Bugula neritina is a sessile marine bryozoan with a pelagic larval stage. Larvae frequently settle on boat hulls, facilitating the introduction of B. neritina to bays and estuaries worldwide. Adrenergic agonists, such as the vertebrate hormone noradrenaline, inhibit larval settlement in a variety of marine invertebrate species, including B. neritina. Light also inhibits B. neritina larval settlement, yet the underlying mechanisms by which light and adrenergic compounds exert their effects on larvae are not well understood. Octopamine is considered the invertebrate analog of noradrenaline, and may be an endogenous hormone involved in larval settlement pathways. I observed the effects of the adrenergic agonist noradrenaline and the adrenergic antagonist phentolamine on larval settlement, and found that high concentrations of noradrenaline increased larval mortality, inhibited larval attachment, and increased larval swimming behavior. High concentrations of phentolamine also increased larval mortality, but increased larval attachment and decreased larval swimming behavior. I used fluorescent labeling and microscopy to localize sensory system components, and found that larvae possess adrenergic-like receptors, as well as tyrosine hydroxylase-like and octopamine-like immunoreactivity. I also exposed larvae to phentolamine in both dark and light conditions, and found that light significantly inhibited larval attachment, but phentolamine blocked those inhibitory effects. These results suggest that B. neritina larvae possess adrenergic-like receptors, which serve as the binding sites for noradrenaline and phentolamine. These are likely octopamine receptors, and octopamine may be one endogenous compound involved in controlling larval phototaxis and settlement behavior. Light may increase octopamine production, thereby stimulating cilial activity, extending swimming behavior, and preventing larvae from attaching to a substrate. This research sheds light on previously unknown sensory mechanisms in B. neritina larvae, and may aid in the development of new biofouling control strategies.

This thesis aims to increase our understanding of mechanisms that influence larval dispersal in marine benthic invertebrates, particularly in the absence of strong oceanographic features (e.g. estuarine plumes, upwelling events, or markedly different water masses). Laboratory experiments identified behavioural mechanisms that regulate the vertical distribution of larvae in response to thermal stratification, and field studies in St. George’s Bay, Nova Scotia (NS), Canada, examined the relationship between larval abundance and physical variables (temperature, salinity, fluorescence, etc) and identified mechanisms that regulate larval distributions in situ. In the laboratory, I demonstrated that thermal stratification affects the vertical distribution of larvae by acting as a barrier to migration, or through temperature-dependent vertical swimming velocities. I also developed a random walk based model which highlighted that the key to successfully simulating larval response to temperature was 1) determining the temperature-dependent distribution of vertical swimming velocities and 2) the temporal autocorrelation in these velocities. In the field, the most striking pattern was that the larval distributions for species with similar swimming abilities were significantly correlated to one another at all scales (0.5 to 40 km). This suggests a common mechanism, related to larval swimming ability, which greatly influences the horizontal larval distribution. I found that the spatial scale of variability in larval distributions (~ 3 km) matches that in both the environmental variables and of coherent structures in current velocities (i.e. the tidal excursion). Results from an aggregation-diffusion model suggest that horizontal larval swimming could not be responsible for the observed level of aggregation in the larval horizontal distributions. I suggest that these horizontal patterns are the result of 1) an aggregative process (i.e. larvae swimming against a vertical current and maintaining their vertical position) and 2) a diffusive process which scales the aggregations to the scale of the coherent structures in current velocity (i.e. tidal excursion). In conclusion, this thesis increases our understanding of larval behaviour and its effects on larval dispersal. The results will be particularly useful to those who are interested in mechanisms regulate population connectivity, particularly those using bio-physical models to model dispersal trajectories.

