Dispio longibranchiata, 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 : 169-171

Dispio longibranchiata sp. nov.

Figure 7 A–T

Material examined. Northeastern Pacific , California, Southern California Bight, San Diego County, 32º32′00″N 11º07′45″W, 7.2 m, medium gray sand, 0.8 km bearing 270ºT (true north) from US-Mexico border monument, Van Veen g rab, R / V Velero IV Sta. 6422-59, coll. Allan Hancock Foundation, 3 Sept. 1959, id. Olga Hartman, holotype ( LACM AHF POLY 6237 ) ; same data for 2 paratypes ( LACM AHF POLY 6237 /1).

Description. Holotype incomplete with 57 chaetigers, 15 mm long, 1.1 mm wide. Paratypes incomplete with 33 – 40 chaetigers, 9.2 – 11.5 mm long, 1.0 – 1.1 mm wide. Color in alcohol off-white, opaque. Body without pigmentation.

Prostomium rectangular-shaped, widest in eye region, slightly truncated anteriorly with short distal conical tip ( Fig. 7 A), posteriorly tapered, with a short, blunt caruncle, and swollen along posterior margin, extending to middle of chaetiger 1 ( Fig. 7 A–B). Two pairs of black subdermal eyes, one pair of small, lateral kidney-shaped eyes, one pair of rounded, medial eyes ( Fig. 7 A–B); all eyes in nearly a straight line between base of palps. Palps long ( Fig. 7 B), extending to chaetiger 10; palps with single band of tranverse rows of cilia on one side of ventral ciliated groove, sheath palpal large, smooth ( Fig. 7 B); palps lost in holotype. Peristomium short, expanded laterally, partially enveloping prostomium and extending around base of palps, forming short lateral wings ( Fig. 7 A), separated from chaetiger 1.

All notopodial postchaetal lamellae slender, long, almost completely fused with branchiae except for free pointed tips ( Fig. 7 C) on anterior chaetigers, partially fused on middle and posterior chaetigers ( Fig. 7 D); notopodial postchaetal lamellae on chaetiger 1 shifted dorsally. Lamellae of chaetiger 1 bearing 1 – 3/2 – 5 (1 left, 2 right in holotype) digitiform lobes along distal margin, basal margin rounded ( Fig. 7 A); notopodial lamellae of chaetigers 2 – 20 entire, narrow, long, slightly ruffled on distal and middle margins, basal margin rounded ( Fig. 7 A, C, E); subsequent lamellae entire, not ruffled ( Fig. 7 F), margin of lamellae becoming triangular, short, slender on chaetiger 21; middle lobe becoming wider with long, pointed ventral edge around chaetiger 30 ( Fig. 7 D); subsequent parapodia decreasing gradually in size. Ventral and dorsal edges of notopodial and neuropodial lamellae not overlapping or touching on any chaetigers examined. All notopodial prechaetal lamellae big, oval ( Fig. 7 B–C), becoming elongated ( Fig. 7 G), and decreasing gradually in size around chaetiger 45; not basally fused with notopodial postchaetal lamellae. Each segment with a pair of dorsal C-shaped double bands of cilia with a transverse band of cilia between them ( Fig. 7 D). Lateral organs between notopodial and neuropodial postchaetal lamellae visible but small on middle chaetigers.

Neuropodial postchaetal lamellae of chaetiger 1 triangular, shifted to dorsal side ( Fig. 7 H); neuropodial lamellae of chaetigers 2–3 subtriangular, with dorsal edge most developed ( Fig. 7 H); lamellae of chaetigers 4–12 rounded, wider ( Fig. 7 E, I); becoming rectangular with well-developed dorsal edge on chaetigers 13–36 ( Fig. 7 J), these forming a pointed upper border from around chaetigers 30–36 ( Fig. 7 K); subsequent parapodia decreasing in size with triangular upper and lower borders up to end of fragments. Neuropodial prechaetal lamellae small, rounded, wide; smaller in middle region ( Fig. 7 J) and decreasing gradually in size on posterior chaetigers, all lamellae not basally fused with neuropodial postchaetal lamellae.

Branchiae present from chaetiger 1, continuing to end of body; all branchiae tapered, smooth, long, overlapping each other on anterior and middle chaetigers ( Fig. 7 A, C–D), almost completely fused to notopodial lamellae; branchial tips free, distally pointed on all chaetigers and longer than notopodial lamellae ( Fig. 7 A, C–D). Each branchiae with a dense band of cilia along inner edge. Accessory branchiae present from chaetiger 12, initially as a simple long digitate lobe that arises from dorsolateral side of body behind notopodial base; number of lobes increasing gradually to 2 or 5 on middle and posterior chaetigers, arranged in 1 or 2 rows (4 or 5 in anterior row, 2 or 3 in posterior row) palmate-shaped ( Fig. 7 L).

