The feeding behaviour of 35 species of Atlantic reef corals was examined in the laboratory and in the field. Observations were made during the day and at night, using freshly hatched brine shrimp nauplii and finely ground, filtered fresh fish as food sources. Three feeding strategies were observed: Group I–feeding by tentacle capture only; Group II–feeding by entanglement with a mucus net or mucus filaments; Group III–feeding by a combination of tentacle capture and mucus filament entanglement. Group I included corals of the families Poritidae and Pocilloporidae which were normally expanded during both day and night. Group II included corals of the family Agaricidae which were normally expanded at night and contracted during the day. Group III included corals of the other families examined which, with the exception of Dendrogyra cylindrus, were normally expanded only at night. Feeding responses were elicited by both chemical and tactile stimuli. A preparatory feeding posture was assumed in response to chemical stimuli and consisted of horizontal positioning of the tentacles, elevation of the oral disk to form a cone‐like mouth, a wide mouth opening and secretion of mucus by the epidermis of the oral disk. Following the assumption of the preparatory feeding posture, food capture and ingestive movements were elicited by tactile stimuli. However, food capture and ingestive movements were also elicited by chemical stimuli alone in those species which were normally contracted during the day. While expanded corals captured food with their tentacles or with mucus filaments, contracted corals were able to feed by capturing fine particulate matter with mucus filaments only and thus acted as suspension feeders. By a combination of feeding strategies, reef corals were able to feed both day and night and a wide range of potential food ranging from fine particulate matter to large zooplankton was available to them.

Patterns of ciliary currents of 35 species of Atlantic reef corals are described and compared with currents of Pacific corals. Observations were made during the day and at night, during feeding and without food. There is a basic pattern of ciliary currents common to both Atlantic and Pacific species. In all but the family Agaricidae currents flow off the oral disk and up or out between the tentacles. In the centre of the disk region currents flow towards the mouth or the peristome. On the polyp stalk or column there was considerable variation between species in both Atlantic and Pacific forms. In some species currents flow downwards toward the coenosarc while in others, current pass up the stalk towards the tentacles. In the Atlantic Agaricidae there may be an inward flow towards the mouth, an outward flow or a unidirectional flow across the corallum. The patterns of flow depend upon the state of contraction of the polyps or the shape and proximity of adjacent polyps. No ciliary current reversal was observed in Atlantic species. Ciliary currents are functional as a cleansing mechanism and facilitated the ability of mucus nets and strands to gather particles.

The production of a pheromone-like spawning substance by male herring is confirmed and biochemical properties of the substance are characterised. A behavioural bioassay is described in which 0.25–0.5 mL of test solution was added to 46 L of water containing a single male herring. The effect of the solution was judged by the degree of extension of the herring gonadal papilla and release of milt. Treatment with fresh milt, extracts of milt, or extracts of mature testes resulted in papilla extension, often with milt release; extracts of ovaries or immature testes were not effective. The milt and testicular extracts retained their bioactivity during purification, including removal of substances soluble in petroleum ether, elution from C-18 Sep-Pak cartridges, and elution from C-18 high-performance liquid chromatography (HPLC) columns. The bioactive substances do not appear to be proteins or peptides, because (i) bioactivity was retained in milt and testicular extracts after the large proteins were precipitated by acetone−HCl solution and discarded, and (ii) bioactivity was present after the remaining soluble peptides were degraded by incubation with pronase E, proteinase K, or protease type VI enzymes. The pheromone is also not a neutral lipid or nonpolar fatty acid, as bioactivity remained in the aqueous phase after extraction with petroleum ether. Rather, the proposed pheromone(s) eluted from Sep-Pak C-18 cartridges with 30% acetonitrile and subsequently from the reverse-phase HPLC column in fractions 33–48 with a gradient of acetonitrile. Several polar steroids, conjugated steroids, and prostaglandin F2α were also shown to elute in this region, whereas a variety of other less polar compounds eluted later. Finally, after the post-Sep-Pak material was extracted with dichloromethane, bioactivity was shown to be present to a lesser extent in the dichloromethane fraction (containing free steroids) and to a greater extent in the water phase (containing conjugated steroids). The bioactivity of the water phase was reduced by incubation with glucuronidase but was eliminated by a combination of glucuronidase and sulfatase treatment. Various synthetic free steroids, conjugated steroids, prostaglandins, and amino acids were tested in the bioassay, but none mimicked the effect of the crude or semipurified testicular and milt extracts. We conclude that at least one substance is active as a pheromone-like spawning substance in males. These substances show hydrophobic properties similar to those of polar steroids, prostaglandins, or their conjugated forms, and at least one form likely contains a sulfate or glucuronide group. The role of a male pheromone may be synchronisation of spawning in schools of herring.

Differences in the morphology of the otoliths of Alosa pseudoharengus (alewife) and Alosa aestivalis (blueback herring) have been found to be reliable criteria in distinguishing the two species.

The size, shape, and arrangement of tentacles in scleractinian coral polyps are likely to affect particle capture yet have not been investigated in a systematic way. Morphometric measurements of tentacles of several coral species found in the Caribbean Sea were taken from macro-photographs, and from these, models were constructed in three postures: straight, upstream-facing, and downstream-facing. These models were placed in a flume to video the flow paths of particles around them. Video analysis indicates tentacles, and their specific postures, have a dramatic effect on micro-flow patterns. The expanded soft tissue tentacles, and their specific postures, greatly increase probability of particle capture by direct impaction, inertial impaction, and gravitational deposition. All tentacle postures cause increased retention time relative to freestream travel in their immediate proximity, as well as increasing both contact with the tentacle surface, and tumbling of particles. Straight and upstream-facing tentacles deflect particles downward to their base, while downstream-facing tentacles deflect particles upwards. When results from individual tentacles are considered in geometric combination, the secondary radial symmetry of the tentacular whorls in simple coral polyps appears to be an optimal strategy to filter suspended particulate material in an oscillating and omni-directional flow environment. In meandrine corals, the hedgerows of straight and curved tentacles appear to draw particles downward, retain them, and direct them onto the oral feeding areas below the thecal ridges. The size, shape, and arrangement of tentacles are thus of key importance in understanding suspension feeding in scleractinian corals.