobasic euryteles undischarged (23.4–26.8 × 9.6–10.8 µm). Two groups of large microbasic euryteles aligned one at the base of the hydranth and the other at the base of the hypostome ( Fig. 5C ). Material examined: VB – abundant colonies, two with female and two with male gonophores, from the dry and rainy season; SE – few infertile colonies from the dry season. CZUFS CNI-00045; CNI-00090; CNI-00091; CNI-00238; CNI-00239. Figure 5. (A-C) Eudendrium merulum : (A) detail of one male colony showing hydranths and gonophores (red arrows); (B) detail of female colony showing hydranths and gonophores (red arrows); (C) detail of a hydranth showing the two groups of nematocysts characteristic of the species (red arrows); (D-G) Eudendrium carneum : (D) part of a female colony without hydranths highlighting the gonophores (red arrows); (E) an undischarged nematocyst; (F) a discharged nematocyst; (G) detail of two female gonophores. Stations: VB – C1P12, C1P34, C1P56, C2P12, C2P34, C2P56, C3P34, C3P56; SE – C3P12, C3P34, C3P56. Distribution: Brazil – the only record of this species from Brazil is to Santa Catarina ( Marques 2001 ), however, this record is considered doubtful ( Marques 2001 , Oliveira et al. 2006 ) because the specimens examined by Marques (2001) were in poor condition. The author also stated an important difference between the specimens that he observed and the type material of E . merulum that had nematocysts arranged in a “gland ring” ( Watson 1985 , Schuchert 2008b ). This gland-ring was observed in material from Sergipe as a group of nematocysts alined in the inferior region of hypostome and another group at hydranth base ( Fig. 5C , red arrows). World distribution – Australia ( Watson 1985 ), western and eastern Mediterranean ( Bavestrello and Piraino 1991 , Marques et al. 2000a , Peña Cantero and García Carracosa 2002), Black Sea, Canary islands, Gulf of Biscaya and English Channel ( Schuchert, 2008b ), and Atlantic region of Morocco ( Iazza et al. 2013 ). Schuchert (2008b) highlights that molecular analysis of 16S DNA suggests that the Atlantic, Mediterranean, and the Black Sea populations were three distinct species and this could indicate that E . merulum is a species complex. Remarks: Colonizing the plates, Bryozoa, Ostreidae , Polychaeta tubes, Ascidiacea, and the hydroids Corydendrium parasiticum and Pennaria disticha . Material from the rainy season was mainly without hydranths.