The importance of parental nutritional status on planktotrophic larvae was investigated in both laboratory-conditioned and field (populations) parents of two New Zealand echinoderms: the sea urchin Pseudechinus huttoni and the starfish Sclerasterias mollis.
Three questions were addressed: (i) Does parental nutritional status affect the reproductive features (gonad index, gametogenesis, fecundity and biochemical composition) both in the laboratory and under natural conditions? (ii) Does parental nutritional status affect egg characteristics (diameter, number, dry weight, fertilization rate and biochemical composition)? (iii) Are the characteristics of larvae (growth, development, morphology, mortality rate and body composition) influenced by parental or larval nutrition (or both)?
To answer the first question, adult P. huttoni and S. mollis were maintained in the laboratory with a low or high diet (in terms of quantity and quality for P. huttoni, and in terms of quantity for S. mollis) for one year. The effect of low and high diets on reproductive features was studied and the same parameters were studied in two parental populations with dissimilar food availability (for P. huttoni: Otago Shelf and Doubtful Sound populations; for S. mollis: Otago inshore and offshore populations). To address the second question, egg characteristics of the laboratory-held and field parents were measured. The third question was answered by rearing larvae of the laboratory and field parents with both low and high concentration planktonic diets.
P. huttoni reared in the laboratory with a higher food ration had greater gonad indices and lipid concentration and larger oocyte area. Sea urchins from the Doubtful Sound population had higher food availability, greater gonad lipid concentration and larger oocytes.
Parental nutrition had some effect on the characteristics of the egg in P. huttoni. The laboratory-held urchins fed a high diet produced larger eggs: P. huttoni from Doubtful Sound produced larger eggs with a greater carbohydrate concentration.
P. huttoni larvae from low-fed laboratory and Otago Shelf parents had faster development The effect of larval nutrition was more important than parental food availability on larval growth and development. Feeding parents in the laboratory had no effect on larval morphology but larvae from Doubtful Sound, which had better food availability, had longer arms relative to body width. A higher cell concentration in the planktonic diet led to shorter larval arm relative to body width.
In S. mollis reared in the laboratory, a higher food ration led to larger gonad and pyloric caeca indices. The starfish from an Otago inshore population mainly had a higher gonad index than those from an Otago offshore population.
In the laboratory-held parents S. mollis, nutrition had no effect on the egg characteristics. In the field, starfish with higher food availability produced smaller eggs with lower carbohydrate concentration.
There was no significant difference between development rates of S. mollis larvae from low and high fed laboratory parents. However, those from the Otago inshore parents, with better food availability, had faster development than the larvae from Otago offshore parents.
In S. mollis larvae, the origin of the parents (either from the laboratory or the field) had no effect on larval shape. A higher concentration planktonic diet led to longer larvae relative to body width in larvae from high-fed laboratory parents.
In both P. huttoni and S. mollis, parental and larval diet had no effect on rate of instantaneous larval mortality.
In both P. huttoni and S. mollis larvae, biochemical composition of the larvae and the egg were different to each other. Egg reserves appear not to be a factor which affects larval characteristics in these species.
| Identifer | oai:union.ndltd.org:ADTP/202525 |
| Date | January 2008 |
| Creators | Poorbagher, Hadi, n/a |
| Publisher | University of Otago. Department of Marine Science |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Hadi Poorbagher |
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