Amphiodia pulchella ( Lyman, 1869 )

Alitto, Renata A. S., Bueno, Maristela L., Guilherme, Pablo D. B., Domenico, Maikon Di, Christensen, Ana Beardsley & Borges, Michela, 2018, Shallow-water brittle stars (Echinodermata: Ophiuroidea) from Araçá Bay (Southeastern Brazil), with spatial distribution considerations, Zootaxa 4405 (1), pp. 1-66 : 31-33

Amphiodia pulchella ( Lyman, 1869)

( Fig. 10 )

Type locality. Florida, United States.

Maximum size. dd up to 5.2 mm ( Thomas 1962).

Material examined. 17 specimens (dd: 1.7–4.7 mm) from subtidal: ZUEC OPH 2132, St. 34, 1 specimen (spm); ZUEC OPH 2176, St. XII, 1 spm; ZUEC OPH 2205, St. XII, 4 spms; ZUEC OPH 2214, St. 71, 1 spm; ZUEC OPH 2276, St. XXVI, 8 spms; ZUEC OPH 2286, St. 147, 1 spm; ZUEC OPH 2347, St. 20H, 1 spm.

Description. Disc: (dd: 4 mm) circular with soft interradial depressions, covered by numerous small and imbricating scales, approximately 25 between the centrodorsal and the edge of the disc. Central primary plate and primary radial plates evident and larger than scales. Radial shields four times as long as wide, narrow and contiguous throughout and separated proximally by three small scales, one elongated wedge-shaped and the others semi-triangular ( Fig. 10A ). Ventral interradius covered by scales similar to the dorsal surface. Bursal slits long and wide ( Fig. 10B ). Oral shields twice as long as wide, narrow proximally, rounded edges distally and small lateroposterior re-entrances. Madreporite larger than other oral shields, more whitish and with pores at the distal margin. Adoral shields semi-triangular and separated proximally. Two lateral oral papillae, distal slightly larger and circular. One pair of elongated infradental papillae widely separated from each other ( Fig. 10C ).

Arms: dorsal arm plates contiguous, twice as wide as long, proximal edge strongly convex, distal edge straight ( Fig. 10D,F ). Ventral arm plates pentagonal, as long as wide, with proximal edge pointed and distal slightly convex, first 4-5 contiguous, and others separated by lateral arm plates ( Fig. 10E,G ). One tentacle scale, half as long as ventral arm plate and attached to lateral plate ( Fig. 10E ). Three arm spines, middle one blunt, flattened dorsoventrally, tip hatchet-shaped.

Lateral arm plates ( Fig. 10H,I ): general outline: ventral portion projecting ventro-proximalwards; ventro-distal tip not 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, restricted to central part; without spurs; central part not protruding; surface without horizontal striation. Spine articulation: on same level as remaining outer surface, sizes all similar; distance between spine articulation equidistant. Lobes simply separated, dorsal lobe clearly larger than the ventral lobe; lobes parallel, straight, and oriented nearly horizontal; stereom massive; sigmoidal fold absent. Inner side, ridges and knobs: inner side 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. 10J ). Zygocondyles dorsalwards converging and zygosphene fused with pair of zygocondyles ( Fig. 10K ). Dorso-distal muscular fossae transformed distalwards projecting but far from distal edge of zygocondyles ( Fig. 10L ). Zygosphene projecting beyond ventral edge of zygocondyles with projecting part longer than zygocondyles ( Fig. 10M ).

Taxonomic comments. This species was easily identified by its single tentacle scale ( Koehler 1914), differentiating it from other Amphiodia species in the present collection. Evident primary plates were observed in specimens up to 4 mm of dd, however in the largest specimen these plates were almost imperceptible. The lateral arm plates are concave, “C” shaped causing them to touch dorsally and ventrally after the first 4–5 segments. This condition is only observed ventrally due to the shape of the ventral arm plate, which is pentagonal, unlike the dorsal surface where the dorsal arm plates cover the lateral arm plates.

Remarks. It occurs in high densities ( Hendler et al. 1995), often with the amphiurid Microphiopholis atra and the ophiactids Hemipholis cordifera and Ophiactis lymani ( Tommasi 1970) . A. pulchella was found with these species and with the amphiurids Amphiodia riisei , Amphipholis januarii , Amphiura kinbergi , Amphiura princeps and Microphiopholis subtilis . As with most amphiurids, A. pulchella extends two to four arms across the sediment surface, with its arm tips slightly raised to feed ( Hendler et al. 1995). This species can be found on coral reefs, seagrass, muddy, rocky and sandy bottom ( Alvarado & Solís-Marín 2013). A. pulchella was collected from sandy bottom (coarse and medium sand), medium silt, and rubble bottom with a dredge (70% of spms) and van Veen grab.

Distribution. Tropical Atlantic (realm), Tropical Northwestern Atlantic (province): Floridian to Eastern Caribbean ( Hendler et al. 1995; Pomory 2007; Miloslavich et al. 2010); Tropical Southwestern Atlantic (province): Northeastern and Eastern Brazil ( Magalhães et al. 2005; Manso et al. 2008). Temperate South America (realm), Warm Temperate Southwestern Atlantic (province): Southeastern Brazil ( Tommasi 1970; Manso & Absalão 1988; Manso 1989, 1993; Pires-Vanin et al. 1997; Netto et al. 2005; Pires-Vanin et al. 2014) and Uruguay – Buenos Aires Shelf ( Alvarado & Solís-Marín 2013).

Commonly found at shallow depths up to 80 m ( Tommasi 1970; Manso et al. 2008), but there are records of up to 370 m ( Alvarado & Solís-Marín 2013). The present study samples occurred at depths ranging from 19 to 22 m.

Selected references. Lyman (1869): p. 337 [as Amphiura pulchella ]; Clark (1915): p. 250; Fell (1962): p. 5; Thomas (1962): p. 641, fig. 5; Parslow & Clark (1963): p. 26; Tommasi (1970): p. 26, fig.18,19; Monteiro (1987): p. 41; Hendler et al. (1995): p. 153, fig. 72, 100J, K; Borges & Amaral (2005): p. 256, fig. a–e; Manso et al. (2008): p. 190, fig. 17 a–c [as Amphiodia pulchella ]; Clark (1915): p. 249; Verrill (1899b): p. 313 [as Amphiodia repens ]; Lyman (1875): p. 18, pl. III fig. 38–40 [as Amphiura repens ].

Figures

FIGURE 10. Amphiodia pulchella ZUEC OPH 2276 (4.4 mm dd). (A) Dorsal view. (B) Ventral view. (C) Detail of the oral view.(D)Detail of dorsalarm.(E)Detailof ventral arm.(F)Dorsal arm plate.(G)Ventral arm plate.(H-I) Lateralarm plate. (J) Vertebra—proximal surface. (K) Vertebra—distal surface. (L) Vertebra—dorsal surface. (M) Vertebra—ventral surface. Abbreviations: ads: adoral shields; as: arm spine; bs: bursal slits; cpp: central primary plate; d: dorsal; dap: dorsal arm plate; ddi: dorso-distal; ddmf: dorso-distal muscular fossae; di: distal; dp: dorso-proximal; ip: infradental papillae; lap: lateral arm plate; lop: lateral oral papillae; ma: madreporite; mas: middle arm spine; os: oral shields; p: proximal; pe: perforation; prp: primary radial plate; rs: radial shields; 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.