Thursday, February 8, 2018

[Invertebrate • 2018] Astrophiura caroleae • A New Species of the Remarkable Brittle Star Genus Astrophiura (Echinodermata: Ophiuroidea) from the western Atlantic Ocean

Astrophiura caroleae  Pawson, 2018


Astrophiura caroleae, new species, is described from off Curacao in the southern Caribbean, and from the western Gulf of Mexico, in depths of 244 to 434 meters. This new species, the first in the genus Astrophiura to be described from the Atlantic Ocean, has a distinctive combination of characters, including regularly arranged primary plates, large radial shields whose radial edges are in contact for their entire visible length, and prominent tubercles on central and radial plates. The mottled reddish coloration of the dorsal surface of this species usually contrasts with the color of the substratum, rendering it readily visible in situ, despite its disc diameter of less than 10 mm. Like its congeners, A. caroleae is gonochoric, the gonads of females containing conspicuous masses of bright orange eggs that are approximately 165 µm in diameter. DNA Barcoding data are provided for this new species, these are the first for Astrophiura.

Keywords: Echinodermata, Ophiuroidea

Class Ophiuroidea
Superorder Euryophiurida O’Hara et al., 2017

Order Ophiurida sensu O’Hara et al., 2017
Family Astrophiuridae Sladen, 1879

Diagnosis. Ophiurids in which enlarged proximal lateral arm plates form the margin of the disc. (Partly after O’Hara, 2017).

Remarks. The paedomorphic (Stöhr and Martynov, 2016) ophiuroid genus Astrophiura has long been placed in the family Ophiuridae. Hugall et al. (2015) noted that Astrophiura is related to Ophiomisidium and Ophiophycis. Then O’Hara et al. (2017) followed the recommendation of Vadon (1990) and formally resurrected the family Astrophiuridae, noting in their Table 4 (p. 422) that the family contains 22 species (presumably Ophiomisidium with eight species; Ophiophycis, seven species; and Astrophiura, approximately seven species; data derived from the World Ophiuroidea Database—Stöhr et al. 2017).

Astrophiura caroleae new species; holotype (USNM 1463102) disc diameter 8.5 mm, recently dead, photographed in laboratory, Note conspicuous female gonads and free arms.

Image: Darryl Felder

Astrophiura caroleae new species

FIGURE 1. A, holotype (USNM 1463102), disc diameter 8.5 mm, in dorsal view (image by A. Nonaka); B, holotype, ventral view (image by A. Nonaka); C, holotype with major dorsal plates labeled; D, paratype 1 (USNM 1463103), disc diameter 7.0 mm, dorsal view; E, detail of holotype showing a pair of radial shields; F, holotype, showing adoral plates, oral plates with oral papillae, and thin plates covering oral interradii.
Abbreviations: AP, adoral plate; B, basal plate; C, central plate; DAP, dorsal arm plate; IB, infrabasal plate; IR, interradial plate; LAP, lateral arm plate; OIP, oral interradial plates; OP, oral plate; R radial plate; RS radial shield. 

FIGURE 2. A, holotype (USNM 1463102) disc diameter 8.5 mm, recently dead, photographed in laboratory (Image: Darryl Felder), Note conspicuous female gonads and free arms. B, holotype in situ on discarded beer bottle; C enlarged image of holotype in situ; D, non-type specimen, in laboratory, disc diameter ca. 8.0 mm, showing color pattern.

Astrophiura caroleae new species

Diagnosis. Astrophiura with disc regularly pentagonal, up to 10 mm in diameter, interradial margins convex. Free portions of arms slightly shorter than disc diameter. In dorsal disc, elongated diamond-shaped radial areas higher than interradial areas. Conspicuous ossicles in dorsal disc include central plate, infrabasals, basals, and radials, three or four interradial plates, the distalmost approximately triangular with a sharp distal point, and large radial shields, pairs of which are contiguous for their entire length. Most plates smooth, but central and radial plates have a single prominent central tubercle, and each radial shield has a more or less conspicuous prominence near the distal edge. Proximal dorsal arm plates on the disc are quadrangular, wider than long. Six or seven oral papillae on each jaw. Adoral plates elongate, visible portions at least 6 times as long as wide, the proximal ends of each pair abutting more or less in line with the apex of each jaw. Color in life variegated brownish to reddish with whitish patches, the tubercles on dorsal plates usually lighter in color than surrounding areas.

 Etymology. It is a pleasure to name this species for Dr. Carole Baldwin, Chair of the Vertebrate Zoology Department, National Museum of Natural History, Smithsonian Institution. Dr. Baldwin founded the Smithsonian’s Deep Reef Observation Project (DROP) in 2011 and she has inspired its steady growth in addition to conducting her own excellent research on fishes.

Preferred Habitats: It is well-known that Astrophiura prefers a hard substratum; individuals can be found attached to dead mollusk shells (Fujita and Hendler, 2001), and rocks (Ziesenhenne, 1951; Matsumoto, 1917). A. caroleae was first observed attached to a discarded Heineken beer bottle, where its reddish coloration contrasted sharply with the green of the bottle. Other specimens were collected from miscellaneous bottles near the type locality

Distribution: This species is known from off Curacao in the southern Caribbean, and also from off Quintana Roo, Mexico, in depths of 244 to 434 meters.

David L. Pawson. 2018. A New Species of the Remarkable Brittle Star genus Astrophiura (Echinodermata: Ophiuroidea) from the western Atlantic Ocean. Zootaxa. 4378(2); 257–264. DOI: 10.11646/zootaxa.4378.2.4