Observations on the life histories of the narcomedusae Aeginura grimaldii, Cunina peregrina and Solmissus incisa from the western North Atlantic
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In this paper, we present evidence of direct development life cycles and brooding behaviour in two narcomedusae species in the family Cuninidae, as well as a histological description of another narcomedusan species from the family Aeginidae. Cunina peregrina were found to be brooding juveniles within the subumbrella. Brood contents varied in size and developmental stage. In addition, pairs of small white spheres enclosed within a membrane, most likely an oocyte and phorocyte (nurse cell) were observed around the stomach wall. It is suggested that two life cycles are occurring simultaneously: (1) asexual budding of actinula larvae from the parent medusa which develop into fully developed medusa; and (2) sexual reproduction producing an egg and phorocyte pair which develops into an actinula and a four-tentacle reduced medusa. In Solmissus incisa opaque spheres of various sizes were attached to the external walls of the gastric pouches. The spheres appeared to start off as a developing oocyte attached firmly to the adult, before developing into a sessile planula larva. The planula had a thick ectoderm and endoderm and was attached to the adult gastric pouches at its oral surface. This attachment appeared to pinch into the adult stomach pouch forcing some stomach tissue into the oral opening of the developing planula, possibly suggesting some nutritional aid from the adult. It is not clear whether this is a parasitism on the adult to gain nutrition or parental brood care. Nine specimens of Aeginura grimaldii were collected. White growths located on the subumbrellar surface in between the gastric pouches were found to be male gonads containing sperm. The gonads had a granular texture consisting of a lightly speckled black pigmentation, which became denser in the red subumbrella tissue. Histology revealed this to be porphyrin bodies.
Medusa samples were collected during the following cruises: Cape Hatteras, September 1994: NOAA/NURP UNCW9406 awarded to Dr. Tom Bailey, NOAA/NURC UNCW9410 and NSF OCE9313872 awarded to Dr. Tammy Frank and Dr. Edith Widder; Gulf of Maine, June 1995: NOAA/NURC UCAP-95-020A and NSF OCE9313872 awarded to Dr. Tammy Frank and Dr. Edith Widder. CHL would like to thank the above PIs for their help and support during her Harbor Branch Oceanographic Institute Fellowship, and the crew of the RV ‘Edwin Link’ and ‘Johnson-Sea-Link II’ submersible for their assistance during field operations. The authors would also like to thank Prof. Paul Tyler, Dr. Sven Thatje and Dr. Mary Arai for helpful discussions and comments on earlier drafts of this manuscript.
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