Prionospio rotunda , Delgado-Blas, Víctor Hugo, 2015

Delgado-Blas, Víctor Hugo, 2015, Prionospio (Polychaeta, Spionidae) from the Grand Caribbean Region, with the descriptions of five new species and a key to species recorded in the area, Zootaxa 3905 (1), pp. 69-90: 87-89

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Prionospio rotunda

sp. nov.

Prionospio rotunda  sp. nov.

Figure 8View FIGURE 8 A – O

Material examined. CARIBBEAN SEA. Quintana Roo: Mahahual 24 October 2008, coll. V.H. Delgado-Blas, holotype (LACM-AHF-POLY 6601); E 31, on the coast at Yalahau, 22 º 30 ’ 990 ’’N, 087º05’010’’W, November 2001, 2 paratypes (ECOSUR0170); GULF OF MEXICO. Yucatan: E 5, on the coast at Progreso, 22 º 47 ’035’’N, 90 º 20 ’ 15 ’’W, October 2001, 1 paratype (LACM-AHF-POLY 6602).

Description. Holotype complete, 5.0 mm long for 49 chaetigers, 0.2 mm wide. Paratypes complete, 45–47 chaetigers, 5.5 mm long, 0.2 mm wide. Color in alcohol pale white. Prostomium pyriform-shaped, rounded anteriorly ( Fig. 8View FIGURE 8 A), tapered posteriorly, with long, blunt caruncle extending to the posterior edge of chaetiger 2 with nuchal organs fused on either side ( Fig. 8View FIGURE 8 A). Specimens with two pairs of red-brown subdermal eyes or eyes absent (1 paratype); anterior pair small, rounded ( Fig. 8View FIGURE 8 B); posterior pair cup-shaped. Palps lost (Holotype), except one specimen with a pair of long palps, grooved, lacking basal sheaths ( Fig. 8View FIGURE 8 C) extending up to chaetiger 12. Peristomium moderate in size, collar-like, surrounding the prostomium, fused dorsally with large, rounded notopodial lamellae of chaetiger 1 ( Fig. 8View FIGURE 8 A, B, D). Neuropodial postchaetal lamellae of chaetiger 1 large, rounded ( Fig. 8View FIGURE 8 B, D), much smaller than half the size of the notopodial lamellae.

Four pairs of long branchiae present on chaetigers 2–5 ( Fig. 8View FIGURE 8 B); first pair longer than fourth pair. Pairs 1 and 4 with a few long, digitiform pinnules on posterior face, branchiae with very long naked, smooth distal tips ( Fig. 8View FIGURE 8 A–B) and naked basal region; pinnules thick, blunt, long on middle region of the branchiae ( Fig. 8View FIGURE 8 A); the central stem of branchial pairs 1 and 4 pinnate, elongate. Pairs 2 and 3 apinnate, cirriform, long with a dense lateral ciliation ( Fig. 8View FIGURE 8 B); subequal in length, shorter than pinnate pairs, but longer than notopodial lamellae.

Notopodial postchaetal lamellae triangular and thinner on chaetigers 2–5 ( Fig. 8View FIGURE 8 D); lamellae larger on chaetiger 4, largest on chaetigers 3–4 and with triangular tips ( Fig. 8View FIGURE 8 D); becoming more oval on chaetigers 7–14 ( Fig. 8View FIGURE 8 E); progressively decreasing in size on middle chaetigers ( Fig. 8View FIGURE 8 F) and becoming more rounded on posterior chaetigers ( Fig. 8View FIGURE 8 G). Notopodial lamellae united across dorsum of chaetiger 7 only, forming a high dorsal crest ( Fig. 8View FIGURE 8 H); chaetiger 8 and subsequent chaetigers without dorsal fold. Ventral and dorsal edges of notopodial and neuropodial lamellae not touching on anterior chaetiger ( Fig. 8View FIGURE 8 B, D). Notopodial prechaetal lamellae very short in branchial region ( Fig. 8View FIGURE 8 B, D), inconspicuous thereafter.

Anterior neuropodial postchaetal lamellae rounded throughout, except the neuropodia on chaetigers 2–3; neuropodium on chaetiger 2 large and subtriangular, ventrally pointed ( Fig. 8View FIGURE 8 D), neuropodium on chaetiger 3 trapezoid, slightly dorsally pointed ( Fig. 8View FIGURE 8 D); second and third pairs larger than the other neuropodial lamellae; subsequent neuropodial lamellae small and rounded on middle chaetigers ( Fig. 8View FIGURE 8 D – F) and subtriangular on posterior chaetigers ( Fig. 8View FIGURE 8 G). Neuropodial prechaetal lamellae very short ( Fig. 8View FIGURE 8 D), rudimentary throughout. Interparapodial pouches lacking.

