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Session Schedule & Abstracts

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Friday 1st July, 2016

General Morphology 5: Climate Change, Environmental Drivers, & Morphological Change

Room: Salon B   2:30 pm–3:45 pm

Moderator(s): Bentley BP, Wyneken J
GEN5-1  2:30 pm  Predicting the effect of climate change on sea turtle embryos in North West Australia. Bentley BP*, The University of Western Australia; Mitchell NJ, The University of Western Australia; Whiting S, WA Department of Parks and Wildlife; Berry O, Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Abstract: Increasing ambient temperatures associated with anthropogenic climate change are anticipated to have wide-scale adverse effects on all ecosystems, ecological processes and taxa across the globe. Sea turtle populations are particularly vulnerable to these changes, with higher temperatures expected to lead to female-biased primary sex-ratios, increased embryonic mortality, and the production of smaller hatchlings. Six of the seven extant species of sea turtle are found in the waters off the Kimberley coast in Western Australia, with globally significant rookeries of three species of sea turtle. While many studies have assessed the impacts of climate change on sea turtle sex-ratios, the Kimberley region is largely unstudied. Additionally, few studies have also investigated the genetic response of developing sea turtle embryos to thermal stress. Here, we predict the effects of climate change on sex-ratios and embryonic mortality at three rookeries in the Kimberley, and present a transcriptome-wide analysis of the response of developing embryos to simulated climate change. Using constant and cycling incubation experiments to resolve baseline thermal biology data, coupled with predictions of future regional temperatures, we show primary sex-ratios skewing towards female bias and increases in mortality while identifying genes associated with thermal stress. We also show a decrease in hatchling weight, but not carapace, head or flipper measurements as temperature increases. Our study explores the effects of climate change on globally significant rookeries of sea turtles in the Kimberley and shows the underlying genetic response to climate change, with 299 genes differentially expressed as a consequence of thermal stress, including decreases in a number of genes associated with development and morphogenesis. Initial results suggest that Kimberley populations may be more resilient to the effects of climate change than first anticipated, at least for the near future.

GEN5-2  2:45 pm  Environmental impacts on reptilian nests and offspring: differential embryonic success and neonate growth. Wyneken J, Florida Atlantic University; Lolavar A*, Florida Atlantic University; Tezak B, Florida Atlantic University
Abstract: Because sex in many reptiles is environmentally determined, thermal effects associated with climate change have been postulated to have profound sex ratio effects, almost to the exclusion of consideration other developmental and morphological consequences. Large-scale modeling approaches infer thermal effects on reptiles, particularly on marine species; these use historic weather data or sea surface temperatures as proxies for incubation conditions that are rarely verified for the eggs, the hatchlings or estimates of the primary sex ratios. In the context of climate change, turtles are particularly interesting because their long evolutionary history includes surviving changing climates. This presentation provides a critical review of the existing approaches to assessing weather and climate-scale impacts on marine turtle eggs, their developmental success and neonate morphology. We present a case study in which in situ results are verified. Experimental laboratory studies aid our understanding of previously under-appreciated impacts. Comparisons among species show that outcomes from nests vary with nest depth. These findings also suggest that most large-scale models disregard important biologically effects upon the incubation environment and fail to consider the impact of embryonic death and sublethal effects on neonate growth and survival. Eggs that experience hyperthermia during development experience stage-related mortality; surviving embryos tend incubate rapidly and hatch at small size, many with scute anomalies. Some show delayed post-hatching growth, which can increase predation risk. Hyperthermia after hatching and during nest emergence can result in bleeding into the aqueous humor of the eye, which can compromise seafinding orientation. Hatchlings from nests that experience heavy rainfall with high incubation temperatures tend to produce hatchlings that emerge larger, grow more uniformly, and experience lower levels of delayed mortality.

GEN5-3  3:00 pm  Virtual fish gills: Computational modeling of gills to quantify hydrodynamic trade-offs in actinopterygian fishes from diverse habitats. Farina SC*, Harvard University
Abstract: When compared with air, water is a poor respiratory fluid, with a high viscosity and low dissolved oxygen concentration. Therefore, fluid dynamics likely play a large role in the evolution of respiratory morphology of vertebrates that rely on aquatic respiration. While the mechanism of aquatic ventilation in non-tetrapod vertebrates is relatively conserved, there is tremendous diversity in the morphology of this system, particularly in the microstructures of gill tissues. Vertebrate gill tissue consists of long filaments (primary lamellae), which are covered with small folds of tissue (secondary lamellae) that are the main site of gas exchange. These secondary lamellae vary considerably in shape, size, and spacing among species. In this study, I quantify hydrodynamics of secondary lamellae morphology in species of actinopterygian fishes representing six ecological categories: open-ocean pelagic, bentho-pelagic, deep sea, benthic, freshwater pelagic, and diel vertical migrators. Using a 3D computational model of the secondary lamellae that I have developed in COMSOL Multiphysics, I model the hydrodynamics of the gills of each species based on measurements from scanning electron microscopy. By measuring flow rate through and around the secondary lamellae over a range of pressures, I examine the trade-off between the total volume of fluid passing over the lamellar surface and the ability of water to pass through the gills.

