Green Fluorescence Patterns in Closely Related Symbiotic Species of Zanclea (Hydrozoa, Capitata)

Abstract

Green fluorescence is a common phenomenon in marine invertebrates and is caused by green fluorescent proteins. Many hydrozoan species display fluorescence in their polyps and/or medusa stages, and in a few cases patterns of green fluorescence have been demonstrated to differ between closely related species. Hydrozoans are often characterized by the presence of cryptic species, due to the paucity of available morphological diagnostic characters. Zanclea species are not an exception, showing high genetic divergence compared to a uniform morphology. In this work, the presence of green fluorescence and the morpho-molecular diversity of six coral-and bryozoan-associated Zanclea species from the Maldivian coral reefs were investigated. Specifically, the presence of green fluorescence in polyps and newly released medusae was explored, the general morphology, as well as the cnidome and the interaction with the hosts, were characterized, and the 16S rRNA region was sequenced and analyzed. Overall, Zanclea species showed a similar morphology, with little differences in the general morphological features and in the cnidome. Three of the analyzed species did not show any fluorescence in both life stages. Three other Zanclea species, including two coral-associated cryptic species, were distinguished by species-specific fluorescence patterns in the medusae. Altogether, the results confirmed the morphological similarity despite high genetic divergence in Zanclea species and indicated that fluorescence patterns may be a promising tool in further discriminating closely related and cryptic species. Therefore, the assessment of fluorescence at a large scale in the whole Zancleidae family may be useful to shed light on the diversity of this enigmatic taxon.

Systematics and character evolution of capitate hydrozoans

“…3c), with the first two, previously ascribed to the genus Zanclea , being sister species (Fig. 3c) and sharing almost identical morphologies (Pica et al., 2017; Maggioni et al., 2020b). Intra‐ and interspecific genetic distances showed some overlapping values in this group, due to the high intraspecific divergence of H. eilatensis (Fig.…”

“…In particular, the distribution of Zanclea pirainoid was extended westward, being reported for the first time in the Maldives, after its description from Papua New Guinea (Boero et al., 2000). Apatizanclea exposita was reported from Eastern Australia, after its description in North Sulawesi, Indonesia (Puce et al., 2002) and the distribution of Halocoryne protecta was extended to the Central Red Sea, being previously only known from the Indo‐Pacific (Boero et al., 2000; Maggioni et al., 2020b). Finally, specimens identified as Zanclea cf.…”

“…Indeed, many species establish symbiotic relationships with other benthic organisms, living on or partially embedded in their hosts, which can be algae, crustaceans, bryozoans, molluscs, polychaetes, poriferans, or other cnidarians such as scleractinian corals and octocorals (Puce et al., 2008). The host specificity of these symbiotic species is variable, with both generalist and specialist taxa (Maggioni et al., 2022a, b), and in some cases the relationships appear to be very intimate, with the hosts showing specific structural modifications (Puce et al., 2005; Manca et al., 2019; Maggioni et al., 2020b). Both mutualistic and parasitic associations are known, with some species in the genus Zanclea Gegenbaur, 1856, for example, protecting their hosts from predators (Osman and Haugsness, 1981; Montano et al., 2017) and at least one Halocoryne species feeding on the lophophores of the host bryozoans (Piraino et al., 1992).…”

Morphological Modifications and Injuries of Corals Caused by Symbiotic Feather Duster Worms (Sabellidae) in the Caribbean

“…Coral barnacles usually become embedded in the coral skeleton and become partly overgrown by coral tissue [44,60]. Some alterations in the coral skeleton morphology are microscopic and hardly visible, such as those caused by coral-dwelling hydroids of the genus Zanclea [78][79][80]. In contrast, vermetid snails that live inside branching Stylophora and massive Porites corals are known to modify the host's morphology on a larger scale by flattening its surface relief, which is attributed to growth inhibition caused by the snail's toxic mucus webs [81][82][83].…”

Environmental gradients and host availability affecting the symbiosis between Pteroclava krempfi and alcyonaceans in the Saudi Arabian central Red Sea

“…families have been confirmed as hosts (Montano et al 2015a, b, Bonito et al 2019, even if the information on scleractinian-associated hydrozoans is constantly updated (e.g. Manca et al 2019, Maggioni et al 2020b. In this context, most of the efforts have focused on hydroids of the genus Zanclea (family Zancleidae), whose patterns of host-specificity, distribution, ecology and evolution of the interactions with reef-building corals and other hosts have been thoroughly investigated (Boero et al 2000, Pantos & Bythell 2010, Hirose & Hirose 2011, Pantos & Hoegh-Guldberg 2011, Fontana et al 2012, Montano et al 2013, Maggioni et al 2017a, 2020c.…”