Prionospio cristaventralis, elgado-Blas, Victor Hugo, iaz-Diaz, Oscar & ieitez, Jose M., 2018

elgado-Blas, Victor Hugo, iaz-Diaz, Oscar & ieitez, Jose M., 2018, Prionospio from the coast of the Iberian Peninsula, with the description of two new species (Annelida, Spionidae), ZooKeys 810, pp. 1-18 : 5-8

Prionospio cristaventralis sp. n. Figure 3 A–Q

Material examined.

Atlantic Ocean. Cantabrian Sea: Holotype (MNCNM 16.01/3983), Between Cabo Vidio and Cabo de Peñas, Asturias, Z2 D59, depth 25.6 m, 43°33'30"N, 6°7'1"W, colls. G San Martin and R Acuña Castroviejo, 1998. 1 paratype (MNCNM 16.01/3984), depth 34.5 m, 43°33'30"N, 6°7'1"W, colls. G San Martin and R Acuña Castroviejo. 1 paratype (MNCNM 16.01/3985), depth 24 m, 43°33'30"N, 6°7'1"W, colls. G San Martin and R Acuña Castroviejo, 1998. 1 paratype (MNCNM 16.01/3986), depth 34 m, 43°33'30"N, 6°7'1"W, colls. G San Martin and R Acuña Castroviejo, 1998.

Description.

Holotype incomplete, 18 mm long with 34 chaetigers, 1.1 mm wide. Paratypes incomplete, 12.0-13.0 mm long, 22-23 chaetigers, 0.9-1.1 mm wide. Color in alcohol pale white. Prostomium bottle-shaped, broadly rounded, flared anteriorly (Fig. 3A), flattened dorso-ventrally on anterior margin (Fig. 3B), posteriorly tapered, with long, narrow caruncle extending to the posterior edge of chaetiger II, with U-shaped nuchal organs on both sides (Fig. 3A). Two pairs of black subdermal eyes in a trapezoidal arrangement; anterior pair small, rounded, posterior pair very large, crescent-shaped (Fig. 3A, B). Palps lost. Peristomium short, collar-like, surrounding the prostomium, not fused dorsally, with moderate, oval notopodial lamellae on chaetiger I (Fig. 3 A–C). Neuropodial postchaetal lamellae on chaetiger I large, oval with ventral edge elongated (Fig. 3 A–C), much larger than the notopodial lamellae; notopodial and neuropodial prechaetal lamellae lacking on chaetiger I.

Four pairs of long branchiae present on chaetigers II–V (Fig. 3A, B), first pair longest (Fig. 3B). Pairs 1 and 4 with long, slender, dense digitiform pinnules on posterior face of stems (Fig. 3A, B); branchiae with very long, naked, smooth distal tips, pinnulated basally; pinnule distribution similar on both pairs; pinnules long, slender, blunt in middle and basal regions of branchiae. Pairs 2 and 3 apinnate, triangular, broad, with short pointed tips, densely ciliated laterally (Fig. 3A, B), subequal in length, shorter than pinnate pairs, but slightly longer than notopodial lamellae. Pairs 3 and 4 each united basally by low crest across dorsum (Fig. 3A).

Notopodial postchaetal lamellae on chaetigers II–VII foliaceous with wide bases (Fig. 3 A–C), distal halves narrow and elongated; larger and wider on chaetigers III and IV, with long, pointed tips; becoming more oval on chaetigers VIII–X (holotype X) (Fig. 3B, D); lamellae progressively decreasing in size and becoming subtriangular on chaetigers XV– XIX, assuming a more angular form with a ventrally-directed process (Fig. 3E). Subsequent lamellae progressively decreasing in size, and becoming subtriangular (Fig. 3F). Notopodial postchaetal lamellae united across dorsum of chaetigers X and XI forming high dorsal crests (Fig. 3G); on chaetigers XII–XXII /XXXIV (end fragment) forming low dorsal crests. Ventral edges of notopodial lamellae and dorsal edges of neuropodial lamellae not touching on any chaetigers (Fig. 3 B–D). Notopodial prechaetal lamellae very large in anterior region, basally fused with notopodial postchaetal lamellae (Fig. 3A, B, D); prechaetal lamellae on chaetigers XI–XV and subsequent lamellae progressively decreasing in size, split, and becoming rounder and smaller (Fig. 3E).

