ALBERT

Notes: Abstract The morphology of the primary tube feet in 15 species of comatulid (unstalked) crinoids from coral reefs in the Palau Islands and Lizard Island, Great Barrier Reef, was investigated using close-up underwater photographs of the tube feet taken in the natural habitat. Measurements of length of the tube feet and their spacing along the pinnule were taken from these photographs. Tube feet of species of the family Comasteridae have a mean length of 0.75 mm and a mean spacing of 6 tube feet mm-1. Tube feet of non-comasterid species occurring in the same environments have a mean length of 0.55 mm and a mean spacing of about 8 tube feet mm-1. The relationship between spacing and length of the tube feet is highty significant for both the Palau and Lizard Island samples (P〈0.01). Species having longer and more widely spaced tube feet live partly concealed within the infrastructure of the reef and hold the arms and pinnules in a multidirectional posture. Species having shorter and more closely spaced tube feet perch on top of reef pinnacles or alcyonarians and form planar filtration fans normal to unidirectional currents or wave oscillations. Longer and more widely spaced tube feet in species dwelling within the reef infrastructure provide more efficient filtration in the slow, meandering flow prevailing there. Closer spacing of the tube feet in species exposed to near-mainstream flow provides a more efficient filtration mechanism at higher flow velocities. Reduced length of the tube feet in these species may be a consequence of closer spacing of the pinnules. Differentiation of these co-occurring species in spacing and length of the tube feet implies differentiation in food particles captured. This may in some cases constitute resource partitioning. Most species which overlap in living habits are significantly different in spacing and length of the tube feet.

Notes: Abstract Changes in the rates of utilization of dissolved compounds during the period of visceral mass regeneration were examined in the crinoid Cenometra bella (Hartlaub). Rates of respiraton and incorporation of labelled amino acids increase, reaching a maximum 2 d after evisceration and returning to normal after 14 d. Rates of incorporation of radioisotope into the organic components of the arms and cirri decrease, while incorporation rate into the visceral mass increases. Incorporation rates of amino acid-derived radioactivity into skeletal carbonate and the ash-free dry weight:protein ratio of arms, cirri and oral disc decrease, reaching a minimum 2 d following evisceration.

Notes: Abstract The movement and digestion of food in the gut ofOligometra serripinna (Carpenter) were studied at Lizard Island (14°38′42″S; 145°27′10″E) in the austral winter of 1986. Feather stars in the laboratory were fed a brief, small meal of brine shrimp nauplii and killed at increasing time intervals thereafter. Histological reconstructions showed that the ingested nauplii progressed along the digestive tract surprisingly quickly. Some nauplii were found in the mid and hind intestine in only 30 min, and all of the nauplii had reached the hind intestine and rectum in 1 h. Digestion of the nauplii had started at 1 h, and only a few fragments of naupliar exoskeleton remained in the hind intestine and rectum 5 h after the start of feeding. Videotape analysis showed that no fecal pellets were released during this experiment. In the natural environment ofO. serripinna, ingested particles may similarly be transported quickly to the hind part of the gut and digested there — when feather stars were fixed in the field, most of the gut contents were found in the hind intestine and rectum.O. serripinna, which efficiently rejects inert particles before they are ingested, usually defecates infrequently (probably not more than once over a span of many hours) and differs from some other feather stars that ingest numerous inert particles and defecate much more frequently. When specimens ofO. serripinna were fed continuously on brine shrimp nauplii,Artemia sp. (San Francisco strain), in the laboratory, the feather stars fed gluttonously, packing their guts with several hundred nauplii in 1 to 2 h. Thereafter, superfluous feeding began (i.e., further ingestions appeared to force undigested nauplii, some of them still living, out of the anus). These observations suggest thatO. serripinna usually feeds at relatively modest rates in its natural habitat, but can feed gluttonously to take advantage of infrequent patches of highly concentrated, nutritious particles (e.g. copepod swarms, migrating demersal zooplankton, and invertebrate gametes from mass spawnings). It is likely that such patches of nutritious particles are usually small enough to drift out of reach of the feather stars before gluttonous feeding proceeds to superfluous feeding. Opportunities for superfluous feeding in nature are probably very infrequent (e.g. ingestion of coral gametes and embryos after a mass spawning), and the feather stars evidently have no behavior that stops further ingestions after the gut becomes filled to capacity.

