Cryptodendrum adhaesivum ( Klunzinger, 1877 )

Titus, Benjamin M., Bennett-Smith, Morgan F., Chiodo, Tommaso & Rodríguez, Estefanía, 2024, The clownfish-hosting sea anemones (Anthozoa: Actiniaria): updated nomenclature, biogeography, and practical field guide., Zootaxa 5506 (1), pp. 1-34 : 30

Cryptodendrum adhaesivum ( Klunzinger, 1877) ( Figure 20 ; Figure S10 )

Among the most spectacularly colored and morphologically distinct host anemones, Cryptodendrum adhaesivum is hard to misidentify in the field and the only host anemone within the family Thalassianthidae ( Figure 20 ; Figure S10 ). Commonly referred to as the “pizza anemone” or “adhesive anemone” C. adhaesivum bears multiple tentacle types that are highly adhesive ( Figure 20B ). The outer marginal tentacles are densely packed and bulbous, and contrast strongly with the inner tentacles which are slender and may branch into five or more projections, giving the anemone an appearance that resembles a pizza with a thick crust ( Figure 20 ; Figure S10 ). Marginal and inner tentacles may be uniformly colored or highly contrasting in color. Immediately adjacent to the bulbous marginal tentacles are a row of branched nematospheres (spherical modified tentacles co-located with exocoelic tentacles at the oral disc margin; Figure 20B ) that attach directly to the oral disc and give the anemone a frilly appearance when exposed. Verrucae are present, non-adhesive, and form longitudinal rows on upper column. Verrucae color is variable and can range from red, purple, or orange that may contrast highly with the column. Oral disc is usually flat and round when expanded ( Figure 20A ), reaching up to 600 mm in diameter, but may also be wavy when wedged into crevices in the reef ( Figure 20C and D ).

Cryptodendrum adhaesivum has a broad geographic distribution and is known to occur from the Red Sea, continental Africa in the Western Indian Ocean, throughout the Coral Triangle, North to Japan, and as far east in the South Pacific as the Marquesas (but not making it to Hawaii; Figure 21 ). This species has a broad depth range and can be found in near-intertidal rocky reef habitats to depths of at least 25 m. On reefs, C. adhaesivum always attaches its pedal disc deep within hard stable substrate and is commonly found wedged in boulder fields. The column is never exposed. When disturbed, C. adhaesivum will retract rapidly into crevices and holes in the reef. This species has the most rapid contraction of any host anemone species and will completely disappear into the reef matrix.

This species is thought to sexually reproduce only and does not form aggregations of individuals on reefs. Although one of ten documented clownfish hosting anemones, it does not host fish in much of its range and has only ever been documented in association with Clark’s anemonefish Amphiprion clarki ( Figure S10 ). In the far western and eastern edges of its range, including the Red Sea, Western Indian Ocean, French Polynesia, and Marshall Islands, this species has never been documented hosting clownfishes.

Figures

FIGURE 10. Representative images of the magnificent sea anemone Radianthus magnifica encompassing a broad range of geographic and phenotypic variation. A) Wide-angle photograph of stereotypical R. magnifica perched prominently on exposed rocky outcrop with fully visible purple column and pedal disc (Maldives). B) Retracted individual with column curled into a ball leaving only a small tuft of tentacles visible (Kimbe Bay, Papua New Guinea). C) Macro photograph of tentacles. Note the blunt-rounded ends that are all alike and the small “dot” present in the center of the tentacle tip (Fares-Maathodaa, Maldives). D) Cluster of at least four anemones on rocky outcrop (Saudi Arabia, Red Sea). E) Large solitary individual with pink tentacle tips. Note that the oral disc is fully expanded over the substrate obscuring the column and pedal disc from view (Kimbe Bay, Papua New Guinea. Photographs by Morgan Bennett-Smith and Benjamin Titus.

FIGURE 20. Representative images of Cryptodendrum adhaesivum encompassing a broad range of geographic and phenotypic variation. A) Wide angle photograph capturing hard substrate microhabitat (Saudi Arabia, Red Sea). B) Macro photograph highlighting distinct tentacle types (i) bulbous outer tentacles, (ii) branched inner tentacles, and (iii) branched fringing nematospheres (Kwajalein Atoll, Marshall Islands). C) Green individual with all tentacles similar in color (Kwajalein Atoll, Marshall Islands). D) Individual with white peripheral tentacles (Saudi Arabia, Red Sea). E) Individual with purple peripheral tentacles (Kwajalein Atoll, Marshall Islands). Photographs by Morgan Bennett-Smith and Scott Johnson.

FIGURE 21. Confirmed geographic range of Cryptodendrim adhaesivum in the Indo-West Pacific. Red dots represent species observations from the Global Biodiversity Information Facility (GBIF). Blue shaded area represents shallow water habitat (60 m bathymetry).