Platynereis karaka Read, 2007, sp. nov.

Platynereis karaka sp. nov.

(Figs. 4, 6H–I)

Diagnosis. Platynereis species with homogomph falcigers absent in adults. Male heteronereid 2-part, with 14 pre-natatory segments, pygidial papillae structure a ring of 12 blunt papillae, posterior midline papillae present. Female heteronereid 2-part, 17 pre-natatory segments, eggs white to pale golden-yellow, first 5 dorsal cirri enlarged. Segment 11 notopodial superior ligule less bluntly rounded than preceding segment. Benthic atoke unknown, probably in life with anterior body yellow-orange.

Heteronereid material examined. Holotype. Wellington, Island Bay, 41° 21.02' S, 174° 46.11' E, stn Y10278, 0 m, 18.viii.1976: het. male, 23 mm, coll G. Read, night light & dip net (NIWA 3365, H-874). Paratypes. Banks Peninsula. Lyttelton Harbour, 43° 36.6' S, 172° 42.6' E:- stn GAK19580000, 0 m, 1.vi.1958: het. 1 male. Menzies Bay, 43° 38.4' S, 172° 57.6' E:- stn GAK19580501, 0 m, 1.v.1958: het. 1 male. Kaikoura Peninsula. Kaikoura, 42° 24' S, 173° 40.8' E:- 0m, 19.viii.1961 (UCANTK): het 2 male; Y10293, 0 m, 26.viii.1972: het. 3 male, 1 female; stn Y10294, 0 m, 30.viii.1972: het. 2 male, 1 female. Wellington Harbour. Greta Point (Evans Bay), 41° 18.6' S, 174° 48' E:- stn Y10155, 0 m, 19.ix.2003: het. 1 male. Karaka Bay, 41° 18.34' S, 174° 49.9' E:- stn Y10208, 0 m, 27.vii.1970: het. 1 male; stn Y10209, 0 m, 25.viii.1970: het. 4 male; stn Y10226, 0 m, 13.x.1971: het. 2 male, 3 female; stn Y10229, 0 m, 8.i.1972: het. 1 female; stn Y10240, 0 m, 2.viii.1972: het. 1 female. Mahanga Bay, 41° 17.4' S, 174° 49.8' E:- stn Y10261, 0 m, 27.ii.1973: het. 5 male; stn Y10269, 0 m, 24.viii.1973: het. 1 male. Wellington, coast south. Houghton Bay, 41° 20.4' S, 174° 46.8' E:- stn Y10249, 0 m, 31.x.1972: het. 1 male. Island Bay, 41° 21.02' S, 174° 46.11' E:- stn Y10250, 0 m, 1.xi.1972: het. 3 male; stn Y10252, 0 m, 2.xi.1972: het. 1 male, 4 female; stn Y10253, 0 m, 6.xi.1972: het. 2 male, 1 female; stn Y10278, 0 m, 18.viii.1976: het. 24 male, 8 female; stn Y10283, 0 m, 4.x.1977: het. 2 male, 2 female; stn Y10285, 0 m, 10.x.1977: het. 1 male. Wellington, coast west. Round Point, nr Titahi Bay, 41° 6.5' S, 174° 49' E:- stn Y10279, 0 m, 16.xi.1976: het. 2 female. West Norfolk Ridge. Wanganella Bank, 32° 36.318' S, 167° 30.702' E:- stn P0004, 126 m, 25.i.1977: het. 1 male.

Size and shape. Atoke length unknown but expected to be smallest of the 4 species as P. k a r a k a heteronereids smallest, with 60-90 segments. Male heteronereid anterior body almost uniform in width and posterior body not strongly tapered. New Zealand specimens mean length 25 mm, range 18–33 mm (std dev. 4 mm, n 19). Female heteronereid body uniform in width. Wellington region specimens mean length 31 mm, range 22– 44 mm. (std dev. 6 mm, n 9).

Atoke description. No atokous specimens that could be placed with certainty under this species found. Paragnath pattern as in P. mahanga, and in comparison to the other three species proboscis (of heteronereids) narrowest in proportion to head and shape of palps differing (Fig. 4A). Atoke live colouration, indicated by dorsal anterior body of spent heteronereids, yellow with slight orange tinge. Shape and distribution (if present) of homogomph notopodial falcigers unknown. Segments 5–10 (female heteronereids) with blunt glandular anterior superior notopodial ligules, segment 11 ligule more conical.

