Brisinga panopla Fisher 1906

Mah, Christopher L., 2022, New Genera, Species and Occurrences of Deep-Sea Asteroidea (Valvatacea, Forcipulatacea, Echinodermata) collected from the North Pacific Ocean by the CAPSTONE Expedition, Zootaxa 5164 (1), pp. 1-75 : 12-15

Brisinga panopla Fisher 1906

FIGURE 3A–H

Brisinga Fisher 1906: 1109 ; Koehler 1909: 117

Craterobrisinga Fisher 1919: 513, 1928: 8

Diagnosis. Arms elongate 15 (14 in holotype). Approximately 25 spinelet-covered costae or ribs present on each arm. Syzygy (nonmuscular symphysis) present among proximal adambulacral plates. Oral plates with 3 spines, each with strongly developed vermiculiform sacculus.

Comments. The species was identified based on the presence of a nonvascular symphysis as well as the absence of papulae, the skeletal costae or ribs as well as the 3 oral spines each bearing well-developed vermiform sacculae.

USNM 1424229 was inadvertently collected with a rock sample and not accompanied by an in situ image. It was recovered damaged with all but three partial arms and one partially grown arm still attached to the disk. This represents a range extension for this species, which was previously known only from the Hawaiian Islands region.

The function of club-shaped spines in Brisingenes margoae has been described as serving as an anchor or aiding movement as the asteroid extends its arms into the water column for suspension feeding. Although this spine morphology was described for other taxa in Mah (2016b), it is noteworthy that these spines were observed in the Brisinga panopla specimen herein with black coloration along the tips matching the dark coloration of the rock substrate from which the specimen was collected, further corroborating their proposed function.

Oral Spine Sheaths: Function & Significance. Examination of this specimen inspired examination of the “vermiform sacculus” which extend from the oral spines of this species appearing almost tentacular. These are tissue sheaths which extend well beyond the length of the oral spine, easily the length of the spine itself and which are inundated with pedicellariae ( Fig. 3H ). Although all brisingids possesses a sheath inundated with pedicellariae it is unusual to observe such an unusual expression of this character. It is beyond the scope of this treatment to seek out the presence of this specific character throughout all species within the Brisingida , however, a survey of other genera indicated absence from Novodinia , Brisingaster , Odinella , Brisingenes , Hymenodiscus (formerly Brisingella ), Freyastera and Freyella . Of the other Brisinga spp. described by Fisher (1906), the holotype of Brisinga alberti also shows this character, although all the oral spination in this another specimens were heavily damaged by trawl collection. If, however, this character is correctly interpreted, it would suggest that Brisinga alberti either demonstrates close affinity if not outright synonymy with Brisinga panopla .

The pedicellariae, location, and tentacular nature of these extensions from the oral spines ( Fig. 3H ) suggest they play a role in the feeding process. Food and prey captured by brisingid lateral spines include various pelagic crustaceans ( Emson & Young 1994) which are captured by pedicellariae on the lateral spine arrays and conveyed via tube feet along the arms to the mouth. This would imply that these extension somehow assist in further conveyance of prey to the mouth. The abundance of these structures around the oral region might alternatively indicate a specialized adaptation for feeding or protection from small organisms, such as crustaceans.

Description. Disk round with oral ring forming distinct edge. Arms 15, 14 fully formed arms with one shortened, regrowing with arm tip present ( Fig. 3D ) on the single available specimen.

Disk uniformly covered by short, uniform spinelets, each about 1–2.0 mm in length. This spinelet covered skin extending to proximal region on arm. Papulae absent. Madreporite irregularly round, raised above disk surface. Arm proximally covered by spinelets, then with approximately 25 spinelet covered costae interrupted by smooth skin with bands of pedicellariae present between them ( Fig. 3A–B ). Lateral spines emerge off arm directly where costae present along arm ( Fig. 3B ). Spines elongate with sheath invested with dense numbers of pedicellariae.

Proximal adambulacral plates forming basal syzygy (aka adoral carina) ( Fig. 3G ). Adambulacral plates short and vertebrae-like. Each plate with two lateral spines projecting at oblique angles with single furrow spine projecting downward. Proximal furrow spines with club-shaped tip, round in cross section ( Fig. 3C ). Tip surface roughened.

Each oral plate with three spines, two projecting into mouth and one into the tube foot groove. One enlarged, elongate spine on oral plate surface projecting at oblique angle. Each spine covered with abundant pedicellariae, each about 0.75 mm in length. Oral spines covered with elongate, pedicellariae invested sheath (Fisher’s “vermiform sacculus”) that extends well beyond the length of the spine itself ( Fig. 3H ), all forming dense tentacular extensions around the mouth.

Pedicellariae of two types but both are three-piece with “forcipulate” type articulation ( Figs. 3E–F ). One with elongate, narrow neck showing relatively small tip displaying approximately six tooth-like projections ( Fig. 3E ). Second type with a thicker neck, valves with 13 to 15 teeth in approximately two rows flanked by enlarged teeth on corners with three to four teeth along lateral edge of valve ( Fig. 3F ).

Tube feet muscular, elongate, extended to adjacent lateral spine.

Occurrence: Hawaiian Islands (Kauai) region, Southwest of Wake Island, Arabian Sea, vicinity of Sri Lanka. 600– 1142 m.

Material Examined: USNM 1424229 Seamount, SW of Wake Island, 18.3285, 165.98, 1142 m. Coll. EX 1606, NOAA ship Okeanos Explorer with ROV Deep Discoverer. 1 wet spec. 15 arms. R =8.6 (broken arm remaining), r=1.4

FREYELLIDAE

Figures

FIGURE 3. Brisinga panopla Fisher, 1906 USNM 1424229. Scale bar=5.0 mm unless otherwise noted. A. Abactinal. B. Close up arm showing costae and lateral spines. C. Arm showing close-up of tube foot groove. Scale bar=1.0 mm. D. Actinal surface. E. Elongate pedicellariae. Scale bar=20 µm F. Squat pedicellariae with wider valve. Scale bar=20 µm G. Lateral view of broken disk showing basal syzygy (aka adoral carina) H. Close-up of oral region showing tentacular sheaths and proximal actinal spines.