Topic Introduction

The previous topic introduced to the huge range of invertebrates that are present in tropical forests. In this topic, we will look at three particular groups: the Spiralia, Gnathifera and Nematoida. These are taxonomic classification units: each is a name given to a group of phyla. For example, the Spiralia include 9 different phyla, such as the Phylum Mollusca and Phylum Annelida. To put this in perspective, module 4 dealt with the vertebrates, which represent part of a single phylum (Phylum Chordata). However, as discussed in the introductory topic, invertebrates are far less studied than are vertebrates, despite the vast majority of species diversity in tropical forests lying with the invertebrates.

The presentations in this topic only touch on each of the groups that might be encountered in a tropical forest. This is partly because there is so little information available about them. It is also because many are extremely difficult to study, being microscopic, nocturnal or otherwise difficult to encounter. Some of the most obvious are better know, such as the slugs, snails and other molluscs. We have concentrated on the slugs and snails, although we are aware that there is a considerable mollusk fauna associated with mangrove forests that we have not dealt with. These may be added at a later date.

By the end of this topic, you should be able to:

• Describe the different roles played by Spiralia, Gnathifera and Nematoida in tropical forests.
• Explain where you would encounter them.
• Contrast the differing life strategies of the various Phyla within these three groups.
• Discuss the differences between free-living and parasitic nematodes.
• Explain the relative advantages and disadvantages of ecto- and endoparasitic lifestyles.

Topic Readings

Required Readings

• Ghazoul, J. and Sheil, D. 2010. Tropical Rain Forest Ecology, Diversity, and Conservation. Oxford, Oxford University Press, 516 pp. Chapter 5.2.2.

Optional Readings

• Brusca, R.C., Moore, W. and Shuster, S.M. 2016. Invertebrates. 3^rd Sunderland, Massachusetts, USA: Sinauer Associates. Chapters 10, 13, 14, 16 and 18.
• Gerlach, J. (ed.) 2011. Crustacea, Platyhelminthes, Nematoda, Nemertea, Annelida, Rotifera and Tardigrada of the Seychelles Islands. Siri Scientific Press. 160 pp.

Fundamental Concepts

PPT Presentations

5.2.1 Spiralia.pptx Download 5.2.1 Spiralia.pptx

5.2.2 Gnathifera.pptx Download 5.2.2 Gnathifera.pptx

5.2.3 Nematoida.pptx Download 5.2.3 Nematoida.pptx

Self-check Quiz

After viewing topic presentations, take this self-check quiz to check your own progress. This quiz is designed to see how well you remember some of the more important issues presented in the topic. There are five questions, and each has a potential of 4 answers, only one of which is correct. When you are ready, click the link Self-check Quiz 5.2 to start taking the quiz.

Pre-readings and Discussion (For certification)

Once you have read Section 5.2.2 of Ghazoul, J. and Sheil, D. 2010. Tropical Rain Forest Ecology, Diversity, and Conservation, choose to post one thought provoking question related to the material that you have read, and remember to answer/respond to at least one other student’s question on the discussion board Online Discussion Module 5.

Graded Assignment (For certification)

• There is no graded assignment associated with this topic.

Topic Summary

This topic has introduced to a wide variety of invertebrates living in tropical forests. In most cases, these represent small parts of the phyla, with the majority of species in each phyla being marine. The terrestrial faunas represent those living animals that have managed to adapt to living in a terrestrial environment. Many still require access to water, or live in water in the terrestrial ecosystem (such as the water films surrounding soil particles.

In some cases, there have been remarkable radiations of invertebrates. This is best illustrated by some of the snails on islands in the Pacific. Unfortunately, the enormous diversity that resulted has proven extremely vulnerable to introduced predators, especially some predatory snails. As a result, there have been a significant number of extinctions amongst these island snail faunas.

Topic Self-review (For self learning)

To review what you have learned in the topic, you are encouraged to use the following reflection questions as a study guide to do a self-review for the topic:

• What ecological roles do the Spiralia, Gnathifera and Nematoida play in tropical forests?
• In which microhabitats would you encounter each of these groups in tropical forests?
• How do the various Phyla within these three groups differ in their lifestyles?
• What are the most important differences between free-living and parasitic nematodes?
• What are the relative advantages and disadvantages of ecto- and endoparasitic lifestyles?