Academic literature on the topic 'Acetes sibogae'

Combining the use of scanning electron microscopy and microcinematography with functional and behavioural observations has clarified many aspects underlying the feeding processes of the small planktonic sergestid shrimp Acetes sibogae australis. In captivity Acetes sibogae australis is an opportunistic feeder that uses four principal feeding modes to capture a wide size range of prey: Artemia nauplii (<0.33 mm), copepods (<1mm) and moribund Acetes (up to 25 mm). Prey capture is effected by combined actions of the first three pairs of pereiopods and the third maxillipeds before transfer to the more dorsal second maxillipeds. The second maxillipeds are the principal appendages used in securing, manipulating, sorting and rejecting prey before insertion into the vicinity of the inner mouthparts.

Epibiosis was studied in dominant mangrove crustacean species in several areas in Malaysia. The observed basibionts were the crustaceans Mesopodopsis orientalis, Acetes japonicus, Acetes sibogae, Acetes indicus and Fenneropenaeus merguiensis and the epibionts found were the protozoan ciliates Acineta branchicola, Lagenophrys eupagurus, Conidophrys pitelkae and Zoothamnium duplicatum. Basibionts from the open sea area (Acetes japonicas) and from a sandy beach of Penang (Mesopodopsis orientalis) showed the lowest epibiont densities. Considering all the colonized anatomical units each basibiont species had a distinct epibiotic distribution and the epibiont species presented a significantly different distribution over each of the basibiont species. In the basibiont M. orientalis a significant difference was observed in epibiotic distribution between populations from different geographical areas. Species sampled on mangrove and offshore areas also differed in this respect The different epibiont species varied among locations according to the structure of the community. We also report on the pattern of epiobiont distribution over the anterioposterior axis of the basibiont, on the influence of physiological characteristics of basibiont and epibiont and on the influence of environmental conditions on the epibiont communities.

Acetes sibogae australis, a small swarming crustacean, is an important component of near-shore systems in eastern Australia. It is considered that densities of A. s. australis are highly variable. However, this variability has never been tested on a fine temporal scale. In this study, densities of A. s. australiswithin swarms, as well as swarm length and width, were recorded once a week for seven months at one locality in Townsville, Australia, and once a fortnight for seven months at two other localities in the region. Length frequency of a sub-sample of individuals caught at each sample time was also recorded. Density of A. s. australis fluctuated significantly during the seven months, with numbers per replicate varying between 0 and 1000 individuals. Swarm width and length were significantly correlated with density, contributing to large-scale differences in overall abundance. Length frequencies revealed at least three dominant cohorts present during the seven months, although appearance and disappearance of these did not correspond to density changes. Patterns recorded were similar at the three spatially separate localities. The large fluctuations in A. s. australis abundance over time are likely to have important effects on the near-shore system of Townsville.

Environmental factors influencing growth during the first stages of an animal's life cycle are determinative. External factors have often been implicated in the determination of rates of development of teleost larvae; however, the first stages of development of cephalopods remain poorly studied. In view of the fact that previous studies had shown that temperature is an important factor affecting cephalopod growth, particularly at high food concentrations, in this study the effect of temperature under conditions of non-satiation were investigated. A food-stress experiment was carried out for 75 days on 80 juvenile cuttlefish (Sepia elliptica) reared under two temperatures (25 and 30°C) and two food rations of glass shrimps Acetes sibogae australis at high and low proportions (2:1, respectively). We examined the effect of temperature and feeding regime on the growth of the whole animal, cuttlebone, and muscle tissue. Mantle-muscle blocks were 15% larger at 30°C than at 25°C, with the greatest difference in the middle mantle region (21% more at 30°C), whereas cuttlebone and somatic growth varied when the combination that included either the higher temperature or the higher food ration was used. Thus, at 30°C under the low feeding regime, final dorsal mantle length (DML) and cuttlebone growth index (CGI) were higher; however, at 25°C, final DML, CGI, and survivorship increased under the higher feeding regime. It was concluded that food scarcity may exaggerate the effect of small temperature differences. The results are discussed in the light of previous findings on the growth of other cuttlefish species, cephalopods, and teleosts.

