Dispio lenislamellata, Delgado-Blas, Víctor Hugo & Díaz-Díaz, Oscar, 2016

Delgado-Blas, Víctor Hugo & Díaz-Díaz, Oscar, 2016, Redescription of two species and five new species of Dispio Hartman, 1951 (Spionidae: Polychaeta) from the eastern Pacific Coast and Caribbean Sea, with a review of the genus, Zootaxa 4178 (2), pp. 151-181 : 166-169

Dispio lenislamellata sp. nov.

Figure 6 A–Z

Material examined. Northeastern Pacific , California, Southern California Bight, San Diego County, 32º32′00″N, 117º07′30″W, coarse gray sand, 0.3 miles bearing 270º T, (true north) from US-Mexico border monument, 5.4 m, Van Veen grab, R/ V Velero IV Sta. 6241-59, coll. Allan Hancock Foundation, 3 Sept. 1959, id. Olga Hartman, holotype ( LACM-AFH POLY 6238 ) and 1 paratype ( LACM-AFH POLY 6238 /1). — San Diego County, La Jolla, Scripps Institution of Oceanography , 32º51′58″N, 117º15′15″W, subtidal beach, coll. J.T. Enright, Nov 1959, id, Olga Hartman, 2 Paratypes (LACM-AHF-POLY 6243); La Jolla, Scripps Beach, 32º51′58″N, 117º15′15″W, coll. J.T. Enright, 1960, id. Olga Hartman, 22 small paratypes ( LACM-AHF POLY 6244 ) .

Description. Holotype incomplete, 6.7 mm long, with 30 chaetigers, 0.6 mm wide. Paratypes incomplete 5.0 – 15.8 mm long, with 26 – 75 chaetigers, 0.6 mm wide. Paratypes complete 8.0 – 9.5 mm long, with 61 – 63 chaetigers, 0.5 – 0.6 mm wide. Small paratypes complete 2.6 – 7.0 mm long, with 34 – 57 chaetigers, 0.3 – 0.5 mm wide. Color in alcohol light brown, no other pigmentation. Prostomium peanut-shaped, slightly wider in eye region, sharply pointed anteriorly ( Fig. 6 A), posteriorly tapered, with short, narrow, raised caruncle extending to middle of chaetiger 1 ( Fig. 6 A). Two pairs of brown subdermal eyes (small specimens with red eyes): one pair of small, lateral kidney-shaped eyes, and one pair of rounded, medial eyes, all eyes in nearly straight line above base of palps. Palps long ( Fig. 6 B), extending to chaetigers 10–12; palps with single band of transverse row of cilia on one side of ventral ciliated groove. Palp sheaths large, smooth, fused to base of palps. Peristomium small ( Fig. 6 B), expanded laterally, partially enveloping prostomium and extending around base of palps, forming small lateral wings ( Fig. 6 B), separated from chaetiger 1.

All notopodial postchaetal lamellae almost completely fused with branchiae but with free and pointed tips; notopodial postchaetal lamellae of chaetiger 1 slightly shifted dorsally. Notopodial postchaetal lamellae of chaetiger 1 and subsequent chaetigers entire ( Fig. 6 C), long and narrow on first five chaetigers ( Fig. 6 C), thereafter slightly wider, partially fused with branchiae; lamellae distally free with pointed tips and entire margins ( Fig. 6 D– E), basal margin wider, rounded ( Fig. 6 D); distal margin becoming wider, ventral edge (lobe) of lamellae oval, long on chaetigers 25–32 ( Fig. 6 E); lamellae of chaetigers 26–33 (33 in holotype) with pointed ventral edge ( Fig. 6 F– G). Ventral and dorsal edges of notopodial and neuropodial lamellae not overlapping or touching on any chaetiger. Anterior notopodial prechaetal lamellae small, oval ( Fig. 6 D), thereafter subtriangular ( Fig. 6 G) on middle chaetigers, then decreasing gradually in size; not basally fused with notopodial postchaetal lamellae. Each segment with a pair of dorsal C-shaped double bands of cilia with transverse band of cilia between them ( Fig. 6 H). Lateral organs between notopodial and neuropodial postchaetal lamellae visible but small on middle chaetigers ( Fig. 6 I).

