Production and recruitment measurements in marine copepods of the genus Calanus have been addressed via the study of genes involved in early embryogenesis. The first sequence from a Calanus helgolandicus (C. helgolandicus) developmental gene (Cal-Antp) has been cloned by screening a C. helgolandicus genomic library with a homologous Calanus homeobox probe. Sequencing of an isolated and sub-cloned fragment of this gene, plus further analysis by Inverse Polymerase Chain Reaction (IVPCR), has shown it to be homologous with other Antennapedia homeobox genes. The temporal expression of Cal-Antp was analysed through its messenger RNA (mRNA) complement by Reverse Transcription Polymerase Chain Reaction (RT-PCR). The gene was expressed in tissue taken from eggs over 18 hours old, and in nauplii and copepodite stages, but no expression was detected in eggs less than 18 hours old or adult tissue. Three further homeobox-containing genes have been identified and analysed through their expression in C. helgolandicus eggs. Two of these are caudal homologues, and the third is homologous to the Antennapedia class of genes. The C. helgolandicus developmental gene sequence data provides a means of developing probes to monitor the temporal expression of such genes and their responses to environmental influence. The applicability of such probes to the investigation of key production and recruitment processes, including egg viability measurement, is discussed. A relatively simple and cost effective method has been developed to identify the four Calanus species common to the North Atlantic. This system involves the PCR amplification of a region of the mitochondrial rRNA gene without prior purification of the DNA, followed by Restriction Fragment Length Polymorphism (RFLP) analysis of the amplified product. The versatility of the method is demonstrated by the unambiguous identification to species of any life stage, from egg to adult, and of any individual body parts. The molecular identification technique has for the first time shown the unexpected presence of three different Calanus species in Lurefjorden, Norway and has proved to be consistently accurate for all individuals tested including geographically distinct conspecific populations.

No description available.

The purpose of this study is to quantify the effect of finescale turbulence on copepod behavior in order to shed light on the influence of turbulence on copepod distribution. Specifically, the study will examine the behavioral response of the marine copepod Acartia tonsa to a steady state Burgers' vortex intended to mimic the characteristics of a turbulent vortex (Jumars et al. [2009]) that a copepod is likely to encounter in the coastal zone. A laboratory apparatus was constructed to create a Burgers' vortex with size and strength consistent with turbulence vortices in the coastal zone (and relevant to the marine copepod species). The radius, circulation, and axial strain of the Burgers' vortex were specified to match typical dissipative vortices corresponding to two turbulence intensity levels. The levels are described by Webster et al. [2004] as Level 2 (ϵ = 0.009 cm²/s³) and Level 3 (ϵ = 0.096 cm²/s³), which span an apparent behavior transition in copepods [Yen et al., 2008]. Tomographic particle image velocimetry (Tomo - PIV) was performed to calibrate the device and verify that it produces the desired vortex characteristics, as well as to provide a three dimensional velocity vector field to compare with behavioral assays. The laboratory apparatus, dubbed the "Burgers' Vortex Apparatus", accurately reproduces the appropriate vortex characteristics of the Turbulence Level 2 and 3 vortex cartoons. Copepod behavioral assays were conducted with Acartia tonsa. When exposed to these vortices, Acartia tonsa did not exhibit a meaningful behavioral response to the Level 2 vortices, but drastically altered their swimming behavior in the presence of Level 3 vortices. In the presence of a Turbulence Level 3 vortex, Acartia tonsa increased relative swim speed, decreased turn frequency, increased the angle of alignment with the vortex axis, increased net-to-gross displacement ratio, and increased escape acceleration (relative to control). These alterations in swimming kinematics all served to move the animal away from the vortex core.

No description available.

Internal waves are ubiquitous features in coastal marine environments and have been observed to mediate vertical distributions of zooplankton in situ. Internal waves create fine-scale hydrodynamic cues that copepods and other zooplankton are known to sense, such as fluid density gradients and velocity gradients (quantified as shear deformation rate). The role of copepod behavior in response to cues associated with internal waves is largely unknown. The objective is to provide insight to the bio-physical interaction and the role of biological versus physical forcing in mediating organism distributions. We constructed a laboratory-scale internal wave apparatus to facilitate fine-scale observations of copepod behavior in flows that replicate in situ conditions of internal waves in a two-layer stratification. Three cases were chosen with density jump of 0.75, 1.0, and 1.5 sigma-t units. Analytical analysis of the two-layer system provided guidance to the target forcing frequency needed to generate a standing internal wave with a single dominate frequency of oscillation. Flow visualization and signal processing of the interface location were used to quantify the wave characteristics. The results show a close match to the target wave parameters. Marine copepod (mixed population of Acartia tonsa, Temora longicornis, and Eurytemora affinis) behavior assays were conducted for three different physical arrangements: (1) no density stratification, (2) stagnant two-layer density stratification, and (3) two-layer density stratification with internal wave motion. Digitized trajectories of copepod swimming behavior indicate that in the control (case 1) the animals showed no preferential motion in terms of direction. In the stagnant density jump treatment (case 2) copepods preferentially moved horizontally, parallel to the density interface. In the internal wave treatment (case 3) copepods demonstrated orbital trajectories near the density interface. Further analysis showed that the copepods swim closer to the interface in the presence of internal waves.

