Histogenesis of the oropharyngeal and oesophageal mucosa as related to early feeding in rainbow trout, Salmo gairdneri Richardson

1977 ◽  
Vol 55 (1) ◽  
pp. 116-128 ◽  
Author(s):  
Timothy K. Twongo ◽  
Hugh R. MacCrimmon
Keyword(s):  
Rainbow Trout ◽  
Epithelial Cell ◽  
Alimentary Canal ◽  
Taste Buds ◽  
Salmo Gairdneri ◽  
Mucous Cells ◽  
Early Feeding ◽  
First Feeding ◽  
Oesophageal Mucosa ◽  
Epithelial Layers

The histogenesis of the oropharyngeal and oesophageal mucosa of rainbow trout, Salmo gairdneri, eleutheroembryos was studied from hatching to day 40 in relation to early feeding. Numbers of epithelial layers of the mucosa increased appreciably until day 20 but little thereafter. Differentiation of mucous cells was evident by day 10 and increased rapidly in number until about day 20. The first structurally distinct taste buds were observed in the oropharyngeal mucosa at day 8 and appeared by day 20 to be fully differentiated. An epithelial cell plug that occluded the upper alimentary canal and would have prevented passage of food into the stomach disappeared at about day 17. Teeth, although developing under the mucosa by day 3, had not yet erupted at day 22, the time of first feeding.It is suggested that the onset of first feeding in rainbow trout is in synchrony with the histogenesis of the oropharyngeal mucosa, notably the mucous cells and taste buds. The oropharyngeal mucosa of the fish that failed to feed by day 37 appeared to have undergone extensive hyperplasia while mucous cells were atypical, and taste buds seemingly deformed.

Effects of Diet, Ambient Temperature, and Holding Conditions on Plasma Thyroxine Levels in Rainbow Trout (Salmo gairdneri)

1977 ◽  
Vol 34 (5) ◽  
pp. 677-682 ◽  
Author(s):  
J. F. Leatherland ◽  
C. Y. Cho ◽  
S. J. Slinger
Keyword(s):  
Rainbow Trout ◽  
Epithelial Cell ◽  
Soybean Oil ◽  
Salmo Gairdneri ◽  
Light Phase ◽  
Cell Height ◽  
Significant Difference ◽  
Pelleted Diet ◽  
Soybean Diet ◽  
Significant Diurnal Variation

Rainbow trout (Salmo gairdneri) acclimated to 19 °C and fed a pelleted diet of either 6% soybean oil or 6% tallow fat had similar plasma thyroxine levels (0.62 ± 0.10 and 0.69 ± 0.08 μg/100 ml, respectively), although fish acclimated to 7 °C and fed the soybean diet gave significantly (P < 0.05) higher plasma thyroxine concentration (1.32 ± 0.13 μg/100 ml) than the group fed the tallow fat diet (0.95 ± 0.12 μg/100 ml). The plasma thyroxine concentration in the fish fed the soybean oil diet was significantly (P < 0.01) higher at 7 °C than at 19 °C. There was no significant difference between the two groups of fish given the tallow fat diet. Epithelial cell heights were largest in groups with the highest plasma thyroxine levels. Epithelial cell height in the two groups at 19 °C were similar, but in both groups of fish at 7 °C, the cell height was significantly greater than in either of the groups at 19 °C (P < 0.01 for comparisons of the 19 °C tallow fat diet with both groups of 7 °C acclimated fish and comparison of the two groups on the soybean oil diet; P < 0.05 for comparisons of the 19 °C, soybean oil diet with the group held at 7 °C and given the tallow fat diet). Fish deprived of food for 40 days had a significantly (P < 0.05) lower plasma thyroxine concentration when compared with fish that had been fed daily. There was no significant diurnal variation in plasma thyroxine over the light phase of a 12 h light: 12 h dark photoperiod, nor did the limitation of light entering the aquaria significantly affect plasma thyroxine values. Key words: endocrine, thyroid, Salmo gairdneri, diet, environmental temperature

Fixation Artifacts in Rainbow Trout (Salmo gairdneri) Gills: A Morphometric Evaluation

