Chaetozone dossena, Blake & Dean, 2019

Blake, James A. & Dean, Harlan K., 2019, New Species of Cirratulidae (Annelida, Polychaeta) from the Caribbean Sea, Zootaxa 4671 (3), pp. 301-338 : 317

Chaetozone dossena new species

Figures 9–10

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Material examined. Caribbean Sea, Venezuela, Bahía de Mochima, off Cumaná , Sucre State, 22 June 1971, coll. Rex Edwards, low water, 6–10 m in calcareous mud, holotype ( USNM 49932 ) .

Description. Holotype complete with about 95 setigers, posterior segments twisted, 10.5 mm long, 0.65 mm wide across anterior segments, 0.8 mm across largest middle body segments, narrowing in far posterior segments. Anterior 30 segments narrow, dorsoventrally flattened, about 8–10 times wider than long, with dorsum smooth, rounded; venter with distinct groove from about setiger 10–12 continuing through posterior segments; ventral groove narrowing, developing mid-ventral ridge or row of mounds at mid-point where left and right sides of parapodia merge. Anterior parapodia with well-developed lateral shoulders below elevated and rounded dorsum ( Figs. 9A ; 10A ). Middle body segments narrower, then becoming larger, more rounded than anterior setigers, but with individual segments still narrow, about 6–8 times wider than long. Color in alcohol light tan, with few weak pigment speckles on ventral lip of mouth and mid-ventral surface of first setiger ( Fig. 9B ). A distinctive dorsal blood vessel and heart body apparent in anterior setigers ( Fig. 10A ).

Pre-setiger region short, about as wide as long ( Figs. 9 A–B; 10A). Prostomium elongate, triangular, tapering to narrow, rounded, slightly pointed tip ( Fig. 9A ); eyespots absent; nuchal organs inconspicuous narrow lateral slits. Peristomium with two rings, first short dorsally ( Fig. 9A ), ventrally larger, forming upper lip of mouth ( Fig. 9B ); second ring large, inflated, producing rounded dorsal crest ( Fig. 9A ), ventrally forming lower lip of mouth ( Fig. 9B ). Dorsal tentacles widely separated, arising from posterior margin of peristomium ( Fig. 9A ). First pair of branchiae arising from anterior margin of setiger 1, lateral and posterior to dorsal tentacles; second pair of branchiae on posterior margin of setiger 1, dorsal to notosetae ( Fig. 9A ), thus with two pairs of branchiae on setiger 1.

Anterior setigers with long, basally thickened capillaries numbering 10–12 in both noto- and neuropodia. Notopodial acicular spines first present from setiger 26–27, numbering 1–2 at first, increasing to 3–4 in middle body segments with number of capillaries decreasing to a number equivalent to spines. Neuroacicular spines from setiger 17, replacing several unusually broad, flattened capillaries ( Fig. 9D ); spines numbering 1–2 initially ( Fig. 10B ), then increasing to 3–4 in middle body segments ( Fig. 10C ), accompanied by an equal number of thin capillaries. In posterior setigers, parapodia becoming elevated, forming full cinctured segments with long spines and companion capillaries ( Figs. 9C ; 10D ). Cinctures with spines of left and right sides not merging dorsally, leaving gap with low mid-dorsal groove ( Fig. 9C ). Cinctured spines numbering 7–9 in notopodia and 6–8 in neuropodia, thus with 13–17 spines on each side. Spines of anterior noto- and neuropodia short, thickened, barely emerging from podial lobes ( Figs. 9 E–F; 10B–C); posterior spines in cinctured segments long, curved, tapering to rounded tip ( Figs. 9G , 10D ).

Pygidial segment with anal opening surrounded by three short dorsal cirri and two somewhat longer ventral cirri ( Fig. 9C ).

Methyl Green stain. No stain retained.

Remarks. Chaetozone dossena n. sp. is a distinctive species. The short pre-setiger region with the bulbous and expanded peristomium with a dorsal crest together with the long, tapering prostomium is unique within known species of the genus. In addition, the short, thick, noto- and neuropodial acicular spines transition to long sigmoid spines in the posterior cinctures. The unusually large capillaries with broad, flattened blades in anterior noto- and neuropodia are also distinct. The first pair of branchiae are interpreted as arising from the anterior edge of setiger 1 resulting in two pairs of branchiae on the first setiger.

Etymology. The epithet, dossena , is from the Latin dossenus for clown or jester, and refers to the pre-setiger region of this worm, which resembles the hat of a jester.

Distribution. Venezuela, known only from shallow subtidal sediments in the Bahía de Mochima.

Figures

FIGURE 9. Chaetozone dossena n. sp. Holotype (USNM 49932): A, anterior end, dorsal view; B, anterior end, ventral view; C, posterior end, posterior view; D, neuropodial capillary seta from setiger 15; E–F, neuropodial acicular spines from setigers 17 and 18; G, notopodial acicular spines and capillary from posterior cinctured segment.

FIGURE 10. Chaetozone dossena n. sp. Holotype (USNM 49932):A, anterior end, dorsal view; B, neuropodial acicular spine and capillaries from setiger 18; C, neuropodial acicular spines and capillaries from about setiger 25; D, notopodial acicular spines and capillaries from posterior cinctured segment.A, Stained with Shirlastain A.