Aphelochaeta glandaria Blake, 1996

Dean, Harlan K. & Blake, James A., 2016, Aphelochaeta (Polychaeta: Cirratulidae) from the Pacific coast of Costa Rica, with a description of five new species, Zootaxa 4103 (2), pp. 101-116 : 104-106

Aphelochaeta glandaria Blake, 1996

Figures 2 C, 3B

Aphelochaeta longisetosa: Dean 1996a (in part). Not Hartmann-Schröder, 1965. Aphelochaeta glandaria: Dean 2004 (in part). Not Blake, 1996.

Material examined. Gulf of Nicoya. Sta. 24, 9°49ʹ25″N, 84°41ʹ20″W, 11 m, sand, Oct 1980 (2); Sta. 29, 9°54ʹ55″N, 8445ʹ15″W, 18 m, muddy sand, Jul 1980 (15, MCZ 132979 (SEM)), Jun 1981 (1), Apr 1982 (2); Sta. 30, 9°54ʹ40″N, 84°45ʹ50″W, 18 m, muddy sand, Apr 1981 (2). Golfo Dulce, Sta. GD–03, 8°35ʹN, 83°16ʹW, 200 m, soft black mud, Dec 1993. Col. R. León-Morales & J.A. Vargas (1).

Description. Robust species with uniformly wide body with a slightly expanded thorax. Complete specimen 10.2 mm long, 1.6 mm wide for 167 segments, Dorsum of thorax rounded, swollen, venter flat with numerous minute glands producing creamy white region extending onto anterior abdomen, with mid-ventral groove only on last thoracic setigers; abdominal setigers approximately six times as wide as long, oval in cross section, about 1.5 times as wide as high, with mid-ventral groove; expanded posterior region 2.0 mm wide with 35 crowded setigers up to 14 times wider than long, with mid-dorsal and mid-ventral groove; pygidium a short rounded lobe ventral to anal opening. Color in alcohol light yellow-brown with thoracic and anterior abdominal region creamy white ventrally.

Prostomium pointed, conical, about as wide as long; peristomium slightly longer than wide, with three welldifferentiated annulations, often deeply cleft dorso-laterally at junctions between annulations ( Fig. 3 B), weak dorsal crest present extending along dorsum of first three or four thoracic setigers as narrow ridge; paired dorsolateral nuchal organs on posterior edge of prostomium; dorsal tentacles arise from peristomium, which extends over dorsum of setiger 1, just anterior to setiger 2. First branchiae dorsal to notosetae of setiger 1 lateral to dorsal tentacles; subsequent branchiae also dorsal to notosetae. Thoracic parapodia well developed dorso-lateral lobes with notopodia forming shoulders; setae emerge ventro-laterally from slightly swollen regions of body wall in abdominal segments. Noto- and neuropodia close to one another throughout.

Setae all capillaries with notosetae 2–3 times longer than neurosetae; with 10–12 notosetae and 6–8 neurosetae in thoracic region, 8–10 setae per fascicle in each ramus in abdominal region, reduced in number in far posterior setigers, notosetal and neurosetal fascicles somewhat separate throughout. Long capillary setae rounded in cross section with short fibrils along one side, shorter setae more flattened with minute fibrils along one edge ( Fig. 2 C).

Methyl green staining pattern. Dorsum of peristomium with scattered blue speckles, greatest density of speckles on peristomium at base of tentacles, extending as a diagonal streak ventrally from lateral edge of dorsal tentacles ( Fig. 3 B). Anterior thoracic region with weak blue stain on venter; remainder of body light blue-green; pygidium and prostomium unstained.

Remarks. The cream colored thoracic venter makes this species easily identifiable in benthic samples. The many crowded setigers, the wide thoracic region, and expanded posterior end with both a dorsal and ventral groove are all easily recognizable characters. The microscopic fibril endings on the otherwise smooth capillary setae ( Fig. 2 C), which were noticed by Blake (1996), are also visible using light microscopy in the Costa Rican specimens. Blake (1996) indicated that this species may either have a wide geographic range or be a complex of sibling species as morphologically similar specimens have been reported from northern Europe, the eastern United States and Australia. Comparison of the Costa Rican specimens with paratypes of A. glandaria from California show similar staining patterns but differences in staining intensity, perhaps due to differences in fixation.

Distribution. Collected in 11–18 m from muddy sand to sandy sediments in the Gulf of Nicoya. This species was previously collected at 76–410 m in the Santa Maria Basin and Western Santa Barbara Channel off California, USA. The presence of this species in the Gulf of Nicoya extends the range of this species from central and southern California to Pacific Costa Rica.

Figures

FIGURE 2. Aphelochaeta antelonga sp. nov. A – B, paratype (MCZ 132795); Aphelochaeta glandaria C, voucher specimen (MCZ 132797); Aphelochaeta guimondi sp. nov. D, paratype (MCZ 132799). A, anterior end, lateral view; B, neurosetae, setiger 4. C, neurosetae, setiger 2. D, noto- and neurosetae, mid body. Scale bars: A = 200 µm, B = 5 µm, C = 10 µm, D = 20 µm.

FIGURE 3. Aphelochaeta antelonga sp. nov. A, Paratype MZUCR 132794; Aphelochaeta glandaria B, voucher specimen (MCZ 132797); Aphelochaeta guimondi sp. nov. C, Holotype MCZ 132798; Aphelochaeta praeacuta sp. nov. D, Holotype MCZ 132801; Aphelochaeta striata sp. nov. E, Holotype MCZ 132803; Aphelochaeta zebra sp. nov. F, Holotype MCZ 132807. A, MGSP of anterior end, ventral view; B, MGSP of anterior end, dorsal view; C, MGSP of anterior end, ventral view; D, MGSP of anterior end, ventral view; E, MGSP of anterior end, ventral view; F, MGSP of anterior end, ventral view. Scale bars; A ‒ F = 500 µm.