The larval fish assemblage in the shallow, nearshore region of a proposed marine protected area (MPA) in eastern Algoa Bay, temperate South Africa was investigated. Current velocities and direction and the swimming abilities of late-stage larvae were further assessed to determine potential larval movement to and from the MPA. In total, 6045 larval fishes were collected along two depth contours (~5m and ~15m) in the shallow nearshore of eastern Algoa Bay using stepped-oblique bongo net tows, twice per season for two years (March 2005 – January 2007). These larvae represented 32 families and 78 species. The Gobiidae, Cynoglossidae, Clupeidae, Engraulidae and Sparidae were the dominant fish families. Catches varied significantly between seasons peaking in spring with a mean of 64 larvae/100m3. Preflexion stage larvae dominated catches (75%). All developmental stages of Diplodus capensis, Engraulis capensis, Heteromycteris capensis, Sardinops sagax and Pomadasys species were found in the study area. It appears that these species use the shallow nearshore as a nursery area. Analysis of 12 months (May 2006 – May 2007) data from a bottom-moored Acoustic Doppler Current Profiler within the study area showed that offshore south eastward (39%) and onshore north westward currents (33%) dominated. The south westward current (15%) and north eastward current (12%) occurred less frequently. Current velocity decreased with depth in the nearshore, with a mean velocity of ~29 cms⁻¹ recorded at a depth of 4 m and a mean velocity of ~11 cms⁻¹ recorded at a depth of 14 m. Understanding the dispersal and movement of marine fish larvae in coastal habitats requires knowledge of active swimming abilities. The critical speed and endurance swimming of late stage larvae of two common inshore species occurring in the study area, Diplodus capensis and Sarpa salpa (Family Sparidae), were measured in a laboratory swimming chamber. The mean U-crit value for D. capensis (18.6 cms⁻¹) was similar to that of S. salpa (18.0 cms⁻¹), whereas mean endurance (km swum) was greater in S. salpa (8.4 km) than D. capensis (5.9 km). These swimming abilities exceed the average current velocities observed in the shallow nearshore providing larvae with the ability to greatly alter their passive dispersal trajectories and ultimately influence their distribution in the nearshore.

This study determined the effect of hypoxia on air-breathing onset and physiological and morphological characters in larvae of the air breathing fishes Trichopodus trichopterus and Betta splendens. Larvae were exposed intermittently (12/12 h daily) to 20, 17, and 14 kPa of PO2 from 1 to 40 days post-fertilization. Survival, onset of air breathing, wet body mass, O2, Pcrit were measured every 5 dpf. Hypoxia advanced by 4 days, and delayed by 9 days, the onset of air breathing in Betta and Trichopodus, respectively. Hypoxia increased larval body length, wet mass, and labyrinth organ respiratory surface of Betta, but did not affect these factors in Trichopodus. Hypoxic exposure increased O2 by 50-100% at each day throughout larval development in Betta, but had no effect on larval Trichopodus. Hypoxia decreased Pcrit in Betta by 37%, but increased Pcrit in Trichopodus by 70%. Larval Betta reared in hypoxia showed a modified heart rate:opercular rate ratio (3:1 to 2:1), but these changes did not occur in Trichopodus. Compared to Betta, the blood of Trichopodus had a higher P50 and much smaller Bohr and Root effects. These interspecific differences are likely due to ecophysiological differences: Betta is a non- obligatory air-breather after 36 dpf with a slow lifestyle reflected in its low metabolism, while Trichopodus is an obligatory air-breather past 32 dpf with an athletic fast lifestyle and accompanying high metabolism.

