Polymniella aurantiaca Verrill, 1900

Londoño-Mesa, Mario H., 2009, Terebellidae (Polychaeta: Terebellida) from the Grand Caribbean region 2320, Zootaxa 2320 (1), pp. 1-93 : 56

Polymniella aurantiaca Verrill, 1900

Figures 16 A-H

Eupolymnia (Polymniella) aurantiaca, Verrill, 1900:661 .— Hartman, 1942:74–75, figs. 149, 151.

Not Terebella hiata, Hessle, 1917:178 .— Hartman, 1956:297.

Type material: Syntype YPM 1237 (1) Castle Harbor, Bermuda, 1898; in dead coral. Coll. A.E. Verrill, Exp.

Additional material: Lesser Antilles: AMNH 2677 B (1) Saba Bank , (17°39'N 63°17'W), 1925; Arcturus Ocean. Exp .

Description: Syntype incomplete, only anterior fragment in moderate state of preservation, with about 24 segments but last segments damaged, 39mm long, thorax 10mm long, 2.8mm wide ( Fig. 16A ). Tentacular membrane short; few short tentacles. Upper lip short, in regular condition, rounded. Lower lip flattened, reduced ( Fig. 16B ). Fourteen ventral shields; shields somewhat deformed, thinner, with some wrinkles, decreasing in width ( Fig. 16C ). Branchiae branched with short stalks, first and third pair of almost similar length, second pair one-fourth smaller ( Fig. 16D ). Base of third pair of branchiae arises over inter-segmental line between segments 7–8, but slightly displaced towards segment 7. Pairs of nephridial papillae between noto- and neuropodia on segments 6–10, posteriorly, as swollen rounded structure. Incomplete syntype with only 19 pairs of notopodia. Notochaetae of two lengths; short and long chaetae narrowly bilimbate in middle region, with distal oblique serrated region ( Figs 16E,F ). First neuropodia oblique to mid body line. Anterior pairs of neuropodia swollen, well-developed; posterior pairs of neuropodia less swollen, long. Anterior thoracic uncini ( Fig. 16G ) MF:4:4; PP rounded heel, PF absent; Oc slightly convex; Cp with 2 series of teeth over long MF; USr wide; SrP triangular; SrA sometimes visible, rounded; LSr long, flat: AP rounded, curved downward; AF absent; Bs smoothly concave. Mid-thoracic uncini larger ( Fig. 16H ), with shorter PP and AP. Pygidium missing in the syntype.

Staining Pattern: Notopodial glandular tissue between notopodia on segments 4–18 ( Fig. 16A ) and ventral shields ( Fig. 16B ) stain deeply. The remaining structures remain pale.

Variations: Treadwell initially identified two specimens ( AMNH 2677) as Loimia bermudensis . One of them belongs to Loimia , but the other to Polymniella . This specimen is complete, with 137 segments, 97 pairs of notopodia, 45mm long, thorax 2mm long, 0.6mm wide. The first 13 pairs of notopodia have long chaetae directed dorsally; then, chaetae decrease gradually in length. All the branchiae are fixed to a free translucent dorsal epithelium. Thus, their scars are easily recognizable under this epithelium; the first pair of branchiae arise from the intersegmental line between segments 2–3. Thoracic dorsum is longitudinally wrinkled, with visible segmentation. The last segments are short, becoming reduced in the last 20–25 segments; the pygidium is smooth.

Discussion: Hartman (1956) regarded Terebella hiata Treadwell, 1931 , from Haiti, as a junior synonym of P. aurantiaca because it shares the same distribution of branchiae. However, they actually differ in the distribution of the branchiae. Terebellobranchia hiata ( Treadwell, 1931) comb. nov., has branchiae on segments 2, 4 and 8, while P. aurantiaca has branchiae on segments 3, 4 and 7. Thus, they belong to different genera.

On the other hand, this species is similar to Terebellobranchia mchughae Londoño-Mesa and Carrera- Parra (2005) in terms of the segments on which the branchiae occur; nevertheless, they differ because P. aurantiaca lacks eyespots, has more pairs of notopodia, and uncini MF:4: 4 in single rows from segment 5–10. Terebellobranchia mchughae has eyespots, about 40 pairs of notopodia, and uncini MF:1:4:4, arranged in single rows from segment 5–9.

Type locality: Castle Harbor , Bermuda .

Distribution: Bermuda, Florida, and Saba Bank (Lesser Antilles).

Figures

FIGURE 16. Polymniella aurantiaca (Syntype YPM 1237): A. Complete. B. Anterior end in frontal view. C. Thoracic region in lateral view. D. Anterior end in dorsal view. E. Long chaeta from segment 10. F. Short chaeta from segment 10. G. Uncini from segment 5. H. Double rows of uncini from mid-thoracic segment. Scale bars: A: 3.3mm; B: 3.5mm; C,D: 1.2mm; E,F: 0.06mm; G,H: 0.04mm.