Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Bibliography: leaves 72-74.

This study investigates the factors affecting larval and postlarval survival and growth of some de capod crustaceans with special emphasis on diets. Investigations were concentrated on the influence o live and artificial diets on larval growth, survival, development and trypsM activity of a cominerciall, important marine penaeid shrimp Penaeus indicus and a freshwater prawn Macrobrachium rosenber gij. In addition, feeding behaviour, gastroevacuation time, trypsM activity of other decapod species wen also studied. Live mixed microalgae Tetraselmis chuii and Skeletonema costatum at 60-70 cells PI-1 promote( highest larval survival, fastest growth and development in P. indicus in comparison to single algal spe cies. Rhinomonas reticulata neither alone nor in combination with other algal species was suitable a! food for the shrimp larvae, A water salinity (S) of 25 ppt was optimal for larval and postlarval cultun of this penaeid species. Postlarvae (PL) of P. indicus reared at lower salinities between PL7 and PL& (20-30 ppt) had a significantly (P<0.05) higher survival and a better growth than those at higher wate salinities. Early PL resisted sudden salinity change of 10 ppt, but required an adaptation period fo greater salinity changes, 10 ppt S was lethal to animals at around PL40-45. A free-living nematode Panagrellus redivivus was found to be a suitable alternative for live algai and Artemia in the culture of P. indicus. The nematodes gave good survival, but lower growth than al gaelArtemia from PZI to PLI. Larval growth and survival were significantly improved when the larvai were fed on either nematodes plus algal co-feeds or liPid-enriched nematodes. Pigmented- (astaxanthin nematodes also improved survival and colour of P. indicus larvae in comparison to non-pigmented ones Conventional live diets were also completely replaced using microencapsulated diets (MED) fo the culture of P. indicus, Like the nematodes, MED as a sole feed resulted In lower survival, slowe growth and development in comparison to algaelArtemia. Addition of 15 cells gl-1 frozen algae signifi cantly improved growth and survival during larval development. The larvae fed MED plus algal co feeds had significantly (P<0.05) higher trypsm activity than those fed MED as a sole feed. Similarly provision of 15 cells gl-' algae with nematodes for only 24h or 48h resulted in significant increase H trypsin activity and improved survival and growth to levels comparable to those obtained from al gaelArtemia. It appears that the presence of an algal diet is necessary to induce larval trypsin activity Mi P. indicus at early protozoeal stages, but algae do not influence trypsin at mysts stages. Results sugges that both nematodes and formulated diets lack gut enzyme stimulants and are less digestible than al gaelArtemia diets. When freeze-dried algal materials were incorporated into MED, it was found tha algal substances which trigger larval digestive enzymes were retained within the capsules. Whether thi will improve growth and survival of penaeid larvae remains to be examined. In contrast to penaeid larvae, a complete replacement of live Artemia with nematodes or artificia diets was not possible for the culture of caridean M rosenbergii and PaIdemon elegans larvae. Fo both species, only a partial replacement was achieved from Z4/5 to metamorphosis by using formulateA diets. It was found that these larvae have very low trypsin activity levels between ZI and Z4/5, but th, levels increase sharply afterwards, coinciding with a vast increase in the hepatopancreas. This sharl increase in digestive enzyme activities and longer food retention time enable these larvae to survive oj less digestible formulated diets. A comparison of specific trypsin activity in several larval decapod crustaceans shows a pattein with high levels in herbivores, low levels in carnivores and intermediate levels M omnivores. Herbivor penaeid larvae (P. indicus) and copepods (Temora longicornis and Centropages typicus) rely on hig digestive enzyme activities to extract nutrients from less digestible algae, whereas carnivorous larvaE the lobsters (Homarus gammarus and Nephrops norvegicus) and carideans (M. rosenbergii and .1 elegans) have limited enzymatic capacity and hence require large and easily digestible prey, but rests long starvation periods. Omnivorous mysis penaeid larvae and Carcinus maenas have intermediat levels of digestive enzymes and are able to transfer from herbivorous to omnivorous feeding. To datE only decapod larvae which show high trypsm activity can be successfidly reared to metamorphosis o: formulated feeds. Inclusion of algal material, as a gut enzyme stimulant, for penaeid protozoeal stage and pre-digested ingredients for later stages into feeds are proposed.

Carapace length, as the best measure of N. marionis body size, is precisely defined. It is shown that N. marionis is a partially protandric hermaphrodite. N. marionis appear to hatch just before April each year, with a little hatching persisting until May. The vast majority of juveniles develop into males. The majority of males transmutate into females in their third year. By April/May the transmutation is probably complete. Reproduction can occur before all male secondary characteristics have been lost. A small minority of individuals develop directly into females without passing through a male phase. At least some of these females can be initially recognized after they have developed mature ovaries by the presence of appendices internae on their first pleopods, a male copulatory structure which all juvenile N. marionis possess. Too few gravid females were recovered to make any statement on whether spawning can occur before this structure is lost. Such females may lose their first pleopod appendices internae in one moult, possibly just before spawning, which may be in late April/early May. Such individuals seem to mature into ovigerous females at a slightly smaller carapace length than do the majority of females which have had a male-phase past. A few females which have passed through a male phase seem to begin developing ovaries at about this small carapace length as well. Once the appendices internae have been lost there appears to be no way of identifying any given female's past life-history. It would seem that during the first year of life N. marionis survive in undetected localities, moult into juveniles, and then settle amongst the benthos from the plankton. Diurnal vertical migration then occurs up to an unknown larger size. It is not known whether the larvae are initially planktonic or not. It is possible that settling of small N. marionis onto the benthos only begins after November. Whether the appendices masculinae of some males only begin growing after they have settled Abstract XIX onto the benthos is unknown, but for the majority at least this begins whilst they are planktonic juveniles. Individuals older than five years are undetectable using samples of the sizes analyzed in this thesis, but they may well persist until quite an advanced age. Niche separation between smaller and larger N. marionis individuals may occur. Diel vertical migration may occur to some extent amongst large N. marionis. Itinerant euphausiids may contribute substantially to the maintenance of top predator populations at the archipelago, either through direct predation by those predators or via predation by N. marionis, which in turn are consumed by those predators. N. marionis itself is an opportunistic feeder, although the majority of its prey seem to be suspension feeders, both benthic and pelagic. In multisample situations, ageing of N. marionis cohorts is made less subjective if one utilizes the phenomenon of synchronized sexual inversion. The von Bertalanffy growth parameters for N. marionis are tentatively identified as k = 0.2353/year, L_ = 12.69mm, to = -0.2828 years and WW_ = 2.03g. The programme FiSAT is discussed, having been found to be extremely useful, but having also been found to have certain faults. Various hypotheses are proposed and are put forward as suggestions for future studies.

