Browsing by Subject "Red drum larvae"

Now showing 1 - 3 of 3

Cholecystokinin and the ontogeny of digestion in the red drum (Sciaenops ocellatus)
(2008-04) Webb, Kenneth Ashley; Holt, J. (Joan)
While substantial progress has been made in replacing live prey with artificial diets in the feeding of marine fish larvae, it still remains impossible to successfully rear larvae on artificial diets without some period of co-feeding live prey or algae. This study investigated the presence and role of the gastrointestinal hormone cholecystokinin (CCK) in the red drum (Sciaenops ocellatus) to gain a better understanding of the factors limiting the utilization of artificial diets by red drum larvae. Work with other fish species has shown that CCK is the principal hormone which regulates the release of pancreatic enzymes into the gut lumen and emphasizes the potential importance of CCK in early red drum larvae. This work investigated the hypothesis that some signal present in the live prey or algae stimulates CCK and thereby initiates the digestive process in the larvae. First, the nucleotide and amino acid sequence of the putative red drum cholecystokinin precursor was determined and the development of CCK immunoreactive cells was examined. This work showed that red drum CCK is highly similar to CCK in other vertebrates and can be detected in the digestive tract of larval red drum within three days after the initiation of exogenous feeding. Next; postprandial trypsin, CCK, and CCK mRNA responses were quantified in red drum juveniles and larvae over a three hour period. Both CCK and trypsin were increased within thirty minutes following feeding while CCK mRNA levels were increased within the next two to three hours. Finally, the trypsin, CCK, and CCK mRNA responses of red drum larvae to homogenates of live prey and algae were examined. Homogenized rotifers appeared to be sufficient to induce both the CCK and trypsin responses in larval red drum. These results suggest that in addition to other factors, some component of live prey may initiate the release of CCK and prime the digestive process. Understanding these factors and their effects in early larvae may allow us to formulate and produce a prepared diet which will support growth and survival to metamorphosis equal to that provided by live feeds.
From viscous to inertial forces : defining the limits of hydrodynamic regimes for larval fishes
(2005) Sarkisian, Brie Laura; Fuiman, Lee A.
The larval period in fishes is characterized by rapid growth which produces significant changes in the hydrodynamic conditions during swimming. The point of this study was to examine the changes in hydro-dynamic forces that act on red drum larvae, Sciaenops ocellatus, and to identify the hydrodynamic transition points throughout their development. I experimentally altered hydrodynamic conditions by changing the size of the fish under study (5-6 mm, 8 - 9.5 mm, 13 - 15.5 mm, and 29 - 35 mm in total length) and the kinematic viscosity of test solutions (0.8, 1.2, 1.6, and 2.0 x 10⁶ m² s⁻¹), in order to achieve a wide range of Reynolds numbers based on body length (ReL ranged from 12 to 4695). Five kinematic variables (swim-ming speed, stride length, tail-beat frequency, transverse tail speed, and tail amplitude) were measured for fish swimming at a constant speed along a linear path. Within a size class, increases in fluid kinematic viscosity reduced only swimming speed and stride length and only for the two intermediate size classes. Transitions in hydrodynamic regimes, from viscous to intermediate and intermediate to inertial, were estimated from plots of stride length against indices of viscous and inertial drag forces. The upper limit of the viscous hydrodynamic regime occurred at ReL approximately 600. The lower limit of the inertial regime was at ReL of approximately 1300. These estimates illustrate that fish are exposed to viscous forces over a wider range of ReL than originally predicted
Intraspecific competition among early life stages and the optimal spawning strategy of red drum (Sciaenops ocellatus)
(2009-12) Nakayama, Shinnosuke, 1978-; Fuiman, Lee A.; Thomas, Peter; Holt, Gloria J.; McClelland, James W.; Cummings, Molly E.
This collection of studies was designed to understand the mechanisms and consequences of competition among early life stages of red drum (Sciaenops ocellatus), with a special attention to asymmetric competition and multiple-breeding strategy of parents. The overall hypotheses were that (1) red drum larvae show behavioral interactions, and the magnitude of these interactions is explained by the sizes of the competing individuals, (2) red drum larvae compete for food and habitat use, and the competition is asymmetric as determined by size and behavioral interactions, and (3) the parents can reduce negative effects of competition among larvae and increase larval survival by altering their multiple-spawning traits. The laboratory experiments showed the existence of sociality in red drum larvae. The magnitudes of aggressive behavior, vigilant behavior and shoaling behavior were explained by a combination of absolute and relative phenotypes of competing individuals, such as body lengths and body condition. A new method of combining the laboratory experiments and the foraging theory disentangled interference competition for food from exploitative competition, revealing that both absolute and relative body lengths of competing individuals influence feeding efficiencies. In addition, vigilant behavior decreased feeding efficiency regardless of body sizes. The competitor size and behavioral interactions between individuals had different effects on competition for habitat use: the existence of larger individuals prevented the newly settled larvae from entering preferred habitats, whereas the aggressive behavior from the occupants of preferred habitats moved newly settled larvae to the unpreferred habitats. Finally, computer simulations using an individual-based model revealed that as interference competition among larvae increased, the number of spawning events and the spawning interval of the parents increased to lessen competition and maximize total survival of offspring.