Clymenura snaiko, Read, Geoffrey B., 2011

Read, Geoffrey B., 2011, A new Clymenura (Polychaeta: Maldanidae) from the intertidal of Banks Peninsula, New Zealand, with a reassessment of Leiochone Grube, 1868 and Clymenura Verrill, 1900, Zootaxa 2934, pp. 39-52 : 46-50

Clymenura snaiko sp. nov.

Figures 1–4

Diagnosis. A Clymenura of up to at least 255 mm length, with red anterior body, 18 chaetigers, 2 preanal achaetous segments with tori, more than 10 manubriavicular uncini present from chaetiger 1, capitium teeth array well developed and similar in all rami. High cephalic rim with lateral dip into a pronounced notch, not incised, dorsal rim entire, weakly crenellate, nuchal organs straight, almost full length of plaque. No ocelli, no segmental collars. Anal funnel present with 16 distinct conical cirri, with the ventral cirrus about twice the length of adjacent; anal cone absent. Chaetiger 8 glandular shield edge a curved line extending anteriorly and ventrally from notochaetal fascicle forming a subtriangular half-oval.

Material examined. Station Y10432 , 19 Feb 2008, Decanter Bay, Banks Peninsula, NIWA 44716 (3 af 2 pf), 43.6599°S, 172.9911°E, 0 m; Y10434 , 20 Feb 2008, Decanter Bay, Banks Peninsula, NIWA 44575 (1 cs 3 af), 43.6599°S, 172.9911°E, 0 m; Y10435, 21 Feb 2008, Okains Bay, Banks Peninsula, NIWA 60439 (1 cs, HOLO- TYPE), NIWA 44599 (1 cs, PARATYPE), NIWA 44600 (7 af 6 pf, PARATYPES), 43.6946°S, 173.0641°E, 0 m; Y10439, 24 Feb 2008, Le Bons Bay, Banks Peninsula, NIWA 44573 (1 broken cs), NIWA 44574 (3af 2 pf), 43.7408°S 173.09610°E, 0 m.

Description. A large maldanid with specimens of preserved length to around 255 mm long, 5.5 mm wide (complete specimens: NIWA lot 44575 160 mm long, midbody 4.7 mm wide; lot 44599 255 mm long, 5.5 mm wide; lot 44573 255 mm long, 5.0 mm wide; holotype lot 60439 210 mm long, 4.5 mm wide). Body with 18 chaetigers, 2 preanal achaetigerous segments with tori ( Fig. 1 ). Body colour more or less uniformly dark red anteriorly, paler red posteriorly, paler chaetal tori and ventral shield area, otherwise without distinctive pigmentation patterns. Scattered fine dark flecks on uncinal tori and surrounds on chaetigers 8–14 apparent after preservation in some specimens (Fig. 2F). Well-developed cephalic plaque with high cephalic rim with lateral dip into a pronounced notch, not incised; dorsal rim entire, weakly crenellate; nuchal organs wide and straight, almost full length of plaque (Fig. 2A–C). Palpode well developed with rounded tip, proximal margin with carina distinct (Fig. 2A). No ocelli. Surface of chaetigers 1–8 with multiple prominent transverse segmental divisions, thereafter body much smoother, but fine divisions still visible. No segmental collars. Ventral shield present just anterior to chaetiger 8 chaetal fascicles as a raised pale glandular zone, with curved lateral margins and subtriangular in shape (Fig. 2E– F), varying in prominence between individuals. Distinct segmental organ apertures (nephridiopores) present posterior to ventral end of uncinal rows on chaetigers 6–9, one pair per segment.

Notochaetae capillaries of one type, smooth but only slightly winged, from chaetiger 1–18. Notochaetae of chaetigers 1–7 in transverse rows, about 20 chaetae in a single row on chaetiger 1, increasing to about 30 irregularly arranged 3-deep on a low parapodial lobe on chaetiger 3. Thereafter notochaetae in each fascicle of similar numbers, but longer. From about chaetiger 12 notochaetae becoming grouped in a tight tuft on a conical parapodial lobe, which becomes longest on far posterior segments, with rows within chaetal tuft with long axis oriented diagonally or longitudinally, sometimes discernibly U-shaped.