Neuropodial postchaetal lamellae of chaetiger 1 shifted to dorsal side; neuropodial lamellae of chaetiger 1 triangular ( Fig. 6 B, J), neuropodial lamellae of chaetiger 2 wide, subtriangular ( Fig. 6 B, J); lamellae on chaetiger 3 and subsequent chaetigers rounded, wider ( Fig. 6 B, K), increasing gradually in size, becoming rectangular with rounded edges from chaetiger 21 ( Fig. 6 I, L), then with triangular upper border from around chaetigers 26–29, forming a pointed upper border from around chaetigers 30–34 ( Fig. 6 F–G) up to posterior chaetiger; becoming rounded at end of body in small specimens. Neuropodial prechaetal lamellae low ( Fig. 6 J–L) along body, all lamellae not basally fused with neuropodial postchaetal lamellae.

Branchiae present from chaetiger 1, continuing to end of body; all branchiae tapered, smooth, long; from chaetiger 3 all branchiae overlapping each other ( Fig. 6 B); almost completely fused to notopodial lamellae, branchial tips free, distally pointed on all chaetigers and longer than notopodial lamellae ( Fig. 6 C–D). Each branchia with a dense band of cilia along inner edge. Accessory branchiae present from chaetigers 11–21 (13 in holotype), initially as a simple long digitate lobe that arising from dorsolateral side of body behind notopodial base; number of lobes increasing gradually to 3–5 on middle and posterior chaetigers, arranged in one row ( Fig. 6 M); on small paratypes only a single digitate lobe observed.

Notochaetae of chaetiger 1 arranged in a dorsal tuft and a ventral fascicle; dorsal tuft comprised of about 10–15 long, smooth, slender, pointed, alimbated capillaries ( Fig. 6 N) extending beyond margins of notopodial lamellae, between palps; ventral fascicle arranged in two rows: anterior row comprised of slender and slightly reticulated, granulated, unilimbated capillaries ( Fig. 6 O), and posterior row of short, slender, smooth, unilimbated capillaries ( Fig. 6 P); fewer than on dorsal fascicle. Notochaetae of chaetiger 2 arranged in same way as on chaetiger 1 and subsequent chaetigers, except that dorsal tufts with 2–3 short, pointed, smooth, unilimbated capillaries ( Fig. 6 Q); chaetae of middle chaetigers show same structure as those of anterior chaetigers, except that anterior row has wider, heavily reticulated, granulated, long, capillaries with wider sheathes ( Fig. 6 R), and posterior row, long, thinner, smooth, unilimbated, capillaries ( Fig. 6 P); fascicles on posterior chaetigers with long, pointed, smooth, slender, alimbate capillary chaetae ( Fig. 6 S). Notopodial hooded hooks absent.

Neurochaetae of chaetiger 1 arranged in two rows: anterior row comprised of stout slightly reticulated, granulated, unilimbate capillaries ( Fig. 6 T), and posterior row of long, smooth, alimbate capillary chaetae ( Fig. 6 U), plus a ventral tuft of 2–3 slender, shorter, smooth, alimbated capillaries located in position of sabre chaetae ( Fig. 6 V). Neurochaetae of chaetiger 2 and subsequent chaetigers similar to those of chaetiger 1, only with additional two sabre chaetae, each chaeta longer, stouter, heavily reticulated, granulated, slightly unilimbated ( Fig. 6 W), except for chaetiger 11 where sabre chaetae are longer. Unidentate ( Fig. 6 X) and bidentate ( Fig. 6 Y) neuropodial hooded hooks integrated in same fascicle from chaetigers 15–21 (18 in holotype), up to five per neuropodium. For small paratypes (juveniles) all hooks bidentate. Hooded hooks distally entire, slightly curved and with hood extended distally ( Fig. 6 X, Y).

Pygidium with midventral flap and a pair of cirri ( Fig. 6 Z), lost in holotype.

