Streblospio padventralis, Delgado-Blas & Díaz-Díaz & Viéitez, 2018

Delgado-Blas, Víctor Hugo, Díaz-Díaz, Óscar & Viéitez, José M., 2018, New species of Dispio Hartman, 1951 and Streblospio Webster, 1879 (Polychaeta, Spionidae) from the coast of the Iberian Peninsula, Zootaxa 4410 (3), pp. 525-538 : 534-535

Streblospio padventralis sp. nov.

Figure 3A–Q

Streblospio benedicti: Viéitez, 1981 ; Junoy & Viéitez, 1990; López Serrano, 1999.

Type material. Atlantic coast. Combarro beach, Ría de Pontevedra, 42°17′N, 8°43′W, intertidal, April 1975, holotype ( MNCNM 16.01 /17907), 1 paratype ( MNCNM 16.01 /17910) (Col. J.M. Viéitez); Meira beach, Ría de Vigo, 41°17′N – 08°43´W, intertidal, October 1976, 1 paratype ( MNCNM 16.01 /17911) (Col. J.M. Viéitez) ; Piedras river mouth, Huelva, 37°12′N, 7°7′W, intertidal, March 1988, 1 paratype ( MNCNM 16.01 /17908) November 1988, 2 paratypes ( MNCNM 16.01 /17909) (Col. L. López Serrano). NE Atlantic: Cantabrian coast . Ría de Foz , Lugo, 43°33′N, 7°14′W, intertidal, April 1984, 1 complete paratype ( MNCNM 16.01 /17912) (Col. J. Junoy).

Description. Holotype complete, 7.5 mm long with 49 chaetigers, 0.3 mm wide at chaetiger 6; paratype complete, 13.0 mm long, with 54 chaetigers, 0.6 mm wide at chaetiger 6; 3 paratypes incomplete, 1.0–8.0 mm long, with 11–34 chaetigers, 0.2–0.6 mm wide at chaetiger 6. Color in alcohol pale white.

Prostomium fusiform, rounded anteriorly ( Fig. 3A–D ), with a long and slender subdistal pad surrounding the ventral region ( Fig. 3A–D ); posteriorly blunt, extending to anterior margin of chaetiger 1 ( Fig. 3A–B ). Two pairs of black subdermal eyes, arranged in a trapezoid; anterior pair small, crescent-shaped, posterior pair large, rounded ( Fig. 3A–B ). Palps located lateral to prostomium (some paratypes with palps lost). Palps long, extending up to chaetiger 5, densely ciliated on frontal surfaces ( Fig. 3E ). Peristomium large, expanded laterally, partially surrounding the prostomium, and extending around base of palps, forming short lateral wings, fused dorsally from chaetiger 1 ( Fig. 3A–B, E–F ).

Branchiae present on chaetiger 1, inserted just posterior to prostomium; surfaces wrinkled, thick ( Fig. 3E ), heavily ciliated; branchiae long, extending up to chaetiger 6, about the same length, but slightly thicker than palps. Conical papilla absent between branchiae ( Fig. 3A–B ).

Parapodia on chaetiger 1 with neuropodial postchaetal lamellae only; notopodial lamellae lacking, but with 1– 4 long capillaries present on the notopodium ( Fig. 3A–B ); neuropodial postchaetal lamellae on chaetiger 1 large, oval ( Fig. 3A–B, F ), slightly inclined. Notopodial postchaetal lamellae on chaetiger 2 dorsally rounded and triangular on ventral edges ( Fig. 3G ); united across dorsum, forming a high dorsal membranous collar ( Fig. 3A–B, G ); notopodium on chaetiger 3 oval large ( Fig. 3H ); notopodia largest on chaetigers 2–3, becoming low, wider and more rounded on chaetigers 4–8 ( Fig. 3I ). Notopodial lamellae disappearing from chaetigers 11–13 until the end ( Fig. 3J ). Anterior notopodial prechaetal lamellae low, middle and posterior chaetigers absent.

Neuropodial postchaetal lamellae rounded throughout ( Fig. 3H, F ), except the neuropodium on chaetiger 2 which is slightly angled and trapezium-shaped, ventrally directed ( Fig. 3G ); larger than other neuropodial lamellae. Neuropodial lamellae disappearing from chaetigers 8–10 until the end ( Fig. 3J, P ). Neuropodial prechaetal lamellae on chaetiger 1 low, rudimentary on succeeding chaetigers. Interparapodial pouches lacking.

