Aphelochaeta arizonae, 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 : 82-84

Aphelochaeta arizonae sp. nov.

Figures 1 A–D, 2 A–F

Material examined. Pearl Harbor, south shore of Oahu, Hawaii. Holotype: Sta. F1R2, fuel pier, 21°21ʹ55.5ʺ N, 157°58ʹ0.21ʺ W, 20 Dec. 1994, coll. R. Brock (USNM 1195144). Paratypes: same locality, date and collector as holotype (2, USNM 1195145; 2 on stub USNM 1195146; 2, BPBM R3639).

Description. Holotype 10.5 mm long, 0.4 mm wide for 82 chaetigers. Paratypes 8–10 mm long, 0.3–0.4 mm wide for 79–88 chaetigers. Body elongate, thin, with slightly expanded anterior end and narrow posterior end; rounded dorsally and ventrally flat; last segments with ventral groove. Body with two distinct regions: thoracic region with 8–10 crowded chaetigers, wider than long, and abdominal region with round to sub-moniliform segments, as long as wide ( Fig. 2 D). Pygidium with a ventral lip, anal aperture placed dorsally ( Fig. 1 C).

Prostomium triangular, as long as 3–4 anterior chaetigers, without eyes; nuchal organs present, postero-lateral as vertical slits ( Figs 1 A, B, 2A–C). Peristomium with three sub-equal annulations; dorsal tentacles arising from anterior margin of chaetiger 1 ( Figs 1 A, B, 2A–C). First pair of branchiae postero-lateral to dorsal tentacles; branchiae more abundant anteriorly but present throughout ( Fig. 1 A, B). Chaetae all capillaries, fibrils not visible in light microscopy; thoracic chaetae numerous, about 10–12 per fascicle, abdominal chaetae longer than thoracic ones, about 4–6 per fascicle; last chaetigers with short neurochaetae ( Fig. 2 E, F).

MGSP. The body stains uniformly. Thoracic ventral bands present on anterior end of segments, extending to parapodial ridges from chaetigers 4–10 ( Fig. 1 D).

Remarks. The nature of posterior segments and methyl green staining patterns seem to be resourceful characteristics to distinguish the four new Aphelochaeta species reported here ( Table 2 ). For instance, Aphelochaeta arizonae sp. nov., does not have an inflated posterior end as in A. honouliuli sp. nov., and A saipanensis sp. nov., and it also only has a ventral groove in posterior segments. Aphelochaeta elongata Blake, 1996 also has a narrow posterior end, but differs from A. arizonae sp. nov., by the elongated peristomium without annulations.

The ventral bands formed by the MGSP in the thoracic segments seem to be common among several Aphelochaeta species (and also present in Monticellina anterobranchiata sp. nov.) but differs in relation to location of these bands, extent on chaetigers, extension to parapodial ridges and margin of the segments stained (i.e. anterior half, posterior half, whole segment, inter-segmental region). Aphelochaeta arizonae sp. nov., has ventral bands stained throughout the thoracic chaetigers but only present on the anterior margin of the segments and extending to the parapodial ridges. This staining pattern is distinct from Aphelochaeta honouliuli sp. nov., which has a very unique pattern with the thoracic region divided in three, including an unstained ‘glandular’ region. Aphelochaeta saipanensis sp. nov., has ventral bands in the posterior margin of the thoracic segments and A. arizonae sp. nov., has ventral bands in the inter-segmental areas only.

Etymology. This species is named in honor of the ship USS Arizona that served during World War I. The USS Arizona sank during the Japanese attack on Pearl Harbor (type locality of this species) on 7 December 1941, taking 1,177 lives.

Biology/Ecology. One specimen with regenerating posterior end ( Fig. 2 C) observed. Specimens collected in shallow subtidal sandy habitats.

Distribution. Pearl Harbor, south coast of Oahu Island, Hawaii, USA.

Ocean compared to the type species A. monilaris (modified from Doner & Blake, 2009).

Species Number peristomial Position of first pair Thoracic profile Abdominal annulations branchiae segments

Figures

FIGURE 1. Aphelochaeta arizonae sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view; C, posterior end with pygidium; D, MGSP of anterior end in ventral view.

FIGURE 2. SEM of Aphelochaeta arizonae sp. nov. A, complete individual; B, anterior end, dorso-lateral view; C, specimen regenerating posterior end; D, mid-body segments; E, thoracic capillary chaetae; F, abdominal capillary chaeta.