Amphipholis januarii Ljungman 1866

Amphipholis januarii Ljungman, 1866

(Fig. 14)

Type locality. Rio de Janeiro, Brazil.

Maximum size. dd up to 6 mm (Paim et al. 2015).

Material examined. 20 specimens (dd: 2.4–5.5 mm) from subtidal: ZUEC OPH 2197, St. VII, 1 spm; ZUEC OPH 2210, St. 71, 1 spm; ZUEC OPH 2245, St. XIX, 1 spm; ZUEC OPH 2249, St. XIX, 1 spm; ZUEC OPH 2268, St. 145, 3 spms; ZUEC OPH 2272, St. XXVI, 6 spms; ZUEC OPH 2327, St. 9H, 2 spms; ZUEC OPH 2340, St. 20H, 2 spms; ZUEC OPH 2352, St. XXXIV, 3 spms.

Description. Disc: (dd: 4.4 mm) pentagonal, covered by irregular and imbricated small scales, approximately 20 between the centrodorsal and the edge of the disc. Radial shields narrow and twice as long as wide, separated proximally by one or two scales (Fig. 14A). Ventral interradius covered by scales similar to the dorsal surface, but more imbricated. Bursal slits narrow and long (Fig. 14B). Oral shields as long as wide, proximal half constricted or much narrower and elongated, distal half much widened and the distal edge with a lobe. Madreporite larger and more whitish than other oral shields. Adoral shields broadened distally and widely separated proximally. Two lateral oral papillae, distal larger and widened. A pair of elongated infradental papillae, widely separated from each other, in almost lateral position (Fig. 14C).

Arms: dorsal arm plates broadly oval, three times as wide as long and contiguous (Fig. 14D,F). Ventral arm plates pentagonal, 1.5 times as wide as long, with pointed proximal angle and straight distal edge, barely contiguous (Fig. 14E,G). Two tentacle scales, the larger inserted on the ventral arm plate and the smaller on the lateral arm plate. Four elongated and blunt arm spines, reduced to three at the end of the arms. In segments with four spines, the second ventral-most hatchet-shaped and smaller thorny denticles at all edges. At segments with three spines, middle one hatchet-shaped (Fig. 14D).

Lateral arm plates (Fig. 14H,I): general outline: ventral portion projecting ventro-proximalwards; ventro-distal tip not projecting ventralwards. Outer surface ornamentation: trabecular intersections protruding to form knobs approximately the same size than stereom pores. Outer proximal edge: surface lined by discernible band of different stereom structure, restricted to central part; without spurs; central part not protruding; surface without horizontal striation. Spine articulation: on same level as remaining outer surface, middle spine articulations larger; distance between spine articulations equidistant. Lobes simply separated, dorsal lobe clearly larger than the ventral lobe; lobes parallel, bent, and oriented nearly horizontal; stereom massive sigmoidal fold absent. Inner side, ridges and knobs: dominated by two separate central knobs; without additional dorsal structure on inner side; single large perforation on inner side.

Vertebrae: zygospondylous of universal type and non-keeled. Proximal side of vertebrae dorsally without large groove on the dorsal-distal muscular fossae (Fig. 14J). Zygocondyles dorsalwards converging and zygosphene fused with pair of zygocondyles (Fig. 14K). Dorso-distal muscular fossae transformed distalwards projecting but far from distal edge of zygocondyles (Fig. 14L). Zygosphene projecting beyond ventral edge of zygocondyles with projecting part longer than zygocondyles (Fig. 14M).

Taxonomic comments. Adoral shields may be joined or separated proximally, depending on the size of the specimen, making this a variable morphological characteristic (Borges 2006). Only two of the analyzed specimens had the adoral shields united proximally. Approximately 80% of the specimens examined were without the dorsal part of the disc.

Remarks. As A. januarii is common in shallow waters and easily recognizable, it can be used as a tool in monitoring coastal benthic communities (Barboza et al. 2015a). It is found in coral reefs, seagrass, bryozoans, muddy, rocky and sandy bottoms (Tommasi 1970; Hendler et al. 1995; Gondim et al. 2013a; Paim et al. 2015). A. januarii was collected from sand (medium sand) and rubble bottom with a dredge (70% of spms) and van Veen grab.

Distribution. Temperate Northern Atlantic (realm), Warm Temperate Northwest Atlantic (province): Carolinian and Northern Gulf of Mexico (Hendler et al. 1995). Tropical Atlantic (realm), Tropical Northwestern Atlantic (province): Southern Gulf of Mexico to Eastern Caribbean (Pomory 2007; Alvarado et al. 2008; Miloslavich et al. 2010); Tropical Southwestern Atlantic (province): Northeastern and Eastern Brazil (Lima-Verde 1969; Avila-Pires 1983; Alves & Cerqueira 2000; Magalhães et al. 2005; Gondim et al. 2008; Oliveira et al. 2010; Lima et al. 2011; Gondim et al. 2013a; Gondim et al. 2013b; Paim et al. 2015). Temperate South America (realm), Warm Temperate Southwestern Atlantic (province): Southeastern Brazil (Ljungman 1867; Tommasi 1970; Pires- Vanin et al. 1997; Netto et al. 2005; Pires-Vanin et al. 2014).

From 0 to 311 m depth (Alvarado & Solís-Marín 2013). The present study samples occurred at depths ranging from 9 to 21.5 m.

Selected references. Ljungman (1866): p. 165; Thomas (1966): p. 827; Tommasi (1967): p. 1, fig. 1; Tommasi (1970): p. 35, fig. 34,35; Monteiro (1987): p. 58, est. III d-f; Hendler et al. (1995): p. 161, fig. 78, 102 c–e; Borges & Amaral (2005): p. 260, fig. a–d; Manso et al. (2008): p. 190, fig. 18 a–d; Gondim et al. (2013a): p. 59, fig. 5 a–f; Paim et al. (2015): p. 3, fig. 2a–c [as Amphipholis januarii]; Thomas (1962): p. 657, fig. 11 [as Amphipholis pachybactra].