Male heteronereid description. A two-part heteronereid. Enlarged eyes dark red and head carried bent down when proboscis retracted. Palps distinctive with palpostyle spherical, nearly as wide as palpophore, separated from it by slight stalk (Fig. 4A, 6H). Pre-natatory region with 14 segments without variation (n 21) and first 7 dorsal and 4 ventral cirri always enlarged with unusually thickened heads (Fig. 4B). Dorsal cirri heads developed into a forward projecting pick-axe-like point on 6–7th cirri, with cirrus S-shaped (Fig. 4A, 6H), and thin terminal part of cirrus projecting backwards and somewhat ventrally. Chaetiger 8–14 parapodia unmodified. Natatory parapodia and chaetae as in P. australis. Last few parapodia with lamellae reduced (Fig. 4C) similar to P. australis, with axes not directed more dorsally. A single fin-like sperm-papilla present on dorsal midline of each posterior segment (Fig. 4D,E, 6I) from midbody. Fin-like papillae rectangular in longitudinal section with central tube. Pygidium additionally with 12 (11–13) blunt, rounded sperm papillae in almost complete ring, each papilla closely contacting those adjacent, except separated ventrally by pair of pads (Fig. 4D). Gravid male in life colouration as in P. australis males except anterior dorsal body yellow-orange, and posterior dorsal cirri bases with golden yellow flecks of pigment. Holotype male 23 mm long, with 87 segments, proboscis everted, paragnaths typical, except lines somewhat thickened, segments 5–10 with glandular anterior superior notopodial ligules, 33 middorsal papillae present, and 13 pygidial papillae.

Female heteronereid description. A two-part heteronereid. Enlarged eyes, head structure and palps as in males. Pre-natatory region with 17 segments and anterior first 5 dorsal and 4 ventral cirri enlarged, without variation (n 20). Enlarged cirri lacking ‘pickaxe’ double-headed appearance characteristic of those in males. Parapodia of chaetigers 6–17 unmodified. Natatory parapodia as in P. australis females. Posterior unmodified region absent with parapodia of last segments with reduced lamellae, few natatory chaetae in notopodia, and few spinigers in neuropodia (Fig. 4F). Pygidium unmodified, except lacking anal cirri. Eggs 170–190 µm in diameter. Gravid females in life colouration pale blue due to colour of eggs masking all other body colouration. Dorsal blood vessel prominent as in males and spent females similar in colouration to spent males.

Juvenile chaetation and colour. Unknown. No successful rearings made.

Reproduction. At Wellington P. karaka swarming occurred from mid winter to late spring, July–November, with outlier captures in January and February. Heteronereids were captured less frequently than the other three species but occurred in higher numbers in late winter to late spring (August–November). Spawning of Platynereis karaka was observed in the laboratory on only two occasions and occurred without rapid swimming in tight circles by males.

Habitat. Subtidal, heteronereids more often found on open coasts, otherwise unknown.

Distribution. Mainland New Zealand (Wellington, Kaikoura, Banks Peninsula), and Wanganella Bank.

Etymology. The epithet karaka is a noun in apposition.

Remarks. There are no prior reports in the literature of heteronereids with the morphology of P. k a r a k a. It differs markedly from P. australis in heteronereid morphology, particularly in male pygidial structure as described. In P. karaka the proboscis is somewhat narrower in proportion to the head than in the other three species. Palps of P. karaka are distinctive in shape, at least in heteronereids.

P. karaka is unique for the morphology of the male heteronereid midline papillae. An anterior dorsal enlarged cirrus of ‘pickaxe’ morphology has also been recorded in Platynereis pulchella Gravier (see Holly 1935, as P. p e s t a i). P. k a r a k a males were significantly smaller than other species (P<0.05) but the females were not. Males had the shortest length pre-natatory region and highest ratio of total length to anterior length of the four species, although having the same number of pre-natatory segments as P. k a u (Table 7). Females had 3 more pre-natatory segments than males.