Dispio Hartman, 1951

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 : 153-154

Dispio Hartman, 1951 emended

Type species: Dispio uncinata Hartman, 1951 , by monotypy.

Diagnosis. Prostomium spindle-shaped, fusiform, peanut-shaped, ovoid-shaped, rectangular-shaped, wedgeshaped, hourglass-shaped, anteriorly bluntly pointed, with narrow or blunt, short or long caruncle extending to middle (short) or posterior margin (long) of chaetiger 1; peristomium well-developed, expanded laterally, partially enveloping prostomium and extending around base of palps, forming low lateral wings (some species with lateral wings more developed than others; lateral wings not attached to prostomium, e.g. D. glabrilamellata , D. latilamella , D. anauncinata sp. nov, and are separated from chaetiger 1; two pairs of eyes, arranged in a nearly straight line or trapezoid, or eyes absent. Well-developed, lobulated, eversible proboscis. Occipital tentacle absent. Palps short, extending to chaetigers 5 – 12; palps with single band of transverse rows of cilia on one side of ventral ciliated groove; palp sheaths large, with smooth edges and without special adornment, fused to base of palps. Anterior postchaetal notopodial lamellae serrated (sometimes slender with longer, or shorter digitiform papillae along margin; papillae found on lamellae up to chaetiger 13; lamellae of subsequent chaetigers lack papillae, or chaetiger 1 much broader (spoon-shaped, with shorter digitiform papillae along margin), or notopodial lamellae entire. Anterior neuropodial lamellae serrated (with shorter digitiform extensions along margin and extensions found on lamellae of up to chaetiger 4; lamellae of subsequent chaetigers lack extension) or neuropodial lamellae entire, rounded or triangular. Prechaetal notopodial and neuropodial lamellae well-developed anteriorly and low posteriorly. Branchiae from chaetiger 1, smooth, fused completely or partially with notopodial lamellae, distal ends free, continuing nearly to end of body. Accessory branchiae on posterior surface of notopodia from chaetigers 8 – 30, initially with a single digitate lobe, increasing to 8 (as short nodules or fingerlike palmate lobes) digitate lobes on posterior chaetigers, or absent ( D. brachychaeta , D. magnus D. oculata ). Each branchiae with a well-developed narrow band of cilia along inner edge, continuous with that of branchiae on other side of body and joined by a narrow transverse band of cilia across dorsum, which on posterior chaetigers runs along dorsal edge of a thin, elevated dorsal crest; ciliary band sometimes interrupted at base of branchiae. Each segment with a pair of dorsal C-shaped or J-shaped (arranged obliquely) double bands of cilia (= metameric dorsal ciliated organs) with a transverse band of cilia between them. Lateral organs between notopodial and neuropodial postchaetal lamellae present or absent. With capillary notochaetae only; notochaetae of chaetiger 1 and succeeding chaetigers in three groups, including a group of capillary chaetae dorsal to an anterior row of stout capillaries, and a posterior row of thinner capillary chaetae. Neurochaetae in three groups, two rows similar in morphology to notochaetae, plus a ventral fascicle of inferior chaetae replacing sabre chaetae; unidentate neuropodial hooded hooks in larvae and juveniles (rare in adults, with bidentate and unidentate hooded hooks integrated in same fascicle). Bidentate hooks in adults replacing anterior row of capillary neurochaetae from chaetigers 15 – 44. Some capillaries and sabre chaetae with a heavily reticulated and granular shaft, others only with granulation ( D. magnus , D. brachychaeta ).

Some capillaries on anterior rows with distinct transverse barring pattern, composed of partitions and chambers in shafts, giving chaetae a cracked appearance; reticulations sometimes interspersed with dense groups of granules. Pygidium with midventral flap or flange and either one ( Dispio lenislamellata sp. nov.) or two pairs of long cirri ( D. anauncinata sp. nov.) or absent ( D. magnus ), or pygidium reduced with small papillae on ventral surface ( D. latilamella ).

Remarks. The present diagnosis is based on examinations of type and non-type specimens, as well as the original descriptions of all species in the genus. The major changes from previous diagnoses concern the chaetal arrangements of the notochaetae in a dorsal tuft and two rows. This proposal is supported by our own observations of the new species. Dispio species do not possess occipital tentacles. Many segments have a pair of dorsal Cshaped or J-shaped (arranged obliquely) double bands of cilia with a transverse band of cilia between them. Lateral organs between notopodial and neuropodial postchaetal lamellae may be present or absent (not visible). It is sometimes difficult to discern where the sabre chaetae begin and detailed examination is thus required (e.g., for D. magnus and D. brachychaeta ). There are almost always 5 – 6 small chaetae in the position of sabre chaetae on chaetiger 1 and along the first 10 or 11 chaetigers. The sabre chaetae increase in size abruptly from chaetigers 10 – 11, and reduce in number to 2 – 3 chaetae, with the shaft showing a greater curvature. The sabre chaetae may be reticulated with uniformly arranged granules, or granulated. The number of notopodial and neuropodial lamellae with digitiform papillae can serve as a useful diagnostic character along with other morphological traits. The first accessory branchiae can be seen on the inside of the celoma, and may start from there with a single external papilla, with the number of papillae increasing along the body to form a clump.