All capillaries on the anterior chaetigers granulated ( Fig. 8View FIGURE 8 I, J); notopodial and neuropodial capillaries of chaetiger 1 arranged in one row, with short, slender chaetae; notopodial chaetae longer. Notopodial capillaries of chaetigers 2–12 arranged in two rows, with very long and very acute unilimbated chaetae ( Fig. 8View FIGURE 8 I); upper chaetae much longer than lower ones, chaetae curving outwards and upwards, in posterior segments becoming shorter. Neuropodial capillaries of chaetigers 2–9 arranged in two rows, with short and very acute alimbated chaetae ( Fig. 8View FIGURE 8 J), anterior row shorter than posterior row, later becoming one row; longer, slender and non-granulated capillaries on median and posterior chaetigers. Sabre chaetae in neuropodia from chaetiger 10, up to two per fascicle, stout, curved, moderately granulated, without sheaths ( Fig. 8View FIGURE 8 K). Neuropodial hooded hooks ( Fig. 8View FIGURE 8 L) from chaetigers 11–12, up to six per fascicle, accompanied by capillaries. Notopodial hooded hooks ( Fig. 8View FIGURE 8 M) from chaetigers 28–32, up to four per fascicle. Accompanied by up to two thin capillaries. All hooks with four pairs of teeth above the main tooth, with large secondary hoods ( Fig. 8View FIGURE 8 L, M).

Pygidium with one long median cirrus and two longer lateral lobes ( Fig. 8View FIGURE 8 N).

One specimen had up to 12 gregarine parasites within the gut, between chaetigers 7 to 24 ( Fig. 8View FIGURE 8 O).

Remarks. Examination of the 35 previously known species of the P. steenstrupi  group ( Sigvaldadóttir & Mackie, 1993: Table 2; Blake, 1996; Sigvaldadóttir 1997; Zhou & Li 2009) reveals that Prionospio rotunda  sp. nov. is very similar to P. fallax Södertröm, 1920  and P. membranacea Imajima 1990  in having a dorsal crest on chaetiger 7 and the same shaped neuropodial lamellae on chaetiger 2. However, Prionospio rotunda  differs from the redescription of P. fallax  by Sigvaldadóttir & Mackie (1993) and the original description of P. membranacea  in that the former has an anteriorly rounded prostomium; a long, blunt caruncle extending to the posterior edge of chaetiger 2 with nuchal organs fused over either side, cirriform second and third branchial pairs; trapezoid, ventrally pointed neuropodial lamellae on chaetiger 3, subtriangular neuropodial lamellae on the posterior chaetigers, and all hooks with four pairs of teeth above the main tooth. In addition, P. ro t u nd a differs from P. fallax  in that the former has branchiae with pinnules arranged along the posterior margins of the stems, and large, rounded neuropodial lamellae on chaetiger 1. Finally, P. rotunda  differs from P. membranacea  in that the former has neuropodial hooded hooks from chaetigers 11–12 and notopodial hooded hooks from chaetigers 28–32. The differences between P. rotunda  and the other species examined are provided in the key and Table 1.

Gregarine parasites were found in the digestive tract of one specimen of P. ro t u nd a sp. nov. Douglas & Jones (1991) reported on gregarine associated with eight spionid species ( Boccardia proboscidea Hartman, 1940  , Boccardiella hamata (Webster, 1879)  (cited as Boccardia hamata  ), Polydora cornuta Bosc, 1802  (cited as Polydora ligni Webster, 1879  ), Polydora nuchalis Woodwick, 1953  , Dipolydora socialis (Schmarda, 1861)  (cited as Polydora socialis  ), Streblospio benedicti Webster, 1879  , Spio maculata (Hartman, 1961)  (cited as Scolelepis maculata  ), and Pygospio elegans Claparède, 1863  ) where the gregarine were found in the gut lumen.

Etymology. The species name is from the Latin rotundus meaning rounded and refers to the anteriorly rounded prostomium.

Type locality. Gulf of Mexico: Yucatan, Caribbean Sea: Mahahual.