Invertebrates cnidarians

Pascoe D., W. Kamtanut, and C.T. Muller (2003). Do pharmaceuticals affect freshwater invertebrates A study with the cnidarian Hydra vulgaris. Chemosphere 51 521-528. 

It is currently unclear whether toxin-mediated prey capture by mobile invertebrates has a significant impact on prey population size or community composition. In freshwater systems, chemically mediated prey capture by flatworms has been demonstrated to significantly impact prey populations in the laboratory. Neurotoxic chemicals released from the mucus webs of the flatworm Mesostoma can drive entire populations of the cladoceran Daphnia magna to extinction in culture, but the concentration these chemicals normally attain under realistic field conditions is unknown. Nevertheless, because the mucus webs these flatworms build function to trap prey, Dumont and Carels163 likened these flatworms to spiders with toxic webs. Similar impacts may occur in open water marine systems where organisms that employ toxin-mediated prey capture are abundant, or even dominant, predators (e.g., chaetognaths and cnidarians). 

Leitz, T., Induction of settlement and metamorphosis of Cnidarian larvae signals and signal transduction, Invertebrate Reprod. Dev., 109, 1997. 

The populations of invertebrates found in intertidal waters are diverse and include hundreds of species. Invertebrates, animals that lack backbones, are generally small and occur in a wide variety of body designs. Some of the less complex invertebrates include sponges, cnidarians, and worms. 

Mollusks, crustaceans, and echinoderms are large groups of invertebrates that demonstrate many evolutionary advances over the systems of such simple invertebrates as sponges, cnidarians, and worms. Complex respiratory, digestive, circulatory, excretory, and reproductive systems cater to the needs of all cells within these large organisms. In many, the soft body parts are protected with shells or skeletal tissue. 

Chapters 3 and 4 investigate representatives of the invertebrate groups in the intertidal zone, the small animals. These organisms include sponges, cnidarians, worms, mollusks, crustaceans, and echinoderms. In the coastal food chain, these invertebrates feed on plants and animals and serve as food for larger organisms. Most are protected by structures such as shells or spines or by toxic chemicals. 

FIGURE 23.1 Organisms discussed in this chapter and their positions on the phylogenetic Tree of Life. Mammals are marked by a bar labeled M. Animals are divided into Vertebrates and Invertebrates, and also divided into five physiological groups, D = Deuterostomes, L = lx)photrochozoans, E = Ecdysozoans, C = Cnidarians, and P = Poriferans. The three domains (supraphyla) are Eukaryotes, Archaens (A), and Bacteria (B). 

Numerous allomones and kairomones imderlie very important phenomena, especially defense systems for algae, invertebrates that are fixed (sponges, cnidarians, bryozoans and ascidians) or have very limited mobility (some molluscs and worms), food stimulants, the prevention of epibiosis (biofouling), and problems related to the recognition of usefiil non-self organisms in the case of symbiosis. The potential applications are enormous. 

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