Remarks. Dispio lenislamellata sp. nov. is similar to D. glabrilamellata from Australia, D. brachychaeta from Argentina, D. magnus from South Africa, and D. oculata from Japan in having entire anterior notopodial postchaetal lamellae. Furthermore, Dispio lenislamellata sp. nov. is similar to the last two species in that the notopodial and neuropodial lamellae do not overlap or touch each other. However, Dispio lenislamellata sp. nov. differs from D. glabrilamellata , D. brachychaeta , D. magnus and D. oculata in that the prostomium is slightly wider in the region of the eyes, the peristomium is shorter, and the neuropodial lamellae are triangular on chaetigers 1 – 2; with, Dispio lenislamellata sp. nov. differs from D. brachychaeta , and D. magnus by the presence of eyes. It also differs from D. brachychaeta and D. oculata as it has accessory branchiae, and the branchial tips are free along the whole body, and from D. magnus and D. oculata in that it has neuropodial hooded hooks from chaetigers 15– 21. Finally, Dispio lenislamellata sp. nov. differs from D. glabrilamellata in that in the former the caruncle is shorter, blunt and swollen along the posterior margin, the neuropodial prechaetal lamellae have lower lobes along the whole body, all branchiae overlap each other, accessory branchiae present from chaetigers 11 – 21, and neuropodial hooded hooks from chaetigers 15–21; with, Dispio lenislamellata sp. nov. differs from D. brachychaeta , in that the former has unilimbated anterior neuropodial chaetae, and smooth, alimbated, ventral chaetae located in the position of the sabre chaetae, and from D. magnus , in having a shorter, blunt, caruncle swollen along the posterior margin, anterior notopodial postchaetal lamellae without ruffled margins, and a pygidium with a midventral flap and a pair of cirri.

In this species we observed that juvenile specimens only have bidentate hooded hooks, whereas unidentate and bidentate hooded hooks were observed in the same fascicle on the posterior chaetiger in adult specimens: this observation is very rare, there are usually one or two teeth in a single fascicle with bidentate hooks along the whole body. This trait has been observed in this study for other species, such as D. bescanzae sp. nov, and D. anauncinata sp. nov. In addition, Foster (1971) reported the presence of bidentate hooded hooks in juveniles of D. uncinata , which have also been observed in the larval stages of the same species ( Blake & Arnofsky 1999, Blake 2006). Blake & Kudenov (1978) have also found such hooks in juvenile D. glabrilamellata , where, in a single fascicle, there is a graduation of wear from the bidentate to the unidentate condition, suggesting that unidentate hooks can result from worn bidentate hooks. These observations lead us to suggest that the larval and juvenile stages of Dispio species have bidentate hooks, whereas adults have only unidentate hooks. Further differences between this new species and the other species examined are provided in the key and Table 1.

Ecology. 5.4 m, coarse gray sand.

Locality type. Northeastern Pacific , Southern California, San Diego County.

Etymology. The specific name is from the Latin lenis meaning smooth and refers to the shaped of the noto-, and neurolamellae.

Figures

FIGURE 6. Dispio lenislamellata sp. nov. Holotype (LACM-AHF POLY- 6238: B-Z; paratype (LACM-AHF POLY- 6238 / 1: A): (A) anterior region, dorso-lateral view; (B) anterior region, lateral view; (C) notopodium of chaetigers 1 – 3; (D) notopodium of chaetigers 8; (E) notopodium of chaetiger 27; (F) notopodium of chaetigers 25 – 33; (G) parapodium of chaetiger 75; (H) middle segment, dorsal view; (I) middle segment, lateral view; (J) neuropodium of chaetigers 1 – 2; (K) neuropodium of chaetiger 5; (L) neuropodium of chaetiger 22; (M) notopodial lamellae and branchiae, dorsal view and accessory branchiae; (N) dorsal tuft notopodial chaeta of chaetiger 1; (O) anterior notopodial chaeta of anterior row; (P) anterior notopodial chaeta of posterior row; (Q) dorsal tuft notopodial chaeta of chaetiger 4; (R) middle notopodial chaeta of anterior row; (S) dorsal tuft chaetae of notopodial chaeta of posterior chaetiger; (T) anterior neuropodial chaeta of anterior row; (U) anterior neuropodial chaeta of posterior row; (V) ventral chaeta located in the position of a sabre chaeta of anterior chaetiger; (W) sabre chaeta of chaetiger 27; (X) unidentate neuropodial hooded hook; (Y) bidentate neuropodial hooded hook; (Z) pygidium, lateral view. N 1 = Notolamellae of chaetiger 1, N 2 = Notolamellae of chaetiger 2, N 3 = Notolamellae of chaetiger 3, CBC = C-shaped double band of cilia. LO = Lateral organ. Scale bars: A, F, H, I, M, Z 0.5 mm; B 1.0 mm; C – E, Q, S 0.005 mm; G 5 0.05 mm; J – L, V 0.0025; N 0.01 mm; O – P, R, T, U, W 0.025 mm; X, Y 0.0125 mm.