Brooding has been reported in at least 57 species of sea anemone. More than three quarters (44/57) of the species that are known to brood have been described since the last comprehensive treatment of brooding in this lineage. Different authors focusing on different taxonomic groups within sea anemones over the last 115 years have collectively produced an imprecise and inconsistent set of terminology with respect to brooding in general and to the variety of conditions of brooding in particular. In this review, I characterize brooding as a behavior in which offspring are retained by the adult to at least the juvenile stage, in contrast with the more common release of eggs, embryos, or larvae. Brooding occurs in two primary modes, internal and external, in which offspring may be produced via sexual or asexual means. I categorize structures associated with external brooding in three types: pits, chambers, and grooves. Early inferences that external brooding has a primarily bipolar distribution continue to be supported with current data, but it is doubtful that small size and simultaneous hermaphroditism are correlated with brooding in sea anemones. Finally, I identify open questions about brooding in sea anemones and suggest future lines of research that will broaden our understanding of this phenomenon.
The externally brooding sea anemone Epiactis fecunda (Verrill, 1899) is redescribed as Urticina fecunda, comb. nov., onthe basis of preserved type material and anatomical and behavioural observations of recently collected animals. The sea-sonal timing of reproduction and aspects of the settlement and development of brooded offspring are reported. Preciselocality data extend the bathymetric range to waters as shallow as 10 m, and the geographical range east to the AvalonPeninsula (Newfoundland, Canada). We differentiate it from other known northern, externally brooding species of seaanemone. Morphological characters, including verrucae, decamerous mesenterial arrangement, and non-overlapping sizesof basitrichs in tentacles and actinopharynx, agree with a generic diagnosis of Urticina Ehrenberg, 1834 rather than Epiactis Verrill, 1869.
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.
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