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Saltville, VA, United States

Salze G.,Virginia Polytechnic Institute and State University | McLean E.,University of Trinidad and Tobago | Craig S.R.,Virginia Polytechnic Institute and State University | Craig S.R.,Virginia Cobia Farms
Aquaculture | Year: 2012

The appearance of stomach pepsin activity in teleosts is one of the last ontogenetic events during the larval stages, and typically marks the completion of the shift from intracellular to extracellular mode of digestion. The present trial describes the morphological and functional ontogeny of cobia's stomach. Larvae were reared in a recirculated system and fed enriched rotifers in green water, followed by enriched Artemia, prior to being weaned on an artificial diet 25days-post-hatch (dph). The stomach commenced differentiation at 6dph, and displayed numerous gastric glands by 16dph (11.1mm TL). However, pepsin-like activity was not detectable prior to 22dph (20.8mm TL, P<0.05), denoting a lack of functionality until this time point. Maximum pepsin-like activity reached 29.09±1.47U Hblarvae -1. Together with the observations of others, the results presented herein shed light on the ontogeny of proteolitic digestion in cobia. © 2011 Elsevier B.V.

Salze G.,Virginia Polytechnic Institute and State University | Craig S.R.,Virginia Cobia Farms | Smith B.H.,University of Toronto | Smith E.P.,Virginia Polytechnic Institute and State University | Mclean E.,Aquaculture Center
Journal of Fish Biology | Year: 2011

The morphological development of larval cobia Rachycentron canadum from 3 days post hatch (dph) until weaning (27 dph) was examined using S.E.M. Two groups of fish were studied: a control group (CF), reared under standard feeding protocol, and a group in which prey items were enriched with supplemental taurine (4 g l-1 day-1; TF). TF fish grew faster (P < 0·001), attained greater size (mean ±s.e. 55·1 ± 1·5 v. 33·9 ± 1·0 mm total length) and had better survival (mean ±s.e. 29·3 ± 0·4 v. 7·1 ± 1·2 %) than CF fish. Canonical variance analysis confirmed findings with respect to differences in growth between the treatment groups with separation being explained by two cranial measurements. S.E.M. revealed that 3 dph larvae of R. canadum (in both groups) possess preopercular spines, superficial neuromasts on the head and body, taste buds in the mouth, an olfactory epithelium which takes the form of simple concave depressions, and primordial gill arches. Gill filaments start to form as early as 6 dph and lamellae buds are visible at 8 dph in both groups. In CF fish, the cephalic lateral line system continues its development at 12-14 dph with invagination of both supra- and infraorbital canals. At the same time, a thorn-like or acanthoid crest forms above the eye. At 14 dph, invaginations of the mandibular and preopercular canals are visible and around 22 dph enclosure of all cranial canals nears completion. In CF larvae, however, completely enclosed cranial canals were not observed within the course of the trial, i.e. 27 dph. In TF larvae, grooves of the cephalic lateral line system form 4 days earlier than observed in CF larvae of R. canadum (i.e. at 8 dph), with enclosure commencing at 16 dph, and completed by 27 dph. Along the flanks of 6 dph larvae of either treatment, four to five equally spaced neuromasts delineate the future position of the trunk lateral line. As myomeres are added to the growing larvae, new neuromasts appear such that at 16 dph a neuromast is associated with each myomere. By 27 dph, the trunk lateral line starts to invaginate in CF larvae, while it initiates closure in TF larvae. These findings elucidate important features of the larval development of R. canadum and show that dietary taurine supplementation benefits larval development, growth and survival in this species. Moreover, they suggest a conditional requirement for taurine in larval R. canadum. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.

Salze G.,Virginia Polytechnic Institute and State University | McLean E.,University of Trinidad and Tobago | Craig S.R.,Virginia Polytechnic Institute and State University | Craig S.R.,Virginia Cobia Farms
Aquaculture | Year: 2012

The establishment of a commercial cobia aquaculture is hampered by high mortality rates (>90%) during the larval rearing. Dietary taurine supplementation has been reported to greatly improve survival rates; however, nutritional role of taurine remains poorly understood in fish. The purpose of this trial was to study the effect of taurine supplementation on growth, amylase, lipase, trypsin, and pepsin-like activities during larval cobia development and weaning. Taurine was delivered using bioencapsulation techniques wherein rotifer and Artemia nauplii were co-enriched with 4gtaurineL-1d-1. At first feeding (3 dph), amylase and trypsin activities were detectable while lipase and pepsin-like activities were not. On a per-larvae basis and regardless of taurine supplementation, enzymatic onset commenced around 16 dph, except for pepsin. However, taurine-supplemented larvae had higher specific trypsin and amylase activities prior to 16 dph. Lipase specific activity was significantly increased only at 11 and 22 dph. Pepsin-like activity remained undetectable until 22 dph, at which point the specific activity was higher (P<0.05) in taurine-supplemented larvae. Overall, specific enzyme activities of control larvae were low during the first half of the larval period (3-16 dph) but increased during the second half (17-27 dph). Specific activities of taurine-supplemented larvae showed the opposite trend. Together with previous work, the present data strongly indicate that taurine is an essential nutrient for cobia larvae. Taurine supplementation does not affect the onset of total enzyme activities, but does increase specific amylase and trypsin activities in early larval stages. These heightened enzymatic activities may lead to enhanced nutrient availability, thus providing some explanation to the improved development, growth, and survival rates observed in taurine-supplemented larvae. © 2012 Elsevier B.V.

Agency: Department of Agriculture | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 90.00K | Year: 2010

Recent studies have demonstrated the importance of ionic composition of water and diets used in inland marine shrimp aquaculture. We propose to develop a feed and/or water additive approach to address this issue by using our knowledge of calcium-sensing receptors (CaSRs) in crustaceans and their roles in osmoregulation, nutrient sensing, and gowth. By supplementing diets with specific CaSR modulators over a range of environmental conditions, we propose to develop an application to address ionic deficiencies or imbalances in inland marine shrimp aquaculture in the U.S. Inland marine shrimp aquaculture is a growing market in the U.S. and technological improvements are necessary to compete. Our goal is to understand the commercially relevant interactions between important dietaray and environmental CaSR modulatory compounds and their effects on growth performance and osmoregulatory stress. Several of the biological and economic problems associated with inland shrimp culture in the U.S. are at least partially due to variable ion deficiencies and imbalances that occur due to the source of water and salts used at each culture facility. We propose to develop a product composed of feed and/or water additives applied under specific environmental contexts that will enhance the performance of U.S. shrimp production. We will test a combination of known modulators of CaSRs in crustaceans and monitor performance over a range of environmental conditions. This will provide the baseline data necessary to determine feasibility of this approach, particularly as it relates to inland recirculating culture of marine shrimp.

Virginia Cobia Farms | Date: 2009-06-30

Fish. Live fish for food purposes.

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