Chaetozone nicoyana, Dean, Harlan K. & Blake, James A., 2007

Dean, Harlan K. & Blake, James A., 2007, Chaetozone and Caulleriella (Polychaeta: Cirratulidae) from the Pacific Coast of Costa Rica, with description of eight new species, Zootaxa 1451, pp. 41-68 : 49-50

Chaetozone nicoyana sp. nov.

Figure 5 A–E, 7 A B.

Material Examined. Costa Rica, Gulf of Nicoya. Holtype: Sta. 29, 9°54'55"N, 84°45'15"W, 18 m, muddy sand, ( MCZ 67145). Paratypes: Sta. 29, 9°54'55"N, 84°45'15"W, 18 m, muddy sand, (10 USNM 80141); Sta. 32, 9°53'47"N, 84°49'35"W, 24 m, mud and sand, 11 Jul 1981, (1 MCZ 67146; 2 UCRMZ 129).

Comparative material examined. Costa Rica, Gulf of Nicoya. Sta. 3, 9°52'00"N, 84°48'10"W, 33 m, sandy mud, 10 Jul 1980 (1 USNM 80130). Sta. 4, 9°53'40"N, 84°46'10"W, 40 m, mud, 10 Jul 1980 (5 HKD). Sta. 12, 9°46'15"N, 84°41'50"W, 44 m, mud, 10 Jul 1980 (2 USNM 80131, 80132). Sta. 13, 9°52'30"N, 84°43'50"W, 26 m, 10 Jul 1980 (4 USNM 80133). Sta. 14, 9°57'05"N, 84°45'30"W, 9 m, sandy mud, 10 Jul 1980 (5 USNM 80134). Sta. 15, 9°57'40"N, 84°47'00"W, 15 m, sandy mud, 10 Jul 1980 (1 HKD). Sta. 22, 9°48'25"N, 84°52'40"W, 22 m, muddy sand, 11 Jul 1980 (2 USNM 80120, 80135). Sta. 23, 9°48'35"N, 84°43'50"W, 35 m, mud, 10 Jul 1980 (2 USNM 80136). Sta. 24, 9°49'25"N, 84°41'20"W, 11 m, sand, 1 Oct 1980 (7 HKD, as sp. B of Dean 1996a and sp. D of Dean 2004), 27 Jan 1981 (2 HKD), 4 Apr 1981 (5 HKD), 7 Jun 1981 (19 HKD), 4 Aug 1981 (16 HKD). Sta. 26, 9°51'50"N, 84°53'20"W, 17 m, muddy sand, 11 Jul 1980 (1 USNM 80137). Sta. 27, 9°51'57"N, 84°50'50"W, 12 m, muddy sand, 11 Jul 1980 (2 USNM 80138). Sta. 28, 9°52'16"N, 84°45'30"W, 26 m, mud, 11 Jul 1980 (1 HKD), 1 Oct 1980 (4 HKD), 4 Apr 1981 (5 HKD), 7 Jun 1981 (7 HKD), 4 Aug 1981 (6 HKD). Sta. 29, 9°54'55"N, 84°45'15"W, 18 m, muddy sand, 11 Jul 1980 (1 USNM 80139), 27 Jan 1981 (4 HKD), 4 Aug 1981 (54 HKD). Sta. 30, 9°54'40"N, 84°45'50"W, 18 m, muddy sand, 11 Jul 1980 (1 USNM 80140), 1 Oct 1980 (6 HKD), 27 Jan 1981 (11 HKD), 4 Apr 1981 (8 HKD), 4 Aug 1981 (15 HKD). Sta. 33, 9°53'40"N, 84°53'20"W, 11 m, mud, 11 Jul 1980 (2 HKD). Sta. 36, 9°55'32"N, 84°45'20"W, 18 m, sandy mud, 10 Jul 1980 (1 HKD). Sta. 44, 9°59'17"N, 84°54'25"W, 24 m, muddy sand, 10 Jul 1980 (1 USNM 80144).

An elongate, medium-size species with wide anterior region of approximately 10 short setigers, middle and posterior region slightly moniliform, with setigers as long as, or longer than wide; podial lobes forming partial cinctures. Holotype 7.45 mm long and 0.3 mm wide for 50 setigers; complete paratypes 4.9 mm long and 0.2 mm wide for 50 setigers and 4.1 mm long and 0.15 mm wide for 47 setigers ( USNM 80141). Pygidium short cone with laterally expanded flap extending ventrally to, and beyond, anal opening ( Fig. 5 C). Color in alcohol uniformly light tan.

Prostomium narrow, tapering with pair of oval, lateral nuchal organs at posterior border ( Figs. 5 A B; 7A). Peristomium slightly overlapping rear of prostomium, with three annulations; second and third annulations subequal in length, each approximately 2× as long as first annulation; second and third annulations with slightly swollen dorsal crest ( Figs. 5 B, 7A). Dorsal tentacles emerging from posterior margin of third peristomial annulation; first pair of branchiae emerging posterior to and slightly lateral to tentacular bases from asetigerous first segment fused with setiger 1; subsequent branchiae on posterodorsal margin of segments dorsal to notosetal fascicles, extending to far posterior region.

Parapodia reduced to simple swollen lobes; notopodial and neuropodial lobes adjacent throughout. Notosetae of anterior region long, finely pilose capillaries, 5–7 per fascicle; long, thin spines from setiger 20 in holotype (16–20 in other specimens), initially with single transitional seta similar to other capillaries but with spinous tip; following setigers with 3–4 spines accompanied by 3–4 pilose capillaries, grading rapidly in subsequent setigers to anterior row of 3–5 spines accompanied by posterior row of 3–4 longer, spines ( Fig. 5 D). Neurosetal fascicles in anterior region with 6–8 pilose capillaries, spines appearing from setiger 12 in holotype (12–15 in other specimens); initially with three spines accompanied by three capillaries, then grading to anterior row of 3–5 spines accompanied by posterior row of 3–5 longer, more narrow spines ( Figs. 5 D, 7B); notosetal and neurosetal fascicles with reduced numbers of setae in far posterior setigers. Spines long, thin and straight with fine tip bending back and adhering to shaft ( Fig. 5 E).

Methyl green staining pattern. Body uniformly light blue with anterior segments staining more intensely; anterior region with darkly staining, midventral line. Prostomium and dorsum of peristomium and asetigerous segments, as well as far posterior body region, unstained.

Habitat. A widespread subtidal species in the Gulf of Nicoya, mud and sand, 9–44 m depth.

Remarks. Chaetozone nicoyana sp. nov. is similar to C. curvata , C. commonalis , Chaetozone anasimus Doner & Blake, 2006 off New England, and Chaetozone allanotai Blake, 2006 from deep water off northern California, in having acicular spines with a fine recurved tip that adheres to the setal shaft. The first occurrence of these spines is much earlier in C. nicoyana sp. nov. (setigers 12–14) than in the related species, where the spines do not begin prior to setiger 40. Additionally, the double row of spines in both rami of C. nicoyana sp. nov. is unlike the single rows of spines that form partial cinctures in the posterior setigers of the related species.

Etymology. The specific name refers to the common occurrence of this species subtidally in the Golfo de Nicoya.

Figures

FIGURE 5. Chaetozone nicoyana sp. nov. A. Lateral view of anterior end B. Dorsal view of anterior end C. Dorsal view of pygidial region D. Posterior setiger, anterior view E. Recurved neuropodial acicular spine. Scale bars: A – C = 0.1 mm, D = 0.5 mm, E = 5 Μm. a = annulations, no = nuchal organ.