Streptosyllis websteri Southern 1914
Feeding Habits: diatoms, foraminiferans, harpacticoid copepods, ostracods
C. nodosa, sandy bottoms, muddy sand, fine sand, medium sand, vertical distribution of 20-30cm
Streptosyllis pettibonae Perkins 1981
The worms are 3.5-5mm long, consisting of 32-49 chaetigerous segments. The head is broader behind than in front, with four large circular reddish-brown eyes provided with lenses. The median antenna is missing. The lateral antennae, rising from the front of the head, are smooth and cylindrical, slightly narrowed at the base. The palps are small and filiform, ventral in position. Between the head and the buccal segment on each side are the ciliated nuchal organs. The buccal segment bears on each side a pair of smooth tentacular cirri, longer than the lateral tentacles but shorter than the anterior dorsal cirri. All the cirri are filled with rounded faintly yellow granules. The anal segment bears two short lateral cirri and a long median one.
The feet are prominent. The anterior region of the body consists of 5 setigerous segments, as in the "S varians" of de Saint-Joseph, but differs from that species in that the spine in the first segment is thin, resembling that in the posterior segments. In segments 2-5 the spine is very large and thick.
The third foot has a blunt setigerous lobe, pierced at the dorsal angle by a thick spine, 7-10 compound setae, of which 1 or 2 have long tips and 6-8 have short tips. A single simple seta is present in the dorsal region of the foot. The dorsal cirrus is long, the ventral cirrus short and thick. The 16th foot has proportionally a much smaller setigerous lobe, with a simple dorsal seta, slender spine and six compound setae with long tips. The ventral cirrus is considerably longer than in the anterior segments.
 The simple seta is present in all segments. In the anterior segments it is slightly curved, serrate near the tip, and the latter is not winged. |
 Further behind, the simple seta is toothed along the convex side and the tip has a delicate wing. |
| The seatae in segments 1-5 are much shorter and thicker than those in the other segments. One or two of them have slender serrate tips with bluntly rounded points. The remaining setae, 6 or 8 in number, have short, thick terminal pieces. All these compound setae have swollen ends of the shafts, which are produced into a number of short rounded lobes. | |||
 |
|
 |
|
Behind the 5th segment the setae are much thinner. The terminal pieces differ only slightly in size and are serrate, with simple rounded tips. The end of the shaft is serrate along one edge and is produced into 4 sharp lobes.
The spine is slender, with a bulbous tip, 1 or 2 in each foot. Capillary setae commence in the 11th setigerous segment and are present in all the following segments except one or two at the posterior end. The length of the capillary setae exceeds the width of the body.
The ventral cirri are much longer in the posterior segments than in the anterior.
The proventriculus occupies 4-5 segments and has about 50 rows of glands.
All the specimens were sexually mature, provided with swimming seate and were taken in the tow.net, usually at the surface, at night. No specimens belonging to this species have been yet found in the bottom fauna, and conseuently their habitat is not known.
All the specimens obtained were mature males, with the body cavity full of sperm. They were taken in April, September and October.
This species seems to be most closely allied to the Streptosyllis varians of de Saint-Joseph. It resembles this species in having 5 setigerous segmens in the anterior region and in having simple tips to the compound setae. It differs in having a slender spine in the first setigerous segment, in the shape of the terminal pieces of the anterior
setae, in the presence of the simple dorsal setae in all segments, in having 3 anal cirri and in other details.
The species S. pettiboneae Perkins, 1981 is closely related to Streptosyllis websteri Southern 1914; both species have enlarged aciculae and modified compound setae in the setigers 2-4, as well as similar type of the compound setae from setigers 7. The type material of S. pettiboneae (Holotype USNM 60448, paratype USNM 60449) examined, agrees quite well with specimens of S. websteri from Canarias and with the original description of Southern.
