Dodecaceria alphahelixae, 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 : 330-332

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Dodecaceria alphahelixae

new species

Dodecaceria alphahelixae new species

Figures 16–17 View FIGURE 16 View FIGURE 17

Material examined. Caribbean Sea, Carib 1, R/V Alpha Helix , Panama, Sta. ND-31, 09°12.8ʹN, 82°02.7ʹW, 08 July 1977, dredged, in grass and sand around Deer Island , NE tip of Isla Popa, specimens removed from coral rock, 4 m, holotype ( USNM 1557518 View Materials ) and paratype ( USNM 1557519 View Materials ) GoogleMaps .

Description of holotype. Holotype complete, with 32 setigers, 6.62 mm long, 0.5 mm across anterior segments, expanded to width of 0.6 mm across middle segments, tapering to a width of 0.55 mm across posterior segments. Anterior segments about three times wider than long ( Fig. 16A View FIGURE 16 ), middle segments larger, swollen, tapering to narrow crowded segments posteriorly ( Fig. 17 View FIGURE 17 ). Body generally cylindrical in anterior and middle segments, with posterior region becoming dorsoventrally flattened. Segmental annular rings poorly developed except in far posterior segments where a few segmental grooves cross individual segments. Color in alcohol dark reddish brown ( Fig. 17 View FIGURE 17 ) with pigment in numerous irregular transverse patches encircling individual segments.

Prostomium conical, tapering to rounded anterior margin ( Fig. 16A View FIGURE 16 ); eyespots absent; nuchal organs longitudinal lateral slits. Peristomium smooth with two achaetous rings with annuli only apparent laterally; first ring longest; second ring possibly an achaetous segment ( Fig. 16A View FIGURE 16 ); no dorsal crest. Tentacles arising laterally on second ring ( Fig. 16A View FIGURE 16 ), these becoming thick, with distinct ventral groove and numerous folds along length. Branchiae four pairs, all of approximately same length or monomorphic (sensu Aguilar-Camacho & Salazar-Vallejo 2011); first pair arising from achaetous segment dorsal to tentacles; branchial pairs 2–4 from setigers 1–3 dorsal to notosetae ( Fig. 16A View FIGURE 16 ). Each branchia relatively thick, with folds or grooves along their length.

Parapodia poorly developed with setae arising directly from body wall or notch. Setigers 1–4 with capillaries only, 5–6 per fascicle; capillaries with fine serrations along one edge ( Fig. 16B View FIGURE 16 ). Heavy hooked setae from setiger 5 in both noto- and neuropodia; neuropodia with five hooks and no capillaries; notopodia with one hook and four capillaries. Neuropodia of setiger 6 with five hooks; notopodia with two hooks and three capillaries. Setiger 7 with five hooks in neuropodia and seven hooks in notopodia; capillaries absent. Numbers of hooks fewer in subsequent segments, decreasing from five to three in neuropodia and seven to three in notopodia to about middle of body or about setiger 15. One to two capillaries resume in notopodia from about setiger 20. Hooks through middle body segments all spoon shaped with large subapical boss ( Fig. 16C View FIGURE 16 ). Hooks in more posterior segments not as heavy, with spoon shape not as evident and subapical boss reduced or absent ( Fig. 16D View FIGURE 16 ). Hooks in last few setigers narrow, pointed acicular spines ( Fig. 16E View FIGURE 16 ), accompanied by 1–2 capillaries.

Posterior segments narrowing to pygidium ( Fig. 17 View FIGURE 17 ) consisting of a simple rounded lobe ventral to anal opening.

Variability. Paratype (USNM 1557519) small, 1.8 mm long, 0.25 mm wide with 22 setigerous segments. Two pairs of branchiae, first on achaetous segment, second on setiger 1; possible scars of a third branchial pair observed. Capillary setae only in setigers 1–4. Spoon-shaped hooks begin on setiger 5 with four hooks in neuropodia and four in notopodia; setiger 6 with four hooks in neuropodia and six in notopodia; setiger 7 with 5–6 hooks in neuropodia and three in notopodia. Most hooks with enlarged spoon-like tip with large subapical boss.

Methyl Green stain. MG largely obscured by heavy dark reddish brown pigment.

Remarks. Among the known species of Dodecaceria , only two have a reduced number of branchiae and hooked setae beginning from an anterior setiger as in D. alphahelixae n. sp.: D. ater ( Quatrefages, 1866) from France and D. gallardoi Carrasco, 1977 from Chile. However, D. ater is described as having chisel-shaped hooks ( Blake & Magalhães 2019: Fig. 4F View FIGURE 4 ) instead of spoon-shaped hooks and has 5 – 6 pairs of branchiae instead of four. Dodecaceria gallardoi is reported to have three pairs of branchiae instead of four and hooks begin on setiger 6 instead of 5 ( Carrasco 1977). In addition, D. gallardoi has two pair of branchiae on the achaetous segment instead of one and the hooks are described as having heavy transverse subapical ribs or ridges instead of with a distinct scoop shape with a prominent boss as in D. alphahelixae n. sp.

Etymology. This species named for the R/V Alpha Helix , the vessel used to support the Caribbean I expedition.

Distribution. Panama, shallow subidal, in hard substrates.