Survival of teleost larvae requires growth and development which depend upon endocrine processes. In this dissertation I have examined the ontogeny of elements of the thyroid hormone (TH) and corticosteroid (CS) systems in red drum (Sciaenops ocellatus). Basal cortisol production was first detected 3 days post-hatch (DPH) and a cortisol stress response was present from 6 DPH forward. Changes in steroidogenic enzyme mRNA (CYP11B and CYP21) levels did not correlate with these events. The time necessary to reach peak cortisol levels as well as return to basal levels declined as larvae developed. A second set of studies examined ontogenetic patterns in levels of mRNAs encoding thyroid (soTR[alpha] and soTR[beta]) and corticosteroid (soGR) hormone receptors and assessed the regulation of these mRNAs by exogenous triiodothyronine (T3) and cortisol. soTR[alpha], soTR[beta] and soGR were expressed in all stages of red drum examined. soTR[alpha] levels increased during the time when surging TH levels have been reported. soTR[beta] levels did not differ significantly during development. soGR levels were strongly correlated with those of soTR[alpha]. T3 up-regulated soTR[alpha] and soTR[beta] levels in 7 DPH, but not older larvae. Cross-regulation of receptor mRNAs by exogenous treatment with T3 or cortisol was not observed. Finally, I assessed the influence of a common herbicide, atrazine, on receptor mRNA, TH levels and growth of red drum. In two experiments, red drum exposed to environmentally relevant levels of atrazine did not alter hormone receptor mRNA levels, or TH content. However, atrazine did depress growth in some instances. In conclusion, the expression patterns of hormone receptor mRNA in embryos suggests receptor proteins could be activated by maternal hormones prior to the onset of endogenous hormone production. A correlation between soTR[alpha] and soGR mRNA levels suggests coordinated function of TH and CS systems, although regulatory interactions between these systems were not evident under the conditions in this study. Patterns in soTR[alpha] and soTR[beta] mRNA levels support an important role for TH in the larval to juvenile transformation of red drum larvae. The results also support growing evidence indicating atrazine exposure effects larval growth and may impact their survival in the wild. / text

While substantial progress has been made in replacing live prey with artificial diets in the feeding of marine fish larvae, it still remains impossible to successfully rear larvae on artificial diets without some period of co-feeding live prey or algae. This study investigated the presence and role of the gastrointestinal hormone cholecystokinin (CCK) in the red drum (Sciaenops ocellatus) to gain a better understanding of the factors limiting the utilization of artificial diets by red drum larvae. Work with other fish species has shown that CCK is the principal hormone which regulates the release of pancreatic enzymes into the gut lumen and emphasizes the potential importance of CCK in early red drum larvae. This work investigated the hypothesis that some signal present in the live prey or algae stimulates CCK and thereby initiates the digestive process in the larvae. First, the nucleotide and amino acid sequence of the putative red drum cholecystokinin precursor was determined and the development of CCK immunoreactive cells was examined. This work showed that red drum CCK is highly similar to CCK in other vertebrates and can be detected in the digestive tract of larval red drum within three days after the initiation of exogenous feeding. Next; postprandial trypsin, CCK, and CCK mRNA responses were quantified in red drum juveniles and larvae over a three hour period. Both CCK and trypsin were increased within thirty minutes following feeding while CCK mRNA levels were increased within the next two to three hours. Finally, the trypsin, CCK, and CCK mRNA responses of red drum larvae to homogenates of live prey and algae were examined. Homogenized rotifers appeared to be sufficient to induce both the CCK and trypsin responses in larval red drum. These results suggest that in addition to other factors, some component of live prey may initiate the release of CCK and prime the digestive process. Understanding these factors and their effects in early larvae may allow us to formulate and produce a prepared diet which will support growth and survival to metamorphosis equal to that provided by live feeds. / text

Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / The goals of this thesis were to quantify the behavior of gastropod larvae (mud snails Ilyanassa obsoleta) in turbulence, and to investigate how that behavior affects larval supply in a turbulent coastal inlet. Gastropod larvae retract their velums and sink rapidly in strong turbulence. Turbulence-induced sinking would be an adaptive behavior if it resulted in increased larval supply and enhanced settlement in suitable coastal habitats. In laboratory experiments, mud snail larvae were found to have three behavioral modes: swimming, hovering, and sinking. The proportion of sinking larvae increased exponentially with the turbulence dissipation rate over a range comparable to turbulence in a tidal inlet, and the mean larval vertical velocity shifted from upward to downward in turbulence resembling energetic nearshore areas. The larval response to turbulence was incorporated in a vertical advection-diffusion model to characterize the effects of this behavior on larval supply and settlement in a tidal channel. Compared to passive larvae, larvae that sink in turbulence have higher near-bed concentrations throughout flood and ebb tides. / (cont.) This high larval supply enables behaving larvae to settle more successfully than passive larvae in strong currents characteristic of turbulent tidal inlets. A study was conducted at Barnstable Harbor, MA to estimate the responses of larvae to turbulence in the field. Gastropod larvae from different coastal environments had genus-specific responses to turbulence, suggesting that larvae use turbulence for large-scale habitat selection. On ebb