Notochaetae of chaetiger 1 arranged in dorsal tuft and ventral fascicle; dorsal tuft with 20–30 long, smooth, alimbated, slender capillaries extending beyond margins of notopodial lamellae, between palps; ventral fascicle arranged in two rows, both rows with slender, alimbated, smooth capillaries; capillaries on posterior row longer than those of anterior row; less numerous than those of dorsal fascicle. Notochaetae of chaetiger 2 and subsequent chaetigers arranged in three groups: capillaries of dorsal tuft long, pointed, slender, smooth, unilimbated, slightly striated ( Fig. 7 M); anterior row with stout, heavily reticulated, granulated, bilimbated capillaries ( Fig. 7 N), posterior row with slender, long, pointed, smooth, bilimbated capillary chaetae, slightly striated basally ( Fig. 7 O), longer than those in anterior row; anterior chaetae on middle chaetigers with same structure, except notochaetae of anterior row slightly reticular, granulated, alimbated, and dorsal tuft with smooth, slender, unilimbated capillaries ( Fig. 7 P). Notopodial hooded hooks absent.

Neurochaetae of chaetiger 1 arranged in two rows: an anterior row comprised of slender, slightly reticulated, granulated, unilimbate capillaries, and a posterior row of pointed, smooth, unilimbated, slender capillary chaetae ( Fig. 7 S), anterior capillaries shorter than posterior ones; in addition, a ventral tuft of 3–4 slender, shorter, smooth, unilimbated capillaries ( Fig. 7 Q) located in position of sabre chaetae; neurochaetae on chaetiger 2 and subsequent chaetigers similar to those on chaetiger 1, except that anterior row bears stout, heavily reticulated capillaries ( Fig. 7 R), ventral tuft with 2 – 3 longer, stouter heavily reticulated, granulated, unilimbated sabre chaetae ( Fig. 7 K); sabre chaetae from chaetiger 11 longer and stouter; on middle chaetigers in two rows: anterior row comprised of hooded hooks, posterior row of long, smooth, unilimbated wide capillary chaetae ( Fig. 7 K, T). Unidentate hooded hooks from chaetigers 22 – 24 (24 in holotype) ( Fig. 7 K), 5 – 7 present per neuropodium, accompanied by very slender, small, smooth, unilimbated capillary chaetae ( Fig. 7 T). Hooded hooks open distally, shaft almost straight ( Fig. 7 K).

Pygidium lost.

Remarks. For differences between Dispio longibranchiata sp. nov. and D. anauncinata sp. nov., see remarks in D. anauncinata sp. nov. D. longibranchiata sp. nov. is similar to D. uncinata and D. maroroi in having the first notopodial postchaetal lamellae with digitiform papillae. D. longibranchiata sp. nov. is also similar to D. uncinata in that the notopodial and neuropodial lamellae do not overlap or touch each other; it is also similar to D. maroroi in having entire notopodial postchaetal lamellae with ruffled margins on chaetigers 3 – 11. However, D. longibranchiata sp. nov. can be distinguished from type material of D. uncinata and D. maroroi in that the former has a rectangular-shaped prostomium that is widest in the eye region, slightly truncated anteriorly with a short distal conical tip, a shorter, blunt caruncle, swollen along the posterior margin, shorter peristomium and lateral wings, triangular anterior neuropodial lamellae on chaetigers 1 – 3, accessory branchiae from chaetigers 12, notopodial lamellae and branchiae overlapping, chaetiger 1 notochaetae with alimbated, smooth capillaries in both rows, and notochaetae on chaetiger 2 and subsequent chaetigers with unilimbated capillaries in the posterior row; with, D. longibranchiata sp. nov. can also be distinguished from D. maroroi in that the former has neuropodial hooded hooks from chaetigers 22 – 24. Further differences between this new species and the other species examined are provided in the key and Table 1.

Ecology. 7.2 m, medium-grained gray sand.

Type locality. Northeastern Pacific , California, Southern California Bight, San Diego County .

Etymology. The specific name is from the Latin longi meaning long and refers to the very long branchiae that overlap each other.

Figures

FIGURE 7. Dispio longibranchiata sp. nov. Holotype (LACM AHF POLY 6237: A, F, H – J; paratype LACM AHF POLY 6237 / 1: B – E, G, K – T): (A) anterior region, dorsal view; (B) anterior region with palps, dorso-lateral view paratype; (C) notopodium of anterior chaetigers; (D) posterior region, dorso-lateral view; (E) parapodium of chaetiger 7; (F) parapodium of middle chaetiger; (G) posterior postchaetal lamellae and chaeta; (H) anterior region, lateral view; (I) parapodium of chaetigers 5 – 12; (J) parapodium of middle chaetigers; (K) neuropodium of chaetiger 49 with unidentate hooded hooks and sabre chaetae; (L) parapodium of posterior chaetigers; (M) anterior notopodial chaeta of dorsal tuft; (N) anterior notopodial chaeta of anterior row; (O) anterior notopodial chaeta of posterior row; (P) middle notopodial chaeta of anterior row; (Q) posterior notopodial chaeta of dorsal tuft; (R) anterior neuropodial chaeta of anterior row; (S) anterior neuropodial chaeta of posterior row; (T) anterior chaeta in position of sabre chaeta. CBC = C-shaped double band of cilia. Scale bars: A, C, D, F, H – J, L 1.0 mm; B 1.5 mm; E, G, K M – T 0.05 mm.