Diadumene leucolena Verrill, 1866

Gusmão, Luciana C., Grajales, Alejandro & Rodríguez, Estefania, 2018, Sea Anemones through X-rays: Visualization of Two Species of Diadumene (Cnidaria, Actiniaria) Using Micro-CT, American Museum Novitates 2018 (3907), pp. 1-47 : 7-13

Diadumene leucolena Verrill, 1866

Figures 1 –5, table 1

Sagartia leucolena Verrill, 1866: 336 ; 1868: 261–262; 1872: 436.

Cylista leucolena Andres, 1884: 157–158 .

Sagartia (Thöe) leucolena Verrill, 1898: 495 .

Diadumene leucolena Carlgren, 1950: 23–24 ; Hand, 1956: 223–230; Hand, 1957: 413.

MATERIAL: BRAZIL, Pará, Salinópolis, Praia do Farol Velho , 0°35′33′′S 47°19′29′′W , collected July 4, 2012, by L. Gusmão (0 m). MZUSP 002481 (10 specimens) . Material examined for comparison. Diadumene leucolena (syntype) YPM 665 (8 specimens); Locality: New Haven Light, Long Island Sound , Connecticut (41.30 N 72.93W) .

DIAGNOSIS: Individuals with conspicuous cinclides on raised columnar projections arranged in longitudinal rows on scapus. Fighting tentacles may be present. No anatomical irregularity due to asexual reproduction; 24 pairs of mesenteries in three cycles of mesenteries at midcolumn; third cycle never with distinct retractor or filaments. No p -mastigophores A on actinopharynx; acontia with one or two categories of p -mastigophores B2a (25.2–34.4 × 5.7–9.1 µm; 30.5–47.0 × 4.9–10.1µm).

EXTERNAL ANATOMY (fig. 2): Live and preserved specimens up to 6.0 mm in length (fig. 2A–C). Most preserved specimens with oral disc relaxed exhibiting visible tentacles (fig. 2C). Pedal disc adherent, flat, circular, diameter 2.0–4.0 mm in preserved specimens (fig. 2C). Column cylindrical, smooth, divided into scapus and capitulum separated by a collar (fig. 2C). Capitulum usually retracted into scapus, not easily visible in live (fig. 2A) or preserved specimens (fig. 2C); margin of capitulum tentaculate. Scapus with conspicuous cinclides positioned on top columnar projections through which acontia protrude (fig. 2A; arrows); cinclides arranged in 12 longitudinal rows with 3–6 cinclides per row distributed on proximal to distal scapus (fig. 2C; arrows). Column beige becoming light brown distally in live specimens, with mesenterial insertions visible as faint white lines on column from limbus to distal scapus (fig. 2A, C). Column diameter 3.0–4.0 mm and length 4.0–6.0 mm in preserved specimens. Oral disc circular, small, approximately as wide as column, with large brown central mouth in live (fig. 2A, B) and preserved specimens. Oral disc yellow or brown with green markings at base of tentacles; diameter 2.0– 4.5 mm in preserved specimens (fig. 2A, B). Tentacles 91–95, smooth, long, slender and pointed, arranged in four cycles (6+6+12+24+ n) in outer half of oral disc in both live and preserved specimens (fig. 2A–C). Tentacles of first and second cycles brown or green with white markings along entire oral side (fig. 2A, B); tentacles of outer cycles white or translucent with no markings in live specimens (fig. 2A, B). All tentacles translucent white in preserved specimens (fig. 2C). Inner tentacles longer than outer ones in both live (fig. 2A, B) and preserved specimens (fig. 2C); longest tentacle up to 3 mm in live and preserved specimens. Fighting tentacles not visibly differentiated.

INTERNAL ANATOMY, HISTOLOGY (figs. 3, 4): Body elongate in preserved specimens (fig. 4A) with wall thickness varying along column: all three body layers thicker in scapus than in capitulum; limit between scapus and capitulum gradual (fig. 4B) with transition zone visible in histological sections (fig. 3A). Cinclides positioned on top of raised projections with thick mesoglea (figs. 3E, 4C). Cinclides distributed in endocoels corresponding to first and second pairs of mesenteries (fig. 4C – E). Longitudinal endodermal musculature of column strong (fig. 3A). Actinopharynx up to 3.5 mm in length in largest specimen, approximately half of column’s length (fig. 4B), longitudinally sulcated with 12 visible folds in distal part but more heavily folded proximally (fig. 4G); with thick and highly glandular epidermis (fig. 3B). Specimens with two differentiated siphonoglyphs (fig. 4G) exhibiting very thin gastrodermis and mesoglea but glandular epidermis as in actinopharynx (fig. 3C). Longitudinal musculature of tentacles ectodermal (fig. 3D).

Mesenteries hexamerously arranged in three cycles (6+6+12 = 24 pairs) spanning most of body length: first cycle perfect, including two pairs of directives, each associated with one siphonoglyph; second and third cycles imperfect (figs. 3E–F, 4G, H). Mesenteries of each second cycle pair unequally developed in specimens examined (figs. 3G, 4K). More mesenteries distally than proximally; mesenteries of third cycle may be absent proximally close to limbus (fig. 4I). Mesenteries of first and second cycles, including directives, fertile and with filaments; those of third cycle sterile and without filaments (fig. 3I). Species gonochoric: major axis of number of capsules measured; F, frequency; +++, very common; ++, common; +, rather common; -, rare oocytes 13.6–48.0 µm in diameter; major axis of spermatic cysts 41.8–110.1 µm in diameter in specimens collected in July. Retractors of first and second cycles strong, most diffuse but some restricted (figs. 3E, F, 4G, H, J); those of third cycle very weak (figs. 3E–F, I, 4G, H, L). Parietobasilar musculature very weak in all mesenteries, with no free mesogleal flap (fig. 3H); not visible in micro-CT images (fig. 4K). Basilar musculature very weak (fig. 4L).

CNIDOM: Spirocysts, basitrichs, p -mastigophores B1, p -mastigophores B2a, and holotrichs. Acontia contain two types of nematocysts: basitrichs and p -mastigophores B2a. See figure 5 and table 1 for size and distribution.

DISTRIBUTION AND NATURAL HISTORY: Diadumene leucolena is known from San Francisco Bay, California ( Hand, 1956) on the West Coast of the United States and from Woods Hole, Massachusetts, to Beaufort, North Carolina (see Verrill et al., 1873; McMurrich, 1887; Verrill,

FIG. 5. Cnidom of Diadumene leucolena ( Verrill, 1866) . A, B, F, J, R, basitrich. C, G, K, L, M, P, Q, S, T, p – mastigophore B2a. D, H, I, holotrich. E, spirocyst. N, O, p –mastigophore B1.

1898; Hand, 1956), on the East Coast of the United States. In Brazil, D. leucolena was collected in Praia do Farol Velho (Salinópolis, Pará) and observed but collected for molecular study only in Praia do Atalaia (Salinópolis, Pará). This species can be abundant locally and is found attached to the underside of rocks or in crevices in the lower intertidal.

Figures

FIG. 1. Detail of collection sites for Diadumene leucolena (Verrill, 1866) (star) and type locality for Diadumene manezinha, sp. nov. (hexagon).