tides, mud snail larvae had a similar response to turbulence as in the laboratory, with greater sinking velocities in strong turbulence. Behavior estimates differed for flood and ebb tides, indicating that additional physical cues influence behavior. Turbulence-induced sinking behavior would enhance retention and promote settlement of mud snail larvae in habitats like Barnstable Harbor. / by Heidi L. Fuchs. / Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005. / Includes bibliographical references. / The geographic distribution and dynamics of coastal benthic populations are shaped by physical - biological interactions affecting larval dispersal and the demography of juvenile and adult individuals. This thesis focused on nearshore patterns of larval distribution and regional patterns in demography of intertidal barnacles in Southern and Baja California. Horizontal and vertical distributions, and the mortality rates of larvae, were assessed from short term (i.e. days) small- scale observations (0.1-1 km) in nearshore waters. Observations on spatial variability of adult barnacle demography were gathered over 1.5 years at scales of hundreds of kilometers. Stage-specific horizontal distributions and nearshore current measurements suggested that larvae of Balanus g-landula and Chthamalus spp. may experience limited dispersal. High mortality rates could further limit travel distances and the exchange of individuals among disjunct populations. Data on vertical distributions indicated that nauplii and cyprids of Balanus nubilus and Pollicipes polymerus occur at different depths. Nauplii remained near the surface at all times, whereas cyprids occurred in the bottom half of the water column. / (cont.) Such distributions, combined with vertical variability in horizontal flows, might cause the observed horizontal segregation of nauplii and cyprids. Differences in survival, growth rate, size structure, and per capita fertility of adult Balanus glandula were observed between Dana Point (Southern California) and Punta Baja (Baja California), a site located near the species' southern limit of distribution. Effects of spatial differences in demography on population persistence were assessed with a stage-structured matrix model. Model analyses indicated that the Punta Baja population is more susceptible to environmental stochasticity and more prone to local extinction than populations located further north. This thesis emphasizes the importance of characterizing factors that affect the dynamics of benthic populations at multiple spatial-temporal scales, and the usefulness of small scale high- frequency observations of nearshore phenomena, especially in relation with the dispersal of larvae. / by Fabián J. Tapia. / Ph.D.

The 1883 discovery, research into generic life histories and taxonomic investigations into the aphytophagous butterfly Thestor brachycerus brachycerus (the Knysna Skolly) from Knysna, South Africa are described. Its slide towards extinction through loss and degradation of habitat in the late 20th century left only one known colony by 2009 leading to it being assessed as Critically Endangered in the 2013 South African Red List and Atlas. During searches for more populations in 2011, a second T. b. brachycerus colony was found which differed markedly with respect to aspect, altitude and vegetation. Study areas were defined around the original colony on the Pezula Golf Estate (Pezula) and the newly discovered coastal colony east of Coney Glen (Coastal site). An assessment is made of the ecological differences and similarities between the two sites. The extent and size of the two known populations was measured; the Extent of Occupancy was found to be 7.5 km2 and the Area of Occupancy as 1.05 x 10-3 km2. During observations over 5 seasons in December and January 2009 – 2014 the average number of butterflies observed at the original Pezula colony varied from 1 – 8 males and 0 – 3 females per survey, compared with 1 – 6 males and 1 – 3 females observed over 3 seasons from 2011 to 2014 at the Coastal colony. The mating, territoriality, oviposition and predation avoidance behaviour of the adult T. b. brachycerus butterflies was studied by direct observation. Males were found to exhibit territorial behaviour, spending long periods of time perched in one spot, particularly in areas where the vegetation was open or low. Oviposition was rapid and no preference was shown by females for any particular plant. Between the two colonies, oviposition was observed on a total of 16 different plants. The vegetation composition at the two study sites was analysed using Braun–Blanquet methodology. Only one plant, Tarchonanthus littoralis, was found to be common to both. There appeared to be no correlation between floristic composition and the occurrence of T. b. brachycerus. All the Thestor species so far studied by other workers have been found to be myrmecophilous, having an association with the pugnacious ant Anoplolepis custodiens. Ant communities were sampled by employing pitfall traps and direct sampling by hand. At both the Pezula and Coastal sites A. custodiens was the most ubiquitous ant species. The insights gained have enabled implementation of a habitat management plan. Experimental management methods are recommended at the Pezula site which include small scale burning and selective cutting of vegetation. Search for more colonies is ongoing, using the improved ecological knowledge of the butterfly. