The influence of simulated exploitation on Patella vulgata populations: protandric sex change is size-dependent

Grazing mollusks are used as a food resource worldwide, and limpets are harvested commercially for both local consumption and export in several countries. This study describes a field experiment to assess the effects of simulated human exploitation of limpets Patella vulgata on their population ecology in terms of protandry (age-related sex change from male to female), growth, recruitment, migration, and density regulation. Limpet populations at two locations in southwest England were artificially exploited by systematic removal of the largest individuals for 18 months in plots assigned to three treatments at each site: no (control), low, and high exploitation. The shell size at sex change (L50: the size at which there is a 50:50 sex ratio) decreased in response to the exploitation treatments, as did the mean shell size of sexual stages. Size-dependent sex change was indicated by L50 occurring at smaller sizes in treatments than controls, suggesting an earlier switch to females. Mean shell size of P. vulgata neuters changed little under different levels of exploitation, while males and females both decreased markedly in size with exploitation. No differences were detected in the relative abundances of sexual stages, indicating some compensation for the removal of the bigger individuals via recruitment and sex change as no migratory patterns were detected between treatments. At the end of the experiment, 0–15 mm recruits were more abundant at one of the locations but no differences were detected between treatments. We conclude that sex change in P. vulgata can be induced at smaller sizes by reductions in density of the largest individuals reducing interage class competition. Knowledge of sex-change adaptation in exploited limpet populations should underpin strategies to counteract population decline and improve rocky shore conservation and resource management

Fatores de risco, achados clínicos, laboratoriais e avaliação terapêutica em 36 bovinos com deslocamento de abomaso

A contínua seleção genética para maior produção de leite em conjunto com o aumento da capacidade digestiva e profundidade corporal aumentou a susceptibilidade à ocorrência de abomasopatias, incluindo o deslocamento do abomaso. Este trabalho objetivou realizar um estudo retrospectivo sobre o deslocamento de abomaso em 36 bovinos atendidos na Clínica de Bovinos, Campus Garanhuns da Universidade Federal Rural de Pernambuco, durante o período de janeiro de 2000 a fevereiro de 2009. Foram diagnosticados 27 casos de deslocamento do abomaso à direita, seis casos de deslocamento do abomaso à esquerda e três casos de vólvulo abomasal. Onze casos considerados moderados, sem grave distensão abdominal, apetite presente para a forragem e delimitação de som metálico até o 8º espaço intercostal, foram tratados clinicamente; enquanto 20 casos com distensão abdominal moderada a severa, associada a distúrbios sistêmicos, foram considerados graves e tratados cirurgicamente. Duas vacas foram eutanasiadas devido peritonite difusa ou alterações graves na serosa do abomaso, totalizando 18 animais submetidos ao tratamento cirúrgico. Dois animais foram encaminhados para abate e três vacas chegaram prostradas e morreram sem receber nenhum tratamento. A análise dos fatores de risco identificou a estação chuvosa como estatisticamente significativa. O maior número de deslocamento do abomaso ocorreu em vacas mestiças com 24 casos (66,6%), seguida por bovinos da raça Holandesa com 11 (30,5%) e Gir com um (2,9%) caso. A composição da alimentação oferecida variou bastante e caracterizou-se por conter excesso de carboidratos e, na maioria dos casos, fibra de baixa qualidade. Os sinais clínicos mais frequentes foram comportamento apático, desidratação, timpanismo ruminal leve a severo com motilidade ausente ou diminuída, som de líquido ao balotamento do flanco direito, som de chapinhar metálico e/ou observação de uma estrutura similar a uma víscera distendida no gradil costal do lado correspondente ao deslocamento; fezes liquefeitas, enegrecidas e de odor fétido. Os achados hematológicos revelaram, na maioria dos casos, leucocitose neutrofílica e hiperfibrinogenemia. Na análise do fluido ruminal havia comprometimento da dinâmica da flora e fauna microbiana, e elevação no teor de cloreto em 93,9% dos casos, com o índice médio alcançando 47,66 mEq/L. O índice de recuperação clínica e cirúrgica alcançou 100% e 72,2%, respectivamente. As condutas descritas são opções viáveis para o tratamento dos deslocamentos leves e severos, no entanto a prevenção permanece a melhor alternativa a ser adotada.The continuous genetic selection for high milk production in association with greater digestive capacity and corporal depth increases the susceptibility for abomasopathies including abomasal displacement. The present work aimed to accomplish a retrospective study on abomasal displacement in 36 cattle attended at Bovine Clinic, Garanhuns Campus, Federal Rural University of Pernambuco, through January 2000 to February 2009. Twenty seven cases of right abomasal displacement, six cases of left abomasal displacement and three of abomasal volvulus were diagnosed. Eleven moderate cases, without severe abdominal distention, appetite for roughage and metallic sound (“ping”) reaching at the most the 8th intercostal space were treated conservatively, and 20 severe cases with moderate to severe abdominal distention associated to systemic disturbances were treated surgically. Two cows were euthanized due to diffuse peritonitis or severe alterations in the abomasal serosa totalizing 18 animals submitted to the surgical treatment. Two animals were slaughtered and three cows arrived prostrated and died without receiving any treatment. Risk factor analysis identified rainy season as statistically significant. The greater number of abomasal displacement was in crossbred cows with 24 cases (66.6%), followed by Holstein and Gir cattle with 11 (30.5%) and one (2.9%) cases, respectively. Food composition varied greatly and characterized by excess of carbohydrates and in most cases low quality fibers. Most frequent clinical signs were apathy, dehydration, light to severe ruminal bloat with reduced or absent motility, splashing sound during right flank ballottement, ping and a distended viscera-like structure in the side of the displacement; liquid, blackish and fetid feces. Hematology reveals leukocytosis with neutrophilia and hyperfibrinogenemia in most cases. Ruminal fluid analysis showed compromised flora and fauna dynamics and increased chloride ion concentration in 93.9% of the cases achieving the media index of 47.66 mEq/L. Clinical and surgical recovery rate achieved 100% and 72.2%, respectively. Those methods described are viable options for the treatment of light and severe displacements but the prevention remains the best choice