Observations of the egg cases from the holopelagic polychaete family: Tomopteridae

Remotely operated vehicle dive video recordings of the pelagic polychaete egg cases, including Tomopteris (Polychaete: Tomopteridae) were examined to gain more information about their reproductive biology. A total of 141 egg cases were found year round with the majority between depths of 200m and 1,000m in the midwater. No direct correlations to temperature, salinity, or oxygen were made. The general color and shape of egg cases were transparent and round; however, 13 green egg cases, 4 chain egg cases, and 1 cone egg case were also recorded. Most egg cases consisted of eggs, but a few did have moving juvenile Tomopterids inside. The majority of the green egg cases were found in Astoria Canyon, Oregon. Amphipods were only seen on green egg cases and this may be related to similar symbiotic relationships found in the midwater. Not all egg cases may be Tomoterid; the chain egg cases could be from a deep sea nudibranch or a pteropod. The cone egg cases may be a result of parental activities or be from another phyla. Larval movement could be stimulated from temperature or the development of eyespots.

There is still debate whether Tomopterid fertilization is internal or external. Future research could include close examinations of various types of Tomopterid egg cases. Better data analyzing could compare changing deep sea currents and Tomopterid distribution patterns. Also comparisons of physical data between Astoria Canyon, Oregon and the Monterey Canyon should be further investigated to determine if there are possible advantages for pelagic polychaetes in either canyon. It is still undetermined if all types of egg cases are Tomopterid. Examining the structure of the egg case and its composition to understand why some may appear different. Closer examinations of the Tomopterid egg case could reveal other sources of food or explanations for amphipods. Also, laboratory experiments to see the chemical composition in green egg cases and any potential benefits among shape, size, or color of egg cases. Laboratory work can consist of sufficiently growing Tomopterid larvae and observing their stimulation for larval movement. Also, key areas of egg cases with larvae could be further investigated to provide more factors that would encourage embryo and larval growth. Successful gene sequencing could also help learn more about Tomopterids and their similarities to other closely related pelagic polychaetes. After observing several types of egg cases, there are many questions to be answered that will provide a better understanding of the reproductive biology of Tomopterids and other pelagic polychaetes.