<p>The phylum Priapulida is a small group of marine worms that is allied with the nematodes, kinorhynchs, loriciferans and nematomorphs in a clade called the Cycloneuralia or Introverta. Together with the arthropods they are generally considered to comprise the Ecdysozoa, a clade of moulting animals. A number of recent priapulid species possess features that resemble the predicted Ecdysozoan ancestor. In addition, recent molecular studies have also shown that they are basal within the Ecdysozoa/Cycloneuralia (Garey 2001, Webster et al. 2006). Their putative basal position thus makes priapulids highly interesting research objects for understanding the evolution of Ecdysozoa. </p><p>Earlier investigations of the early embryology of the priapulid <i>Priapulus caudatus</i> are critically revised with the aid of modern techniques and equipment, confirming earlier studies that the early cleavages are highly symmetrical, total, subequal, radial and stereotypical. New results show that up to the sixth cleavage, the spindles are oriented along the animal/vegetal axis at both poles. This unique cleavage pattern has only limited similarities to other animals. During the sixth cleavage two cells move inwards and gastrulation commences. If the mesoderm is derived from both cells, its origin differs from that of many other protostomes.</p><p>Two previously undescribed larval stages of <i>P. caudatus</i>; the light bulb shaped hatchling and the first lorica larva are described. The second lorica larva superficially resembles the previously described type 2 lorica larva (Higgins et al 1993). Differences between the second lorica larva and the type 2 lorica larva, with respect to possible ecophenotypical variation and sub-specialization, are described. </p><p>Preliminary data are presented on musculature development of <i>P. caudatus</i>. Preliminary data have also been obtained on the early development of a second priapulid, <i>Halicryptus spinulosus</i>. Comparison of <i>Halicryptus</i> and <i>Priapulus</i> may help to resolve developmental ground pattern of the priapulids.</p>

The pre-metamorphic behaviors and settlement preferences of larvae can have significant effects on the success of adult invertebrates. This study describes various aspects of pre-metamorphic and post-metamorphic life stages of the bryozoan

The Dungeness crab fishery is the most economically important on the West Coast; however, it has experienced dramatic fluctuations in annual catch. Previous research has shown the annual catch of megalopae is correlated with the commercial catch. The catch of megalopae is correlated with the phase of the Pacific Decadal Oscillation (PDO), the day of the year of the spring transition and the amount of upwelling following the spring transition. Further, the daily catch of megalopae is correlated with the internal tide. We developed individual based models of Dungeness crab dispersal, which we validated with results from a light trap. We demonstrated that the retention of larvae in the California Current is enhanced during negative phase PDOs. Further, we suggest that larvae migrate to or almost to the bottom each day. Specifically, megalopae exhibit a twilight vertical migration off of the continental shelf and remain in the neuston on the continental shelf. This concentrates megalopae at the continental shelf break. We also observed megalopae in situ and demonstrated that they swim in the neuston with the surface current at speeds of ~ 10 cm s-1. Using these results and data from a mooring, we demonstrated that this behavior would increase the distance internal waves would transport larvae. We analyzed mooring data and suggest that catch of megalopae is greater when the thermocline is deep and weak and there is less horizontal shear. We hypothesize this allows internal waves to remain coherent longer on the continental shelf. We show that the spring transition coincides with a shallowing of the thermocline, which would ultimately lead to the development of internal waves of depression rather than elevation. We hypothesize that the change in surface flow, based on whether the wave is one of elevation or depression, explains why most megalopae are caught following the spring transition. In general, these findings help us better understand the dispersal of Dungeness crabs. We suggest the dispersal patterns support Michael Sinclair’s member vagrant hypothesis. Further, we suggest these findings apply to many of the continental shelf species in the California Current. This dissertation includes both published and unpublished co-authored materials.

Ocean acidification (OA) refers to the increase in acidity (decrease in pH) of the ocean’s surface waters resulting from oceanic uptake of atmospheric carbon dioxide (CO2). Mounting experimental evidence suggests that OA threatens numerous marine organisms, including reef-building corals; however, few studies have focused on the effects on early life history stages. Coral recruitment is critical to the persistence and resilience of coral reefs and is regulated by several early life processes, including: larval availability (gamete production, fertilization, etc.), larval settlement, post-settlement growth, and survival. Environmental factors that disrupt these early life processes can result in compromised or failed recruitment and profoundly affect future population dynamics. To evaluate the effects of OA on the sexual recruitment of corals, sexual reproduction (including fertilization and sperm swimming speeds) and several critical early life history stages (including larval metabolism, larval settlement, and post-settlement growth) were tested in common Caribbean coral species. Three pCO2 levels were used: ambient seawater (380 µatm) and two pCO2 scenarios that are projected to occur by the middle (560 µatm) and end (800 µatm) of the century as determined by the Intergovermental Panel on Climate Change. Results show that fertilization success, larval metabolic rates, larval settlement rates, and post-settlement growth rates are all compromised with increasing pCO2. This dissertation demonstrates that OA has the potential to negatively impact sexual reproduction and multiple early life history processes of several common Caribbean coral species and may contribute to substantial declines in sexual recruitment that are felt at the community and/or ecosystem scale.

