Cryptic species and host specificity in the bryozoan-associated hydrozoan Zanclea divergens (Hydrozoa, Zancleidae)

Abstract

Zanclea divergens is a tropical hydrozoan living in symbiotic association with bryozoans and currently reported from Papua New Guinea, Indonesia, and Maldives. Here, we used an integrative approach to assess the morpho-molecular diversity of the species across the Indo-Pacific. Phylogenetic and species delimitation analyses based on seven mitochondrial and nuclear loci revealed four well-supported molecular lineages corresponding to cryptic species, and representing a Pacific clade, an Indian clade, and two Red Sea clades. Since the general polyp morphology was almost identical in all samples, the nematocyst capsules were measured and analysed to search for possible fine-scale differences, and their statistical treatment revealed a significant difference in terms of length and width among the clades investigated.All Zanclea divergens specimens were specifically associated with cheilostome bryozoans belonging to the genus Celleporaria. The Pacific and Indian clades were associated with Celleporaria sp. and C. vermiformis, respectively, whereas both Red Sea lineages were associated with C. pigmentaria. Nevertheless, the sequencing of host bryozoans revealed that one of the Red Sea hydrozoan clades is associated with two morphologically undistinguishable, but genetically divergent, bryozoan species. Overall, our results show that Z. divergens is a species complex composed of morphologically cryptic lineages showing partially disjunct distributions and host specificity. The presence of two sympatric lineages living on the same host species reveal complex dynamics of diversification, and future research aimed at understanding their diversification process will likely improve our knowledge on the mechanisms of speciation among currently sympatric cryptic species.

Hydromedusae observed during night dives in the Gulf Stream

“…Aequorea species). Recent molecular analyses showed that many hydroids have a very high genetic diversity and are likely species complexes (Moura et al, 2008;Schuchert, 2014;Maggioni et al, 2018Maggioni et al, , 2020Postaire et al, 2017;Miglietta et al, 2018a;Boissin et al, 2018). Our medusa samples were all collected in a quite narrow region, but several morphospecies proved to be composed of two or more deeply separated molecular clades (Zancleopsis dichotoma, Laodicea undulata, Orchistoma pileus, Pseudaegina rhodina) or they were split here into sister species if the clades correlated with morphological differences (Pandeopsis ikarii and P. prolifera n.…”

Diversity, host specificity and biogeography in the Cladocorynidae (Hydrozoa, Capitata), with description of a new genus

“…However, no differences were detected in eurytele size between clade Ia and IIa and stenotele size among all clades. The statistical treatment of cnidocyst size data was previously used to search for fine‐scale variations in other hydrozoan species, revealing in some cases no differences (Wollschlager et al., 2013) or significant differences among genetic clades (Arrigoni et al., 2018; Manca et al., 2019; Maggioni et al., 2020c). Similar studies were performed also on sea anemones, in which only some cnidocysts, coming from particular structures, varied among morphs (González‐Muñoz et al., 2017), or did not vary at all (González‐Muñoz et al., 2018), showing a high intraspecific variability (Garese et al., 2016).…”

“…Additional DNA samples of Cladocoryne floccosa colonies from the Caribbean and Mediterranean Sea were obtained from Peter Schuchert (Mus eum d'Histoire Naturelle of Geneva, Switzerland, Table S1). Seven gene regions were amplified using the primers and protocols described in Maggioni et al, (2020c), namely portions of the mitochondrial large ribosomal RNA (16S rRNA), cytochrome oxidase subunit I (COX1), cytochrome oxidase subunit III (COX3), and nuclear small ribosomal RNA (18S rRNA), large ribosomal RNA (28S rRNA), internal transcribed spacer (ITS; including partial ITS1, 5.8S, and partial ITS2 regions), and histone H3 (H3) (Table 1). PCR products were checked through 1.5% agarose electrophoretic runs, purified with Illustra ExoStar (GE Healthcare: Amersham, UK) and sequenced in both directions with ABI 3730xl DNA Analyzer (Applied Biosystems: Carlsbad, CA, USA).…”

Integrative systematics illuminates the relationships in two sponge-associated hydrozoan families (Capitata: Sphaerocorynidae and Zancleopsidae)

“…Briefly, dna was extracted from a single polyp or medusa by digesting the specimen in a mixture of proteinase K and MilliQ water in the first case, or following the CTAB protocol (Coffroth et al, 1992) in the second case. Six molecular markers were amplified using the primers and protocols described in Maggioni et al (2020b), including portions of the mitochondrial large ribosomal rRNA gene (16S rRNA), cytochrome oxidase subunit I gene (cox1), cytochrome oxidase subunit iii gene (cox3), and nuclear small ribosomal rna gene (18S rRNA), large ribosomal rna gene (28S rRNA), and internal transcribed spacer region (its; including partial its1, 5.8S, and partial its2 regions). The success of polymerase chain reactions (pcr s) was checked through 1.5% agarose electrophoretic runs and pcr products were then purified with Illustra ExoStar (ge Healthcare) and sequenced in both directions by Macrogen Europe (Amsterdam, The Netherlands).…”