‘Putting names with faces’: a description ofEpiactis handisp. nov helps to resolve taxonomic confusion in species of the sea anemoneEpiactis(Actiniaria, Actiniidae)

Abstract

We resolve taxonomic confusion regarding brooding sea anemones in the genus Epiactis Verrill 1869a in the North Pacific Ocean based on newly collected material from Hokkaido (Japan), Haida Gwaii (British Columbia, Canada), and Kodiak and Adak Islands (Alaska, USA), and museum specimens collected from the Kurile Islands (Russia), Alaska, British Columbia, Oregon (USA), and California (USA). We find that the internally brooding individuals identified by Hand & Dunn (1974) as Cnidopus ritteri (Torrey, 1902) and placed in the genus Epiactis by Fautin & Chia (1986) belong to a new species which we describe and name Epiactis handi sp. nov. Epiactis handi and E. ritteri can be differentiated by morphological and behavioural features including ornamentation and structure of the column and mode of brooding offspring. To highlight and clarify these differences, we redescribe E. ritteri based on specimens from Alaska. We provide the first account of external brooding in E. ritteri, which necessitates a clarification of the differences between E. ritteri and another externally brooding species from the North Pacific, E. japonica Verrill, 1869b. Epiactis ritteri and E. japonica differ in sex allocation, ornamentation of the column and details of external brooding: members of E. ritteri are gonochoric with a smooth column and brood groove which tightly closes, whereas those of E. japonica are hermaphroditic and have mid-column spherules.

Brooding sea anemones (Cnidaria: Anthozoa: Actiniaria): paragons of diversity in mode, morphology, and maternity

“…On the other hand, individuals from relatively larger species of Epiactis and its relatives (i.e., E. japonica [ Verrill 1869], E. ritteri, U. fecunda [ Verrill 1899]) may hold hundreds of juveniles which are fairly uniform in size, at least at the beginning of their seasonal reproductive cycle, with the number decreasing and/or the diversity of sizes increasing over the reproductive season (Larson et al. ; Larson & Daly ).…”

“…data). In E. ritteri , another species often found on steep or vertical substrates, the brood groove is further specialized in that the column tissues above and below the groove meet and become tightly sealed together, fully enclosing the offspring (Larson & Daly ). Dunn () described a groove‐like structure in E. georgiana Carlgren 1927 that forms near the distal portion of the adult's column and in which offspring are brooded.…”

“…data). Offspring of E. ritteri and of E. georgiana may achieve a relatively large size while remaining on the parent, reaching a pedal disk diameter of up to 16.5 mm (Larson & Daly ) and up to 13.0 mm (Rodríguez et al. ), respectively.…”

Sea Anemones through X-Rays: Visualization of Two Species ofDiadumene(Cnidaria, Actiniaria) Using Micro-CT

“…Fukui (1986) also noted that fighting tentacles of D. lineata were similar to feeding tentacles in coloration and shape when contracted, becoming differentiated only when expanded in the manner characteristic of these structures. Likewise, Larson and Daly (2015) hypothesized that a non-differentiated tentacle with holotrichs and rare spirocysts in one specimen of the actineoidean Epiactis ritteri Torrey, 1902, is a fighting tentacle. Alternatively, it is possible that contamination of other parts of the tentacle with cnidae typical of feeding tentacles occurred during sampling of the tip of tentacles in which holotrichs are concentrated in fighting tentacles (Watson and Mariscal, 1983a).…”

“…Despite the obvious polyphyly of Sagartiidae (Daly et al, 2008;Rodríguez et al, 2012Rodríguez et al, , 2014), a close relationship among Metridiidae, Diadumenidae, and some sagartiids (e.g., V. paguri, S. troglodytes) with fighting tentacles has been recovered in phylogenetic analyses (Gusmão and Daly, 2010;Rodrí-guez et al, 2012Rodrí-guez et al, , 2014, which suggests fighting tentacles have putatively independently evolved fewer times than suspected. In addition to metridioideans, tentacles with holotrichs have been found in actinioideans belonging to family Actiniidae Rafinesque, 1815: Epiactis japonica (Verrill, 1869a) (as Cnidopus japonicus: Sanamyan and Sanamyan, 1998;Larson and Daly, 2015), Pacific populations of Aulactinia stella (Verrill, 1864) (Sanamyan and Sanamyan, 1998), and Epiactis ritteri Torrey, 1902 (Larson andDaly, 2015). Earlier, Fautin and Chia (1986) found holotrichs in tentacles of Epiactis lisbethae Fautin and Chia, 1986, Epiactis fernaldi Fautin and Chia, 1986, and Epiactis prolifera Verrill, 1869b.…”