62 



T.G. PILLAI AND H.A. TEN HOVE 



abdomen is 9.9mm long, with about 98 segments, and capil- 

 laries in the last 20. 



The pinnule-free tips (Fig. 8, E) are quite conspicuous and 

 much longer than those of S. ypsilon, being up to about 

 1.9 mm. They constitute nearly half to more than half the 

 length of the radioles (about 3.7 mm). The number of 

 radioles, 11 on each side, is higher than that of S. ypsilon 

 (maximum 8). They bear at intervals what appear to be 

 narrow, transverse, lenticular lacunae. Two pigmented pros- 

 tomial ocellar clusters are present. 



The rest of the body (Fig. 8, F) is similar to that of S. ypsilon 

 in many respects. In alcohol, the abdomen has an overall 

 pinkish colour, with clusters of reddish-brown pigmented 

 cells ventro-laterally. 



Thoracic chaetigers number 7 on both sides. Thoracic 

 membranes end on the third thoracic chaetiger (second 

 uncinigerous segment) on both sides of the thorax. Paired 

 ventral thoracic glands were not seen. 



A collar fascicle of the holotype has five fully formed 

 bayonet chaetae, and a developing one deep within. A 

 paratype from Karpata has 6 fully formed bayonets and one 

 newly forming one within the fascicle. Each bayonet chaeta 

 consists of a long, narrow serrated blade, and a considerably 

 expanded basal boss bearing several moderately large, some- 

 what pointed teeth (Fig. 8, G-L). The serrations are short and 

 fine proximally, but longer and pilose distally. The unser- 

 rated notch may be very short, up to about twice the length of 

 the longest teeth, or almost lacking (Fig. 8, I). The thoracic 

 and anterior abdominal uncini bear 5 teeth in a single row. 

 They differ from all the other known species of the subgenus 

 in possessing minute denticles on their sides (Fig. 8, M,N). 



The adaptations of the worm in relation to ITS are similar 

 to those of S. ypsilon. The dorsal longitudinal abdominal 

 groove is applied to the serrated dorsal ridge of the tube, and 

 the Y-shaped ventral ridge is enclosed within a ventral 

 abdominal groove. Within the latter, a cord-shaped abdomi- 

 nal ridge fits into the gutter-shaped part of the Y. 



The paratype from the type locality is a juvenile. Its tube 

 (Fig. 9, A) shows faint transverse grooves mainly, but the 

 beginnings of a granular overlay and longitudinal ridges can 

 also be seen. ITS and adaptations of the body are identical to 

 those of the holotype (Fig. 9, B,K,L). Measurements and 

 counts of the worm are as follows: Length 6.2 mm, thoracic 

 width 0.5 mm, radiolar length 2.1 mm, pinnules 1.1 mm, 

 abdomen 4.2 mm, 53 segments, with capillaries on the last 

 10. The number of thoracic chaetigers, ending of the thoracic 

 membranes (Fig.9,E), and colour, are the same as in the 

 holotype. 



The 7 pairs of radioles already approach the maximum 

 number in other material, except the holotype, and their long 

 pinnule-free tips are similar to those of the holotype (Fig. 9, 

 C). However, there is a very short and slender rudimentary 

 operculum on one side, while it is lacking on the other (Fig. 9, 

 C), indicating that both may become completely lost in older 

 specimens (holotype). A similar condition is found in one of 

 the specimens from Karpata (below). 



Collar fascicle with four fully formed bayonet chaetae 

 (Fig. 9, F-I) and a developing one deep within (Fig. 9, J). 

 Their basal bosses are not as expanded as in the holotype and 

 the blades are shorter. The uncini are similar to those of the 

 holotype. 



The tubes of the three specimens from Karpata agree with 

 those from the type locality in being white externally, pinkish 

 internally, and bearing the Y-shaped ventral ridge and ser- 



rated dorsal ridge. The serrations of the latter bear posteri- 

 orly directed tapered tips (Fig. 9, K,L). The radioles of all 

 specimens are detached, highly contracted, and do not clearly 

 show the extent of the pinnule-free tips. One crown has a 

 short rudimentary operculum on each side, the second has a 

 rudimentary operculum on one side but lacks it on the other, 

 and the third half crown has a rudimentary operculum which 

 is very reduced and filamentous. The thoracic width ranges 

 between 0.5 mm and 0.7 mm. The abdomen of the longest 

 specimen is 10.8 mm long and has about 59 segments, with 

 capillaries on the last six; that of the shortest is 7.3 mm, but 

 has about 86 segments, with capillaries on the last six. The 

 numbers of radioles, thoracic chaetal tufts and the extent of 

 the thoracic membranes in the three specimens is provided in 

 Table 11. 



In two specimens the broad thoracic membranes are folded 

 outwards against the sides of the thorax (Fig. 9, M,N). 

 Bayonet collar chaetae (Fig. 9, O-R) are similar to those of 

 the holotype, but lack an unserrated notch. Thoracic and 

 anterior abdominal uncini are also similar to those of the 

 holotype, with 4 or 5 teeth in a single row. Flat trumpet 

 chaetae number 6-8 in a bundle. Preserved in alcohol, the 

 abdominal segments show clumps of reddish-brown pig- 

 mented cells ventrolaterally, and of larger yellowish or orang- 

 ish cells ventrally (Fig. 9, N). 



The tube of the single juvenile paratype from Curacao 

 resembles that of the holotype; its diameter is 1.5 mm. The 

 worm has 6 radioles on the left and 5 on the right. As in the 

 specimens from Bonaire, the pinnule-free tips are very long. 

 However, both rudimentary opercula have already been lost 

 at this stage. The thorax is 0.5 mm wide and has 7 pairs of 

 chaetigers. The thoracic membranes end on the third thoracic 

 chaetiger. Two clusters of prostomial ocelli are present. 

 Thoracic glands were not seen. The chaetae also agree with 

 those of the specimens from Bonaire. In recently collected 

 material (Curacao, Piscaderabaai, 10. i. 1990), thoracic mem- 

 branes end at 4/5, 4/4 respectively; the pinnule-free tips 

 generally are very long, rarely short; rudimentary opercula 

 are present in four specimens, absent in three. 



Live material. According to the field notes, rudimentary 

 opercula could not always be found, even in living specimens 

 from Curasao with radioles extended. The colouration of the 

 radioles is somewhat variable, often (transparently) whitish 

 to creamish, rarely yellowish to slightly orange or even 

 completely hyaline. At the base of the radioles there is a 

 series of up to six pairs of reddish spots, absent however in 

 the dorsal- and ventralmost radioles. Body predominantly 

 orange-brownish with up to 15 greenish-brown granules per 

 segment ventro-laterally in the abdomen and dorsally in the 

 thorax. 



Etymology. The specific name paraypsilon indicates the 

 close resemblance of the species to S. ypsilon. 



Habitat and distribution. Occurs in shallow, clear, oce- 



Table 11 S. paraypsilon sp. nov. Meristic and other data from 

 specimens. 



Specimen nos. 



No. of radioles 



No. of thoracic chaetal tufts 



Thoracic membrane ends 



1 



2 



3 



8/? 



8/8 



8/7 



?/? 



8/9 



7/7 



?/? 



3/3 



3/3 



