Chaetozone michellae, 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 : 94-96

Chaetozone michellae sp. nov.

Figures 10 A–E, 11 A–E

Material examined. Holotype: Mamala Bay, south shore of Oahu Island, Hawaii, Sta. S1R1B, 21°14ʹ57.23ʺ N, 157°56ʹ41.82ʺ W, 428 m, Jan. 1995 (USNM 1195157). Paratypes: same locality and date as holotype, Sta. S15R1A, 21°14ʹ42.50ʺ N, 157°58ʹ35.05ʺ W, 417 m (1 lacking pygidium, BPBM R3646); Sta. S17R2A, 21°14ʹ12.56ʺ N, 157°52ʹ50.71ʺ W, 502 m (1, BPBM R3647); Sta. S2R1A, 21°15ʹ0.20ʺ N, 157°55ʹ51.26ʺ W, 443 m (1 lacking pygidium, USNM 1195158); Sta. S11R2B, 21°12ʹ49.29ʺ N, 157°56ʹ49.94ʺ W, 507 m (1, USNM 1195159); Sta. S14R2B, 21°14ʹ43.76ʺ N, 157°58ʹ4.45ʺ W, 426 m (1 on stub, USNM 1195160).

Description. Holotype 6.0 mm long, 0.4 mm wide with 66 chaetigers. Paratypes ranging between 5.0–6.0 mm long, 0.3–0.5 wide per 60–89 chaetigers. Body divided into three parts: thoracic region, slightly expanded with crowded chaetigers, faintly rounded dorsally, ventrally flattened with dorsal and ventral grooves ( Figs 10 A, 11A); anterior abdominal region with dorsally inflated segments, ventrally flat, dorsal groove only; and posterior abdominal region, with partial cinctures ( Fig. 10 C). Pygidium with a simple ventral lobe ( Fig. 11 E). Color in alcohol pale yellow, lacking distinctive body pigment.

Prostomium long, triangular, pointed, no nuchal organs or eyes observed; Peristomium with three sub-equal annulations ( Figs 10 A, B, 11A, B). Dorsal tentacles arising on anterior margin of chaetiger 1 ( Fig. 11 B). First pair of branchiae postero-lateral to dorsal tentacles anterior to chaetiger 1 ( Fig. 11 B). Branchiae slender; more abundant in anterior end and absent in last third of the body.

Thoracic chaetigers with short capillaries ( Fig. 11 C); notochaetae long natatory capillaries from chaetiger 15–30 in some specimens. Neuroacicular spines from about chaetiger 40, 2–3 spines per fascicle alternated by 3–4 companion capillaries. Notoacicular spines from chaetiger 50–60, posterior segments bear 6–7 acicular spines in noto- and neuropodia alternating with same number of normal capillaries ( Figs 10 E, 11D, E). Partial cinctures with large dorsal gap and smaller ventral and lateral ones ( Fig. 10 E). Fascicles from modified segments directed anteriorly ( Fig. 11 E).

MGSP. Whole body stains a greenish blue; prostomium with anterior tip unstained. Distinctive band encircling the body with dark speckles between chaetigers 22–25 ( Fig. 10 D).

Remarks. Chaetozone michellae sp. nov., is distinct from other Chaetozone species by the presence of a deep mid-dorsal groove throughout the body. Blake (1996b) described a shallow mid-dorsal groove for Chaetozone setosa Malmgren, 1867 but this species differs from C. michellae sp. nov., by its extreme development of posterior cinctures as well as the position of the dorsal tentacles and the first pair of branchiae (Table 3). Chaetozone michellae sp. nov., seems to be a close relative of C. columbiana Blake, 1996 with an elongate and narrow prostomium, presence of three annulations in the peristomium and MGSP leaving the anterior tip of the prostomium unstained and forming complete bands over some mid-body chaetigers. They differ by the absence of a mid-dorsal groove, presence of geniculate spines and a pygidium with a thin filament in C. columbiana (see also Table 3).

Etymology. Named after Ms. Michelle McGurr, a former wormlab staff member and polychaete enthusiast who processed many of the samples from where this species was found.

Biology/Ecology. This species was sampled in deep waters (417–507 m) during a study of harbor dredge disposal sites. This region has received dredge spoil sediments from Honolulu and Pearl Harbors over the last few decades and deposits of more than 30 cm thickness cover relict natural sediment and reefs (Hampton et al. 1997). Distribution. Mamala Bay, south shore of Oahu Island, Hawaii, USA.

TABLE 3. Synoptic table of morphological characteristics of five closely related species of Monticellina including the new species from Hawaii compared to the type species Monticellina heterochaeta Laubier, 1961 (modified from Dean & Blake 2009)

Species Prostomium Number of Nature of Position of first pair First appearance of Nature of denticulate Posterior end

peristomial segment 1 of branchiae denticulate chaetae (max. chaetae

annulations number of chaetae)

. heterochaeta Long , conical 1 Chaetigerous, Lateral to dorsal 12 notopodia (4–5) Short with blades Unknown Laubier, 1961 complete tentacles; on 12 neuropodia (5) expanded basally and

peristomium distinct dentition

. serratiseta Short, triangular 2–3 Chaetigerous, Lateral to dorsal Posterior noto- and Numerous denticles, Tapers posteriorly Banse & Hobson, to conical complete tentacles; on neuropodia (5–6 per 1–2 enlarged near to toward pygidium 1968) chaetiger 1 fascicle) base

. tesselata Short , conical 2–3 Chaetigerous, Postero-lateral to Absent on notopodia Expanded blades with Inflated, narrowing to Hartman, 1960) complete dorsal tentacles; on 14 neuropodia (20) distinct dentition pointed pygidium

chaetiger 1

. cryptica Blake, Short , triangular 2 Fused with Postero-lateral to 21 notopodia (3) Widely spaced teeth Tapers posteriorly 1996 peristomium dorsal tentacles; on 22 neuropodia (2–3) seen at 400× toward pygidium

peristomium

. antelaxa (Dean Short, conical 3 Chaetigerous, Postero-lateral to Absent on notopodia Strongly serrated with Unknown Blake, 2009) complete dorsal tentacles; on 34 neuropodia (30) broad blade and long

chaetiger 1 fibril-like teeth

. carrikeri (Dean Long, conical 3 Chaetigerous, Lateral to dorsal Absent on notopodia Sub-distally widened Expanded, pygidium Blake, 2009) complete tentacles; on 31–33 neuropodia (2–4) with numerous small with cone-shaped

chaetiger 1 denticulations terminal papillae. Short, conical 3 Chaetigerous, Antero-lateral to Notopodia 40–44 (3–4) Short with expanded Tapers posteriorly anterobranchiata complete dorsal tentacles; on Neuropodia 13–16 (3–4) blades basally and toward pygidium. nov. peristomium denticulated edge

seen at 400×

. hanaumaensis Short , conical 1–2 Chaetigerous, Postero-lateral to From far posterior Very fine dentition Slightly expanded,. nov. complete dorsal tentacles; notopodia (2–4) not seen at 1000× pygidium with simple

between peristomium Neuropodia after dorsal lobe

and chaetiger 1 chaetiger 30–35 (2–4)

Figures

FIGURE 10. Chaetozone michellae sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view; C, posterior modified segments with spines pointed onwards; D, MGSP showing transversal rings from chaetiger 24 to 28; E, cross section of a modified chaetiger showing the cincture with large dorsal gap and smaller ventral and lateral ones.

FIGURE 11. SEM of Chaetozone michellae sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view showing position of dorsal tentacles and branchial filaments; C, thoracic capillary chaetae; D, abdominal spines; E, posterior end with pygidium.