Dispio maroroi Gibbs, 1971

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 : 157-160

Dispio maroroi Gibbs, 1971

Figure 3 A–P

Dispio maroroi Gibbs, 1971: 166 –167, fig. 11 A–D.

Type material. Solomon Islands: Komimbo Bay (Holotype) ; Graham Pt. (Paratypes), clean sand at LWM British Museum (Natural History) Registration No. Holotype 1970.53, paratype 1970.53

Redescription. Holotype incomplete, anterior fragment with 45 chaetigers, 18 mm long, 2 mm wide. Paratype incomplete, anterior fragment with 86 chatigers, 45 mm long, 2 mm wide. Color in alcohol light brown, no other pigmentation present. Prostomium peanut-shaped, pointed anteriorly ( Fig. 3 A), posteriorly tapered, with a long, narrow caruncle observed as a longitudinal large nuchal ridge, extending to posterior margin of chaetiger 1 ( Fig. 3 B). Two pairs of black-brown subdermal eyes, all kidney-shaped in a trapezoidal arrangement. Palps lost. Peristomium short, expanded laterally, partially enveloping prostomium and extending around base of palps forming moderate lateral wings, separated from chaetiger 1 ( Fig. 3 A–B).

Notopodial postchaetal lamellae of chaetiger 1 expanded, bearing 7 digitiform papillae along distal and middle margins ( Fig. 3 A); notopodial lamellae on chaetiger 2 with 5 digitiform papillae along distal and middle margins, basal margin entire. Lamellae of chaetiger 3 and following to end of fragment entire, with ruffled distal and middle margins, basal margin rounded ( Fig. 3 A); lamellae with ventral edge pointed from chaetiger 22 ( Fig. 3 C). Ventral and dorsal edges of notopodial and neuropodial lamellae not overlapping or touching on any chaetigers. Notopodial prechaetal lamellae large, oval on anterior chaetigers ( Fig. 3 D) thereafter increasing in size, rounded, wider on middle and posterior chaetigers ( Fig. 3 E); all lamellae 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. 3 C). Lateral organs between notopodial and neuropodial postchaetal lamellae visible but small on middle chaetigers ( Fig. 3 F).

All neuropodial postchaetal lamellae rounded on chaetigers 1 – 5 ( Fig. 3 A), lamellae rectangular, wider on chaetigers 6 – 10 ( Fig. 3 G); becoming rectangular with a well-developed dorsal edge on chaetigers 10 – 21 ( Fig. 3 H), developing into a pointed upper border from around chaetigers 22 – 40 ( Fig. 3 I); subsequent parapodia decreasing in size with triangular upper and lower borders up to end of fragments. Neuropodial prechaetal lamellae large, rounded, wide ( Fig. 3 A, G); smaller on middle chaetigers ( Fig. 3 H), decreasing gradually in size on posterior chaetigers; all lamellae not fused basally with neuropodial postchaetal lamellae.

Branchiae present from chaetiger 1, continuing to end of body; all branchiae smooth, long, tapering ( Fig. 3 A), touching each other mid-dorsally on middle chaetigers; almost completely fused to notopodial lamellae, branchial tips free, distally pointed in a spear shape on all chaetigers ( Fig. 3 E), slightly longer than notopodial lamellae ( Fig. 3 A, D, E). Each branchia with a dense band of cilia along inner edge ( Fig. 3 A, E). Accessory branchiae present from chaetigers 18 – 20, on posterior side of notopodial base ( Fig. 3 J). Each palmate group comprising 6 to 8 lobes, with each lobe containing a vascular loop ( Fig. 3 J).

Notochaetae of chaetiger 1 arranged in a dorsal tuft and a ventral fascicle: dorsal tuft with long, smooth, slender capillaries extending beyond margins of notopodial lamellae, between palps; ventral fascicle arranged in two rows: an anterior row of broad, unilimbated, heavily reticulated, pointed capillaries ( Fig. 3 K) and a posterior row of long, slender, alimbated, smooth capillaries ( Fig. 3 L), capillaries of posterior row longer than those of anterior row; less numerous than those of dorsal fascicle. Notochaetae of chaetiger 2 and subsequent chaetigers arranged similarly as those of chaetiger 1; posterior chaetigers with an anterior row of broader chaetae and narrower unilimbated, reticulated capillaries ( Fig. 3 M); orange-tipped chaetae on several posterior chaetigers ( Fig. 3 J). Notopodial hooded hooks absent.

Neurochaetae of chaetiger 1 arranged in two rows: an anterior row comprised of stout, slightly reticulated, granulated, unilimbated capillaries, and a posterior row of long, smooth, alimbate capillary chaetae; in addition a ventral tuft of 4–5 slender, shorter, smooth, alimbated capillaries located in position of sabre chaetae. Arrangement of neurochaetae on chaetiger 2 and subsequent chaetigers similar to those of chaetiger 1, except for three additional longer, stouter slightly reticular, granulated, unilimbated sabre chaetae ( Fig. 3 P) (longer, stouter from chaetigers 14 – 15; 15 in holotype). Neurochaetae of middle chaetigers arranged in two rows: anterior row comprised of hooded hooks ( Fig. 3 N), posterior row of long, smooth, unilimbated, wide capillary chaetae ( Fig. 3 O). Unidentate hooded hooks from chaetigers 28 – 29, 28 in holoype ( Fig. 3 N), up to 5 per neuropodium. Hooded hooks opening distally ( Fig. 3 N).

Pygidium lost.

Remarks. The original description given by Gibbs (1971) was brief and also incorrect in a number of aspects (e.g., we did not find any specimens with a small occipital tentacle, two small eyes (possibly the first pair of eyes lost due to discoloration of the preserved samples over time), low and rounded prechaetal lamellae). We reexamined the D. mororoi holotype and paratype, and the description of this species here agrees somewhat with that of Gibbs (1971), but with differences such as the presence of a long, narrow caruncle with a large longitudinal nuchal ridge, two pairs of eyes, and large oval prechaetal notopodial lamellae on anterior chaetigers. In addition, we provide further information regarding the postchaetal notopodial and neuropodial lamellae along the body, as well as lateral and dorsal organs, which were not noted by Gibbs (1971) and few drawings were included.

Distribution. Solomon Islands: Komimbo Bay; Graham Pt., clean sand at LWM.

Figures

FIGURE 3. Dispio mororoi Gibbs, 1971. Holotype (BMNH- 1970.53: A – J; paratype BMNH- 1970.54: K – P): (A) anterior region, lateral view right; (B) anterior region, lateral view left; (C) middle region, dorsal view; (D) parapodium of anterior chaetigers; (E) notopodium of middle chaetigers; (F) parapodium of middle chaetigers; (G) neuropodium of anterior chaetigers; (H) parapodium of chaetigers 10 – 14; (I) parapodium of chaetigers 30 – 35; (J) notopodium of posterior chaetigers with accessory branchiae; (K) anterior notopodial chaeta of posterior row; (L) anterior notopodial chaeta of anterior row; (M) middle notopodial chaeta of posterior row; (N) hooded hook; (O) neuropodial chaeta of posterior chaetiger; (P) sabre chaetae. CBC = C-shaped double band of cilia. Scale bars: A – I 0.5 mm; mm; J 0.25 mm; K – P 0.03 mm.