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

Systematics and character evolution of capitate hydrozoans

Capitate hydrozoans are a morphologically and ecologically diverse hydrozoan suborder, currently including about 200 species. Being grouped in two clades, Corynida and Zancleida, these hydrozoans still show a number of taxonomic uncertainties at the species, genus and family levels. Many Capitata species established symbiotic relationships with other benthic organisms, including bryozoans, other cnidarians, molluscs and poriferans, as well as with planktonic dinoflagellates for mixotrophic relationships and with bacteria for thiotrophic ectosymbioses. Our study aimed at providing an updated and comprehensive phylogeny reconstruction of the suborder, at modelling the evolution of selected morphological and ecological characters, and at testing evolutionary relationships between the symbiotic lifestyle and the other characters, by integrating taxonomic, ecological and evolutionary data. The phylogenetic hypotheses here presented shed light on the evolutionary relationships within Capitata, with most families and genera being recovered as monophyletic. The genus Zanclea and family Zancleidae, however, were divided into four divergent clades, requiring the establishment of the new genus Apatizanclea and the new combinations for species in Zanclea and Halocoryne genera. The ancestral state reconstructions revealed that symbiosis arose multiple times in the evolutionary history of the Capitata, and that homoplasy is a common phenomenon in the group. Correlations were found between the evolution of symbiosis and morphological characters, such as the perisarc. Overall, our results highlighted that the use of genetic data and a complete knowledge of the life cycles are strongly needed to disentangle taxonomic and systematic issues in capitate hydrozoans. Finally, the colonization of tropical habitat appears to have influenced the evolution of a symbiotic lifestyle, playing important roles in the evolution of the group.

Being Safe, but Not Too Safe: A Nudibranch Feeding on a Bryozoan-Associated Hydrozoan

Nudibranchs have a mostly carnivorous diet, and they prey on a wide variety of other animal taxa. Many species, mainly belonging to the Cladobranchia suborder, feed on cnidarians, including member of the class Hydrozoa. Several hydrozoan species display a symbiotic lifestyle, being associated with other benthic invertebrates, including for instance bryozoans, corals, octocorals, and sponges. In our knowledge, no record of nudibranch predation on symbiotic hydrozoans has been reported so far, possibly thanks to the protective action by the host towards its symbiotic hydrozoan. Here, we show the unexpected case of a nudibranch belonging to the recently described species Sakuraeolis marhe (Fernández-Simón and Moles, 2023) feeding on Zanclea sp. 2, a hydrozoan associated with the cheilostome bryozoan Celleporaria sp. This trophic association is confirmed by the presence and storage of the nematocysts into the nudibranch cnidosacs. Moreover, the nudibranch appears to selectively store mostly a single type of nematocyst, that is large size stenotele. The observation here reported represents the first well-documented record of a nudibranch feeding on a symbiotic hydrozoan and the first confirmed case of predation on Zanclea polyps. Moreover, we provide additional genetic information and the first description of the internal anatomy of S. marhe.

The First Deep-Sea Stylasterid (Hydrozoa, Stylasteridae) of the Red Sea

The Stylasteridae, commonly known as lace corals, is a family of colonial calcifying hydrozoans mostly inhabiting deep waters. Stylasterids show a cosmopolitan distribution but, in some areas, they are characterized by low species diversity, such as in the Red Sea, where only a shallow-water species has been reported so far. With this work, we provide the first evidence of a deep-sea stylasterid inhabiting the NEOM region in the northern Saudi Arabian Red Sea, at depths ranging between 166 and 492 m. Morphological examinations revealed that this species was previously unknown and belonging to the genus Stylaster. We, therefore, describe Stylaster tritoni sp. nov., representing the first record of the genus in the Red Sea. Lastly, the phylogenetic position of the species within the Stylasteridae was evaluated, revealing a close relationship with shallow-water Indo-Pacific and Western Atlantic Stylaster species and confirming the polyphyletic nature of the genus Stylaster.

Phylogeny and evolutionary history of the Sombre Tit, Poecile lugubris in the western Palearctic (Aves, Paridae)

Few studies have delimited evolutionary entities within the Sombre Tit, Poecile lugubris. Here, we explored its morphological and genetic variability using 24 morphometric variables, two mitochondrial (COX1 and ND2), two nuclear (ODC and MB), and 10 microsatellite loci. Genetic and morphometric characters supported the species status of the Caspian Tit, Poecile hyrcanus with a separation from P. lugubris more than 4.5 MYA. The phylogenetic analyses uncovered three distinct clades within P. lugubris. The subspecies P. l. lugubris, with strong genetic differences from the other subspecies (4.5%), diverged at ∼1.1 MYA. Samples from Iran formed the remaining two clades. Individuals from western and northwestern Iran were placed in a single clade (anatoliae), while those from southern and southwestern Iran were in another independent clade (dubius-kirmanensis). Morphometric analyses also confirmed this pattern. The microsatellite results discriminated Iranian subspecies as discrete clusters with signs of nuclear admixture between dubius and anatoliae in the Zagros Mountains. Signs of population expansion for anatoliae and dubius-kirmanensis coincided with the late LGM. Our results shed new light on the phylogenetic relationships, evolutionary history, and past demographic processes of P. lugubris.

A New Species of Sea Whip Gorgonian-Associated Zoantharian (Cnidaria: Anthozoa: Hexacorallia: Parazoanthidae) from the Ryukyu Islands, Japan, with Subgeneric Subdivision of Genus Umimayanthus

Symbioses between invertebrates are common in the ocean although usually the diversity and specificity of their interactions are not well understood. Parazoanthidae (Cnidaria: Anthozoa: Zoantharia) is one of the most diverse zoantharian families in terms of numbers of genera and species. Species in this family are commonly associated with various other invertebrates that they utilize as their substrate. Previous studies have re-organized the taxonomy of Parazoanthidae and revealed a strong specificity between many parazoanthid species and genera and their substrates. However, our understanding of the species diversity of Parazoanthidae is far from complete, as parazoanthids are often overlooked in sampling surveys. In this study, we establish three subgenera under the genus Umimayanthus Montenegro, Sinniger, and Reimer, 2015; the nominotypical Umimayanthus, Paraumimayanthus subgen nov., and Gorgoniazoanthus subgen. nov., based on the finding of a new species, Umimayanthus (Gorgoniazoanthus) kanabou sp. nov., associated with the sea-whip gorgonian Ellisella sp. from approximately 30 m depth in shallow mesophotic coral reef communities in Oura Bay on Okinawajima Island and in Oshima Strait near Amami-Oshima Island, in the Ryukyu Islands, southern Japan. We additionally report on gastropods and crustaceans observed in association with U. kanabou, and these species are thought to potentially prey upon the zoantharians or on gorgonian polyps. Umimayanthus kanabou is phylogenetically closely related to congeneric sponge-associated Umimayanthus spp., further supporting the recent hypothesis that substrate preferences may change during the evolutionary history of zoantharians.