The Digestive System of the Arctocephalus australis In Comparison to the Dog as a Land-Carnivore Model
Animals
Abstract and Figures
Marine mammals play a critical ecological role as both predator and prey. They are divided into three groups that share similar adaptations to their aquatic life, but that have very different origins and life patterns: sirenians, pinnipeds, cetaceans. The species object of our interest is the South American fur seal or Arctocephalus australis, a carnivore classified within the group of pinnipeds. The objective of the present study was to evaluate whether the anatomical characteristics of the Arctocephalus australis’ digestive system are similar to that of other land-carnivores or if, on the contrary, this species shows anatomical adaptations related to their life in the ocean. The study was carried out on 11 cadavers of the species Arctocephalus australis, made up of two adults and nine juveniles, by means of the anatomical dissection of their entire isolated digestive system. We demonstrate that, with several exceptions, the anatomical characteristics of the digestive system of the Arctocephalus australis are similar to those in other carnivores. Therefore, our data constitute an important contribution for clinical diagnostic and conservation purposes, for both veterinarians and biologists.
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... The present study focused on the South American fur seal or Arctocephalus australis, an otariid included in the taxonomic family of pinnipeds (Order Carnivora), such as the dog or the cat [6,7]. Surprisingly, although it is generally accepted that anatomy is crucial to a better understanding of different physiological adaptations [2], and although studies on the physiology of diving are numerous [1,[8][9][10][11][12][13][14][15][16][17][18][19], only a small number of them analyze the anatomical characteristics of marine mammals [5,[20][21][22][23][24], and even fewer are focused on the anatomy of the respiratory system [2,3,[25][26][27]. ...
Marine mammals are divided into three groups, with similar adaptations resulting from their aquatic lifestyle: sirenians, pinnipeds, and cetaceans. The present work focused on the South American fur seal, or Arctocephalus australis, a carnivore included in the pinnipeds group. We assessed whether the anatomical features of the Arctocephalus australis’ respiratory system are comparable to those of other land-carnivores or whether these individuals show anatomical adaptations related to their ability to dive or their breath-holding capacities. We studied 11 cadavers of Arctocephalus australis, which included adult (n = 2) and juvenile (n = 9) individuals, by anatomically dissecting their isolated entire respiratory system. Although it is generally similar to that in land-carnivores, we demonstrated that the Arctocephalus australis’s respiratory apparatus shows several specific characteristics. Therefore, our results are of great importance for clinical diagnostic and wildlife conservation purposes.
Objectives
Proximal duodenal ulceration is often characterised by continuous bleeding, and treatment is challenging. The aims of this study were to investigate the role of vascularisation in proximal duodenal ulceration and describe clinical aspects, endoscopic features and treatment in dogs.
Material and Methods
Polyurethane foam casts of gastroduodenal vessels were obtained from five dogs which had died from disorders unrelated to the digestive system. In addition, 12 dogs having proximal duodenal ulcers diagnosed by endoscopic examination were enrolled in a treatment trial. After the endoscopic diagnosis of a duodenal ulcer, all the dogs were treated medically and, in the absence of resolution, were subsequently treated by endoscopic electrocauterisation or by surgery.
Results
A submucosal vascular network was evident in all the casts, with a prominent venous plexus seen exclusively in the first half inch of the duodenum. In clinical cases, on endoscopic examination, the duodenal ulcer was located at the proximal part of the duodenum, involving the mesenteric portion of the wall. The dogs not responding to medical treatment (6/12) were treated with endoscopic electrocauterisation, surgical coagulation or resection of the proximal duodenal portion. All the dogs survived until discharge, and the median survival time following discharge was 107.5 days.
Clinical Significance
Based on the anatomical details highlighted in this study, the continuous bleeding observed in our patients may have been due to the prominent venous plexus evidenced at the level of the proximal duodenum. Surgical and endoscopic treatments in six patients resolved the ulcer bleeding with no recurrences noted during follow‐up.
