ALBERT

Notes: Summary The drinking response of rats seen after the hypotensive drugs phentolamine, isoproterenol and hydralazine/bretylium can be abolished by nephrectomy. It is postulated, that the dipsogenic activity of these drugs is mediated by renin.

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).