Laonome triangularis Hutchings and Murray, 1984

Laonome triangularis Hutchings and Murray, 1984 View in CoL

( Figure 12 View Figure 12 ) Laonome triangularis Hutchings and Murray 1984: 106 , fig. 32.5–9; Capa 2007: 547,

Figs 4C,D View Figure 4 , 5 View Figure 5 .

Material examined

ESFM-POL/2005-282 , 9 September 2005, I skenderun Bay, G 1, 36°35′37″ N, 36°11′09″ E, 8 m, mud, 2 specimens GoogleMaps ; ESFM-POL/2005-495 , 17 September 2005, Mersin Bay, G 7, 36°46′41″ N, 34°39′39″ E, 10 m, mud, 110 specimens GoogleMaps ; ESFM-POL/ 2005-1392 , 17 September 2005, Mersin Bay, G 11, 36°45′47″ N, 34°51′54″ E, 5 m, mud, 148 specimens GoogleMaps .

Description

Largest specimen complete, pale brownish; total body 17.3 mm long, 1.3 mm wide (thorax), with eight thoracic and 52 abdominal chaetigers ( Figure 12A View Figure 12 ). Branchial crown 5.3 mm long, with 20 pairs of radioles, with four or five narrow transverse bands of dark brown pigmentation on inner radiole margins and adjacent one to three pairs of pinnules; radiole surface smooth; tip of radioles extending to form a long narrow filament; palmate membrane present, joining radioles proximally at about 1/10 of radiole length ( Figure 12A,C View Figure 12 ). Anterior peristomial ring not developed ventrally. Dorsal lips erect, lamellar, distally tapered; radiolar appendages present, with two rows of skeletal cells extending through most of length of appendage ( Figure 12G View Figure 12 ). Ventral lips about twothirds lengths of dorsal lips. Lateral collar margin entire, oblique, without incisions. Ventral collar margin distinctly higher than dorsal and lateral margins, as pair of broadly triangular lobes ( Figure 12B View Figure 12 ). Thin, white transverse ridge present at junction of posterior peristomial ring and chaetiger 1; complete except middorsally ( Figure 12B View Figure 12 ). Notochaetae on chaetiger 1 in two distinct groups; three superior elongate narrowly hooded, five inferior paleate. Notochaetae on chaetigers 2–8 with superior group of four elongate narrowly hooded chaetae and inferior group of 10 paleate chaetae; all paleate chaetae with hoods gradually narrowing distally to thin mucro. Neuropodial uncini on chaetigers 2–3 with main fang surmounted by three or four rows of teeth, one tooth per row, breast well developed, handles absent ( Figure 12E View Figure 12 ). Companion chaetae absent. Thoracic neuropodial tori longest on chaetiger 2, extending to near ventral midline. Anterior abdominal neuropodia each with two chaetal rows, anterior row with broadly hooded chaetae, posterior row with elongate, narrowly hooded chaetae; posterior neuropodia with single rows of elongate, narrowly hooded chaetae. Abdominal notopodial avicular uncini with a main fang surmounted by three rows of teeth, one tooth per row, occasionally two teeth on last row; breast well developed, handles absent ( Figure 12F View Figure 12 ). Posterior part of body including last 17 chaetigers with a depression ( Figure 12A View Figure 12 ). Pygidium triangular, without a terminal cirrus; anus mid-ventral, near anterior margin. Tubes large, muddy ( Figure 12D View Figure 12 ).

Remarks

This species differs from Laonome kroyeri Malmgren, 1865 , which was previously reported from the Mediterranean, in having pigmentation on the branchial crown (absent in L. kroyeri ), anal depression (absent in L. kroyeri ) and triangular lobes in collar (thick and glandular in L. kroyeri ). The other species that was cited under the genus Laonome in the Mediterraenean, L. salmacidis Claparède, 1870 , was transferred to the genus Euratella (see Fauchald 1977). The Mediterranean specimens of L. triangularis coincide with its original and subsequent descriptions by Hutchings and Murray (1984) and Capa (2007). However, there are some slight differences between the distant populations. The Australian specimens described by Capa (2007) have thoracic uncini with three rows of teeth above main fang (three or four rows of teeth above main fang in Mediterranean specimens), abdominal uncini with four rows of teeth above fang (two or three rows of teeth above main fang in Mediterranean specimens) and seven transversal bands of dark brown pigmentation in radioles (four or five in Mediterranean specimens).

Distribution

This species was only reported from Australia on sandy mud at depths to 20 m, in salinities of 19–35% ( Hutchings and Murray 1984). As it was only found near harbours in I skenderun and Mersin Bays, this species could have been introduced to the area by ballast waters of ships. It is a euryhaline species that can easily adapt to a new environment.