The similarity of the trophic ecology of Arctocephalus australis and Otaria flavescens in Uruguay was studied to help understand a possible trophic competition between the two species and its relation with artisanal fisheries. Dietary data for both pinnnipeds together with artisanal fisheries catch data were analyzed to estimate the overlap in prey species and sizes. Diet overlap was very high (Colwell and Futuyma overlap index, C = 0.80), with three fish species ( Anchoa marinii, Cynoscion guatucupa, and Trichiurus lepturus) comprising more than 90% of the total number of individuals consumed by both species. In addition, the length of these three fish prey taken by fur seals and sea lions was similar, suggesting a large overlap not only in species but also in the size of prey ingested. The main difference between the two pinniped diets was that O. flavescens showed a more diverse diet than A. australis. Concerning pinniped fisheries interactions, a low level of overlap was observed between the diet of each pinniped and artisanal fisheries catches (C = 0.22 for O. flavescens, and C = 0.09 for A. australis). Possibly, sea lion diet is broader than artisanal fisheries catches. Length comparisons for C. guatucupa, the only species well represented in both pinniped species diet and fisheries catches, indicated that individuals taken by the latter were larger than those consumed by the pinnipeds. However, the use of different age classes of the same resource, at different times or spatial locations do not imply less intensity of the interaction.
In South American fur seals (Arctocephalus australis) breeding in dense colonies at Punta San Juan, Peru, mothers are regularly separated from pups when they forage at sea throughout lactation and as a result of disturbances among females during on-beach nursing periods. Unattended pups risk injury or death from aggressive females and predatory sea lions, so the ability of mothers and pups to recognize and reunite is an essential component of breeding success. I investigated the relative importance of vocal, visual, olfactory, and spatial cues in the reunion process and examined how these behaviors are related to search context and success. Behavior of 10 tagged mother–pup pairs was recorded during 118 searches, 67% of which resulted in reunion. Mothers and pups appeared to recognize one another by vocal signatures over distance, and mothers used naso-nasal investigation before accepting or rejecting pups. Mothers supplemented their calling behavior with a variety of low-cost strategies such as frequenting a consistent “home spot” (76%), moving about the colony (49%), and investigating approaching pups (42%), but the best predictor of search success was pup response: after pups called and moved toward mothers, pairs were reunited 95% of the time regardless of mothers’ behavior. Pups responded infrequently (18%) to the wrong female, suggesting that pups’ acceptance criteria are conservative when risk of injury from unrelated females is high.
Fur seals alternate foraging at sea and fasting periods ashore. During fasting, energy and water are supplied by fat stores, but little is known about the transition from feeding to fasting metabolism. To evaluate the variation on land of significant parameters of urea and hydromineral metabolism, urine pH, plasma and urine osmolality, creatinine, urea, Na + , K + , Cl -an Ca 2+ were determined in 65 wild South American fur seals (Arctocephalus australis) from Lobos Island, Uruguay. Urine/plasma ratio (U:P) and fractional excretion (FE) were calculated for creatinine, urea, Na + , K + , Cl -and Ca 2+ . As no significant differences were found between categories (immature, pregnant and non lactating, pregnant and lactating females, and immature males), pooled data allowed to perform correlation and regression tests. Correlated variables allow to characterize a post-absorptive (high FE of urea, urine urea and osmolality, associated with low U:P quotient for creatinine and urea) as well as fasting condition (low FE of urea, urine urea and osmolality, associated with high U:P quotient for creatinine and urea). The FE of urea versus log creatinine U:P plot suggests active urea secretion at low urine flows. Comparative urine analysis is consistent with a possible event of seawater ingestion in a young male: highest urine Na + (336mmol.l -1) and Cl -(265.74mmol.l -1) concentrations associated with low urine urea concentration (657.24mmol.l -1). Resumen Los lobos marinos alternan períodos de forrajeo en el mar con ayuno en tierra. Durante el ayuno, energía y agua son provistos por las reservas grasas, pero poco se conoce sobre la transición del metabolismo de alimentación al de ayuno. Para evaluar la variación en tierra de parámetros relacionados al metabolismo hidromineral y de la urea, se determinó el pH urinario, así como los títulos plasmáticos y urinarios de osmolalidad, creatinina, urea, Na + , K + , Cl -y Ca 2+ a partir de 65 ejemplares de lobo fino sudamericano (Arctocephalus australis) en Isla de Lobos, Uruguay. El cociente orina/plasma (U:P) y la tasa de excreción (FE) fueron calculados para creatinina, urea, Na + , K + , Cl -y Ca 2+ . No encontrándose diferencias significativas entre categorías (hembras inmaduras, preñadas no lactíferas, preñadas lactíferas y machos inmaduros), el pool de datos permitió realizar tests de correlación y regresión. Las variables correlacionadas permiten caracterizar estados post-absortivos (altas FE de urea, urea urinaria y osmolalidad, asociadas con bajos cocientes U:P de creatinina y urea) así como estados de ayuno (bajas FE de urea, urea urinaria y osmolalidad, asociadas con altos cocientes U:P de creatinina y urea). La relación entre la FE de urea y el log del cociente U:P de creatinina sugiere secreción activa de urea asociada a débitos urinarios bajos. El análisis comparativo de orina es consistente con un posible caso de ingestión de agua de mar por parte de un macho joven: las mayores concentraciones de Na + (336mmol.l -1) y Cl -(265.74mmol.l -1), asociadas con bajo nivel de urea urinaria (657.24mmol.l -1).
