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Leptothecata
Thecate Hydroids
GBIF:712
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Descriptions(13)
Boissin et al. (2018) assessed the genetic diversity of Nemalecium from the Indo-Pacific, including specimens belonging to N. lighti (Hargitt, 1924) and an unnamed congener (identified as Nemalecium sp.), and found a high genetic diversity in the latter, hypothesizing the presence of multiple cryptic species. We provide an updated 16 S rRNA phylogenetic hypothesis for the genus, including sequences of N. caeruleus sp. nov., Nemalecium sp. and N. lighti from Bali (Fig. 30). Nemalecium caeruleus clusters within a clade comprising sequences of Nemalecium sp. 1 sensu Boissin et al. (2018), even though that clade shows low statistical support. The overall genetic distance within the clade composed of N. caeruleus and Nemalecium sp. 1 sensu Boissin et al. (2018) is relatively high (2.5 ± 0.4 %), and so is the genetic distance between N. caerulues and Nemalecium sp. 1 from all western Indian Ocean localities (3.5 ± 1.0 %). These relatively high genetic distance values, together with the absence of any morphological and ecological information on Nemalecium sp. 1, leave open the question whether they belong to the same species or not. Specimens morphologically indistinguishable from N. caeruleus surprisingly clusters with sequences of Nemalecium sp. 2 sensu Boissin et al. (2018) in a well-supported clade (BPP = 1, MLBS = 98), showing a genetic distance of 7.3 ± 1.0 % from the clade composed of N. caeruleus and Nemalecium sp. 1, and an intra-clade distance of 2.0 ± 0.4 %. Finally, the sequence of the Balinese N. lighti clusters in a fully supported clade together with other conspecific sequences from the Indian Ocean and Caribbean Sea. It is evident that a great genetic diversity, with genetic distance values much higher than typical intra-specific values for most hydrozoan species (i. e., pairwise genetic distances between the supposedly cryptic species ranging 7.1 – 7.6 %), occurs among Indo-Pacific Nemalecium specimens studied herein and by Boissin et al. (2018), even between the morphologically indistinguishablesamples analyzed in this study. However, the absence of taxonomical accounts for the specimens dealt with by Boissin et al. (2018), together with the lack of any information about their habitat, hamper a clear understanding of the diversity of this group and, similarly, a correlation with the hydroid inhabiting coral crevices (Gravier-Bonnet & Mioche 1996) could not be established with certainty for all their clades.
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
As equally shown in Fig. 32, genetic data (16 S rRNA) on the family Halopterididae are provided for the first time for A. sibogae (Billard, 1911 b), as well as for Balinese specimens of Halopteris vervoorti Galea, 2008 and Polyplumaria cornuta (Bale, 1884), supplementing those obtained earlier (P. Schuchert, unpublished results; Galea et al. 2018; Galea & Maggioni 2020) for A. billardi Galea (in Galea et al.), 2021, H. diaphana (Heller, 1868), H. longibrachia Calder & Faucci, 2021, H. plagiocampa (Pictet, 1893), H. platygonotheca Schuchert, 1997 and H. polymorpha (Billard, 1913). 16 S rRNA sequences of H. diaphana, H. plagiocampa, H. platygonotheca, H. vervoorti and P. cornuta cluster with conspecific sequences from other localities (Fig. 32). Finally, several Antennella secundaria - like colonies, white- to pale-green-colored and not morphologically separable from Gmelin’s (1791) hydroid were collected from the island, showing an overall high genetic divergence from each other (sequences OR 872075, OR 872076, OR 872077, OR 872078, OR 872079, MF 784533) and suggesting that the diversity of A. secundaria - like hydroids is currently underestimated (Fig. 32).
