Aphelochaeta honouliuli, Magalhães, Wagner F. & Bailey-Brock, Julie H., 2013

Magalhães, Wagner F. & Bailey-Brock, Julie H., 2013, Bitentaculate Cirratulidae (Annelida: Polychaeta) from the northwestern Pacific Islands with description of nine new species, Zootaxa 3630 (1), pp. 80-116 : 85-87

Aphelochaeta honouliuli sp. nov.

Figures 3 A–E, 4 A–F

Material examined. Mamala Bay, Sand Island outfall, south shore of Oahu Island, Hawaii. Holotype: Sta. E6R3, 21°15ʹ50.8ʺ N, 157°50ʹ57.8ʺ W, 105 m, Aug. 2008 (USNM 1195147). Paratypes: Sta. E6R3, 21°15ʹ50.8ʺ N, 157°50ʹ57.8ʺ W, 105 m, Aug. 2008 (1, BPBM R3640); Sta. E5R2, 21°16ʹ22.7ʺ N, 157°51ʹ41.2ʺ W, 101.8 m, Aug. 2008 (2, USNM 1195148); Sta. E1R3, 21°17ʹ10.6ʺ N, 157°55ʹ33.5ʺ W, 102.1 m, Aug. 2008 (2, BPBM R3641), Sta. D3R3, 21°16ʹ55.7ʺ N, 157°53ʹ48.3ʺ W, 50.9 m, Aug. 2008 (2, on stub, USNM 1195149).

Description. Holotype 11 mm long, 0.7 mm wide in thoracic segments, 0.5 mm wide in abdominal segments, for 107 chaetigers. Paratypes 3–10 mm long, 0.2–0.5 mm wide, for about 65–120 chaetigers. Body slender and elongate, divided into three regions: expanded thoracic region with short and crowded chaetigers (10–15 chaetigers), cylindrical in cross section; abdominal region with chaetigers as long as wide, rounded, with a shallow ventral groove ( Fig. 4 C); and a posterior expanded region of 15–20 crowded chaetigers with dorsal and ventral grooves ( Figs 3 C, 4D). Pygidium a simple lobe with anal opening placed dorsally ( Fig. 4 D).

Prostomium conical, as long as 2–3 anterior chaetigers, without eyes and with a pair of postero-lateral nuchal organs, rounded ( Figs 3 A, B, 4A, B). Peristomium with three annulations, third annuli slightly longer than first and second one; dorsal crest present on second and third annuli ( Figs 3 A, B, 4A, B). Dorsal tentacles inserted above posterior end of third peristomial annulation ( Fig. 4 A). Branchiae from chaetiger 1, postero-lateral to dorsal tentacles; present until posterior abdominal chaetigers ( Fig. 4 A).

Chaetae all capillaries, fibrils not visible in light microscopy. Thoracic chaetigers with 10–12 capillary chaetae per fascicle, reduced to 8–10 in abdominal chaetigers ( Fig. 4 E). Abdominal notochaetae 3–4 times longer than abdominal neurochaetae ( Fig. 4 F).

MGSP. Anterior end of prostomium and first peristomial annulation stained densely; second peristomial annulation with irregular speckles and third annulation densely stained ( Fig. 3 D). Transverse ventral bands present on thoracic segments ( Fig. 3 E); anterior third of thoracic segments with bands only on the anterior margin of segments, extending laterally to parapodial ridges, middle third with a lightly speckled ‘glandular’ area of 4–5 segments, and posterior third with the whole segmental area stained intensely, not extending laterally to parapodial ridges ( Fig. 3 E).

Remarks. Aphelochaeta honouliuli sp. nov., seems to be closely related to Aphelochaeta glandaria Blake, 1996 and a group of undescribed species with an expanded thoracic region with several crowded chaetigers, posterior end expanded with dorsal and ventral grooves, and MGSP distinct with an unstained ‘glandular’ area on the ventrum of the thorax (Blake 1996b). Apparently, the Hawaiian species A. honouliuli sp. nov., differs from A. glandaria mainly by the MGSP. The prostomium is stained in A. honouliuli sp. nov., while the tip is not stained in A. glandaria ; peristomium with an anterior and posterior bands stained intensely in A. honouliuli sp. nov., and not reported to be intensely stained in A. glandaria . The unstained region on mid-thoracic segments is followed by complete bands in A. honouliuli sp. nov., while in A. glandaria the glandular region extends throughout the thoracic region. See Remarks for Aphelochaeta arizonae sp. nov., for further information.

Etymology. Honouliuli in Hawaiian language means ‘dark harbor’ and it is the name of the sewage plant outfall in which this species thrives, being the most abundant cirratulid species found.

Biology/Ecology. Two specimens were found regenerating the posterior end. Found on sandy bottoms at 50–105 m in depth.

Distribution. Mamala Bay, south shore of Oahu Island, Hawaii, USA.

* The original description of this species states that the branchiae arise from above the peristomium, lateral to dorsal tentacles. The key to species in the same paper describes the position as being from chaetiger 1. The drawings indicate that the first pair of branchiae are peristomial but chaetiger 1 seems to be reduced.

Figures

FIGURE 3. Aphelochaeta honouliuli sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view; C, posterior end with pygidium in dorsal view; D, MGSP of anterior end in lateral view; E, MGSP of anterior end in ventral view.

FIGURE 4. SEM of Aphelochaeta honouliuli sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view; C, mid-body segments; D, posterior end with pygidium in ventral view, ventral view; E, thoracic capillary chaetae; F, abdominal capillary chaeta.