J. Zool., Lond. (1978) 186, 393-396

Feeding mechanisms in black corals (Antipatharia)

J O H N B . LEWIS The Redpath Museum and The Marine Sciences Centre,

McGill University, Montreal, Canada

(Accepted 9 May 1978)

(With 1 plate in the text)

Feeding in the Antipatharia is very similar to that of reef corals. Food capture is accom- plished by the tentacles with their nematocysts, by mucus nets and strands, by directional ciliary currents, and by mesenterial filaments.

Contents Page

Introduction. . . . . . . . . . . . . . . . . . . . . . 393 Materials and methods . . . . . . . . . . . . . . . . . . 393

References . . . . . . . . . . . . . . . . . . . . . . 396 Feeding behaviour . . . . . . . . . . . . . . . . . . 394

Introduction The Antipatharia are typically deep sea organisms and are most abundant in tropical

and subtropical oceans. Because they are known chiefly from preserved specimens our lack of knowledge of the food and feeding habits of this group is not surprising. They are apparently carnivorous planktivores for Grigg (1965) observed the polyps of Antipathes grandis ingesting amphipods, copepods, and chaetognaths under laboratory conditions. Warner (1977) who studied the orientation to water currents of several species of anti- patharians in Trinidad, regards them as passive suspension feeders. The following notes on feeding behaviour are intended to supplement the brief observations of Grigg.

Materials and methods This investigation was carried out at the Bellairs Research Institute of McGill University at

Barbados, West Indies. Specimens were obtained at a depth of about 35 m on the seaward slope of a deep bank reef (Macintyre, 1967), placed in polythene bags and carried to the laboratory in buckets of water without exposure to the air. Colonies were then placed in running sea water aquaria and small fragments, clipped from the collected branches, were placed in finger bowls containing about 350ml of sea water. Feeding behaviour was observed through a Wild M-5 stereoscopic microscope and photographs were obtained with a Nikoii F camera attached to the microscope. Live brine shrimp nauplii (Arternia sp.), freshly caught zooplankton, ripe sea urchin ova, a commercial aquarium fish food (Tetra Min), and a ground filtered fish homogenate were offered as food. A suspension of powdered graphite was added to the fish homogenate in order to make it readily visible. Feeding observations were made during both day and night.

The following species were available for study: (1) Cirripathes lutkeni Brook (2) Antipathes pennacea (Pallas) ( 3 ) Antipathes sp. related to A . pedata Gray, but very likely a distinct and undescribed species.

All three species thrived in the laboratory in sea water aquaria for at least a month. 393

394 J . B. LEWIS

Feeding behaviour Limited field observations indicate that colonies of the Antipatharia were expanded

during the day, while in the laboratory polyps were observed to be expanded both day and night. The degree of expansion was variable but was characterized by extension of the tentacles and elevation of the oral region to form a cone-like mouth. The tentacles were capable of extension up to two or three times the width of the polyp. Plate I(a) is an underwater photograph of a colony of an unidentified species with the tentacles fully expanded.

The general body surface of the polyps of the three species is ciliated. Ciliary currents are directed distally along the aboral surface and ventrally towards the mouth and the tentacles. Currents also flow towards the tips of the tentacles and, in the mouth, down into the pharnyx. This pattern is identical to that observed in A . grandis by Grigg (1965).

The presence of fine food particles in the vicinity of the polyps caused polyp expansion, extension of the tentacles, a wide mouth opening, mucus production and increased ciliary current velocity. MLICUS nets and strands were formed over the general body surface in all three species and were drawn rapidly into the mouth as feeding began. Suspended particles of fish homogenate and other particles were readily caught in the nets and strands and drawn into the mouth by strong ciliary currents in the pharynx (Plate I(b), (c)). Tentacle turning and twisting occurred and the ingestion of food was aided by the thrusting of tentacles into the mouth. Enormous expansion of the mouth occurred as large particles caught in the mucus nets were swallowed. On a number of occasions mesenterial filaments

PLATE I(a).

F E E D I N G I N A N T I P A T H A R I A N S 395

PLATE I(b).

PLATE I(c).

PLATE I . (a) Underwater photograph of an unidentified antipatharian showing expanded tentacles ( x 4). (b) Polyps of Civripathes lufkeni Brook showing ingestion of mucus strac,ds ( X 20). (c) Polyps of Antipatha sp. showing ingestion of mucus strands ( x 20).

396 J . B . LEWlS

were extruded through the mouth and attached to food particles as has been observed in reef corals (Yonge, 1930; Goreau, 1956).

The presence of live plankton in the vicinity of polyps evoked similar responses. The capture of live zooplankton, including brine shrimp and sea urchin ova, was accomplished by a combination of tentacle activity and by mucus strands. The tentacles are covered with numerous clusters of nematocysts and when fully expanded wave about vigorously upon stimulation. Zooplankton was caught by the nematocysts and trapped in the mucus which covers the tentacles. Subsequently the tentacles were turned inwards toward the mouth and the prey is sucked off into the pharnyx. The mouth is closed as the prey is then further ingested. The flow of mucus and of particulate material towards the mouth was enhanced by directional ciliary currents. Grigg (1965) observed that the tentacles of A . grandis served to turn ciliary currents towards the mouth but did not hold prey.

Feeding in the Antipatharia is very similar to feeding in reef corals and the same strategies are employed (Lewis & Price, 1975, 1976). Food capture is accomplished by the tentacles, by mucus nets and strands. directional ciliary currents, and occasionally by the mesenterial filaments. Zooplankton is captured by the tentacles with their nematocysts and attached mucus strands. Fine suspended particulate matter in the water is caught by the mucus nets and strands which cover the surface of the polyps. There is thus a broad range of food available to antipatharians. Tentacle capture appears to be less rapid and efficient than in those reef corals which have long tentacles but the ability of antipatharians to feed by mucus nets and strands was impressive.

This study was supported by a grant in aid of research from The National Research Council of Canada. I am grateful to Dr D. M. Opresko for identifying the antipatharians, and to Dr H. M. Reiswig for the photograph in Plate I(a).

R E F E R E N C E S Goreau, T. F. (1956). A srudy ofrhe biology and histochemistry of corals. Ph.D. Thesis, Yale University. Grigg, R. W. (1965). Ecological studies of black coral in Hawaii. Pucif. Sci. 19: 244-260. Lewis, J. B. & Price, W. S. (1975). Feeding mechanisms and feeding strategies of Atlantic reef corals. J. Zool.,

Lewis, J. B. & Price, W. S. (1976). Patterns of ciliary currents in Atlantic reef corals and their functional signi-

Macintyre, I. G. (1967). Submerged coral reefs, west coast of Barbados, West Indies. Can. J . Eurfh Sci. 4: 461-474. Warner, G. F. (1977). On the shapes of passive suspension feeders. In (11th European Symposium on Marine

Ecology) Biology of benthic organisms: 567-576. Keegan, B. F., Ceidigh, P. 0. & Boden, P. J. S. (Eds). Oxford : Pergamon Press.

Yonge, C. M. (1930). Studies on the physiology of corals. I. Feeding mechanisms and food. Scienr. Rep. Gr. Barrier Reef Exped. 1: 13-57.

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