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
The sequenced plumulariid species from Bali include: Dentitheca elongata (Billard, 1913), Cladacanthella scabra (Lamarck, 1816), Plumularia procumbens Spencer, 1891 and Sibogella flabellata Di Camillo & Galea, 2020, for which genetic data are provided for the first time, and P. badia Kirchenpauer, 1876, P. strictocarpa Pictet, 1893, Sciurella cylindrica (Kirchenpauer, 1876) and S. erecta Billard, 1911 a (Fig. 31 A), with available sequences so far. A multi-locus phylogenetic hypothesis based on 16 S, 18 S and 28 S rRNA was also produced to assess the phylogenetic position of C. scabra, which results to be closely-related to P. badia, P. spiralis Billard, 1911 b and D. bidentata (Jäderholm, 1905) (Fig. 31 B).
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
The 16 S rRNA region of M. fallax could not be amplified, despite several attempts, while other regions were successfully amplified and sequenced (COI, 18 S rRNA, and 28 S rRNA). Specifically, a phylogenetic hypothesis based on the COI region was obtained to assess the relationships between M. fallax and other aglaopheniid species (Fig. 34). The two COI sequences obtained for M. fallax are identical to each other and closely related to sequences obtained from M. philippina Kirchenpauer, 1872 and M. filamentosa (Lamarck, 1816). However, they show high genetic distances from these two species, viz. 9.9 ± 1.2 % and 11.1 ± 1.2 %, respectively.
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
According to the 16 S rRNA phylogenetic reconstruction, Halecium turbinariae sp. nov. is divergent to all other sequenced congeners, thus supporting its establishment (Fig. 29). Halecium halecinum var. minor Pictet, 1893, originally described based on sterile material, reminds Linnaeus’ (1758) species through the regularly pinnate structure of its colonies. The species was rediscovered in Bali, although the available specimens are equally devoid of gonothecae. However, upon comparison with a profuse, fully fertile, female colony of H. halecinum (Linnaeus, 1758) from Britanny, France, it is realized that Pictet’s hydroid builds less robust colonies, with comparatively slenderer internodes, and the regular occurrence of a moderately-long, tubular, athecate internode at the origin of its cladia is distinctive. The two 16 S rRNA sequences obtained from Balinese specimens are divergent from Atlantic H. halecinum sequences (Fig. 29), also showing a genetic distance of 11.6 ± 1.4 %. Based on both morphological and genetic evidence, the so-called variety is raised to species, as H. minor, nov. status. Additionally, one newly-obtained and two unpublished 16 S rRNA sequences of Halecium sibogae Billard, 1919 form a fully-supported monophyletic group with minimal intra-specific distance (0.1 ± 0.1 %) (Fig. 29).
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
The 16 S rRNA sequence of Tridentata borneensis Billard, 1925 a from Bali did not match any other sequenced sertulariids, but clustered with other Tridentata species (Fig. 28) in a well-supported clade (BPP = 1, MLBS = 89). Tridentata loculosa (Busk, 1852) has hydrothecae lacking the prominent, lateral, marginal cusps characteristic of the genus Tridentata, its hydranths are strikingly provided with a ligula, and its gonothecae (although transverselyringed) are closed by a watch-glass-shaped operculum (Migotto 1996: 72), making it somehow distinct from members assigned to that genus so far. Additionally, the 16 S rRNA sequence obtained from a Balinese specimen does not cluster with other Tridentata sequences, the latter forming a well-supported monophyletic group (Fig. 28) also including a sequence of T. trigonostoma (Busk, 1852) from Bali, which is identical to a conspecific sequence from Thailand. Two other sertulariids, namely Idiellana pristis (Lamouroux, 1816) and Diphasia mutulata (Busk, 1852), were also sequenced. The first clusters with a sequence of the same species from Thailand (with an intra-specific genetic distance of 0.4 ± 0.2 %), whereas the second, here sequenced for the first time, is sister to all other Diphasia sequences included in the analyses, even though the support values for the genus are low (Fig. 28).
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
Genetic data (16 S rRNA region) for Sertularella decipiens Billard, 1919 and S. quadridens (Bale, 1884) are provided for the first time, whereas the sequence of S. diaphana (Allman, 1885) appears to be slightly divergent from that of a specimen from the Philippines (Fig. 27 B), with an intra-specific genetic distance of 2.7 %.