The phylum Priapulida is a small group of marine worms that is allied with the nematodes, kinorhynchs, loriciferans and nematomorphs in a clade called the Cycloneuralia or Introverta. Together with the arthropods they are generally considered to comprise the Ecdysozoa, a clade of moulting animals. A number of recent priapulid species possess features that resemble the predicted Ecdysozoan ancestor. In addition, recent molecular studies have also shown that they are basal within the Ecdysozoa/Cycloneuralia (Garey 2001, Webster et al. 2006). Their putative basal position thus makes priapulids highly interesting research objects for understanding the evolution of Ecdysozoa. Earlier investigations of the early embryology of the priapulid Priapulus caudatus are critically revised with the aid of modern techniques and equipment, confirming earlier studies that the early cleavages are highly symmetrical, total, subequal, radial and stereotypical. New results show that up to the sixth cleavage, the spindles are oriented along the animal/vegetal axis at both poles. This unique cleavage pattern has only limited similarities to other animals. During the sixth cleavage two cells move inwards and gastrulation commences. If the mesoderm is derived from both cells, its origin differs from that of many other protostomes. Two previously undescribed larval stages of P. caudatus; the light bulb shaped hatchling and the first lorica larva are described. The second lorica larva superficially resembles the previously described type 2 lorica larva (Higgins et al 1993). Differences between the second lorica larva and the type 2 lorica larva, with respect to possible ecophenotypical variation and sub-specialization, are described. Preliminary data are presented on musculature development of P. caudatus. Preliminary data have also been obtained on the early development of a second priapulid, Halicryptus spinulosus. Comparison of Halicryptus and Priapulus may help to resolve developmental ground pattern of the priapulids.

The subfamily Cyclidiinae is a small macroheteroceran group, which is endemic to the Oriental region and comprising 13 species in 2 genera, e.g. Cyclidia Guen&#x00E9;e, 1857 and Mimozethes Warren, 1901. The larvae of the subfamily are specialists on Alangium (Cornaceae) and exhibit conspicuous colouration and gregariousness that may possibly function as aposematism. Historically this subfamily was inconsistently treated as either a separate family from Drepanidae, or lumped as a subordination of Drepanidae. Although both the two recent molecular phylogenetic hypotheses support the monophyly of Drepanidae, the morphological characters supporting the monophyletic status of Cyclidiinae and Drepanidae, however, have never been examined using modern methods. In the present study I investigated the phylogenetic relationships of Cyclidiinae based on morphological characters obtained from all the described species (13 species, including 4 subspecies) and the representatives of Drepaninae, Thyatirinae and Hypsidia. Cimeliidae and Doidae were chosen to be the outgroup taxa. In total 72 adult characters (32 binary, 40 multistate) were obtained and analyzed using Maximum Parsimony based on two character inclusion schemes (including or excluding wing pattern characters). The results showed the monophyletic status of the two Cyclidiinae genera, each subfamily of Drepanidae and the entire Drepanidae were recovered no matter which character inclusion scheme was adopted. The sistergroup of Cyclidiinae is confirmed to be ((Thyatirinae + Hypsidia) + Drepaninae). Although including wing pattern characters in the analysis does not significantly increase phylogenetic resolution within the Cyclidiinae, this scheme has great influence on the internal relationship of the subfamily. Meanwhile the present study reveals that most synapomorphies of Cyclidiinae proposed by previous studies are in fact plesiomorphic.

