Morphometrics and reproduction of Terebrasabella heterouncinata (Polychaeta : sabellidae), infesting abalone (Haliotis midae) from different culture environments
A change in abalone diet from kelp to Abfeed resulted in smaller adult sabellids (p?0.001), larvae (p?0.001) and eggs (p?0.0001), compared to sabellids from abalone that experienced a diet change from Abfeed to kelp. Abalone diet history and growth rate did not influence the occupation level of tubes (p>0.05) or the sabellid intensity (i.e. number of tubes per centimeter of the shell edge) (p>0.05). Sabellids from slower growing abalone were larger in various body measurements and other characteristics; (length (p<0.0001); base width (p<0.0001); stage 2 larvae length (p<0.001); egg volume (p<0.001); number of stage 1 and stage 2 larvae per adult (p?0.0004); and number of eggs per brood (p?0.0001). The combined effect of slow abalone growth and the feeding of Abfeed resulted in increased number and size of the sabellids, indicating a confounding effect of these two conditions.
This study suggests that sabellids are essentially K- selected, exhibiting variation in reproductive and morphometric characteristics under different conditions. The number of larvae per adult (CV= 113- 79%), number of eggs per brood (CV= 86- 58%), sabellid intensity (CV= 79- 39%) and number of larvae per egg (CV= 126- 84%) were the lifehistory-related variables that exhibited the greatest variation for all studies. The smallest variation in sabellid characteristics included the larval length (CV= 11- 17%), base width (CV= 12- 31%) and occupation level (CV= 19- 27%). Thus, in all studies the numbers of individuals of the life-cycle stages were more variable than the sizes. The greatest variation occurred between the farms with the least variation occurring between abalone of different growth rate. Larval settlement was greatest on the thinnest and fastest growing region of the shell edge. Larvae settled most successfully at high tides. This study suggests that sabellid larval settlement is principally determined by abalone shell region, then by a change in diet, and least by abalone growth.
School Location:South Africa
Source Type:Master's Thesis
Keywords:ichthyology fisheries science
Date of Publication:01/01/2004