GEN5-4  3:15 pm  Pattern of habitat use of the parasitic nematode Crassicauda within its host, the pygmy sperm whale (Kogia breviceps). Keenan-Bateman T.F.*, University of North Carolina Wilmington; McLellan W.A., University of North Carolina Wilmington; Costidis A.M., University of North Carolina Wilmington; Harms C.A., North Carolina State University ; Rotstein D.S., Marine Mammal Pathology Services; Rommel S.A., University of North Carolina Wilmington; Potter C.W., Smithsonian Institution; Pabst D.A., University of North Carolina Wilmington
Abstract: Giant nematodes (>3m) of the Genus Crassicauda infect kogiid whales. Only three studies to date have provided detailed descriptions of these Crassicauda worms, which were based upon fragmented specimens (Johnston and Mawson 1939, Dollfus 1966, Jabbar et al. 2014). These studies described worms within the neck region of kogiids, an unusual anatomic site for this parasite. Keenan-Bateman et al. (2015) demonstrated crassicaudids to be a species-specific parasite among kogiids, infecting only Kogia breviceps, and confirmed its primarily cervico-thoracic distribution. To date, though, the pattern of habitat use within the host, and transmission path of this parasite are unknown. This study utilized necropsy reports (n=32), detailed gross and micro-dissections (n=12), histological examination of host tissues (n=5), and scanning electron microscopy of excised worms (n=7) to enhance our understanding of this host-parasite relationship. Results reveal a critical habitat for the worm is a previously undescribed compound tubuloalveolar exocrine gland, which opens at the terminus of the “false gill slit” pigmentation pattern in the whale’s neck. Crassicauda male and female tails were found hanging freely in the glandular central lumen, and eggs have been observed in its presumed secretion, indicating the likely transmission path out of the host body. The cephalic ends of these worms were found, often meters away (curvilinearly), embedded deeply within the host’s epaxial muscle. A single worm’s complete, tortuous 312cm course from the gland to its termination in the contralateral epaxial muscle of its definitive host, K. breviceps, is described for the first time. The species-specific nature of Crassicauda infection, the exocrine gland, and the distinct features of the false gill slit pigmentation pattern associated with the gland, suggest that they are all useful characters to identify kogiid species in the field.

GEN5-5  3:30 pm  Identification and characterization of ionocytes in branchial epithelium of catfish Heteropneustes fossilis and the effect of salinity on their morphometry. Abidi S, Aligarh Muslim University, India; Parwez I*, Aligarh Muslim University, India   Aligarh Muslim University, Aligarh, India
Abstract: The identification and characterisation of ionocytes in the branchial epithelium of the catfish Heteropneustes fossilis was done employing light microscopy and immunohistochemistry. Among successful stains, the acid haematein (AH) and osmium zinc iodide (OZI) selectively stained ionocytes which were round or ovoid, located singly or in clusters of 2-4 cells mainly in the interlamellar area and at the tip region and only occasionally at the lamellae. The ionocytes stained black with OZI and blue with AH exhibiting granulation in the latter. The ionocytes were also localized immunohistochemically using monoclonal antibody specific to α subunit of chicken Na+/K+-ATPase. Transmission electron microscopy (TEM) revealed ionocytes, pavement cells, accessory cells, pillar cells and undifferentiated cells. The ionocytes were characterized by high mitochondrial density, extensively amplified basolateral membrane and narrow apical pit which was either flat or slightly convex without microvilli. Two subtypes of ionocytes, designated as CcI and CcII, were differentiated on the basis of round mitochondria and electron dense cytoplasm in CcI and round and elongated mitochondria and electron lucent cytoplasm in CcII. Under scanning electron microscopy (SEM), pavement cells were characterized by concentrically arranged microridges, the mucous cells had flocculent mucus near their openings and the ionocytes appeared as swollen structures with faint concentric rings. In 25% sea water adapted catfish, the number of ionocytes, visualized under light microscopy, was significantly decreased but their size remained unchanged. Similarly, an increase in the number of mucous cells openings under SEM and an increase in the number of lamellar accessory cells under TEM were observed in 25% SW catfish. The identification of ionocytes in this study may help to elucidate the role of these cell types in stenohaline FW teleosts in higher salinities.

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