Learning outcomes:
- To become familiar in identifying digestive anatomy
- To be able to calculate the gut length to body length ratio and determine differences between carnivorous and. herbivore teleosts.
- To identify special adaptations in fish [spiral valves], impacted intestinal length, pyloric caecae.
Introduction:
Recognizing that each species have the ability to digest feed at different capacities is pertinent when determining their feed requirements. Commencing with their mouth, the structure [examples: suction; gape size; quantity of teeth] will enable optimum feeding ability. Gape size is relative to their body size and is key when determining pellet size requirements. Anatomically, the ratio of intestinal length: body length varies between species and their feed source [Table 1.0]. A herbivorous and detritivorous fish, where the diet that is dominantly consisted of indigestible matter tend to have longer intestines than those that contain a carnivorous diet.
Table 1.0- The intestinal lengths of a range of fish species in relation to their feeding habits [Source Jobling: 1998].
Prerequisites:
- Video: Module 2 Lab: Comparative Teleost Digestive Anatomy
- Excel file Module 2 Fish Nutrition Anatomy containing data from six Arctic charr [Salvelinus alpinus], Atlantic halibut[Hippoglossus hippoglossus] and Nile tilapia [Oreochromis niloticus]. Please make note of the recorded units when analyzing the data.
Assignment:
Follow previously provided Guidelines for Reports. Be sure to format Tables and Figures properly.
- Abstract [10%]: A summary of the report in one paragraph, no more than half a page. State the main findings for each tested species. Never cite references. Never cite figures. Do not repeat information already in the title.
- Introduction [20%]: 3/4 to 1 page max. Introduce each species and their native habitat. State their relevance in aquaculture. Consider using the following terms: euryphagous, stenophagous, and monophagous.
- Materials and methods: Include statement ‘refer to video’. State software used to analyze findings.
- Results- Tables and Figures[30%]: Table 1: Prepare a Table including characteristics such as a] mean number of pyloric caeca; b] teeth orientation; c] number of gill rakers; d] herbivorous/ carnivorous / omnivorous.
Table 2: Prepare a Table including mean and standard error for each of the 3 species: a] ratio of gape size to fork length; b] ratio of oesophagus: fork length; c] ratio of stomach length : fork length; d] total length of intestinal tract [oesophagus to anus]: fork length. Beneath the table, report the results in one or two paragraphs.
Figure 1: Calculate the relative intestinal length:
[[mean pyloric caeca [ if present] x number of pyloric caeca] + [total intestinal length]]
Fork length
With data from all three species, prepare a scatterplot regression graph- fork length [X-axis], relative intestinal length [Y-axis].
Beneath each table and figure include a summary of findings.
5.Discussion [30%]: Discuss the feeding mechanisms, source of prey and habitat for each species: Arctic charr [Salvelinus alpinus], Atlantic halibut[Hippoglossus hippoglossus] and Nile tilapia [Oreochromis niloticus]. State how these mechanisms would influence aquaculture practices. End the discussion with a short summary: “In conclusion…..”
- References: [10%]: List only the references cited in your report following formatting guidelines.