Abstract
Abstract Species boundaries delineating tropical sea anemones (Cnidaria, Actiniaria) of the zooxanthellate genus, Heteranthus Klunzinger, 1877, are unclear. There are currently two valid Heteranthus species: type species Heteranthus verruculatus Klunzinger, 1877, first reported from Koseir, Egypt, and H. insignis Carlgren, 1943, from Poulo Condore, Vietnam. In describing the latter from a single, poorly preserved specimen, zoologist Oskar Carlgren expressed apprehension with traits he had used to establish this species. Carlgren’s doubts persisted later in writing when he found a similar-looking sea anemone from the Great Barrier Reef. Crucial details to positively identify either species have since remained limited. Here, we re-diagnosed Heteranthus and re-described its type species based on observations of specimens we have obtained from Singapore and Pulau Ambon (Indonesia), and of museum material collected elsewhere across the Indo-West Pacific region (n > 180). Supported by molecular phylogenetic evidence, the family Heteranthidae Carlgren, 1900 was reinstated and re-diagnosed. Heteranthus verruculatus is encountered in the lower intertidal region amongst seagrass, in rocky crevices, or coral rubble. It occurs as solitary individuals or in clonal clusters, well-camouflaged against the substratum. Individuals were observed to frequently propagate by longitudinal fission, resulting in a varied appearance. Type material of H. verruculatus and H. insignis were re-examined and as we found no differences between them, the two were synonymised. We inferred that Carlgren probably misinterpreted cnidae and histological data in defining H. insignis as a distinct species. This revision clarifies the taxonomy and geographic range of H. verruculatus, an Indo-West Pacific species that is found from the Red Sea to subtropical Australia and Hawaii.
Highlights
As prolific as Swedish zoologist Oskar Carlgren was in describing hundreds of sea anemones (Cnidaria, Actiniaria) during his lifetime, uncertainties pervaded him as he struggled to distinguish between two species of the zooxanthellate genus Heteranthus Klunzinger, 1877
When Carlgren (1943: 32) first described H. insignis from a single, poorly preserved specimen collected from Puolo Condore [= Côn Sơn Island, Vung Tau] Vietnam, he stated, “I have with some hesitation referred the specimen to a new species, not to verriculatus [sic; = H. verruculatus].”
Later, when he applied the name H. verruculatus to a specimen obtained from the Great Barrier Reef, his doubts further the sea anemone heteranthus verruculatus lingered as he admitted (Carlgren, 1950: 440), “I have referred the single specimen with some hesitation to verruculatus ...”
Summary
As prolific as Swedish zoologist Oskar Carlgren was in describing hundreds of sea anemones (Cnidaria, Actiniaria) during his lifetime, uncertainties pervaded him as he struggled to distinguish between two species of the zooxanthellate genus Heteranthus Klunzinger, 1877 This genus comprises two valid species: Heteranthus verruculatus Klunzinger, 1877 and H. insignis Carlgren, 1943, the former being the type species of Heteranthus by monotypy (Daly & Fautin, 2020). When Carlgren (1943: 32) first described H. insignis from a single, poorly preserved specimen collected from Puolo Condore [= Côn Sơn Island, Vung Tau] Vietnam, he stated, “I have with some hesitation referred the specimen to a new species, not to verriculatus [sic; = H. verruculatus].” Later, when he applied the name H. verruculatus to a specimen obtained from the Great Barrier Reef, his doubts further the sea anemone heteranthus verruculatus lingered as he admitted (Carlgren, 1950: 440), “I have referred the single specimen with some hesitation to verruculatus ...”. Carlgren was doubtful of traits he had used to define species of Heteranthus, in particular, its type species H. verruculatus
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