Leptothecata, Cornelius, 1992

Galea, Horia R. & Maggioni, Davide, 2024, On some tropical hydroids (Cnidaria: Hydrozoa), with descriptions of four new species, Zootaxa 5428 (1), pp. 1-57 : 41

Leptothecata : Thyroscyphidae

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 16S sequences obtained from Balinese samples are almost identical, despite their respective colonies showing a different coloration: MG811641 corresponds to a yellow hydroid, while MG811642 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. 27A ). Indeed, their sequence MH392732 clustered with our sequences and is clearly divergent from the well-established Atlantic T. ramosus ( Fig. 27A ). 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. 27A ), 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 .

Figures

FIGURE 27. Phylogenetic hypotheses of the families Thyroscyphidae (A) and Sertularellidae (B) based on the 16S rRNA region. Numbers at nodes represent BPP and MLBS, respectively. N.B.: According to Galea et al. (2017: 263) and Galea & Schuchert (2019: 2), Sertularella sanmatiasensis El Beshbeeshy, 2011 FN424141 should be correctly regarded as S. antarctica Hartlaub, 1901.