Single row of manubriavicular uncini present from chaetiger 1–18, with capitium teeth and subrostral bristles well developed on all uncini, with single row of 5 in-line capitium teeth above rostrum ( Fig. 3 ). In chaetiger 1 uncini subrostral isthmus distal to manubrial constriction 60 µm long ( Fig. 3 A), in posterior chaetiger uncini isthmus 140 µm long with larger chaetal capitium ( Fig. 3 B), otherwise ornamentation similar; uncinal shaft length increases modestly from ~250 µm in anterior chaetigers to ~350 µm posteriorly. More than 10 uncini in chaetiger 1, with number increasing to about chaetiger 9, so that in a large specimen chaetiger 1 has 16 uncini, chaetiger 3 FIGURE 2. Clymenura snaiko sp. nov. head, body segments, and pygidium. A–B, anterior lateral head and lateral head, specimen of lot (s.o.l.) 44575; C, lateral anterior to chaetiger 4 (s.o.l. 44600); D, lateral pygidial funnel and 2nd achaetous segment (s.o.l. 44600); E, lateral chaetiger 8 (s.o.l. 44599); F, ventral chaetiger 8 (holotype); G, posterior end (s.o.l. 44716); H, pygidial funnel posterior view (s.o.l. 44600). Scale bars 1 mm.

has 27, 5 has 43, and chaetigers 9–18 about 60 uncini in each row. Raised neuropodial rami on chaetigers 3–8, less distinct on chaetigers 9–10, extending around the circumference to meet the ventral midline and increasing in height and bulk over chaetigers 11–13, thereafter of similar size. Chaetal fascicle on chaetigers 1–7 on anterior third of segment, chaetiger 8 fascicle in midsegment, thereafter at posterior of segment. First and second preanal segments about 2/3 and 1/2 length of last chaetigerous segment respectively, with achaetous reduced torus at posterior of each (Fig. 2G). In one specimen second achaetous segment regenerating, without tori.

Pygidial funnel well developed, ending with 16 distinct flattened blunt cirri (n14, range 14–18, mode 16, sd 1.37), well separated and varying little in size except ventral cirrus usually about twice the length of adjacent ones (Fig. 2D, G, H). Holotype funnel length 3.5 mm from callus ring to cirral base, with ventral cirrus 1.8 mm long, other cirri up to 1.0 mm. Medial thickest part of each cirrus distinct as a pale ridge in some specimens (Fig. 2D). Anus terminal without valve, flush, not raised on a cone (Fig. 2H), except as distorted in preservation in some specimens. Ventral midline ridge prominent, from postperistomial segment to end of body ( Figs. 1 , 2F).

Type locality. Intertidal sands of Okains Bay, Banks Peninsula, 43.6946°S, 173.0641°E.

Etymology. The word ‘ snaiko ’ is coined to form a sinuous-sounding recombination of the letters of the type locality place name, and is to be treated as a noun in apposition.

Habitat and ecology. Worms were present on low-tidal flats on moderately exposed sand beaches ( Fig. 4A ), occurring sporadically as isolated individuals, or in small groups of estimated maximal density 5–7 m - 2 in a group ( Fig. 4 B). The beaches are at the head of bays of narrow width, laterally bounded by abrupt basaltic slopes or cliffs, and surrounded by farmland. The largest population was found on the Okains Bay sand beach ( Fig. 4A ), which is 0.9 km long, the largest beach on which the worm was present. Le Bons Bay sand beach is 0.7 km long, and the sand beach at Decanter Bay extends for less than 200 m. The species was not detected at Little Akaloa Bay, which adjoins Decanter Bay and has a comparable, slightly larger beach.

