Shallow-water brittle stars (Echinodermata: Ophiuroidea) from Araçá Bay (Southeastern Brazil), with spatial distribution considerations
Author
Alitto, Renata A. S.
Author
Bueno, Maristela L.
Author
Guilherme, Pablo D. B.
Author
Domenico, Maikon Di
Author
Christensen, Ana Beardsley
Author
Borges, Michela
text
Zootaxa
2018
2018-04-06
4405
1
1
66
journal article
30325
10.11646/zootaxa.4405.1.1
55df350b-41c6-4f2e-9a18-c0be6d47498b
1175-5326
3097993
D33BF380-5AF7-4645-86C7-9981C528EAF0
Ophioderma januarii
Lütken, 1856
(
Fig. 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. 3A
). Ventral surface of the disc and arms whitish. Two bursal slits along each arm, distal slightly wider than the proximal (
Fig. 3B
). 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. 3C
).
Arms: with bright green and dark green bands. Dorsal arm plates trapezoid, twice as wide as long and contiguous (
Fig. 3D,F
). Ventral arm plates fan-triangular with a slight lateral notch, twice as long as wide and contiguous (
Fig. 3E,G
). 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. 3E
).
Lateral arm plates (
Fig. 3H,I
): 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. 3J
). Zygocondyles dorsalwards converging and zygosphene fused with pair of zygocondyles (
Fig. 3K
). Dorso-distal muscular fossae transformed distalwards not projecting (
Fig. 3L
). Zygosphene projecting beyond ventral edge of zygocondyles with projecting part as long as zygocondyles (
Fig. 3M
).
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.
FIGURE 3.
Ophioderma januarii
ZUEC OPH 2202 (7.9 mm dd). (A) Dorsal view. (B) Ventral view. (C) Detail of the oral view. (D) Detail of dorsal arm. (E) Detail of ventral arm. (F) Dorsal arm plate. (G) Ventral arm plate. (H-I) Lateral arm plate. (J) Vertebra—proximal surface. (K) Vertebra—distal surface. (L) Vertebra—dorsal surface. (M) Vertebra—ventral surface. Abbreviations: ads: adoral shields; ap: apical papilla; as: arm spine; bs: bursal slits; d: dorsal; dap: dorsal arm plate; ddi: dorsodistal; ddmf: dorso-distal muscular fossae; di: distal; dp: dorso-proximal; gr: granules; lap: lateral arm plate; lop: lateral oral papilla; no: notch; os: oral shields; p: proximal; pe: perforation; ri: ridge; sf: sigmoidal fold; sp: spurs; tn: tentacle notch; ts: tentacle scale; v: ventral; vap: ventral arm plate; vdi: ventro-distal; vp: ventro-proximal; zd: zygocondyle; zp: zygosphene. Stereomicroscope photos: (A)–(E), scale bar equal to 0.5 mm. SEM photos: (F)–(M), scale bar equal to 100 µm.
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.