The structure and optics of the compound eyes of the neritic sergestid shrimp, Acetes sibogae , are described. The eyes are nearly spherical and heavily pigmented. The facets are square, indicating that the eye operates by the recently recognized mechanism of reflecting superposition. The most distal portion of each ommatidium is the corneal lens, which is secreted by two underlying corneagenous cells. These two cells surround the crystalline cone and cone stalk and the four cells of which they are composed and extend proximally at least as far as the distal rhabdom. Near the base of the cone stalk the extensions of the corneagenous cells swell and enclose spheres which bear on their surfaces small particles similar to ribosomes in appearance. Beneath the corneagenous cells lie four crystalline cone cells, parts of which differentiate to form the crystalline cone and cone stalk. The latter structures are compound, one quarter of each being contributed by each crystalline cone cell. Distally the crystalline cone cells send a small projection, which is surrounded by the corneagenous cells, to the cornea. Proximal extensions of each of the four parts of the cone stalk extend between the retinula cells and meet within the basement membrane. Between the base of the cone stalk and the regularly layered rhabdom lies the distal rhabdom. It is surrounded by a cell that we have termed retinula cell eight (R8), by analogy with other crustacean systems, and consists of unordered microvilli projecting from the cell membrane into the extracellular space above the layered rhabdom. In addition to R 8, which contributes only to the distal rhabdom, seven other retinula cells contribute to the proximal rhabdom, which consists of alternating ordered layers of orthogonally arranged microvilli. Four of these retinula cells are arranged orthogonally and extend far distally along the crystalline tract. The other three do not extend as far distally and alternate with the first four in their position around the axis of the ommatidium. R8 is located still further proximally at the level of the distal rhabdom. All seven of the retinula cells which contribute to the proximal rhabdom contain proximal pigment and extend through the basement membrane. The basement membrane consists of a meshwork grid with each intersection supporting a rhabdom so at this point the retinula cell axons project into different squares of the meshwork. Tapetal pigment cells are present in the vicinity of the basement membrane and extend downward to the lamina. The granules of tapetal pigment are covered or exposed by movements of the proximal pigment and also change their intracellular distribution depending on illumination. In addition to the proximal (retinula cell) pigment and the tapetal pigment the eye contains four types of distal pigment. Moving inward from the cornea these are the distal yellow pigment (DYP) which surrounds the entire eye; the distal reflecting pigment (DRP), which forms a thin layer and is continuous with the tapetal pigment at the edge of the eye; and the black distal pigment and the mirror pigment (MP) both contained within distal pigment cells (DPC). In the light-adapted state the proximal pigment moves distally, surrounding the rhabdoms, and the tapetal pigment granules move proximally so that they are mainly found beneath the basement membrane. Movements of the distal pigments are less clearcut, but they all appear to move somewhat proximally in the light-adapted state. Multivesicular bodies are more abundant in the retinula cells shortly after dawn, and are possibly related to membrane turnover. Interommatidial angle, as measured on both fixed and fresh material, varied from 2.8 to 3.8° in different parts of the eye. The crystalline cones were found to have a uniform refractive index radially, which, combined with their square shape, indicates that they function by reflecting superposition. Total internal reflection from the sides of the cones is adequate to explain the maximum diameter of the eyeshine from the dark-adapted eye at night without the need for additional mirrors. Nevertheless, from its organization and appearance the mirror pigment could act as a reflector in the dark-adapted eye. Also, the size of the glow patch indicates that there would be a gain of nearly two log units in image brightness in going from the light-adapted to the dark-adapted state. Each corneal facet was found to act as a weak converging lens, with a focal length of approximately 300 μm. The eye structure of Acetes is discussed in relation to that of other shrimp and to the natural history of Acetes .

