Dispio latilamella, Williams, Jason D., 2007

Williams, Jason D., 2007, New records and description of four new species of spionids (Annelida: Polychaeta: Spionidae) from the Philippines: the genera Dispio, Malacoceros, Polydora, and Scolelepis, with notes on palp ciliation patterns of the genus Scolelepis, Zootaxa 1459, pp. 1-35 : 7-10

Dispio latilamella sp. n.

( Figs. 4–5)

Material examined. Holotype. Philippines, Morong, Bataan, 14°41´N, 120°16´E, sandy beach, 1 Mar 1999, ( USNM 1096794).— Paratypes. Same data as holotype (one anterior end, one posterior end, one middle section in alcohol, USNM 1096795; one anterior end on SEM stub, USNM 1096796).

Etymology. The species epithet latilamella (derived from the Latin adjective latus for broad, wide and the Latin noun lamella for a small plate) refers to the large, spoon-shaped postsetal notopodial lamellae on setiger 1.

Diagnosis. Prostomium bluntly pointed anteriorly, with narrow, short caruncle extending to posterior margin of setiger 1; peristomium expanded laterally, partially enveloping prostomium and extending around base of palps. Two pairs of eyes present or eyes absent. Postsetal notopodial lamellae of setiger 1 large, spoonshaped, notopodial lamellae of setigers 1–13 with 2–8 digitiform extensions along margin, lamellae fused with base of branchiae. Notosetae of setiger 2 and succeeding setigers in three groups, including a group of capillary setae dorsal to an anterior row of stout capillaries, and a posterior row of thinner capillary setae. Neurosetae in three groups, two rows similar in morphology to notosetae, plus ventral fascicle of inferior sabre setae; unidentate neuropodial hooded hooks replacing anterior row of capillary neurosetae from setiger 19. Branchiae from setiger 1, smooth, partially fused with notopodial lamellae, distal end free. Accessory branchiae from setiger 19, initially with single digitate lobe, increasing to six digitate lobes in posterior setigers. Lateral organ between notopodial and neuropodial lamellae present from setiger 1. Pygidium reduced, with small papillae on ventral surface.

Description. All specimens incomplete; largest anterior fragment with 42 setigers, 18.3-mm long, 1.4- mm wide at setiger 10. Holotype with 37 setigers 14.5-mm long, 0.9-mm wide at setiger 10. Color in alcohol opaque off-white, no pigmentation present.

Prostomium elongate, bluntly pointed ( Figs. 4 A–C, 5A–C); anterior edge of peristomium with small papillae ( Figs. 4 B, 5A); peristomium expanded laterally, partially enveloping prostomium and extending around base of palps ( Figs. 4 B, 5A–C). Caruncle short, ending in middle of setiger one, rounded along posterior margin ( Fig. 4 D, 5C). Occipital tentacle absent. Two pairs of eyes present (may be obscured by palps and notopodial lobes of setiger 1), one pair of lateral small kidney-shaped eyes and one pair of rounded eyes medially, all eyes in nearly straight line between base of palps, or eyes absent. Palps short, extending to setiger 5; palps with single band of transverse rows of cilia on one side of ventral ciliated groove, rows of cilia approximately 44-µm long ( Fig. 5 A, E).

g

B

A E F D C G H I J K L M N O Setiger 1 with large, spoon-shaped postsetal notopodial lamellae, bearing 2–8 digitiform extensions along margin, fused with base of branchiae ( Figs. 4 A–C, E, 5B–D); setiger 1 with approximately 30–40 long, thin capillary notosetae extending beyond margins of notopodial lamellae, between palps ( Figs. 4 A–C, 5A–C), Capillaries with minute spinelets ( Fig. 5 B inset); small, rounded neuropodial lamellae, one row of 6–8 stout, capillary neurosetae, plus ventral fascicle of smaller sabre setae. Notopodial lamellae of setigers 2–13 may exhibit digitiform extensions along margin, lamellae of succeeding setigers smooth, fused with branchiae along most of length, basal end rounded, thinner toward distal end, with pointed tip, free from branchiae.

