The functional anatomy and histology of the alimentary canal of the maldanid polychaetes Clymenella torquata and Euclymene oerstedi

Abstract

The alimentary canal of the maldanid polychaetes Clymenella torquata (Leidy), and Euclymene oerstedi (Claparède (=Caesicirrus neglectus Arwidsson, 1911) resembles, in many ways, that of the arenicolids. It is divided into buccal mass, pharynx, oesophagus, stomach and intestine, the three latter regions showing further subdivision. The buccal mass and anterior pharynx together form an eversible proboscis. The pharynx, oesophagus, and greater part of the intestine are ciliated. Simple feeding experiments, and histochemical tests, suggest that the stomach is concerned with the digestion and absorption of proteins, fats and carbohydrates, that the anterior intestine is a digestive and major absorptive region, and that the posterior intestine is a storage region. Waste materials are stored mainly in the wall of the oesophagus. A certain amount of intracellular digestion is carried out in the intestine of Euclymene but not in Clymenella. The difference is attributed to the richer, diatomaceous diet of Clymenella. British individuals of this species, being apparently selective feeders, differ not only from Euclymene but also from American ones, both of which ingest the substratum non‐selectively. The pharynx, oesophagus and rectum are surrounded by plexuses of blood capillaries, while the remaining regions are associated with a blood sinus system which varies in position and form in the different regions, lying deepest in the absorptive intestine. The gut muscle seems to be more concerned with moving the blood forward through the sinus system and into the anterior plexus than with moving the food backward. One region of the stomach musculature is especially concerned with this circulation. Rectal respiration probably occurs.

Chaetal loss and replacement in Pseudopotamilla reniformis (Sabellida, Annelida)

“…Müller 1766) by Tzetlin (), Scolelepis squamata ( Müller 1806) by Hausen & Bartolomaeus (), and Dipolydora concharum ( Verrill 1880) by Radashevsky & Fauchald (). In large polychaetes that grow dramatically in their lifetime, small juvenile chaetae are replaced by larger adult chaetae (Pilgrim ; Bhaud ; Duchene & Bhaud ). In addition, worn‐out and broken adult chaetae are replaced by new chaetae (Hausen ).…”

An Atlantic infaunal engineer is established in the Northeast Pacific: Clymenella torquata (Polychaeta: Maldanidae) on the British Columbia and Washington Coasts

“…Past studies have described the British Clymenella as unusually large (maximum length 15 cm) when compared to American populations (11 cm) (Mangum 1964;Pilgrim 1965), however, samples from Massachusetts suggest American Clymenella are capable of surpassing this length (19.5 cm) (Rankin 1946).…”

The morphology of the head, thorax, proboscis apparatus and pygidium of the maldanid polychaetes Clymenella torquata and Euclymene oerstedi

“…However, as they emerge along two parallel lines from between the muscles of the internuchal ridge, they divide into two sets, the inner dorsal retractors (Figs 2, 4, idabr) the anteriormost of which are inserted on the roof of the buccal cavity below the cerebral ganglia, and the outer dorsal retractors (odabr) which are inserted on the dorso-lateral walls of the anterior buccal pouch. The latter, unlike the completely circular pouch to which the retractor sheath is attached, is incomplete in the mid-dorsal and mid-ventral lines (Pilgrim, 1966, Fig. 2).…”

“…This is imperforate except for a median gap in its mid-ventral line of origin, the ventral valve (Pilgrim, 1966, Fig. 2, wl), through which pass the ventral transverse vessels of the head (Pilgrim, 1960), and a gap at its mid-dorsal, anterior end, through which the dorsal longitudinal vessel passes into the prostomial lobe.…”

“…The tail, which is usually uppermost in the tube when worms are collected, seems to be concerned mainly with defaecation, though it may also play a part in excretion (Pilgrim, 1965) and in respiration (Pilgrim, 1966). Chapman (1950) points out that the system by which worms move, namely by a hydrostatic pressure in conjunction with two sets of antagonistic muscles, can only result in a limited number of movements, provided that the whole coelom is in continuity.…”