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Abstract

Despite their ecological importance, research on symbionts of amphipods has been limited in South America. The present study provides a comprehensive overview of symbiont organisms in the freshwater amphipods of the genus Hyalella in South America. Our findings reveal various taxa such as Apicomplexa, Microspora, Peritrichia, Folliculinidae, trematodes, nematodes, cestodes and acanthocephalans, often involving complex life cycles. Studies on symbionts have been done almost exclusively in Argentinean Patagonia. The present overview allows us to know the species that use amphipods, to elucidate their lifecycles and to know their occurrence values.

In: Crustaceana
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In: Crustaceana

Abstract

The aim of this work was to characterize the growth and reproduction dynamics of shrimp in the Lac Nokoué-Chenal de Cotonou complex. The results of one year’s sampling from five stations (North, South, East, Central and West) of the lagoon complex revealed that linear growth in size in Lake Nokoué is decreasing over time in Macrobrachium macrobrachion (the most representative species of the genus Macrobrachium), but positive in Penaeus notialis (the most representative species of the genus Penaeus). Size-weight relationships indicate that the lowest growth coefficient ( b = 1.56 ) is obtained in immature males of Macrobrachium felicinum, while the highest growth coefficient ( b = 3.39 ) is obtained in mature females of Macrobrachium vollenhovenii, with an average of 2.84 for all shrimp species over both sexes considered. The χ 2 test indicated that only the species Macrobrachium vollenhovenii has a significant sexual imbalance in favour of females in Lake Nokoué. Fisher’s Least Significant Difference test indicated that the estimated first sexual maturity sizes in Macrobrachium vollenhovenii and M. macrobrachion are significantly different from those estimated in M. felicinum at the α = 0.05 threshold. However, the same test indicates that there is not enough evidence to differentiate the sizes of first sexual maturation in M. vollenhovenii and M. macrobrachion. This work revealed that Penaeus monodon was the only species to show better positive growth within all its groups in Lake Nokoué while exposed to anthropogenic effects. A gradual average increase in the size of Penaeus notialis in Lake Nokoué is found between the beginning and end of the saline intrusion (which confirms the life cycle of the species presented). Species of the genus Macrobrachium showed good reproductive capacity, with the absence of sexually mature Penaeus in this lagoon.

In: Crustaceana
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Abstract

Reductions in the size of mature blue crabs, Callinectes sapidus, which are commercially harvested, are of concern to the aquaculture industry. Through their role in the production of viable offspring, aquaculturists focus their attention in particular on female crabs, although the phenomenon will, of course, also affect the males. Meanwhile, decreases in size at maturity throughout the crab population may be the result of temperature alterations, at present also due to global climate change. Temperature-based shifts in growth can lead to changes in reproductive efficiency, as well as in size and age at maturity. In this study, the effects of temperature on the moulting frequency of blue crabs were investigated and survival rates have been calculated. The purpose of this study was to investigate the temperature dependence of survival and of the moulting processes for blue crab larvae, and to determine the effect of increasing temperature on moulting. The stages from zoea-1 to zoea-5 were examined at 16, 22, 26 and 30°C. The results show that there is a significant difference in growth and moulting, depending on the rearing temperature. As the temperature increases, the interval between moulting days can be seen to be shortened, and increasingly so with the progress in the growth of the crabs. Moulting-interval days became less with the growth of the crabs. The effect of a rise in temperature on growth per moult is also significant, and along the temperature range tested the optimum temperature was found to be 26°C. A reduction in the length of the intermoult period was observed from the lowest to the optimum temperature, while a sudden, sharp increase in the intermoult period above 26°C was observed as well.

In: Crustaceana

Abstract

In a closed, or zero water exchange, greenhouse aquaculture system, this study examined the interaction between the aggregation flocs in the mono- and co-cultivation of Pasific white shrimp, Litopenaeus vannamei (300 individuals/m3) with macroalgae, Ulva lactuca f. fasciata at different densities of Ulva (1, 2 and 3 g/l). The investigation was conducted under zero water exchange conditions. The accumulated flocs were compared between the various treatment groups: without Ulva (Treatment Control Group), Ulva at 1 g/l density (T1: Treatment 1), Ulva at 2 g/l (T2: Treatment 2), and Ulva at 3 g/l (T3: Treatment 3). Ultimately, it was determined that Ulva cultivation using the Biofloc system actually helped to ensure the water quality in the zero water exchange culture system during the 35-day experimental period with reduced cyanophyte densities, that can cause toxic algal blooms in aquaculture systems. This was interpreted to result from the fact that Ulva is a naturally occurring bioremediation agent.

In: Crustaceana

Abstract

During a series of irregular visits to Inhaca Island, Mozambique in the years 1982-1987, J.H.C. Walenkamp, often aided by students and staff of the Faculty of Biology in Maputo, made extensive collections of littoral and infralittoral invertebrates. Among the extensive collections of Brachyura, several caridean shrimps were encountered, upon which we herein report. Cuapetes cf. ensifrons is recorded from Mozambique for the first time.

Open Access
In: Crustaceana

Abstract

The amphipods of the genus Hyalella have many endemic species throughout South America, and these may have poorly studied associated species as epibionts. The aim of the present study was to review the literature on the presence of the protozoon Lagenophrys lenticulata (Kellicott, 1885) on species of Hyalella and contrast the results with the geographical distribution of the reported hosts. The literature records the presence of L. lenticulata on populations of H. azteca from Canada, Mexico and the United States of America, and on populations of H. curvispina from Uruguay. The literature also reports that H. curvispina is widespread throughout southern South America, including Argentina and Chile, and that it would be possible to find the presence of epibionts on other populations of H. curvispina. The corresponding biogeographical and evolutionary topics are discussed.

In: Crustaceana
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Abstract

Biacanthus pleuronichthydis (Yamaguti, 1939) is redescribed based on specimens of the female, recovered from the body surface of the bastard halibut, Paralichthys olivaceus (Temminck & Schlegel, 1846) (Pleuronectiformes, Paralichthyidae), which is a new host for the species.

In: Crustaceana