As part of population dynamics studies of the South American fur seal (Arctophoca australis gracilis) rookery at Punta Weather in Guafo Island (43°36'S, 74°43’W), the causes and extent of pup mortality were monitored. During four breeding seasons, daily counts of live and dead pups were carried out to determine pup production and pup mortality. Dead pups were retrieved from the rookery to perform necropsies. The mean pup production was 1,735.5 ± 336 pups and the mean pup mortality up to 12 wk old was 6.0%± 2.6%. The major causes of death were enteritis with microscopic lesions of bacteremia (28.4%), starvation (23.5%), drowning (21%), trauma (19.8%), and stillbirths (2.5%). Enteritis with microscopic lesions of bacteremia, and starvation had higher incidence during January (beginning and middle of the breeding season) while most trauma and drowning occurred during February (end of the breeding season). In the 2006–2007 breeding season there was an increase in mortality due to starvation and trauma. Most pup deaths at Guafo Island are generated by extrinsic factors; therefore, additional studies that assess the impact of environmental changes and fishing activities, are needed in order to determine the exact causes of the decline of this species along Chilean coasts.
The mucosal attachment pattern of Corynosoma australe in the intestines of Arctocephalus australis is described. Normal and abnormal tissue were sampled from 32 hosts to be submitted to histological routine protocol to embedding in paraffin and permanent mounting in balsam. Corynosoma australe shows three different degrees of body depth intestinal attachment (BDINA-1–3). BDINA-1: it is exclusive of the small intestine and the parasite attaches on the villi; BDINA-2: parasite affects the Lieberkühn crypts in several depth levels and, BDINA-3: the parasite reaches the submucosa. These attachment patterns alter the mucosa by degeneration and dysfunction due to necrosis of mucosal structure, great quantities of cellular debris and significant reduction of the mucosal thickness. Other aspects are crater-like concave holes (CLCHs) as sites where C. australe could be attached–detached several times according to adult migratory processes within luminal intestine space. The submucosa shows edema probably due to the local mucosal alterations resulting in homeostatic break. There is no severe inflammatory response by host but BDINA-1 to BDINA-3 and CLCH could represent foci to secondary opportunistic infections and significant areas of malabsorption in severally infected hosts contributing to increase clinical signs of preexistent pathologies.
A critical review of metabolic rate determinations for pinnipeds (seals, sea lions, fur seals, and walrus) and cetaceans (whales, dolphins, and porpoises) does not support the widely accepted generalization that they have higher metabolic rates than terrestrial mammals of similar size. This finding necessitates a rethinking of the thermoregulatory adaptations of these marine mammals for an aquatic existence and has important implications in comparative studies of mammals, which frequently omit marine forms because they are perceived to be "different" from other mammals. It also suggests that numerous studies have overestimated food consumption by marine mammal populations.
