Stephanauge prima sp. nov.

urn:lsid:zoobank.org:act: 88789488-9677-45D4-A0E9-007C3FF79A3A

(Figs. 2, 3; Tables 1, 2)

MATERIAL EXAMINED. Holotype: MNRJ 9080 (one specimen), South Atlantic Ocean, Potiguar Basin, Rio Grande do Norte, Brazil, station MT83 (04° 28' 21'' S, 36° 24' 45'' W), May 4, 2011, 1950 m. Paratypes: MNRJ 9078 (one specimen), South Atlantic Ocean, Potiguar Basin, Rio Grande do Norte, Brazil, station MT83-2 (04° 27' 01'' S, 36° 25' 36'' W), May 21, 2011, 2123 m. MNRJ 9091 (one specimen), South Atlantic Ocean, Potiguar Basin, Rio Grande do Norte, Brazil, station MT84 (04° 25' 49'' S, 36° 37' 22'' W), May 6, 2011, 1964 m. MOUFPE-CNI 875 (one specimen), South Atlantic Ocean, Potiguar Basin, Rio Grande do Norte, Brazil, station MT84 (04° 25' 49'' S, 36° 37' 22'' W), May 6, 2011, 1964 m. LC 153 (one specimen attached on Diacria sp.), South Atlantic Ocean, Potiguar Basin, Rio Grande do Norte, Brazil, station MT85 (04° 21' 21'' S, 36° 44' 16'' W), May 6, 2011, 2057 m.

DIAGNOSIS

Body short, cylindrical, with wide, grasping base. Tubercles in 24 longitudinal rows at distal scapus. Tentacles 96, in four cycles. Number of tentacles is the same as number of mesenteries at base. Mesenteries of first three cycles perfect, except the directives. Acontia mostly inconspicuous, may be absent in some individuals.

DESCRIPTION

EXTERNAL MORPHOLOGY. In preservation, body cylindrical, short, 90-150 mm in height (100 mm in holotype) and 80-250 mm in diameter (250 mm in holotype). Color pale orange to pale pink/purple in preserved specimens. Base wide, variable in shape: circular in outline or more oval when grasping shells or rocks (Fig. 2A). Column divisible into scapus and scapulus. Mesoglea thick (Fig. 2B). Distal portion of scapus with distinct tubercles arranged in 24 longitudinal rows, 3 or 4 per row. Longitudinal ridges between each tubercule row, 12 in total (Fig. 2C). Proximal part with weak remains of brownish cuticle, soft depressions and reduced tubercules. All tubercules dome-shaped, varying only in size with smaller tubercles proximally. Scapulus concealed by retraction of oral disc. Two cinclides distally, on opposite sides of column, on mesogleal papillae above directive endocoels (Fig. 2C). Oral disc with central oval mouth, two visible siphonoglyphs (Fig. 2B). Tentacles smooth, short and filiform, some with thickening at base (Fig. 2F), 96 in total and arranged in 4-5 cycles (Fig. 2H).

INTERNAL ANATOMY. Two siphonoglyphs, each attached to a directive pair of mesenteries. Sphincter mesogleal, strong, alveolar, nearer endoderm than ectoderm, occupying most of mesoglea proximal to oral disc (Fig. 2E). Longitudinal muscles of tentacles ectodermal. Mesenteries slender, visible as rows through column. On holotype, four cycles of mesenteries hexamerously arranged 6+6+12+24, total of 48 pairs (Fig. 2D) near base; and 48 mesenteries near mouth (Fig. 2H). First cycle perfect. Mesenterial arrangement constant among examined individuals. All cycles well-developed with exception of last cycle (Fig. 2I), with mesenteries shorter, barely breaking through the mesoglea, and some with tiny mesenterial filaments. Mesenterial filaments more developed on older mesenteries. Retractors diffuse, often weak, stronger near the mesenterial base (Fig. 2G). Parietobasilar muscles poorly developed. Gametogenic tissue present in the first three cycles of mesenteries except directives. Acontia inconspicuous and poorly developed.

CNIDOM. Spirocysts, basitrichs, and microbasic p -mastigophores B1 (Fig. 3, Table 2).

TYPE LOCALITY. Potiguar Basin, Rio Grande do Norte, Brazil.

BIOLOGICAL CHARACTERISTICS. Sediment found on the stations ranged from rocks to mud. Paratype LC 153 attached to snails of the genus Diacria . Some of the paratypes were attached to rocks, with small fragments of rocks and broken shells attached to the pedal disc.

ETYMOLOGY. From latin “prima ” = the first, so named because this is the first species of the genus recorded on the South Atlantic and in the XXI century.

REMARKS/COMPARISON. Of the 11 valid species within the genus Stephanauge, seven are reported in the Atlantic Ocean (Table 1). Stephanauge prima sp. nov. possesses a unique set of characters that differentiates it from its counterparts in this region. Stephanauge prima sp. nov. primarily differs from S. nexilis and S. abyssicola in possessing more tentacles and mesenteries and bearing no gametogenic tissue on the younger cycle of mesenteries (only mesenteries of first cycle are fertile in S. nexilis; only mesenteries of first cycle are sterile in S. abyssicola). Stephanauge inornata, and S. spongicola also have fewer tentacles (60 in S. inornata vs. maximum of 80 in S. spongicola vs. 96 in S. prima sp. nov.) and neither has tubercles on the distal part of the column. Stephanauge prima sp. nov. can be distinguished from S. annularis, because the latter has a smooth column and all cycles of mesenteries fertile, except the directive ones (vs. a tuberculated column and the directives and fourth cycle of mesenteries sterile in S. prima sp. nov.). Stephanauge impedita has similar morphological features to S. prima sp. nov., but has fewer cycles of tentacles (3 vs. 4 in S. prima sp. nov.) and longer tentacles in the outer vs inner cycle, and lacks acontia. The remaining species, S. acanellae, found on Acanella sp. branches, has more numerous tentacles (140 vs. 96 in S. prima sp. nov.) and cycles of mesenteries (5 vs. 4 in S. prima sp. nov.), and has no tubercles on the column and no trace of acontia.