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
Colonies of Thyroscyphus fruticosus Esper, 1793 from Bali comprise unbranched, up to 7 cm high cauli, sparinglybranched stems, with 1 – 3 irregularly-placed side branches not exceeding 9 cm in height, and more robust, pinnatelybranched stems reaching (or even exceeding) 12 cm in height. The first two display the same phenotype as the material assigned by Pictet (1893: 37, pl. 2 fig. 32) to Lytoscyphus junceus (Allman, 1876), and subsequently considered by Splettstösser (1929, as T. bedoti) to represent a species distinct from the widely-spread T. fruticosus 13. A careful microscopical examination off all morphotypes, supported by a comparison of their corresponding line drawings, revealed no difference, suggesting that T. bedoti is an artificially-created nominal species. Schuchert’s (2003: 194, fig. 48) account, based on the reexamination of Pictet’s material, confirms, in our view, this assumption. Our specimens from Bali, clearly do not belong to another congener, e. g. T. torresii (Busk, 1852), also known to occur in Indonesia (Schuchert 2003: 196), and conform to the concept of the species highlighted by Watson (2000: 39), i. e. more straggling colonies vs. a tidier aspect, and the absence of internodes from the stems and branches vs. a regular division by distinct nodes, respectively. Colonies of T. fruticosus from Bali display many colors: yellow, orange, pink and purple. The 16 S sequences obtained from Balinese samples are almost identical, despite their respective colonies showing a different coloration: MG 811641 corresponds to a yellow hydroid, while MG 811642 to a purple one. The material from India assigned by Arun et al. (2020) to the western Atlantic T. ramosus Allman, 1877 is obviously based on a misidentification (Fig. 27 A). Indeed, their sequence MH 392732 clustered with our sequences and is clearly divergent from the well-established Atlantic T. ramosus (Fig. 27 A). Boissin et al. (2018) identified two main clades of Indo-Pacific Thyroscyphus that they assigned to T. fruticosus and T. bedoti. However, they did not provide any morphological information on their samples. According to our data, their clade called T. bedoti, with which our Balinese sequences clusters (Fig. 27 A), appears to be T. fruticosus, whereas their other clade, called T. fruticosus, is likely another species (indicated in our tree as Thyroscyphus sp.). Of note, T. aequalis Warren, 1908, a species known to occur in the tropical East Africa and Madagascar (Millard 1975), builds similar colonies, and specific differences are mainly noted in the morphology of their hydrothecae; this species could have been erroneously taken for T. fruticosus.
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
Synthecium flabellum Hargitt, 1924, here sequenced for the first time, forms a well-supported monophyletic group (BPP = 0.99, MLBS = 95) with both S. evansi (Ellis & Solander, 1786) and S. tubithecum (Allman, 1877) (Fig. 26 B).
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
Genetic data for Hebella laterocaudata Billard, 1942 are produced for the first time, and so are the two sequences of a hydroid recalling H. furax Millard, 1957. The latter, however, are quite divergent from one another (genetic distance of 8.2 %), and one of them is very similar to the sequence JN 714647 provisionally assigned to Anthohebella parasitica (Ciamician, 1880) from the Azores, this actually appearing not to belong to that nominal species (Fig. 26 A).
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
Campanularia spinulosa Bale, 1888, originally described without its gonosome and also sterile in the material at hand, recalls Obelia bidentata Clark, 1875 but, unlike that species, it builds flabellate instead of cypress-shaped colonies “ with lateral branches tending to be in right-angled pairs, successively on opposite sides of stem ” (Cornelius 1995: 292, fig. 68 A). Superposition of line drawings of specimens from Bali with Bale’s (1888) pl. 12 fig. 5, Thornely’s (1900, as Gonothyraea longicyatha) pl. 44 fig. 4, and Schuchert’s (2003, as O. bidentata) fig. 24 (right hand side drawing), revealed the same shape and proportions, suggesting that all are very likely conspecific. According to the present molecular evidence based on the combined 16 S, 18 S, and 28 S rRNA (Fig. 35 A), the species obviously belongs to the genus Obelia Péron & Lesueur, 1810, and it should be confidently referred to as O. spinulosa (Bale, 1888) 14. Two 16 S rRNA sequences of Clytia linearis (Thornely, 1900) were also obtained from Balinese samples, both clustering with other available sequences of C. linearis from the Atlantic Ocean and Mediterranean Sea (Fig. 35 B).
