Sigambra papagayu Bamber, 2008

Muir, Alexander I. & Bamber, Roger N., 2008, New polychaete (Annelida) records and a new species from Hong Kong: the families Polynoidae, Sigalionidae, Chrysopetalidae, Pilargiidae, Nereididae, Opheliidae, Ampharetidae and Terebellidae, Journal of Natural History 42 (9 - 12), pp. 797-814 : 803-805

Sigambra papagayu Bamber sp. nov.

( Figure 1 )

Material

Holotype (Registration No. NHM.2003. 1081) mature, containing eggs, Fan Tsang Chau (Conic Island) Cave , Hong Kong, 22 ° 219540 N 114 ° 239220E; sample C2, sediment 18% gravel, 25% sand, 57% silt/clay, depth 15 m, water temperature 22 ° C. Coll. N.J. Evans and P.F. Clark, 21 October 2002 . Paratypes: 1 further specimen from sample C2, 1 specimen, Conic Island sample C5 (NHM.2003.1082–1083) (data as holotype) .

Description

Holotype, 22.81 mm long for 122 chaetigers, greatest width 1.5 mm; mature paratype from C5, 17.25 mm for 126 chaetigers. Greatest width around chaetigers 10 to 15.

Prostomium, peristomium and anterior 2 to 4 chaetigers pale to white; remainder of body brown to reddish brown. Integument generally smooth; evidence of segmentation more obvious in posterior chaetigers.

Prostomium ( Figures 1A, B ) truncate, slightly indented anteriorly at insertion of palps. Palps short, biarticulate; palpodes rounded, fused dorsally. Three antennae, median antenna 1.75 times length of lateral antennae. Eyes absent. Pharynx without jaws but with eight conspicuous rounded papillae.

Peristomium twice as long as first chaetiger. Two pairs of tapering tentacular cirri both longer than lateral antennae, dorsal cirri longer than ventral.

Pygidium ( Figure 1C ) rounded, with two long cirri, 0.85 times length of median antenna; anus ventrodistal.

Parapodia ( Figure 1D ) biramous, lateral. Notopodia with straight, blunt-tipped internal acicula. Dorsal cirrus of chaetiger 1 longest, longer than median antenna; subsequent dorsal cirri shorter (on average 0.6 of median antenna, 2.5 times length of neuropodium), those of chaetigers 2 to 4 shorter than subsequent cirri. Large hooks emergent from between chaetiger 3 to 5 and the last chaetiger, with two papillae adjacent to point of emergence but no other chaetae.

Neuropodia pointed, with aciculum tapering to a point. Ventral cirri absent on second chaetigers, otherwise present, tapering, shorter than dorsal cirri. Neurochaetae ( Figures 1D, E ) 12 or 13 chaetae dorsal of aciculum, including slender, curved, serrate capillaries, their serrations low and rounded, otherwise simple capillary chaetae; 20 to 30 simple capillaries ventral of aciculum; pair of distinct pectinate chaetae distal on neuropodium, each with 14 to 17 ‘‘teeth’’ and naked slender distal extension.

Etymology

Named for a parrot which was an integral part of the field and laboratory team in Hong Kong.

Remarks

The familial association of the genus Sigambra is discussed by Paterson and Glover (2000). With their description of the abyssal species Sigambra magnuncus , there are 17 species of Sigambra previously described. Sigambra magnuncus differs from the present species in many ways, notably in having notochaetae adjacent to the hooks. The remaining 16 described species of the genus are reviewed by Licher and Westheide (1997), who present a key to the genus.

Sigambra papagayu sp. nov. is a large species, falling into that group of the genus with eight pharyngeal papillae, no ventral cirrus on chaetiger 2, ventral cirri shorter than dorsal cirri, and no eyes. In having no notochaetae adjacent to the dorsal hooks it is distinct from all species in that group. It is most similar to S. qingdaoensis Licher and Westheide, 1997 , taken from muddy sediments at Qingdao, China, at an undescribed depth; that species has a single ‘‘long’’ capillary notochaeta. Sigambra qingdaoensis also has the serrated neurochaetae as found in S. papagayu , but not the pair of short pectinate neurochaetae; chaetae similar to the latter are described for S. phuketensis Licher and Westheide, 1997 from the Andaman Sea, a species with single capillary notochaetae and 14 subequal pharyngeal papillae.

Sigambra papagayu was collected from 14 to 20 m depth in muddy sand sediments with shell breccia. The species was characteristic of the muddier cave community, while never being abundant. Four further specimens were recorded at stations A, at the mouth of, and one at station B, a few metres inside the mouth of, Conic Island Cave (sediments 38% sand, 39% silt-clay, and 25% sand, 57% silt-clay respectively).

Figures

Figure 1. Sigambra papagayu sp. nov., holotype: A, anterior end, dorsal; B, anterior end, ventral; C, pygidium, dorsal; D, 40th parapodium; E, detail of, from left to right, serrate capillary neurochaeta,pectinate chaeta and tipof neuroaciculum.Scale line51mm for A to C, 0.3 mm for D.