A New Species ofParamacrochiron(Copepoda: Cyclopoida: Macrochironidae) Associated with the Rhizostome MedusaRhopilema hispidumCollected from the Gulf of Thailand, with a Phylogenetic Analysis of the Family Macrochironidae

Abstract

Paramacrochiron thailandicum n. sp. (Copepoda: Cyclopoida: Macrochironidae) is described from the rhizostome medusa Rhopilema hispidum occurring in the Gulf of Thailand. The new species is distinguishable from other congeners mainly by detailed features of the fourth legs and the urosome in both sexes. Copepodid and adult stages of the genus Paramacrochiron seem to be host-specific to rhizostome medusae, but may spend periods free in the plankton or benthos during the absence of the host. A cladistic analysis shows that the Macrochironidae comprises two main lineages. Paramacrochiron is recovered as a monophyletic group, located on one lineage together with Pseudomacrochiron, which appears as a paraphyletic taxon with the limited character set used. The other main lineage comprises the genera Macrochiron and Sewellochiron, but the sole species of the latter genus, Sewellochiron fidens, is nested within Macrochiron. This analysis provides little support for maintaining Sewellochiron as a separate genus.

Planktonic associations between medusae (classes Scyphozoa and Hydrozoa) and epifaunal crustaceans

“…Twelve records reported the edible jellyfish Rhopilema spp. as hosts (Berggren, 1994;Pagès, 2000;Hayashi, Sakagami & Toyoda, 2004;Towanda & Thuesen, 2006;Ohtsuka et al, 2010;Ohtsuka, Boxshall & Srinui, 2012;Boco & Metillo, 2018). The commercially harvested shrimp, Penaeus stylirostris (Stimpson, 1871), was found on Stomolophus meleangris (Riascos et al, 2018).…”

A new species of Pseudodiaptomus (Crustacea, Copepoda, Calanoida, Pseudodiaptomidae) from the Prasae River Estuary, Gulf of Thailand

“…We have been intensively investigating the taxonomy, biology and ecology of gelatinous and crustacean zooplankters in Thailand since 1997 (Pinkaew et al 1997, 2000; Pinkaew 2003; Ohtsuka et al 1999, 2003, 2010, 2012; Fukuoka and Pinkaew 2003; Fukuoka et al 2005; Nishida and Nishikawa 2011; Nishikawa et al unpublished). Special attention has been paid to copepods, mysids and rhizostome jellyfish, due to their numerical importance in the plankton communities in the coastal and estuarine waters.…”

Observations on the specific associations found between scyphomedusae and commensal fish and invertebrates in the Philippines

“…Alepes djedaba fish, C. feriata crab and Paramacrochiron sp. copepods associated with several species of rhizostome jellyfish, but these animals are known commensals of different species of jellyfish (Panikkar and Prasad 1952;Browne and Kingsford 2005;Towanda and Thuesen 2006;Cevik et al 2011;Ohtsuka et al 2009Ohtsuka et al , 2010Ohtsuka et al , 2012Ohtsuka et al , 2013Kondo et al 2014; see also Table 3). We note, however, that some of them could be kleptobionts or kleptoparasites, symbionts that steal food from their hosts (see definitions in Vollrath 1984; Iyengar 2008), but proving this hypothesis requires further work.…”

“…Microscopic animal commensals were examined by direct observation of medusa tissues under a microscope and by washing the medusae with filtered seawater and examining the supernatant filtered using a 100-µm mesh sieve. Invertebrate commensals were identified using the descriptions by Kaburaki (1923), Fielder et al (1984), Poore (2004), Abelló and Hispano (2006), and Ohtsuka et al (2012). Fish symbionts were identified using the descriptions by Iwatsuki andKimura (1996), Miller andTsukamoto (2004), Allen (2009), and Golani et al (2011).…”