Notes: Abstract We describe a portable, non-motorized device for delivering a tracer dye into seawater under field conditions. Dye is ejected at a constant flow rate over a period of tens of minutes. The ejector works in a wide range of ambient pressures without external energy requirements. The flow rate is adjusted simply by varying the length of the delivery tube. The dye streams permitted observations of the upcurrent and downcurrent flow regimes for a filter-feeding crinoid (Comanthus bennetti) living at a depth of 8 m on a coral reef. The results indicate that the crinoid may enhance the rate of particle capture by changing the scale of turbulence in the water passing through the mesh of the filtration fan.

Notes: Abstract Aspects of feather star behavior and ecology were recorded by time-lapse cinematography approximately 1 frame min-1 on the Great Barrier Reef, Australia over a 1 mo period in 1983. The current regime influenced body postures of most species studied, whether nocturnal or not. Moreover, feather stars of several species crawled on the substratum with their arms; each crawling episode lasted roughly 10 min, and the maximum speed attained was about 1 arm length min-1. Nocturnal feather stars crawled to their nighttime feeding perches around dusk and crawled back to their daytime hiding places around dawn. Surprisingly, some species of feather stars living on the reef surface both day and night also crawled around at dawn and dusk for reasons that are not known. In the time-lapse films, and individual of Comanthus bennetti (sex undetermined) spawned for about 2 min just after dark on 5 July 1983. Another film showed possible predation on a feather star (Himerometra robustipinna) by a saddled coralfish (Chaetodon ephippium).

Notes: Abstract The feeding behavior, living position, and skeletal morphology of 8 species of reef-dwelling Caribbean comatulid crinoids are intimately related to the regime of water movement prevailing in the microhabitat. These adaptations are related to the dependence of the crinoid suspension-feeding mechanism on externally produced water movements for a continuous food supply. Greater numbers of co-occurring comatulid species (6 to 7) and larger populations have been found off Colombia and Panamá than off Curaçao and Jamaica (4 species). It is suggested that these differences may be related to increased or diversified primary productivity close to the larger land masses. Overal food availability as determined by primary productivity may, thus, be an important factor controlling the regional diversity and abundance of these species.

Notes: A fairly realistic nonlinear model of a water reservoir system with multiple uses has been developed based on available data, and the optimum of the system based on the developed model has been determined by the combined use of dynamic programming and the pattern search techniques. Both the simplex search and the Hooke and Jeeves pattern search have been used. The approach in modeling and optimization can treat complex inequality constraints. The benefits or losses resulting from four purposes or uses of water, namely, urban water supply, hydroelectric power generation, irrigation, and recreation, are taken into account in the profit function. Other uses such as flood control, navigation, and fish and wildlife enhancement are considered indirectly by the use of inequality constraints. It appears that the approach developed in this work can treat a water resource allocation problem involving complex inequality constraints.

Notes: Summary The catfishSynodontis nigriventris normally swims upside-down but can assume any posture in response to a substrate it swims close to. Postural reflexes of the body and the eyes, labyrinthine anatomy and passively maintained posture were investigated to obtain indications for possible mechanisms controlling the peculiar postural behavior of this fish. Saccade-like resetting movements of the eyes during counter-roll to body tilt about the longitudinal axis, and maintained tilted swimming positions in blinded fish suggest that these animals reset their vestibular CNS circuits to zero when in tilted positions.Synodontis nigriventris is thus able to maintain any posture without interference from tilt-counteracting vestibular reflexes. The normal upside-down swimming apparently results from a central bias for this position and a supporting ventral light response. We conclude that if the “reafference principle” applies to the phenomena investigated, the efference copy may be fed through an integrator before reaching vestibular reflex circuits.

Notes: Summary 1. By videorecordings we studied ocular counterroll in fishes during actively and passively induced postures. 2. During active body roll in response to the presence of obstacles, during Ventral Substrate Response (VSR) induced pitch-up, and during active pitchdown in a “head-standing” fish ocular counterroll occurs with the same gain as when the same posture is induced passively. 3. During VSR induced roll and under certain conditions also during Dorsal Light Response (DLR) induced roll ocular counterroll is absent. 4. During tail bending in the horizontal plane ocular counterrotation is more distinct during active movements than during passive ones. 5. During certain cases of DLR induced roll as well as during DLR induced pitch-up and pitch-down ocular counterroll is present, but less pronounced than during passively enforced abnormal postures. 6. We interpret the different types of oculomotor behavior during active changes of body posture as indicating that there are different modes of interaction between postural change commands initiated by higher CNS centers and vestibular circuits which are thereby set-point changed.