Notosetae of setiger 2 and succeeding setigers in three groups, a group of 2–3 thin, capillary setae dorsal to an anterior row of approximately eight stout heavily reticulated and granulated, unilimbate capillaries ( Fig. 4 M), and a posterior row of approximately eight shorter unilimbate capillary setae ( Fig. 4 N), all notosetae with minute spinelets along distal ends. Presetal notopodial lobes present from setiger 1 continuing through anterior and middle setigers, absent in posterior setigers, each presetal lobe with rounded basal portion extending into small triangular lobe. Neuropodial lamellae of setiger 2 and succeeding setigers rounded, becoming broader in posterior setigers; neurosetae in three groups, two rows similar in morphology to notosetae ( Fig. 4 J–K), plus ventral fascicle of 2–3 sabre setae ( Fig. 4 L), stouter in posterior setigers; unidentate neuropodial hooded hooks ( Fig. 4 O) replacing anterior row of capillary neurosetae from setiger 19 (7–9 in number), accompanied by row of capillary setae and ventral fascicle of 2–3 sabre setae ( Fig. 4 F). Presetal neuropodial lobes present from setiger 1 until posterior setigers, lobes rounded.

Branchiae from setiger 1, smooth, fused along length of notopodial lamellae, distal end free. Accessory branchiae from setiger 19, initially with single digitate lobe, increasing to six in posterior setigers ( Figs. 4 H–I, 5G–H). Lateral organs present between notopodial and neuropodial lamellae from setiger 1 ( Fig. 5 F–H).

Pygidium reduced, with small papillae on ventral surface ( Fig. 4 G).

Remarks. To date, six species of Dispio have been described [ Dispio brachychaeta Blake, 1983 (from Argentina), Dispio glabrilamellata Blake & Kudenov, 1978 (from Australia), Dispio magna ( Day, 1955) (from South Africa), Dispio maroroi Gibbs, 1971 (from the Solomon Islands), Dispio oculata Imajima, 1990 (from Japan), and Dispio uncinata Hartman, 1951 (from Gulf of Mexico, Massachusetts to Florida, Caribbean, California, Japan)]. Dispio latilamella sp. n., is most similar to D. maroroi from the Solomon Islands. However, D. maroroi has expanded notopodial lamellae on setigers 1 and 2, rather than only on setiger 1 as in D. latilamella . In addition, the lamellae of setigers 1 and 2 in D. maroroi are thinner with longer, digitiform extensions, and lamellae of subsequent setigers lack extensions whereas in D. latilamella the lamellae of setiger 1 are much broader (spoon-shaped) with shorter digitiform extensions along the margin and extensions are found on lamellae of up to setiger 13. There is variation in the degree of expansion of the lamellae in setiger 1 of the Philippine specimens, two specimens exhibit the broad spoon-shaped morphology with extensions while the third specimen exhibit more narrowly expanded lamellae with extensions. Similar variation in lamellar structure was documented by Foster (1971a) who showed that the number of lamellar extensions varied within Dispio uncinata ; however, D. uncinata does not exhibit expanded notopodial lamellae as observed in D. latilamella and D. maroroi . Unfortunately the morphology of the pygidium in D. maroroi is not known and the presetal notopodial and neuropodial lobes and lateral organs were not noted by Gibbs (1971), although they are presumably present.

Distribution. Sandy beach in Morong of the Bataan province in the Philippines; shallow subtidal (<5 m).

Figures

FIGURE 5. Dispio latilamella sp. n. A – H, paratype (USNM 1096796) SEM micrographs. A, anterior end, lateral view (arrowhead shows papillae on prostomium); B, anterior end, lateral view (opposite side of specimen in A, palp missing); inset shows spinelets on notoseta of setiger 1; C, anterior end, dorsal view; D, setiger 1 notopodia; E, proximal to middle region of palp, frontal view (arrowhead indicates a transverse row of cilia on one side of ventral ciliated groove); F, setigers 10 – 14 (left to right), lateral view; G, setigers 18 – 20 (left to right), lateral view (first accessory branchiae on setiger 19 shown by arrowhead; horizontal arrow indicates lateral organ); H, setiger 30 – 33 (right to left), lateral view. Scale bars: A – C = 500 µm; D = 100 µm; E = 50 µm; F – H = 250 µm; inset of B = 2.5 µm.