The assemblage composition, biomass and dynamics of zooplankton and epibenthos were examined in a commercial prawn pond in southeast Queensland over two seasons. Physico-chemical characteristics of the pond water were measured concurrently. Numbers and biomass of zooplankton in the surface tows (140 micrometre mesh) varied from 8 ind. L-1 (44 micrograms L-1) to 112 ind. L-1 (324 micrograms L-1) in the first season, with peaks in biomass corresponding to peaks in numbers. In the second season the zooplankton numbers varied from 12 to 590 ind. L-1, but peaks in numbers did not correspond with peaks in biomass, which varied from 28 to 465 micrograms L-1. This was due to differences in the size of the dominant taxa across the season. Although this occurred in both seasons, the effect on biomass was more pronounced in the second season. In both seasons, immediately after the ponds were stocked with prawn postlarvae there was a rapid decline in zooplankton numbers, particularly of the dominant larger copepods. This was probably due to predation by the postlarvae. Subsequent peaks in zooplankton numbers were principally due to barnacle nauplii. The largest peaks in zooplankton numbers occurred before stocking in the first season, but the largest peaks were in the middle of the second season. While changes in abundance and biomass of the zooplankton assemblage were not correlated with physico-chemical characteristics in the first season, there were correlations between zooplankton numbers and temperature, dissolved oxygen, pH and secchi disk readings in the second season. No correlations were found with zooplankton biomass and physico-chemical characteristics in the second season. The correlations in the second season were mainly due to the high prevalence of barnacle nauplii through the middle part of the season, and may reflect suitable conditions for barnacle reproduction. Epibenthic faunal abundance in the beam trawls (1 mm mesh) peaked at 14 ind. m-2 and 7 ind. m-2 in the first and second seasons respectively and the biomasses at 0.8 g m-2 and 0.7 g m-2. Peaks in abundance of epibenthos did not correspond to peaks in biomass. This was due to large differences in the size of the taxa across the seasons. Sergestids (Acetes sibogae) and amphipods were the most abundant taxa in beam trawl samples. Amphipods were only abundant in the first season, with their numbers increasing towards the end of the grow out period. Acetes were abundant in both seasons, but were dominant in the second season. Correlations between physico-chemical parameters and epibenthos numbers were found to be strongly influenced by the dominant taxa in each season. In the first season, negative correlations were found between epibenthos abundance and pH and temperature. These relationships may reflect an effect on the growth of macroalgae in the pond, with which the amphipods were strongly associated, rather than a direct effect on the epibenthos. In the second season, a positive correlation existed between temperature and epibenthos abundance, however this was strongly influenced by the very high abundance of Acetes in the last sampling period. No correlations were found between epibenthic fauna biomass and physico-chemical parameters. Abundances of epibenthic fauna were not related to zooplankton densities indicating this source of food was not likely to be a limiting factor. Neither the pond water exchange regime nor moon phase could explain changes observed in abundances of zooplankton or epibenthos assemblages in the first season, however the sampling regime was not designed to specifically investigate these effects. In the second season water exchanges were sampled more rigorously. The density of zooplankton in the outlet water was from 2 to 59% of the density of zooplankton in the pond, and the zooplankton density of the inlet water was from 9 to 50% of the outlet water. The number of zooplankton recruited into the pond from the inlet water, after the prawns were stocked, was negligible and contributed little to changes observed in zooplankton assemblages. Reproduction of barnacles within the pond appeared to play the most important role in changes in the assemblage. Water exchange did, however, appear to play a greater role in the changes observed in epibenthic fauna assemblages. In the last season of sampling the feeding of the dominant epibenthic species, Acetes sibogae, was examined using a combination of gut content and stable isotope analysis. Acetes gained little nutrition directly from the pelleted feed, probably relying primarily on zooplankton as their direct food source. Other dietary items such as macroalgae also played a role in the nutrition of the Acetes. If Acetes numbers were high at the beginning of a season they may compete with the newly stocked prawns for the zooplankton resource. However, they will not compete with the prawns later in the season when the prawns are gaining most of their nutrition from the pelleted feed. Overall it appears that zooplankton are important to the nutrition of the prawns at the beginning of the season when the assemblage is usually dominated by copepods. Later in the season the assemblage is dominated by barnacle nauplii which are recruited from within the pond. The establishment of an abundant assemblage of suitable zooplankton species before stocking prawn postlarvae would appear to be beneficial, if not essential. The assemblage of epibenthic fauna changes throughout the season as new recruits are brought in from outside the pond. Epibenthic faunal assemblages in ponds from southeast Queensland are dominated by Acetes which are not likely to adversely affect the production of prawns unless they are particularly abundant early in the grow out season when the prawns would be utilising the same food resources as Acetes.

