Mantle Lobe Research Articles

Form and habit inPinna carneaGmelin

Form and habit in<i>Pinna carnea</i>Gmelin

Cercaria milfordensis nov. sp., a Microcercous Trematode Larva from the Marine Bivalve, Mytilus edulis L. with Special Reference to Its Effect on the Host

Cercaria milfordensis was found by the writer in April, 1951 in 4 of 93 (4.3%) intertidal specimens of the common mussel, Mytilus edulis, from Mill Neck, Long Island, New York. Subsequently, this larva was found in Mytilus from Milford and Bridgeport, Connecticut, in both intertidal and subtidal areas where 30 of 454 (6.6%) mussels collected in 1951 and 44 of 567 (7.7%) in 1952 were found to be infected. Consultation with Dr. V. L. Loosanoff, Director of the U. S. Shellfish Laboratory at Milford, revealed that in 1936, he also had observed the parasite in M. edulis from Milford Harbor. Dr. Loosanoff kindly made available a collection of slides of adult Mytilus gonad tissue collected at biweekly intervals during the period June 1936-June 1937. Examination of this material showed that 12 of 174 (6.9%) specimens of Mytilus were infected with the microcercous larvae. Previous records of cercariasis in Mytilus spp. are European in origin and pertain to the larvae of three trematode species. Dubois (1901, 1903, 1907, 1909) described larval stages of Gymnophallus margaritarum [= Distomum margaritarum Dubois, 1901] from M. edulis and M. gallo-provincialis. The metacercaria of this species has held particular interest as a cause of formation in Mytilus and other bivalve species, and many conflicting accounts were rendered concerning its biology and identity. Palombi (1924) re-studied the species in M. gallo-provincialis in an attempt to clarify the conflicting opinions of the time and concluded that the pearl trematodes of Jameson (1902) and later authors were identical with the species of Dubois. Cole (1935) described two cercarial forms, Cercaria tenuans and Bucephalus mytili, from M. edulis in British waters; infection with the former species was termed orange-sickness from the orange color imparted to the mantle lobes of infected mussels by masses of orange-pigmented sporocysts. A similar gross appearance is characteristic of mussels heavily infected with the trematode larvae discussed here.

On the structure and adaptions of the Tellinacea, deposit-feeding Eulamellibranchia

On the structure and adaptions of the Tellinacea, deposit-feeding Eulamellibranchia

Memoirs: On the Ciliary Mechanisms and Interrelationships of Lamellibranchs

A form of fusion involving only the cuticle has been found in certain Lamellibranchs between the outer demibranchs and the mantle or the visceral mass; between the two inner demibranchs; and, in forms possessing a fourth aperture, between the mantle lobes in the mid-ventral line between this and the pedal aperture. The histological structure of the junction is described, and is especially considered in relation to the condition of the fourth aperture in the Solenidae.

PULSATION OF BLOOD VESSELS IN OYSTERS, OSTREA LURIDA AND O. GIGAS

1. In the mantle of Ostrea lurida is a series of slowly pulsating blood vessels. 2. The many radial vessels are associated with the bundles of retractor muscle fibres of the mantle. The "accessory hearts" appear to be similar to these, though much larger. 3. The waste canal, a band of tissue running anteroposteriorly in the ventral wall of each mantle lobe and covered with cilia beating posteriorly, overlies a pulsating vessel which crosses and is continuous with many radial vessels. 4. All of the pulsating vessels communicate distally with the circumpallial sinus, which appears in this species not to be directly connected with the heart. 5. The vessels described pulsate at a slow rate and their activity is loosely coördinated. 6. The wave of contraction of the radial vessels originates centrally and travels slowly distally, forcing the blood outward into the circumpallial sinus. The pulsation of the vessel underlying the waste canal appears to begin at the anterior end. 7. The absence of effective valves is shown by the reversal of direction of flow of the blood as relaxation takes place. 8. The blood supply of the radial vessels appears to come from the blood spaces of the excretory organs and nearby tissues. 9. Isolated portions of the mantle of O. gigas, including an accessory heart, live for weeks, the accessory heart pulsating at approximately its normal rate. The rate of transmission of the impulse of contraction is slow, 4 to 8 mm. per second. The activity is compared to that of vertebrate smooth muscle. 10. The pulsating vessels appear to be indefinite spaces within the sub-epithelial matrix of connective tissue and smooth muscle, and an endothelium and other well-defined structures characteristic of formed blood vessels may be lacking.

ACCESSORY HEARTS IN THE OYSTER, OSTREA GIGAS

In three species of Ostrea a pair of actively pulsating accessory hearts was observed in the lateral walls of the cloacal chamber. They appear to pump blood from the lacunae of the excretory organs into the large marginal arteries of the mantle lobes and into the gills.Counts of the rate of pulsation of heart and accessory hearts in O. gigas show that they act independently, the rate of pulsation of the accessories probably being determined by the rate at which they fill with blood. Only in this respect is their rate dependent upon the heart rate.The accessory hearts appear to be homologous to the gill hearts of cephalopods.The course of circulation, as influenced by the accessory hearts, is apparently as follows: blood from the ventricle passes through large arteries to the viscera, adductor muscle, and palps; the anterior aorta is directly continuous with the marginal arteries of the mantle; venous blood from viscera, palps, gills, and muscle passes to the excretory organs from which it is pumped by the accessory hearts into the marginal arteries of the mantle and to the gills; blood collected from the mantle returns directly to the auricles.Heart and accessories both pump blood into the marginal arteries, which therefore receive both venous and arterial, purified and unpurified blood.