Analysing the physiological adaptations of marine mammals and seabirds, this book provides a comprehensive overview of what allows these species to overcome the challenges of diving to depth on a single breath of air. Through comparative reviews of texts on diving physiology and behaviour from the last seventy-five years, Ponganis combines this research into one succinct volume. Investigating the diving performance of marine mammals and seabirds, this book illustrates how physiological processes to extreme hypoxia and pressure are relevant to the advancement of our understanding of basic cellular processes and human pathologies. This book underscores the biomedical and ecological relevance of the anatomical, physiological and molecular/biophysical adaptations of these animals to enable further research in this area. An important resource for students and researchers, this text not only provides an essential overview of recent research in the field, but will stimulate further research into the behaviour and physiology of diving.
In this study, we aimed to describe the morphological characteristics of the lingual papillae in two species of Otariidae family by stereomicroscopy and scanning electron microscopy. We used tongues of two South American Otariidae species. The tongues were elongated and terminated in bifid apex and there was no median sulcus on the dorsal lingual surface. The most numerous type of lingual papilla was filiform in the South American fur seal (SASL) and entire dorsal lingual surface was covered by these filiform papillae but the dorsal surface of the tongue of the South American sea lion was covered by numerous polygonal projections, which were different in size. Fungiform papillae were detected in only SASL and they randomly distributed on the lingual apex and body, and some fungiform papillae were collected into twosome or threesome groups on the posterior part of the lingual body. Circumvallate papilla was found in the center of the lingual radix of South American sea lion. Thread-like conical papillae were common for both species and they located on the lingual radix. We determined that lingual surface morphology was completely different in each species, although they were members of the same family, Otariidae.
Body size plays an important role in pinniped ecology and life history. However, body size data is often absent for historical, archaeological, and fossil specimens. To estimate the body size of pinnipeds (seals, sea lions, and walruses) for today and the past, we used 14 commonly preserved cranial measurements to develop sets of single variable and multivariate predictive equations for pinniped body mass and total length. Principal components analysis (PCA) was used to test whether separate family specific regressions were more appropriate than single predictive equations for Pinnipedia. The influence of phylogeny was tested with phylogenetic independent contrasts (PIC). The accuracy of these regressions was then assessed using a combination of coefficient of determination, percent prediction error, and standard error of estimation. Three different methods of multivariate analysis were examined: bidirectional stepwise model selection using Akaike information criteria; all-subsets model selection using Bayesian information criteria (BIC); and partial least squares regression. The PCA showed clear discrimination between Otariidae (fur seals and sea lions) and Phocidae (earless seals) for the 14 measurements, indicating the need for family-specific regression equations. The PIC analysis found that phylogeny had a minor influence on relationship between morphological variables and body size. The regressions for total length were more accurate than those for body mass, and equations specific to Otariidae were more accurate than those for Phocidae. Of the three multivariate methods, the all-subsets approach required the fewest number of variables to estimate body size accurately. We then used the single variable predictive equations and the all-subsets approach to estimate the body size of two recently extinct pinniped taxa, the Caribbean monk seal (Monachus tropicalis) and the Japanese sea lion (Zalophus japonicus). Body size estimates using single variable regressions generally under or over-estimated body size; however, the all-subset regression produced body size estimates that were close to historically recorded body length for these two species. This indicates that the all-subset regression equations developed in this study can estimate body size accurately.
The objective of the present study was to verify if polyurethane foam is a suitable material to make accurate casts of vessels and viscera, and to develop a method based on its use for anatomical studies. This new technique has been tested primarily on the lungs of different animals, but also on the renal, intestinal and equine digital vessels. It consisted of three steps: specimen preparation, injection of the foam and corrosion of the cast. All structures injected with foam were properly filled. The bronchial tree and the vessels could be observed up to their finer branches. The method is inexpensive, simple and requires no special equipment. The pre-casting procedure does not require perfusion of the specimens with formalin, or prolonged flushing with carbon dioxide gas or air for drying. The polyurethane foam does not need a catalyst. It is simply diluted with acetone, which does not cause shrinkage of the cast due to evaporation during hardening. The foam naturally expands into the cavities without high pressure of the inoculum, and hardens in just 2 or 3 h at room temperature. Only two drawbacks were observed. The first is the fact that multiple injections cannot be made in the same cavity since the foam solidifies quickly; the second is the slight brittleness of the cast, due to the low elasticity of polyurethane foam. In conclusion, polyurethane foam was a suitable material for producing accurate casts of vessels and viscera.