Calanus helgolandicus is a key copepod species occurring in the North East Atlantic that is responding to oceanic warming through an expansion of its geographic range. This range extension has led to concerns about how this may affect ecosystem trophodynamics. Here I investigate the interannual variability and seasonality of C. helgolandicus, using a ~28 year time-series from the western English Channel (station L4). I focus specifically on the role of mortality, as a key life history process that is challenging to quantify and historically has received little attention. C. helgolandicus abundance remained within a narrow ~four-fold interannual envelope, which was a consequence of multiple losses that removed ~99% of the potential population. Loss of early life stages occurred through the incidence of non-viable eggs and abnormal nauplii (both higher in spring), and via predation; egg mortality rates were positively correlated with C. helgolandicus copepodite abundance and total copepod biomass, indicative of intraguild predation and cannibalism. By contrast, late-stage copepodite mortality rates were highest in autumn, and were positively related to gelatinous predator abundance and biomass (medusae, ctenophores and chaetognaths). Molecular gut-content analyses revealed that two abundant jellyfish species present during 2015 (Pleurobrachia pileus and Leuckartiara octona) both preyed on C. helgolandicus. Adult male consumptive mortality rates were ~6 times higher than that of adult females; whereas male non-consumptive rates were only ~1.5 times that of females, providing evidence that predation was the primary mortality source in males. Non-consumptive mortality rates contributed 0-54% (median of 4.5%) to total mortality and were positively related to the 72-hour maximum wind speed, implying that turbulence created during extreme weather events may increase zooplankton mortality. I conclude that C. helgolandicus population control is modulated via a series of mortality-related losses occurring through the different development stages; from reduced egg viability to predation of copepodites by gelatinous carnivores. Although I find little evidence for changing ecosystem trophodynamics at L4, my results contribute to the knowledge of C. helgolandicus population dynamics at a site near the centre of its distribution, and suggest that a future expanding population may be a valuable food source for a variety of predators.

No description available.

In recent years there has been growing environmental concern regarding ‘microplastics’: microscopic plastic granules, fibres and fragments, categorised as <1 or <5 mm diameter. Microplastics are manufactured to be of a microscopic size, or derive from the photo- and mechanical degradation and subsequent fragmentation of larger plastic litter. Microplastics debris has been identified in the water column and sediments of marine and freshwater ecosystems across the globe, although difficulties in sampling and isolating smaller particulates has resulted in the abundance of <333 µm microplastics being under-reported. Microplastics are bioavailable to a range of aquatic organisms, including fish, seabirds and benthic invertebrates, and can be trophically transferred. The consumption of plastic debris can result in gut blockages, heightened immune response and a loss of lipid reserves. The potential risk to food security, and thereby human health, has led regulators to call for better understanding of the fate and effects of microplastic debris on marine life. Here I tested the hypothesis that microplastics can be ingested by and may negatively impact upon zooplankton. Zooplankton encompass a range of aquatic animals that form a key trophic link between primary producers and the rest of the marine food web. I used a suite of feeding experiments, bio-imaging techniques and ecotoxicological studies to explore the interactions and impacts of polystyrene microplastics on marine zooplankton. My results demonstrate that a range of filter-feeding zooplankton taxa, including copepods and bivalve and decapod larvae, have the capacity to ingest microplastics. Microplastics significantly reduced algal feeding in the copepods Centropages typicus and Calanus helgolandicus. With prolonged microplastic exposure C. helgolandicus produced smaller eggs with reduced hatching success, and had reduced survival owing to declining energetic reserves. Microplastics egested by copepods significantly altered the properties and sinking rates of faecal pellets, with potential repercussions for marine nutrient flux. This investigative work highlights that microplastics pose a significant risk to the health of animals at the base of the marine food web.