The assemblage composition, biomass and dynamics of zooplankton and epibenthos were examined in a commercial prawn pond in southeast Queensland over two seasons. Physico-chemical characteristics of the pond water were measured concurrently. Numbers and biomass of zooplankton in the surface tows (140 micrometre mesh) varied from 8 ind. L-1 (44 micrograms L-1) to 112 ind. L-1 (324 micrograms L-1) in the first season, with peaks in biomass corresponding to peaks in numbers. In the second season the zooplankton numbers varied from 12 to 590 ind. L-1, but peaks in numbers did not correspond with peaks in biomass, which varied from 28 to 465 micrograms L-1. This was due to differences in the size of the dominant taxa across the season. Although this occurred in both seasons, the effect on biomass was more pronounced in the second season. In both seasons, immediately after the ponds were stocked with prawn postlarvae there was a rapid decline in zooplankton numbers, particularly of the dominant larger copepods. This was probably due to predation by the postlarvae. Subsequent peaks in zooplankton numbers were principally due to barnacle nauplii. The largest peaks in zooplankton numbers occurred before stocking in the first season, but the largest peaks were in the middle of the second season. While changes in abundance and biomass of the zooplankton assemblage were not correlated with physico-chemical characteristics in the first season, there were correlations between zooplankton numbers and temperature, dissolved oxygen, pH and secchi disk readings in the second season. No correlations were found with zooplankton biomass and physico-chemical characteristics in the second season. The correlations in the second season were mainly due to the high prevalence of barnacle nauplii through the middle part of the season, and may reflect suitable conditions for barnacle reproduction. Epibenthic faunal abundance in the beam trawls (1 mm mesh) peaked at 14 ind. m-2 and 7 ind. m-2 in the first and second seasons respectively and the biomasses at 0.8 g m-2 and 0.7 g m-2. Peaks in abundance of epibenthos did not correspond to peaks in biomass. This was due to large differences in the size of the taxa across the seasons. Sergestids (Acetes sibogae) and amphipods were the most abundant taxa in beam trawl samples. Amphipods were only abundant in the first season, with their numbers increasing towards the end of the grow out period. Acetes were abundant in both seasons, but were dominant in the second season. Correlations between physico-chemical parameters and epibenthos numbers were found to be strongly influenced by the dominant taxa in each season. In the first season, negative correlations were found between epibenthos abundance and pH and temperature. These relationships may reflect an effect on the growth of macroalgae in the pond, with which the amphipods were strongly associated, rather than a direct effect on the epibenthos. In the second season, a positive correlation existed between temperature and epibenthos abundance, however this was strongly influenced by the very high abundance of Acetes in the last sampling period. No correlations were found between epibenthic fauna biomass and physico-chemical parameters. Abundances of epibenthic fauna were not related to zooplankton densities indicating this source of food was not likely to be a limiting factor. Neither the pond water exchange regime nor moon phase could explain changes observed in abundances of zooplankton or epibenthos assemblages in the first season, however the sampling regime was not designed to specifically investigate these effects. In the second season water exchanges were sampled more rigorously. The density of zooplankton in the outlet water was from 2 to 59% of the density of zooplankton in the pond, and the zooplankton density of the inlet water was from 9 to 50% of the outlet water. The number of zooplankton recruited into the pond from the inlet water, after the prawns were stocked, was negligible and contributed little to changes observed in zooplankton assemblages. Reproduction of barnacles within the pond appeared to play the most important role in changes in the assemblage. Water exchange did, however, appear to play a greater role in the changes observed in epibenthic fauna assemblages. In the last season of sampling the feeding of the dominant epibenthic species, Acetes sibogae, was examined using a combination of gut content and stable isotope analysis. Acetes gained little nutrition directly from the pelleted feed, probably relying primarily on zooplankton as their direct food source. Other dietary items such as macroalgae also played a role in the nutrition of the Acetes. If Acetes numbers were high at the beginning of a season they may compete with the newly stocked prawns for the zooplankton resource. However, they will not compete with the prawns later in the season when the prawns are gaining most of their nutrition from the pelleted feed. Overall it appears that zooplankton are important to the nutrition of the prawns at the beginning of the season when the assemblage is usually dominated by copepods. Later in the season the assemblage is dominated by barnacle nauplii which are recruited from within the pond. The establishment of an abundant assemblage of suitable zooplankton species before stocking prawn postlarvae would appear to be beneficial, if not essential. The assemblage of epibenthic fauna changes throughout the season as new recruits are brought in from outside the pond. Epibenthic faunal assemblages in ponds from southeast Queensland are dominated by Acetes which are not likely to adversely affect the production of prawns unless they are particularly abundant early in the grow out season when the prawns would be utilising the same food resources as Acetes.
Thesis (Masters)
Master of Philosophy (MPhil)
School of Environmental and Applied Science
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