Apoprionospio sanguarensis sp. nov.

Figures 2A–G; 3A–C

Material examined: Caribbean Sea: Sanguaré Natural Reserve, Gulf of Morrosquillo, Sucre (09°42′30.6″ N, 75º41´29.0″ W), in Thalassia testudinum seaweeds, holotype (CEMUA: ANNE: 002065) ; three paratypes (CEMUA: ANNE:002281), colls. Delgado-Blas, VH., Fonseca-González, I., and Londoño-Mesa, MH., June 12 th 2019 .

Description: Holotype complete, 7.9 mm long for 53 chaetigers, 0.3 mm wide. Two paratypes complete, 7.2– 7.3 mm long for 44–58 chaetigers, 0.4 mm wide; one paratype incomplete, 4.5–11 mm long for 28–50 chaetigers, 0.4 mm wide, color in alcohol opaque white.

Prostomium triangular, broadly flared, truncate, flattened anteriorly, with a slight wide medial protuberance, tapered posteriorly, with a narrow caruncle ending at base of chaetiger 2 (Figs 2A, 3A). Three pairs of small brown eyes present, arranged in a trapezoid, anterior pair crescent-shaped, widely spaced; posterior pairs small, rounded shaped, closely spaced (Figs 2A, 3A). Peristomium surrounding posterior half of prostomium and clearly separated from chaetiger 1 (Fig. 2A, B). A pair of palps short, extending to chaetiger 2 (Figs 2B, 3A).

Branchiae present from chaetiger 2, numbering four pairs; pairs 1–3 cirriform, wrinkled, first pair thinner and smaller than the second and third pair (Fig. 2A); pair of branchiae 2–3 equal in size; branchiae much shorter than notopodial lamellae (holotype), in other specimens, branchiae same size as notopodial lamellae; fourth pair longer, with plate-like pinnules arranged in two rows along the shaft of branchiae, and long, naked, wrinkled, distal tips (Fig. 2A, B).

Parapodia of chaetiger 1 with small, oval notopodial postchaetal lamellae and rounded neuropodial postchaetal lamellae (Figs 2B, 3B); neuro-, and notopodial lamellae almost in the same position (Figs 2A, B, 3B). Notopodial postchaetal lamellae foliaceous, wider on chaetigers 2–8, lamellae shorter, thinner, and subtriangular on chaetiger 2, largest on chaetigers 4–6 (Figs 2A, B, 3B), becoming elongate, symmetrical, forming V-shaped cup (Figs 2B, 3B); lamellae of chaetigers 7–8 subtriangular (Fig. 2C), subsequent notopodial lamellae subtriangular and small on far posterior chaetigers (Fig. 3C). Dorsal ridges on the middle and posterior segments absent. Notopodial prechaetal lamellae very large in anterior chaetigers (Figs 2B, 3B), basally fused with notopodial postchaetal lamellae, and subsequent lamellae small in the middle and posterior region. Very low dorsal crest across the dorsum on chaetiger 7 (Fig. 2A).

Neuropodial postchaetal lamellae on chaetiger 2 rounded, erect, large (Figs 2A, B, 3B), 2/3 larger than subsequent neuropodial lamellae; following neuropodial postchaetal thinner and bluntly rounded (Figs 2C, 3B), and small on far posterior chaetigers (Fig. 3C). Neuropodial prechaetal lamellae very small in anterior region (Fig. 2B), but rudimentary in middle and posterior chaetigers.

Anterior notopodial chaetae heavily granulated, basally striated, thick, long, broadly sheathed capillaries, with long capillary tips (Fig. 2C). Notopodial chaetae longer, thicker, and more broadly sheathed than those of neuropodial chaetae (Fig. 2C). Notopodial capillaries of chaetiger 1 arranged in one row, from chaetiger 2 onwards arranged in three rows up to chaetiger 14, thereafter in one row; anterior row shorter than posterior rows; chaetae dorsal much longer than ventral ones (Fig. 2C). Chaetae on middle and posterior of the body very thin, smooth, long. Neuropodial capillaries chaetae very short, with very long capillary tips, arranged in one row, from chaetiger 2 onwards arranged in two rows; anterior row with chaetae short, smooth, and alimbate, posterior row with chaetae long, granulate and bilimbate (Fig. 2C); neurochaetae on middle and posterior segments very thin, smooth. Sabre chaetae in neuropodia from chaetiger 11, one or two per fascicle; each chaeta robust, very long, striated, moderately granulated, broadly sheathed, with short tips (Fig. 2D). Neuropodial hooded hooks (Fig. 2E) from chaetiger 16, up to 9 per fascicle, accompanied by up to 5 capillaries. Notopodial hooks (Fig. 2F) from chaetiger 33–34, numbering 4–6 per fascicles; hooks with long primary hoods, and secondary hoods absent, with 2–4 small teeth visible in profile above main tooth (Fig. 2E, F).

Pygidium with long mid-dorsal and 2 shorter lateral anal cirri (Fig. 2G).

Type locality. Caribbean Sea, Sanguaré Natural Reserve, Gulf of Morrosquillo, Sucre, Colombia .

Etymology. The species name is referring to the Sanguaré Natural Reserve, whose staff, headed by Alvaro Roldan Maya, has been dedicated to recovering, preserving, and protecting terrestrial and aquatic ecosystems in the Gulf of Morrosquillo, Colombian Caribbean.

Remarks. Apoprionospio sanguarensis sp. nov. is distinguished from the three previously described Apoprionospio species by having the smallest body size, triangular prostomium, three pairs of eyes, the branchial pairs 1–3 are cirriform, wrinkled, the post-, and prechaetal notopodial lamellae of chaetigers 1–2 not fused, the anterior notochaetae arranged from chaetiger 2 onwards arranged in three rows, and all hooded hooks lack secondary hoods.

Closely related species are A. dayi Foster, 1969, and A. japonica Imajima, 1989 by the presence of a dorsal membranous crest across the dorsum on chaetiger 7. However, Apoprionospio sanguarensis sp. nov. differs from A. dayi and A. japonica in that the former has the notopodial lamellae on chaetiger 2 triangular, the notopodial lamellae on middle and/or posterior chaetiger not forming low ridges approximately level with dorsum. In addition, A. sanguarensis sp. nov. differs from A. dayi in that the former, the peristomium is not fused with chaetiger 1, neuropodial lamellae on chaetiger 2 rounded, and the notochaetae of chaetiger 2 arranged in three rows. Also, A. sanguarensis sp. nov. differs from A. japonica in that the former has smaller branchiae, the branchial pairs 2–3 are cirriform, wrinkled, and the posterior notopodial lamellae without cilia-like tufts along margin. Other differences are described in Table 1.