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The 1883 discovery, research into generic life histories and taxonomic investigations into the aphytophagous butterfly Thestor brachycerus brachycerus (the Knysna Skolly) from Knysna, South Africa are described. Its slide towards extinction through loss and degradation of habitat in the late 20th century left only one known colony by 2009 leading to it being assessed as Critically Endangered in the 2013 South African Red List and Atlas. During searches for more populations in 2011, a second T. b. brachycerus colony was found which differed markedly with respect to aspect, altitude and vegetation. Study areas were defined around the original colony on the Pezula Golf Estate (Pezula) and the newly discovered coastal colony east of Coney Glen (Coastal site). An assessment is made of the ecological differences and similarities between the two sites. The extent and size of the two known populations was measured; the Extent of Occupancy was found to be 7.5 km2 and the Area of Occupancy as 1.05 x 10-3 km2. During observations over 5 seasons in December and January 2009 – 2014 the average number of butterflies observed at the original Pezula colony varied from 1 – 8 males and 0 – 3 females per survey, compared with 1 – 6 males and 1 – 3 females observed over 3 seasons from 2011 to 2014 at the Coastal colony. The mating, territoriality, oviposition and predation avoidance behaviour of the adult T. b. brachycerus butterflies was studied by direct observation. Males were found to exhibit territorial behaviour, spending long periods of time perched in one spot, particularly in areas where the vegetation was open or low. Oviposition was rapid and no preference was shown by females for any particular plant. Between the two colonies, oviposition was observed on a total of 16 different plants. The vegetation composition at the two study sites was analysed using Braun–Blanquet methodology. Only one plant, Tarchonanthus littoralis, was found to be common to both. There appeared to be no correlation between floristic composition and the occurrence of T. b. brachycerus. All the Thestor species so far studied by other workers have been found to be myrmecophilous, having an association with the pugnacious ant Anoplolepis custodiens. Ant communities were sampled by employing pitfall traps and direct sampling by hand. At both the Pezula and Coastal sites A. custodiens was the most ubiquitous ant species. The insights gained have enabled implementation of a habitat management plan. Experimental management methods are recommended at the Pezula site which include small scale burning and selective cutting of vegetation. Search for more colonies is ongoing, using the improved ecological knowledge of the butterfly. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The causes of Amyotrophic Lateral Sclerosis (ALS), a fatal neurodegenerative disease that results in skeletal muscle paralysis, remain unclear. However, a nuclear DNA and RNA binding protein called TAR DNA binding protein 43 (TDP-43) has emerged as a critical marker of ALS pathology. A previous drug screen conducted in the Zarnescu laboratory showed that anti-diabetic drugs can rescue lethality in a fruit fly model of ALS based on TDP-43. These results suggested that the insulin signaling pathway might be altered in motor neurons in a TDP-43 dependent manner. Therefore, we hypothesized that the insulin pathway is interacting with TDP-43 in vivo and may be contributing to TDP-43neurotoxicity. Using genetic interaction approaches in flies we found that TDP-43dependent locomotor defects are sensitive to the levels of insulin receptor activity. In addition, genetic interaction data suggest that Akt is hyperactivated in motor neurons expressing TDP-43, possibly as a compensatory mechanism to enable survival. Finally, upregulating protein synthesis through S6K and 4EBP appears to have beneficial effects. These findings support our hypothesis and provide insights into potential therapeutic strategies to help treat this devastating disease.

Larval development and reproduction of 19 species of Central Amazonian fish (five cichlids, two siluriforms, one osteoglossiform and 11 characiforms) were studied over two years. Most species spawn during the flooding season. The cichlids, the siluriforms and two species of characiform are nest spawners, reproducing in the littoral areas of the floodplain. The osteoglossiform is a mouth-brooder. The remaining characiforms spawn in the river channels and show no parental care. Two main strategies explain 90% of the variability of reproductive traits found among the 19 species. The first strategy is used by riverine spawners (characiforms). They have high fecundity , high to very high reproductive expenditure (calories per spawn per wet weight of female) and spawn once a year during a short season. Their eggs vary in size from 0.06 to 0.3 mg and have intermediate to high calorific value. The second strategy is used by the cichlids and two species of characiforms. They have low fecundity, low reproductive expenditure, long spawning season, multiple spawnings per season and some of them show parental care. Their eggs vary in size from 0.4 to 1.2 mg and have an intermediate calorific content. The other three species show distinct combinations of reproductive traits, but have as common feature a high reproductive expenditure, a short annual spawning season and parental care. Patterns of larval development are correlated with egg size and adult spawning sites. Egg size explained most of variability of larval body size at hatching, pectoral fin bud, eye pigmentation, jaw formation, swim bladder inflation, onset of swimming, first feeding and maximum size attained with exclusively endogenous feeding. The pattern of blood circulation of the larvae was correlated with the spawning sites. Larvae of riverine spawners are small, utilize yolk efficiently and are relatively resistant to starvation. Newly hatched larvae of riverine spawners seem to be very sensitive to physico-chemical conditions of the floodplain lakes, but by the first feeding stage they develop some resistance to the low availability of oxygen. Larvae of littoral spawners are large, utilize yolk less efficiently, and seem to be resistant to low concentrations of oxygen. The resistance of larvae to oxygen deficiency is correlated with the development of the larval respiratory system. It is suggested that egg size of riverine spawners was selected to optimize the distance of the dispersal of the larvae in a range of floodplain lakes. Conversely, egg size of floodplain spawners seemed to be selected to optimize larval survival in the spawning lake. The results are further discussed in relation to life history models.