Surface signs of the worm’s presence included shallow stopings of about 20-mm diameter as well as castings ( Fig. 4 B). Pieces of worm tube recovered with worms were unlined fragile sandgrain aggregations with a wall thickness about 1–1.5 mm. Two of the 16 specimens were regenerating the head and first chaetiger, suggesting that Cly. snaiko sp. nov. may be subject to ‘browsing’ attacks from predators such as shorebirds and fish. A large Disconatis accolus (Estcourt) polynoid scaleworm (NIWA lot 44782) was found as a commensal in the tube of the specimen from station Y 10432 in Decanter Bay.

Distribution. Known only from the intertidal of bays of eastern Banks Peninsula, South Island, New Zealand.

Remarks. Clymenura snaiko sp. nov. and Cly. longicaudata from Japan are distinct from other Clymenura species (in which chaetiger total is known) in having 18 chaetigers. Most Clymenura are subtidal, but remarkably Cly. longicaudata occurs from the sandy intertidal of its type locality to 1500 m depth. The two species also share the character states of two preanal segments, a well-developed pygidial funnel with a ring of cirri, fully dentate rostrate uncini on first chaetigers, long nuchal grooves, and well-developed cephalic rims. However, Cly. longicaudata differs considerably from Cly. snaiko sp. nov. in lacking lateral notches in the cephalic rim, having anal cirri of alternating rather than similar length, having ocelli on the palpode, and having ornamented notochaetae present. Cly. columbiana from the Canadian Pacific has similar pygidial funnel structure to the above species but has 19 chaetigers with 3 or more preanals. Cly. lankesteri from Japan and Cly. borealis from Norway also have 19 chaetigers; the former has a very short, pleated pygidial funnel, the latter only an anal cone, but both have a number of very long pygidial cirri. All three species have uncini on the first chaetigers which are few in number and of reduced dentition. Cly. polaris from Novaya Zemlya and Cly. polaris lena from the Laptev Sea lack cephalic rims and have only one pygidial cirrus. Finally Cly. aciculata from Japan and Cly. cirrata from Florida are incompletely known, but they possess first chaetiger uncini which are acicular or of reduced dentition respectively, and notably Cly. cirrata has a pygidium with four long cirri.

The new Clymenura is large and inhabits beaches which, while rather remote of access, are visited frequently for recreation, and also at times for faunal studies. For example, during the years 1950–1980, polychaetes of eastern Banks Peninsula were often collected by G. A. Knox and students from Canterbury University, Christchurch, and the uncommon open beach onuphid Hartmanonuphis pectinata ( Knox & Hicks, 1973) was first discovered there. As this species was found living on Decanter Bay beach together with Cly. snaiko when the beach was visited in 2008, Knox might also have come across the maldanid during visits decades earlier. However, the presence of Cly. snaiko has never been noted before, perhaps a consequence of its relatively low densities intertidally and intermittent populations, which currently are too sparse to be conspicuous. No specimens were found in the late Professor Knox’s polychaete collection, nor are any Banks Peninsula maldanids entered in his register books (collection and registers held at NIWA). Additionally, in relation to the possible wider distribution of the species, no specimens of it from offshore have been found amongst the New Zealand Maldanidae in the NIWA Invertebrate Collection, derived from over 10,000 benthic samples ( Gordon et al. 2010). It appears that any significant undetected populations of Cly. snaiko sp. nov. are most likely to be in the northeastern Banks Peninsula shallows beyond low water in Okains, Le Bons, and Decanter bays.

Figures

FIGURE 1. Clymenura snaiko sp. nov. Holotype. Scale bar 10 mm.

FIGURE 3. Clymenura snaiko sp. nov. uncini. A, chaetiger 1 row in situ; B, chaetiger 14 row in situ; C, chaetiger 14 uncinal head; D, chaetiger 15 row in situ. A – B at actual relative sizes, scale bars 50 µm, C – D scale bars 20 µm.

FIGURE 4. A, Okains Bay beach type locality, with sampling equipment in foreground; B, cast and stopings of Clymenura snaiko sp. nov., Okains Bay beach. Scale bar 20 mm.