Polyphyly of the genus Zanclea and family Zancleidae (Hydrozoa, Capitata) revealed by the integrative analysis of two bryozoan-associated species

Abstract

The Zancleidae is a hydrozoan family that currently comprises three genera and 42 nominal species. The validity of numerous taxa in this family still needs to be assessed with integrative analyses and complete life cycle descriptions. The vast majority of its species live symbiotically with other organisms, among which cheilostomate bryozoans are the most common hosts. These bryozoan-associated zancleids are host-specific and encompass all species of the genera Halocoryne and Zanclella, as well as several species in the genus Zanclea. Zancleids show variable morphologies, including highly reduced polyps and medusae. Their phylogenetic history is uncertain due to the often intergrading morphologies and the shortage of molecular data. In the present study, two species of Zanclea from the Indian Ocean and the Red Sea are analysed, using morphological and DNA-based approaches. Morphological analyses of the polyp and medusa stages show that, despite a general resemblance with each other and with Zanclella diabolica, the two species differ in some characters, and this is supported also by molecular investigations. The DNA analyses show that the two species are monophyletic and closely related, but divergent from other Zanclea lineages. This newly recovered clade may correspond with the genus Zanclella or with a cryptic genus. The lack of both morphological and molecular data for several zancleid species did not allow to address this issue. Additionally, the singleand multi-locus phylogeny reconstructions reveal that both the family Zancleidae and the genus Zanclea are polyphyletic taxa, since they are composed of at least three divergent lineages. Most zancleid species have polyps and medusae similar to other closely related taxa, and this conserved general morphology poses a challenge in the delimitation of species, genera and even families in this group. Consequently, further conjunct morphological and molecular efforts are strongly needed to clarify the diversity and evolution of the family Zancleida as a whole.

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

“…The phylogenetic tree was rooted using Pennaria disticha [22,32] and, despite the overall poorly supported relationships (Figure 9), it agrees with previous reconstructions of Zanclea phylogeny [22]. Specifically, coral-associated Zanclea resulted in a fully supported clade, similarly to the clade composed of Zanclea sp.…”

“…The genus Zanclea and family Zancleidae are challenging taxa both from an evolutionary point of view and for species identification or description [19,22]. Indeed, the genus and family are polyphyletic [22,33], and further analyses are needed to establish new genera or even families.…”

“…The genus Zanclea and family Zancleidae are challenging taxa both from an evolutionary point of view and for species identification or description [19,22]. Indeed, the genus and family are polyphyletic [22,33], and further analyses are needed to establish new genera or even families. Their taxonomy is complicated by the fact that polyps often have intergrading morphologies, and the adult medusa must be observed and characterized for correct species identification and description [20,22].…”

“…Indeed, the genus and family are polyphyletic [22,33], and further analyses are needed to establish new genera or even families. Their taxonomy is complicated by the fact that polyps often have intergrading morphologies, and the adult medusa must be observed and characterized for correct species identification and description [20,22]. Indeed, cryptic or unidentifiable species are common in the Zanclea genus [18,19,22].…”

“…Yet, along with the morpho-molecular analyses, we investigated the informativeness of green fluorescence patterns of polyps and medusae to discriminate between closely related taxa. [22]. For each Zanclea species three colonies were collected, whereas two colonies of A. ryniensis were analyzed, for a total of 20 samples.…”