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

Prionospio rotunda sp. nov.

Figure 8 A – O

Material examined. CARIBBEAN SEA. Quintana Roo: Mahahual 24 October 2008, coll. V.H. Delgado-Blas, holotype (LACM-AHF-POLY 6601); E31, on the coast at Yalahau, 22º30’990’’N, 087º05’010’’W, November 2001, 2 paratypes (ECOSUR0170); GULF OF MEXICO. Yucatan: E5, on the coast at Progreso, 22º47’035’’N, 90º20’15’’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. 8 A), tapered posteriorly, with long, blunt caruncle extending to the posterior edge of chaetiger 2 with nuchal organs fused on either side ( Fig. 8 A). Specimens with two pairs of red-brown subdermal eyes or eyes absent (1 paratype); anterior pair small, rounded ( Fig. 8 B); posterior pair cup-shaped. Palps lost (Holotype), except one specimen with a pair of long palps, grooved, lacking basal sheaths ( Fig. 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. 8 A, B, D). Neuropodial postchaetal lamellae of chaetiger 1 large, rounded ( Fig. 8 B, D), much smaller than half the size of the notopodial lamellae.

Four pairs of long branchiae present on chaetigers 2–5 ( Fig. 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. 8 A–B) and naked basal region; pinnules thick, blunt, long on middle region of the branchiae ( Fig. 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. 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. 8 D); lamellae larger on chaetiger 4, largest on chaetigers 3–4 and with triangular tips ( Fig. 8 D); becoming more oval on chaetigers 7–14 ( Fig. 8 E); progressively decreasing in size on middle chaetigers ( Fig. 8 F) and becoming more rounded on posterior chaetigers ( Fig. 8 G). Notopodial lamellae united across dorsum of chaetiger 7 only, forming a high dorsal crest ( Fig. 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. 8 B, D). Notopodial prechaetal lamellae very short in branchial region ( Fig. 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. 8 D), neuropodium on chaetiger 3 trapezoid, slightly dorsally pointed ( Fig. 8 D); second and third pairs larger than the other neuropodial lamellae; subsequent neuropodial lamellae small and rounded on middle chaetigers ( Fig. 8 D – F) and subtriangular on posterior chaetigers ( Fig. 8 G). Neuropodial prechaetal lamellae very short ( Fig. 8 D), rudimentary throughout. Interparapodial pouches lacking.

All capillaries on the anterior chaetigers granulated ( Fig. 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. 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. 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. 8 K). Neuropodial hooded hooks ( Fig. 8 L) from chaetigers 11–12, up to six per fascicle, accompanied by capillaries. Notopodial hooded hooks ( Fig. 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. 8 L, M).

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

One specimen had up to 12 gregarine parasites within the gut, between chaetigers 7 to 24 ( Fig. 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.

Figures

FIGURE 8. Prionospio rotunda sp. nov. holotype (LACM-AHF-POLY 6601: A, H – M; paratype LACM-AHF-POLY 6602: B – G, N – O): (A) anterior region, dorsal view; (B) anterior region, lateral view; (C) left palp; (D) parapodium of anterior chaetigers (1 – 5); (E) parapodium of chaetigers 7 – 8; (F) parapodium of chaetiger 14; (G) parapodium of chaetiger 40; (H) notopodium of chetigers 5 – 7 and high dorsal crest; (I) anterior notopodial chaeta; (J) anterior neuropodial chaeta; (K) sabre chaeta; (L) neuropodial hooded hook; (M) notopodial hooded hook; (N) pygidium, dorsal view; (O) parasite shown within the host´s body cavity between chaetigers 25 – 27. Scale bars: A – M 50 µm; N – O 100 µm.