Edwardsiella loveni ( Carlgren, 1892 )

Edwardsiella loveni ( Carlgren, 1892) View in CoL

Table 4 View Table 4 ; Figs. 6–8 View Fig View Fig View Fig .

Milneedwardsia loveni Carlgren, 1892: 456 View in CoL ; 1893: 17; 1921: 60.

Fagesia loveni View in CoL : Carlgren, 1940: 23.

MATERIAL EXAMINED. KBPGI 475 /1, Howe Sound , British Columbia, Canada, 49°27.036′N, 123°14.494′W, 20 m, protruding from crevices in bedrock vertical wall, 5 March 2016, 5 specimens, collector Alex English, in formalin GoogleMaps ; KBPGI 476 /2, same locality, 13 December 2015, 7 specimens, collectors Alex English and Douglas Swanston, in 90% ethanol GoogleMaps .

DESCRIPTION.Thespecimensareattached to bedrock in very narrow crevices and cracks and, according to collectors’ notes are extremely tiny, measuring only 5–7 mm tall. This, however, applies only to scapulus and a very distal part of the scapus while the remaining part of column is hidden in the crevices of bedrock and not visible from exterior ( Fig. 6B, C View Fig ). All collected specimens lack proximal parts of their bodies so the specimens were probably deeply inserted in the crevices and since the scapulus on preserved specimens constitutes only a small fraction of the body length the specimens actually should be significantly longer ( Fig. 6A View Fig ). The column of living specimens is approximately 1.5 mm in diameter. The diameter of tentacular crown is up to 10 mm. The largest preserved specimen is 14 mm long (without proximal part of column), diameter of its column varies from 1 mm distally to 4 mm in most proximal part. The scapulus on preserved specimens is 0.7–2 mm in length. The scapus is covered by grayish-brown cuticle. The surface of the cuticle is clean, without attached sand grains and other foreign matter. The scapulus and the tentacles are not retracted and visible in all preserved specimens, although live the specimens are capable of retracting their tentacles completely (as seen in the specimen on top left corner of the Fig. 6C View Fig ). The scapulus is naked, slightly and gradually tapering to the distal end. It has eight prominent longitudinal ridges which are present on the scapus too (at least on its distal part). Very short thin walled capitulum is discernible between the bases of the tentacles and the scapulus. The tentacles are slender, very gradually tapering to pointed tips, all of about the same length, up to 5 mm in living specimens. The number of the tentacles, as counted on underwater photographs in full-size specimens, varies from 22 to 42; one small specimen had 12 tentacles. The arrangement of the tentacles appears to be hexamerous, in up to four cycles. The oral disk is very small with prominent oral cone.

The overall colour of the distal part of the anemone, including the scapulus, tentacles and oral disc, is translucent beige or pale orange. Orange tint is darker on the actinopharynx visible though the translucent wall of the scapulus and the oral disc. Longitudinal whitish lines on the scapulus run along the crest of each scapular ridge.

Eight longitudinal columnar ridges are formed by thickened mesogloea (up to 90 µm) and ectoderm (up to 70 µm on the crests of the ridges) between the insertions of macrocnemes. Between the ridges both mesogloea and ectoderm are thinner (10 and 20 µm respectively). Columnar endoderm is thin (10–15 µm) and of the same thickness beneath and between the ridges ( Fig. 7A, C View Fig ). Column has no nemathybomes and tenacules. The cuticle is thin and not stratified, covered by thin mucus-like layer, closely bearing against the ectoderm and fastened by numerous thin evenly distributed mesogloeal strands. Radial muscles of the oral disc and longitudinal muscles of the tentacles are ectodermal ( Fig. 7 D View Fig ). Actinopharynx has no discernible siphonoglyphs and has eight internal longitudinal ridges, formed by thickened ectoderm, corresponding to eight macrocnemes ( Fig. 7 E View Fig ). Mesogloea of the actinopharynx is thin. Eight macrocnemes, arranged as in Edwardsia , are present along the whole length of the body and small microcnemes in the capitulum only ( Fig. 7B View Fig ), at the bases of the tentacles. Microcnemes of the first cycle (four microcnemes paired with lateral macrocnemes) in most distal part are attached to actinopharynx.

Retractor muscles are large, restricted, with large pennon, with about 20–30 muscle processes, some of which are branched. On transverse sections retractors are situated close to actinopharynx and attached to the body wall by long thin mesenterial lamella ( Fig. 7A View Fig ). Parietal muscles are well developed. On transverse sections of the scapulus they are circumscribed and form either a fan or a pennon on each side of the mesentery ( Fig. 7A View Fig ) but in the scapus they may be more diffuse, triangular or oval in outline ( Fig. 7F View Fig ).

Cnidom includes robust and gracile spirocysts, heterotrichs, basitrichs, p-mastigophores A ( Table 4 View Table 4 , Fig. 8 View Fig , cnidae of the scapus, scapulus and tentacles were studied in three specimens, those of the actinopharynx in two specimens, those of the filaments and endoderm in one specimen). Basitrichs on the scapulus are concentrated along the crests of the scapular ridges forming a kind of nematocyst battery ( Fig. 7C View Fig ). Large thick basitrichs of the column and tentacles are often somewhat curved. We identify the capsule from the tentacles depicted on Fig. 8F View Fig as heterotrich since basal part of the tubule in unfired capsule looks like a stick (5–8 µm long) that suggests that either basal part of the tubule is larger in diameter than the rest of the tubule, or it has longer barbs. This capsule probably has no apical flap and is not stained by basal dyes as basitrichs.

HABITAT. All recorded specimens were attached to bedrock in narrow crevices, not covered by sand at a depth of about 20 m.

REMARKS. The genus Edwardsiella comprises four valid species, none of which was known previously from the North Pacific.

Edwardsiella loveni View in CoL was known previously from original and subsequent descriptions by Carlgren (1892, 1893, 1921) based on several lots of specimens dredged from depths of 90 to 640 m in waters around Sweden and Norway. Unlike many members of Edwardsiidae View in CoL the specimens do not live buried in sediment but are anchored in crevices of solid objects such as dead calyces of Lophelia View in CoL , dead Paragorgia View in CoL or other octocorals ( Carlgren, 1921). Despite the large geographic distance between our specimens from British Columbia and previously known locations, all features of our specimens correspond well to detailed descriptions provided by Carlgren (1892, 1893, 1921) and we identify them as E. loveni View in CoL . That constitutes the first record of the species and genus in the North Pacific. Most probably E. loveni View in CoL , and other Edwardsiella species, have much wider distribution than might be inferred from existing records, but the specimens inhabiting crevices in bedrock cannot be caught by trawls or dredges.