All notopodial and neuropodial capillaries arranged in one row. Notopodial and neuropodial capillaries on anterior chaetigers slightly granulated, alimbate ( Fig. 3K, L ); notopodial capillaries on middle and posterior chaetigers slender, smooth and alimbate. Sabre chaetae on neuropodia from chaetiger 3 (stouter on chaetiger 7), up to two per fascicle; each chaeta stout, curved, slightly granulated, alimbate ( Fig. 3M ). Neuropodial hooded hooks ( Fig. 3N ) from chaetigers 7–9 (holotype 9), up to nine per fascicle, accompanied by short, slender, alimbate capillaries ( Fig. 3O ); all hooks with 4–5 pairs of small teeth above main tooth, without secondary hoods; main hood very large ( Fig. 3 N’). Notopodial hooded hooks absent.

Pygidium with lappets ( Fig. 3P ).

Some of the specimens examined were females with oval-shaped oocytes in brood structures in the coelomic cavities ( Fig. 3Q ) between segments 21–31, measuring 38/50–66/90 µm in diameter. Females carried eggs in spring.

Methyl green staining pattern: from posterior margin of chaetiger 3 up to chaetiger 8 tissues stained profusely with methyl green ( Fig. 3C ).

Etymology. The specific name refers to the pad-like structure located in the antero-ventral region of the prostomium.

Type locality. Atlantic coasts. Combarro beach, Ría de Pontevedra.

Habitat. Intertidal muddy soft bottoms.

Geographical distribution. Cantabrian coast: Ría de Foz, Lugo. Atlantic coast: Combarro beach, Ría de Pontevedra; Meira beach, Ría de Vigo; Piedras river mouth, Huelva.

Remarks. Streblospio padventralis sp. nov. is similar to S. shrubsolii ( Buchanan, 1890) in not having a dorsal papilla between the branchiae. However, Streblospio padventralis sp. nov. can be distinguished from the original description of S. shrubsolii ( Buchanan, 1890) and the redescription of S. shrubsolii given by Rice & Levin (1998) in that in the former the dorsal membranous crest is entire (one piece), rather than bilobed on chaetiger 2; sabre chaetae are present, as opposed to being (apparently) absent; the hooks have 4–5 pairs of small teeth, rather than 3–4; the pygidium has ventral lappets, rather than being simple, and the brooding structure is formed by coelomic cavities on each segment rather than transverse, mid-segmental ridges. In addition, Streblospio padventralis sp. nov. is similar to S. benedicti Webster, 1879 in the brooding structure occurs in the coelomic cavities. However, Streblospio padventralis sp. nov. can be distinguished from S. benedicti Webster, 1879 , S. gynobranchiata Rice & Levin, 1998 and S. japonica Imajima, 1990 in that it does not have a dorsal papilla between the branchiae. Furthermore, Streblospio padventralis sp. nov. can be distinguished from S. benedicti Webster, 1879 and S. gynobranchiata Rice & Levin, 1998 in that it has sabre chaetae from chaetiger 3, rather than chaetiger 7; the hooks have 4–5 pairs of small teeth, rather than 3–4; and the pygidium has ventral lappets, rather than being simple or lobed. Also, S. padventralis sp. nov. can be distinguished from S. gynobranchiata Rice & Levin, 1998 in that the brooding structure is composed of coelomic cavities on each segment rather than being branchiate.

The identity of the specimens recorded as S. shrubsolii from Iberian coasts by Quintino et al. (1987) and S. benedicti by Ibáñez et al. (1984), still needs to be verified.

Figures

FIGURE 3. Streblospio padventralis sp. nov. Holotype: (MNCNM 16.01/17907: E; paratype MNCNM 000: A–D, F–Q): A) anterior region, dorsal view; B) anterior region, latero-dorsal view; C) anterior region, ventral view; D) same anterior region showing prostomial ventral pad, ventral view; E) anterior region, lateral view; F) anterior region and chaetiger 1, lateral view; G) chaetiger 2, anterior view; H) parapodium of chaetiger 3; I) parapodium of chaetiger 7; J) parapodium of chaetiger 13; K) notopodial capillary chaeta; L) neuropodial capillary chaeta; M) sabre chaeta; N–N´) hooded hook in front and lateral view, respectively; O) companion chaeta; P) posterior region, dorsal view; Q) schematic drawing of inner brood chamber (Vp: ventral pad).