Cochliomyia macellaria (Fabricius) has great importance in forensics and is commonly utilized in estimating the period of insect activity (PIA) on a corpse due to its rapid colonization time of fresh remains, active oviposition during daylight, and its abundance throughout the southern United States. The purpose of this study is to determine what effects tissue and temperature will have on C. macellaria. The purpose of my secondary studies on attraction to larval resource is to gain insight into the behavior of adult blow flies in order to determine what factors drive colonization of remains. Forensic entomology can use development data of calliphorid flies to estimate their PIA on human remains. C. macellaria has major implications in medico-legal entomology as well as in veterinary entomology and are often found on human remains in Texas during the warm months of the year. Furthermore, C.macellaria is a secondary myiasis producer; this means that its larvae may be found infesting living animal or human muscle tissue and potentially could be involved in veterinary forensic cases. This study will help provide better insight on the behavior of C. macellaria in Texas as it relates to tissue type and temperature. In this experiment larvae were reared at three separate temperatures (21°C, 24°C, and 27°C) on either equine or porcine striated muscle tissues. Eggs were inoculated onto each tissue and monitored every hour for hatch. Once hatch occurred, observations were shifted to every twelve hours. Three larvae were sampled during each observation period. Sampled larvae were weighed and length was recorded. Additionally, stage of development was determined. Pupae were collected and time to adult emergence recorded. Furthermore, life-history traits, such as emergence pattern and adult longevity, were recorded. This study is the first in Texas and second in the United States to examine the development of C. macellaria and could provide significant information for cases of myiasis and neglect of both humans and animals. In contrast, rearing flies on beef liver or pork chops, which tends to be a standard procedure often employed may not be applicable to myiasis cases of equines. Data from this study could provide greater insight to developmental differences of forensically important blow flies on striated muscle from different vertebrate species. Since porcine tissue was used in the Florida study, it was also utilized in our study in order to allow a comparison. To date there is only one data set on the development of C. macellaria in the United States. Fly populations in different climates are suspected to have different development rates. This study will compare data from central Texas to data generated in Florida. If variation of development rates is demonstrated for different populations, then forensic entomologists should use data that are more conducive to their given geographic area. My secondary objective first looked at whether larval resource had an attraction effect on the subsequent adult C. macellaria flies. One cohort of larvae was reared on bovine testicles, while another was reared on bovine liver. The subsequent adults were then tested in a dual-choice olfactometer which possessed testicles at one end and liver at the other end. The second set of experiments also involved using a dual-choice olfactometer; however, all larvae were reared on bovine liver and fresh liver was placed at one end of the olfactometer, while fresh liver with conspecific larvae was placed at the end of the other. The purpose of this experiment was to assess whether adult C. macellaria flies were more attracted to the presence of conspecific larvae. These experiments will give us more insignt into adult blow fly behavior and help us to understand what factors drive colonization of remains.

Flow disruption resulting from interactions between currents and abrupt topography can have important consequences for biological processes in the ocean. A highresolution three-dimensional hydrodynamic model is used to study topographically influenced flow at the Flower Garden Banks, two small but thriving coral reef ecosystems in the northwest Gulf of Mexico. Flow past the modeled banks is characterized by vortex shedding, turbulent wake formation and strong return velocities in the near-wake regions. The speed of the oncoming current, strength of water-column stratification, and level of topographic detail used in the model each serve to modulate these basic flow characteristics. Larval retention and dispersal processes at the Flower Garden Banks, and specifically the dependence of these processes on the nature of flow disruption, are explored by coupling a Lagrangian particle-tracking algorithm to the hydrodynamic model. Passive particles released from the tops of the modeled banks as mimics of coral larvae can remain trapped in the wake regions very close to the banks on time scales of hours to days, depending primarily on the speed of the free-stream current. Most particles are swept quickly downstream, however, where their trajectories are most strongly influenced by the topography of the continental shelf. Modeled dispersal patterns suggest that there is an ample supply of larvae from the Flower Garden Banks to nearby oil and gas platforms, which can provide suitable benthic habitat for corals. The flow disturbances generated by the modeled banks result in the mixing of nutrients from deeper water into shallower, nutrient-depleted layers in the wakes of the banks. The ability of the planktonic system to respond to such an injection of nutrients is tested by embedding a simple nutrient-phytoplankton-zooplankton ecosystem model into the hydrodynamic model. Plankton biomass in the flow-disturbed wakes is shown to increase in response to the additional nutrients. This study shows how flow-topography interactions at the Flower Garden Banks can exert critical control over local larval transport processes and plankton dynamics. More generally, it demonstrates the usefulness and feasibility of using numerical models as tools to uncover important mechanisms of physical-biological interaction in the ocean.