1989 ◽  
Vol 46 (5) ◽  
pp. 780-785 ◽  
Author(s):  
D. J. Speare ◽  
H. W. Ferguson
Keyword(s):  
Rainbow Trout ◽  
Epithelial Cell ◽  
Chloride Cells ◽  
Salmo Gairdneri ◽  
Histopathological Changes ◽  
Whole Mount ◽  
Gill Lamellae ◽  
Linear Manner ◽  
Morphometric Evaluation ◽  
Fixation Delay

Epithelial capillary separation (E.C.S.) and epithelial cell hypertrophy (E.H.) of the gill lamellae of fish are two histopathological changes frequently described in association with toxic insults. Both of these gill changes increased in a significant linear manner over delay periods of 20–900 s from death to first entering either Bouin's or 10% formalin fixative. E.C.S. also occurred rapidly when gills were examined as whole mount preparations. The presence of occasional necrotic epithelial and chloride cells resembled apoptosis and is not in itself abnormal, nor did the type of fixative used or fixation delay have an effect on their extent. Gills from fish killed by either MS-222 or cervical spinal severance were similar, except that the latter also had multifocal lamellar telangiectasis. We conclude that E.C.S. and E.H. are readily mimicked by preparation and postmortem artifacts that occur rapidly after death when this is caused by either MS-222 or spinal severance. Bouin's fixative should be used to minimize these changes.

Acute Toxicity of Methyl Mercury Chloride and Mercuric Chloride for Rainbow Trout (Salmo gairdneri) Fry and Fingerlings

1975 ◽  
Vol 32 (11) ◽  
pp. 2005-2013 ◽  
Author(s):  
G. Wobeser
Keyword(s):  
Rainbow Trout ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Acute Toxicity ◽  
Mercuric Chloride ◽  
Methyl Mercury ◽  
Tolerance Limit ◽  
Cell Swelling ◽  
Salmo Gairdneri ◽  
Mercury Chloride

The median tolerance limit (MTL) for methyl mercury chloride at 24, 48, and 96 h was 0.084, 0.045, and 0.024 mg/liter as mercury, respectively, for fry; and 0.125, 0.066, and 0.042 mg/liter as mercury, respectively, for fingerlings. The MTL (24 h) for mercuric chloride for fingerlings was 0.90 mg/liter as mercury. Fingerlings exposed to methyl mercury chloride concentrated mercury in their tissues much more rapidly than did those exposed to mercuric chloride. The acute toxic action of both compounds was exerted on the gills. Mercuric chloride caused severe epithelial necrosis. Poisoning by methyl mercuric chloride was characterized by epithelial cell swelling and hyperplasia, a marked increase in the number of epithelial cells in mitosis, and terminal epithelial desquamation.

Ontogeny of feeding behaviour in hatchery-reared rainbow trout, Salmo gairdneri Richardson

1980 ◽  
Vol 58 (1) ◽  
pp. 20-26 ◽  
Author(s):  
Hugh R. MacCrimmon ◽  
Timothy K. Twongo
Keyword(s):  
Rainbow Trout ◽  
Feeding Behaviour ◽  
Feeding Activity ◽  
Artemia Salina ◽  
Artificial Feeding ◽  
Food Type ◽  
Salmo Gairdneri ◽  
Agonistic Behaviour ◽  
Exogenous Feeding ◽  
First Feeding

Development of feeding behaviour in young rainbow trout, Salmo gairdneri, from "swim-up" to day 57 after hatch at 8.5 °C is described relative to food type (live Artemia salina or dry trout ration) and water flow (current or no current). Earliest signs of feeding behaviour appear during the process of swim-up at days 27 to 29, with the movement of the eyes to fixate particles and the beginning of a snap response which intensifies within 2 days. Initially the alevins are nonselective between food and inert targets, but by about day 25 at the test temperature they have become able to discriminate food from nonfood items, and show a marked increase in exogenous feeding activity. The timing, which will differ at different rearing temperatures, coincides approximately with final absorption of the visible yolk sac and follows disappearance of the oesophageal plug by about 10 days. This would seem to be the best time to initiate artificial feeding of hatchery-reared alevins, with the fish showing a preference for ingestion of live food (shrimp nauplii) over dry rations. Despite evident behavioural differences in current and no-current conditions this factor had little effect on timing or ultimate success of first feeding. Failure of some alevins to begin feeding, or feed adequately for survival, is associated with the agonistic behaviour of more aggressive siblings.

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