Non-Arthropod Invertebrates

Non-Arthropod Invertebrates.— The Protozoa are able to synthesise terpenoids [e.g. (99)]. However, there is no evidence for squalene or steroid biosynthesis in Coelenterata, Echinodermata, Nematoda, or Platyhelminthes. In some cases they may once have been able to synthesise their own steroids, and not need a dietary source. Hymenolepis dimunuta is able to synthesise famesol from mevalonic acid. In the phylum Annelida the position is less clear. While some species can synthesise steroids others are only able to synthesise squalene.  

It is possible that this difference reflects a distinction between the two classes Polychaeta and Oligochaeta. Nematodes are able to metabolise steroids to give 

Salaque, M. Barbier, and E. Lederer, Comp. Biochem. Physiol., 1966, 19, 45. 

A -dienes from cholesterol or -sitosterol, and to reverse the alkylation of the side chain of the latter steroid (86 R = Et) (84)- (74).  

The Mollusca are an interesting phylum taxonomically. From the limited data available the classes Bivalva and Cephalopoda are not able to synthesise steroids or squalene. However, in the class Gastropoda only the order Stenoglossa cannot synthesise steroids. In the order Stylommatophora there is a limited ability, and steroid biosynthesis is present in Archaeogastropoda, Mesogastropoda, and Basommatophora.  

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Tebufenozide s high safety to certain non-arthropod invertebrates such as earthworms 4) and nematodes can be explained similarly. 

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