Considering South Africa’s richness in aquatic species, very little knowledge exists regarding copepods that are symbiotic on hosts ranging from invertebrates to marine mammals. In order to have any indication of the existing biodiversity of this group of organisms in South African waters, a thorough investigation of all possible hosts needs to be conducted, which in turn will most likely increase the number of recorded symbiotic copepods considerably. The current descriptive study was done in an effort to contribute to a larger study of metazoan parasites of elasmobranch hosts along the KwaZulu-Natal coast of South Africa. A total of 40 (31 Mobula kuhlii; two Mobula eregoodootenkee and seven Manta alfredi) mobulids were examined for infection by symbiotic copepods at the KwaZulu-Natal Sharks Board (KZNSB). More than 90% of all examined hosts were infected with different types of symbiotic siphonostomatoids. Collected copepod specimens were fixed and preserved in 70% ethanol and studied with both the stereo- and light microscopes using the wooden slide technique. Some selected specimens were further studied using Scanning Electron Microscopy (SEM) to elaborate on ill-defined features. A total of 13 different species of the order Siphonostomatoida distributed over five families were identified. The five families include Eudactylinidae (Eudactylina oliveri, Eudactylina diabolophila and Nemesis sp.); Caligidae (Caligus crysophrysi, Pupulina sp. 1, Pupulina sp. 2; Pupulina sp. 3, Unidentified sp. 1, Unidentified sp. 2 and Unidentified sp. 3); Kroyeriidae (Kroeyerina mobulae); Dichelesthiidae (Anthosoma crassum) and Cecropidae (Entepherus laminipes). Two of the 13 species (E. laminipes and A. crassum) are monotypic and were therefore easily identified. Eudactylina oliveri exhibited a prevalence of 75% and 100%; mean intensity of 42 and 130 parasites per host and a mean abundance of 32 and 130 individuals per host while Pupulina sp. 1 exhibited a prevalence of 61.29% and 100%; mean intensity of 41 and 5 individuals per host and a mean abundance of 2 and 5 individuals per host on M. kuhlii and M. eregoodootenkee respectively. Component populations of E. oliveri and Pupulina sp. 1 exhibited an aggregated distribution pattern on their examined hosts. The phylogenetic relationship between nine caligid species (three known Pupulina species, three collected Pupulina species and three Unidentified sp. species as ingroup) with Caligus glandifer as out-group was determined and analysed using a morphological dataset (40 characters) from previous and current descriptions. The ii exhaustive search with PAUP* retained a single most parsimonious tree with a tree length (TL) = 85; consistency index (CI) = 0.7; retention index (RI) = 0.7; homoplasy index (HI) = 0.3 and a rescaled consistency index (RCI) = 0.5. Bootstrap support for the estimated clades was mostly low with values less than 95%. The phylogenetic hypothesis of the 10 caligid species presented in the current study was derived from the phylogenetic analysis of the information for adult females and is therefore not intended to be a definitive theory but should be treated as a testable hypothesis that can be further analysed using more data. The current study provides the first record of C. chrysophrysi, Pupulina sp. 1, Pupulina sp. 2, K. mobulae and E. laminipes on M. kuhlii; E. oliveri, Pupulina sp. 1, Pupulina sp. 2 and Pupulina sp. 3 on M. eregoodootenkee; and E. diabolophila, Nemesis sp., C. chrysophrysi, E laminipes, A. crassum and the three Unidentified species on M. alfredi frequenting the east coast of South Africa and thus contributes to the knowledge of our marine biodiversity. Mobulid hosts were not carefully studied for copepod infection previously and the copepods that were reported from the mobulids were probably found by chance. Therefore future investigation into the symbiotic siphonostomatoids of more mobulid hosts and other host species may result in more reports of symbiotic Copepoda from South African waters. / Thesis (MSc. (Zoology)) -- University of Limpopo, 2013

Increasing temperatures are expected to cause secondary salinisation in freshwater systems, such as the zooplankton community of Churchill, Manitoba. Salinity is a key environmental factor structuring these communities, thus, increasing salinity should cause these communities to change; however, previous research has shown that they are resilient. In order to ascertain how changing salinity will affect these communities I conducted toxicity tests for five crustacean species, individually and in a community setting. I sampled several pools throughout the season to ascertain the salinity level at which those same species were most abundant in the field. While the species had significantly different field distributions along the salinity gradient, the salinity levels associated with maximum densities did not correlate with the lab tolerances. However, lab tolerances were outside the field salinity range, thus providing an unexpected result. Local interactions appear to be very important in determining final community composition along this salinity gradient. / Northern Scientific Training Program, Northern Research Fund