Neuropodial postchaetal lamellae large, triangular, with ventrally-directed process, enlarged on chaetiger II (Fig. 3B); neuropodial lamellae oval on chaetigers III-IX (Fig. 3B), small and rounded on chaetigers X–XIII (Fig. 3D), thereafter, becoming triangular with long, pointed tips (Fig. 3E); subsequent neuropodial lamellae more small (Fig. 3F). Anterior neuropodial prechaetal lamellae short (Fig. 3B, D), progressively increasing in size, becoming rounded and very large on chaetigers XI–XII, connected through well-developed ventral crests forming U-shaped depressions at midline (Fig. 3H); large crests continuing through chaetigers XV–XIX (Fig. 3H); subsequent chaetigers without ventral crests. Interparapodial pouches lacking.

Notopodial capillaries on chaetigers I–V arranged in two rows: anterior row short, heavily granulated, unilimbate (wide limbation), very acute (Fig. 3I); posterior row longer, thinner, more heavily granulated (Fig. 3J); capillaries arranged in three rows on chaetiger VI, similar to anterior chaetae. Notopodial capillaries in middle chaetigers arranged in two rows: anterior row short, granulated, unilimbate (Fig. 3K); posterior row granulated, unilimbate, with very long and pointed tips (Fig. 3L); posterior chaetigers with very long, slender, smooth, alimbate chaetae (Fig. 3M). Neuropodial capillaries on chaetigers I–V arranged in two rows; neuropodial capillaries on chaetigers VI–X arranged in three rows; all capillaries with same structure as notopodial chaetae. Sabre chaetae in neuropodia from chaetiger X, one per fascicle, each chaeta stout, distinctly curved, basally smooth, heavily granulated medially and distally, without sheaths (Fig. 3N). Neuropodial hooded hooks (Fig. 3O) from chaetiger XV, up to 10 per fascicle, accompanied by thin, alimbate capillaries (Fig. 3P). All hooks with six pairs of small teeth above large main tooth, and short, small secondary hoods (Fig. 3O). Notopodial hooded hooks not present on incomplete XXXIV-chaetiger holotype.

Pygidium missing.

Remarks.

Prionospio cristaventralis sp n. is similar to P. multicristata Hutchings & Rainer, 1979, P. nirripa Wilson, 1990, P. nielseni Hylleberg & Nateewathana, 1991, P. cornuta Hylleberg & Nateewathana, 1991, and P. paradisea Imajima, 1990 in that all show the same prostomial shape and neuropodial postchaetal lamellae on chaetigers II–III. However, P. cristaventralis sp. n. differs from these species due to the presence of ventral crests and dorsal crests limited to chaetigers X–XI, and low dorsal crests on chaetigers XII–XXII /XXXIV (end fragment) compared to low dorsal crests from chaetigers VII to XXV-XXX in P. multicristata , low dorsal crests from X–XIII to XXVIII–XXXVII in P. nirripa , P. nielseni and P. cornuta and high crests from X to LX in P. paradisea . Prionospio cristaventralis sp. n. is also similar to P. pacifica Zhou & Li, 2009 in that both species have dorsal and ventral crests or folds. However, P. cristaventralis sp. n. can be distinguished from P. pacifica by having a prostomium that is rounded anteriorly (instead of being truncate), dorsal crests on chaetigers IV–V (instead of lacking such crests), and ventral crests on chaetigers XI–XIX (instead of only on chaetiger IX). The presence of ventral crests appears to be a unique feature of these two species.

Etymology.

The specific name is from the Latin crista meaning crests and ventralis meaning ventral.

Type locality.

Between Cabo Vidio and Cabo de Peñas, Asturias, Spain.

Habitat.

Specimens were collected in shallow water (24-34.5 m depth).

Distribution.

Atlantic Ocean. Cantabrian Sea: Between Cabo Vidio and Cabo de Peñas, Asturias, Spain.