Annotated bibliography

Hesslring, Rene, Westheide, Wilfried. 2002. Are echiura derived from a segmented ancestor? Immunohistochemical analysis of the nervous system in developmental stages of Bonellia viridi. 252:100-113

• Echiura have many homologous characteristics with the Annelids, although they lack any segmentations. The author sets out to discover, are Echiura derived from asegmented ancestor?
• There are many debates as to how Echiura were derived as well as what their phylogenetic position is. There are two different hypotheses considered for this phylum: The Echiura are considered a different taxon from Annelida, or the Echiura are a subtaxon of the Annelida.
• Immunohistochemical analysis shows serially segments units in the nervous system of the species Bonellia viridis. Using confocal laser-scanning mircoscopy, many similarities were noticed between Echiurans and Annelids: a spcialized supraesophageal ganglion was not clearly distinguishable from very similar circumsophageal connectives in Echiurans. In both phylums the ventral nerve cord develops as two separated trunks and then develop into one.
• Using only the homology of segmentation would not justify classifying the Echiurans as a subtaxon of annelida, however the others mentioned adds support. The results indicate that there is support for including Echiura in Annelida

Saiz-Salinas, Jose I., Dean, Harlan, K. Cutler, Edward, B. 2000. Echiura from the antarctic and adjacent waters. Polar Biology. 23:661-670.

• There has been approximately 555 Echiura discovered in the Antarctic seas, with 9 species found. Zoogeographical analysis shows differential distribution along horizontal gradients and depth being important, but is this true?
  
• Over 25 years of research has been done in collecting the Echiura, however some species have onylbeen classified by their proboscis, for example and many important characters have been ignored. So re-examination is in order to discover whether the above question is true.
• Samples came from different depths as well as latitudes, using trawls, dredges and grabs, and dissecting microscopes and techniques for analysis. Eight species were examined. Some of the characters looked at were rings of anal setae, gonopores, gonoducts, ventral setae, and anal vesicles. It was noted that many species had not been properly classified.
• The results showed that differential distribution along longitudinal and latitudinal gradients were not shown,, but depth remained an important factor.

Guidici, M de Nicola. 1984. Defence Mechanisms of Bonellia viridis. 78:271-273

• May marine species have microorganisms and benthic animals living on their body, do the Echiuran, bonellia viridis have such organisms as well?
• Many sutdies have shown that these worms do not have such life forms, however they live in an environment filled with these types of organisms.
• 14 Echiurans were collected throughout different months of the year. No life forms were found on any of the samples. This suggests that the pigment bonellin present in the worm may be a chemical defence system. This chemical is known to stop embryonic development in echinoderms, however it makes the worm very sensitive to light.
  
• bonellin is, quite reasonably the cause of the lack of any microorganisms on Bonellia viridis.