No description available.

Demographic parameters and the general biology of the subantarctic shrimp Nauticaris marionis from the Prince Edward Islands were investigated. The carapace length is the most accurate indicator of body size and it was confirmed that N. marionis is a partially protandric hermaphrodite. Gravid females of N. marionis observed mainly in March with negligible hatching persisting until April/May. The majority of juveniles develop into males. Juveniles are characterised by an appendage on the endopodite of the first pleopod called the appendix interna or a.i.1. Juveniles that develop into males do so by growing a further appendage on the endopodite of the second pleopod. This appendage characterises males and is called the appendix masculina (or a.m.). Juveniles may develop directly into primary females through the development of an ovary and the loss of the a.i.1. The sequence differs among individuals, with some developing the ovary before losing the a.i.1 and others losing the a.i.1 first. Loss of the a.i.1 appears to be by shedding during a single moult, rather than by atrophy. Females can also develop by an alternative route as secondary females. Such animals first become males with an a.m. and then develop an ovary, thus forming an intermediate form called a tertium quid, or “third thing”. Again, there are two forms of tertium quid. Tertia quae a have the a.m. as well as the a.i.1. Tertia quae b have the a.m. in combination with an ovary but no a.i.1. Either form of tertium quid can develop into a secondary female through loss of the a.m., and in the case of the tertium quid a, loss of the a.i.1. It is unclear whether sexual differentiation occurs in the plankton or just after N. marionis settles on the benthos. The results of gut content analysis suggest that N. marionis is an opportunistic feeder, preying on a variety of prey with a preference for detritus, benthic amphipods and gastropods. Cannibalism of conspecific pleopods by large individuals of N. marionis occurred mostly in females, particularly in incubation containers. Cannibalism also occurs in males, and its occurrence depends on individual size, not gender. No diel patterns were observed in the feeding activity of N. marionis. In situ daily rations of males (carapace length <7mm) and females (>7mm) were equivalent to ≈10% and ≈5% of body dry weight, respectively. The von Bertalanffy growth curve parameters were empirically identified, by cohort analysis of data collected during 4 years, as K = 0.22239/year, L[subscript]∞ = 14.05789mm, t₀ = -0.05174, L₀ = 0.16083mm. N. marionis can survive up to seven years under natural conditions.

The recruitment of Palaemon pacificus to the Bushmans River estuary was studied over a 12 month period. The dynamics of a population of shrimps in a small, tidal channel in the lower reaches of the estuary was investigated over a similar time span. Temperature and salinity tolerances of various stages and sizes of shrimps were compared in controlled experiments and are discussed in the light of the distribution and general ecology of the shrimp. Stage 6 zoeae and post-larvae entered the estuary on nocturnal flood tides throughout the year with peak recruitment occurring in March/April. The population of shrimps in the study site was predominantly juvenile for most of the year, with peak sub-adult numbers occurring in midsummer. The sex ratio was female-biased throughout the year except for short bursts of male predominance in February and April. Average growth rate was 0,043 mm carapace length per day. Maximum residence time in the study site was estimated to be four months and in the estuary at least six months. Flooding of the estuary resulted in a considerable reduction in juvenile numbers in the study site and some loss of sub-adults. Shrimps tolerated a temperature range of 4,3 to 30,9⁰C for 144 hours. Their long term tolerance range is probably narrower (10 to 28⁰C) because of the effects of temperature related factors such as starvation and disease. Their distribution in South Africa (Olifants River to Kosi Bay ) is consistent with this tolerance range. Sub-adults tolerated salinities of 1 to 79 ‰ and post-larvae 2 to 60 ‰ at 15⁰C for 144 hours. Low moulting success (low and high salinities ) and starvation (high salinities) would probably reduce these tolerance ranges to 2 to 56 ‰ (sub-adults) and 4 to 56 ‰ (post-larvae). Higher and lower temperatures (10 and 20⁰C) reduced the tolerance of post-larvae to low salinities, but sub-adults were only affected at 30⁰C. Stages 4 and 5 and stage 6 zoeae were intolerant of salinities below 14 ‰. The development of salinity tolerance with age is consistent with the retention of a marine breeding phase. It also explains the high loss of juveniles from the study site following the flood. It is postulated that recovery of the population after a flood would be fairly rapid except in extreme cases when estuarine vegetation is severely affected.

No description available.

published_or_final_version / abstract / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (M.S.)--Mississippi State University. Department of Food Science, Nutrition and Health Promotion. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D.)--University of Western Australia, 2007.