Disruptive coloration and habitat use by seahorses

Predation avoidance is a primary factor influencing survival. Therefore, any trait that affects the risk of predation, such as camouflage, is expected to be under selection pressure. Background matching (homochromy) limits habitat use, especially if the habitat is heterogeneous. Another camouflage mechanism is disruptive coloration, which reduces the probability of detection by masking the prey's body contours. Here we evaluated if disruptive coloration in the longsnout seahorse, Hippocampus reidi, allows habitat use diversification. We analyzed 82 photographs of animals, comparing animal and background color, and registering anchorage substrate (holdfast). We tested whether the presence (disruptive coloration) or absence of bands (plain coloration) predicted occupation of backgrounds of different colors. We also calculated the connectance between seahorse morph and background color or holdfast, as well as whether color morph differed in their preferences for holdfast. Animals with disruptive coloration were more likely to be found in environments with colors different from their own. Furthermore, animals with disruptive coloration occupied more diversified habitats, but as many holdfasts as plain colored animals. Therefore, animals with disruptive coloration were less selective in habitat use than those lacking disruptive color patterns, which agrees with the disruptive coloration hypothesis.(AU)

Evitar a predação é um dos principais fatores que influenciam a sobrevivência. Portanto, qualquer traço que afete o risco de predação, como a camuflagem, deverá estar sob forte pressão de seleção. Confundir-se com a cor do fundo (homocromia) limita o uso do habitat, especialmente se ele é heterogêneo. Outro mecanismo de camuflagem é a coloração disruptiva, que reduz a probabilidade de detecção mascarando o contorno do corpo da presa. Aqui nós avaliamos se a coloração disruptiva no cavalo-marinho de focinho comprido, Hippocampus reidi, permite diversificar o uso do habitat. Analisamos 82 fotografias de animais, comparando a cor do animal à do fundo, e registrando o substrato de apoio (holdfast). Nós testamos se a presença (coloração disruptiva) ou ausência de bandas (coloração lisa) predizia a ocupação de substratos de cores diferentes. Nós também calculamos a conectância entre o morfo do cavalo-marinho e a cor do fundo ou o substrato de apoio, bem como se o morfo diferiu em suas preferências por substratos de apoio. Animais com coloração disruptiva eram mais encontrados em ambientes com cores diferentes de sua própria cor. Além disso, os animais com coloração disruptiva ocupavam habitats mais diversificados, mas tantos substratos de apoio quanto animais lisos. Portanto, animais com cores disruptivas eram menos seletivos do que animais lisos quanto ao habitat que utilizavam, o que concorda com a hipótese da coloração disruptiva.(AU)

Discrimination of habitat use between two sympatric species of mullets, Mugil curema and Mugil liza (Mugiliformes: Mugilidae) in the rio Tramandaí Estuary, determined by otolith chemistry

Two sympatric species of marine mullets, Mugil curema and M. liza, use the rio Tramandaí Estuary as nursing grounds. When two closely related species are sympatric, various mechanisms may permit their coexistence, including spatial or temporal segregation that results in the divergent use of the resources for which they compete. To investigate the spatial segregation, we used otolith chemistry inferred through laser ablation-inductively coupled plasma mass spectrometry. Our results indicate that in the rio Tramandaí Estuary, M. curema is associated with high salinity waters and can be classified as a Marine Migrant in the Marine Estuarine-opportunist subcategory. Mugil liza is associated with lower salinity and can be classified as a Marine Migrant in the Estuarine Dependent subcategory. The intra-specific variation in estuarine habitat use indicates that the migratory behaviors in mullets are far more complex than previously known.(AU)

Duas espécies de tainha simpátricas, Mugil curema e M. liza, usam o estuário do Rio Tramandaí como zona de berçário. Quando espécies do mesmo gênero são simpátricas, vários mecanismos podem permitir sua coexistência, incluindo segregação espacial ou temporal que resultam no uso distinto dos recursos pelos quais elas competem. Para investigar a segregação espacial nós usamos a análise de elementos químicos em otólitos inferidos por espectrometria de massas através de plasma indutivamente acoplado com amostras extraídas a laser (LA-ICPMS). Mugil curema está associada a águas de alta salinidade podendo ser classificada como Marinho Migrante sub-categoria Marinha estuarina-oportunista. Mugil liza está associada a águas menos salinas, devendo ser classificada como Marinha Migrante sub-categoria Estuarina Dependente. A variação intraespecífica no uso do habitat estuarino indica um comportamento migratório mais complexo que o previsto em tainhas.

Moderate pathogenic effect of Ligophorus uruguayense (Monogenoidea, Ancyrocephalidae) in juvenile mullet Mugil liza (Actinopterygii, Mugilidae) from Brazil

ABSTRACT Monogenoidea pathogenic activity can elicit various histological responses in fish. Species of Ligophorus are specific parasites of mullets, and its relationship with host fish may result in a moderate pathogenic action. In order to ascertain this relationship, estuarine mullets (Mugil liza) were collected in an estuary, reared in laboratory, for three weeks, and forwarded for histological and parasitological analyses. Ligophorus uruguayense (Monogenoidea) infestation in the gills of the mullets was identified. The severe infestation by only one species of Monogenoidea may result from the specificity of these parasites to mullets. Mullets submitted to histological analysis exhibited respiratory epithelium detachment; mild, moderate and severe hyperplasia of the respiratory epithelium; atrophy; and telangiectasia of the gills. This is the first study reporting that mullets highly infested by Monogenoidea can show mild (100%) to severe (20%) gill changes with a distinct frequency of occurrence. Because of the high prevalence of mild alterations observed, it is possible to accept that L. uruguayense is moderately pathogenic to M. liza, even during high prevalence and intensity of infestation, as a result of its specificity.