Ophioderma januarii Lütken, 1856,

Alitto, Renata A. S., Bueno, Maristela L., Guilherme, Pablo D. B., Domenico, Maikon Di, Christensen, Ana Beardsley & Borges, Mic, 2018, Shallow-water brittle stars (Echinodermata: Ophiuroidea) from Araçá Bay (Southeastern Brazil), with spatial distribution considerations, Zootaxa 4405 (1), pp. 1-66: 13-15

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Ophioderma januarii Lütken, 1856


Ophioderma januarii Lütken, 1856 

( Fig. 3View FIGURE 3)

Type locality. Rio de Janeiro, Brazil. 

Maximum size. dd up to 26 mm ( Paim et al. 2015).

Material examined. 89 specimens (dd: 3.9–22.39 mm) from subtidal: ZUEC OPH 2199, St. XII, 3 spms; ZUEC OPH 2202, St. XII, 4 spms; ZUEC OPH 2216, St. XI, 13 spms; ZUEC OPH 2239, St. XVIII, 6 spms; ZUEC OPH 2240, St. XIX, 8 spms; ZUEC OPH 2241, St. XVII, 1 spms; ZUEC OPH 2243, St. XIX, 3 spms; ZUEC OPH 2248, St. XIX, 1 spm; ZUEC OPH 2270, St. XXIV, 30 spms; ZUEC OPH 2280, St. XXVI, 1 spm; ZUEC OPH 2358, St. 21H, 2 spms; ZUEC OPH 2359, St. XXXIV, 3 spms; ZUEC OPH 2360, St. XXXIV, 14 spms.

Description. Disc: (dd: 7.9 mm) pentagonal, greenish, with some lighter and irregular patches, covered dorsally and ventrally by granules. Radial shields not evident. Radial dorsal region of the disc with a recess showing two to three arm plates, lined by small scales without granules ( Fig. 3AView FIGURE 3). Ventral surface of the disc and arms whitish. Two bursal slits along each arm, distal slightly wider than the proximal ( Fig. 3BView FIGURE 3). Oral shields trapezoid-shaped, distally almost as wide as long, proximally just over half as wide as long, lateral edges straight, proximal and distal edges convex. Adoral shields triangular, small (about one-third of the oral shield) and separated proximally. Jaws covered by granules. Five to seven lateral oral papillae, distal rounded and proximal tapered. One apical papilla, similar to lateral oral papillae, but more elongated ( Fig. 3CView FIGURE 3).

Arms: with bright green and dark green bands. Dorsal arm plates trapezoid, twice as wide as long and contiguous ( Fig. 3D,FView FIGURE 3). Ventral arm plates fan-triangular with a slight lateral notch, twice as long as wide and contiguous ( Fig. 3E,GView FIGURE 3). Two rounded tentacle scales, attached to the lateral arm plate. Eight to ten short arm spines (shorter than the length of an arm segment) and adpressed ( Fig. 3EView FIGURE 3).

Lateral arm plates ( Fig. 3H,IView FIGURE 3): general outline: ventral portion projecting ventro-proximalwards; ventro-distal tip projecting ventralwards. Outer surface ornamentation: trabecular intersections protruding to form knobs larger than stereom pores on most of outer surface. Outer proximal edge: surface lined by discernible band of different stereom structure, over most of the proximal edge; large, oblique and elongated spurs on ventro-proximal tip of outer surface; central part not protruding; proximal edge of outer surface with horizontal striation, but restricted to small area—between spurs. Spine articulation: in notches of distal edge, ventralwards increasing in size; distance between spine articulations equidistant. Lobes merged at their proximal tips by smooth connection, dorsal lobe clearly larger than the ventral lobe; lobes shifted, dorsalmost bent, and tilted orientation; stereom with perforations; sigmoidal fold weakly developed. Inner side, ridges and knobs: inner side dominated by more or less continuous ridge; ridge on inner side with separate knob on the ventral tip; ridge on inner side composed of more compact or more densely meshed stereom; ridge shape without major kink and with tongue-shaped dorsal tip; with vertical row without furrow 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. 3JView FIGURE 3). Zygocondyles dorsalwards converging and zygosphene fused with pair of zygocondyles ( Fig. 3KView FIGURE 3). Dorso-distal muscular fossae transformed distalwards not projecting ( Fig. 3LView FIGURE 3). Zygosphene projecting beyond ventral edge of zygocondyles with projecting part as long as zygocondyles ( Fig. 3MView FIGURE 3).

Taxonomic comments. The arm ossicles, especially the lateral arm plates and vertebrae, are more robust than those of the other brittle stars of the present study, except for Ophioplocus januarii  , which are similar. This robustness could aid in its epifaunal lifestyle, as more robust arms are more suitable to live on the substrate. However, this hypothesis needs to be tested. Ophioderma januarii  has various combinations of greenish, greenishbrown, and brown pigments on the disc and with bright green and dark green bands on the arms ( Tommasi 1970; Monteiro et al. 1992). All of these colors were noted and often were accompanied by a whitish patch in the middle of the disc. O. januarii  is similar to O. brevispina  , but O. brevispina  is more common in northern and northeastern Brazil ( Paim et al. 2015). Furthermore, some authors have reviewed these species and concluded that the only morphological difference is the shape of the arm ( Costa & Costa 1962): in O. januarii  it tapers towards the distal end, whereas in O. brevispina  the same diameter is maintained throughout the arm. These differences are not clear, and a broader biogeographic and taxonomic revision is needed, preferably using SEM and molecular methods.

Remarks. This species is gonochoric with lecithotrophic development, reproduces year-round, but increases its gonadal activity during summer ( Borges et al. 2009). A member of the epifauna, it lives mainly on sandy, muddy, rubble bottoms and shell fragments ( Borges & Amaral 2005). O. januarii  was collected on rubble bottom with dredge and van Veen grab.

Distribution. Tropical Atlantic (realm), Tropical Northwestern Atlantic (province): from Southern Gulf of Mexico to Eastern Caribbean ( Pomory 2007; Alvarado & Solís-Marín 2013); Tropical Southwestern Atlantic (province): Northeastern, and Eastern Brazil ( Magalhães et al. 2005; Gondim et al. 2008; Lima & Fernandes 2009; Paim et al. 2015), Trindade and Martin Vaz Islands ( Tommasi & Aron 1988). Temperate South America (realm), Warm Temperate Southwestern Atlantic (province): Southeastern Brazil ( Manso & Absalão 1988; Monteiro et al. 1992; Pires-Vanin et al. 1997; Borges & Amaral 2005; Oliveira et al. 2010; Pires-Vanin et al. 2014).

From intertidal to 1,500 m depth ( Alvarado & Solís-Marín 2013). The present study samples occurred at depths ranging from 19 to 21.5 m.

Selected references. Lütken (1856): p. 7; Lütken (1859): p. 199, fig. 5a –5c; Tommasi (1970): p. 69, fig. 68, 69; Albuquerque (1986): p. 275, fig. 40a –c, Monteiro (1987): p. 105, est. IXe –f, Xa,b; Borges & Amaral (2005): p. 243, fig. a –d; Paim et al. (2015): p. 11, fig. 8a –c.