On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
Order Leptothecata Cornelius, 1992
Suborder Lafoeida Bouillon, 1984
On a collection of hydroids (Cnidaria, Hydrozoa) from the southwest coast of Florida, USAMagnoliaPress via PlaziNo known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
Order Leptothecata Cornelius, 1992
Aglaopheniid hydroids (Cnidaria: Hydrozoa: Aglaopheniidae) from bathyal waters of the Flemish Cap, Flemish Pass, and Grand Banks of Newfoundland (NW Atlantic)MagnoliaPress via PlaziNo known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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Thecate Hydroids★
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FIGURE 30. Phylogenetic hypothesis of the genus Nemalecium based on the 16S rRNA region. Numbers at nodes represent BPP and MLBS, respectively.
Imageimage/png© Galea, Horia R.;Maggioni, DavideOn some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
FIGURE 32. Phylogenetic hypothesis of the family Halopterididae based on the 16S rRNA region. Numbers at nodes represent BPP and MLBS, respectively. N.B.: According to Galea et al. (2021: 341), Antennella varians (Billard, 1911b) MF784528 should be correctly regarded as A. billardi Galea (in Galea et al.), 2021. Sequences MF784526 and MF784531, identified in GenBank as Halopteris sibogae (Billard, 1913) (Galea et al. 2018: fig. 9), should bear the recently-introduced taxon name, H. longibrachia Calder & Faucci, 2021.
Imageimage/png© Galea, Horia R.;Maggioni, DavideOn some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
FIGURE 31. Phylogenetic hypotheses of the family Plumulariidae based on the combined 16S, 18S and 28S rRNA dataset (A), and on COI region (B). Numbers at nodes represent BPP and MLBS, respectively. N.B.: According to Schuchert (2014: 2), Plumularia cf. lagenifera Allman, 1885 FJ550491 should be correctly regarded as P. gaimardi (Lamouroux, 1824).
Imageimage/png© Galea, Horia R.;Maggioni, DavideOn some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
FIGURE 33. Phylogenetic hypothesis of the family Aglaopheniidae based on the 16S rRNA region. Numbers at nodes represent BPP and MLBS, respectively.
Imageimage/png© Galea, Horia R.;Maggioni, DavideOn some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species
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References(8)
Bouillon, J.; Boero, F. (2000). Synopsis of the families and genera of the Hydromedusae of the world, with a list of the worldwide species. <i>Thalassia Salent. 24</i>: 47-296
basis of recordWorld Register of Marine Species
Bouillon, J.; Boero, F. (2000). Synopsis of the families and genera of the Hydromedusae of the world, with a list of the worldwide species. <i>Thalassia Salent. 24</i>: 47-296
basis of recordWRiMS
Calder (2010) Check list of Hydroids and Hydromedusae reported from the Skagerrak and Kattegat, Southern Scandinavia. WORKSHOP ON MARINE MACROFAUNA (September 2010). Sweden.Hydroids.Checklist.002.DOCX
Dyntaxa. Svensk taxonomisk databas
Calder (2012) On a collection of hydroids (Cnidaria, Hydrozoa, Hydroidolina) from the west coast of Sweden, with a checklist of species from the region
Dyntaxa. Svensk taxonomisk databas
Cornelius, P.F.S., 1992. Medusa loss in leptolid Hydrozoan (Cnidaria) hydroid rafting, and abbreviated life-cycles among their remote-island faunae: an interim review. In: J. Bouillon, F. Boero, F. Cicogna, J.M. Gili & R.G. Hughes, eds., Aspects of hydrozoan biology. Scientia Marina 56 2-3: 245-261.
original descriptionWorld Register of Marine Species