Efecto de la temperatura y concentración de microplásticos en la tasa de filtración del mejillón Semimytilus algosus (Mytiloida: Mytilidae)

Introducción: La presencia de microplásticos (MPs, partículas menores a 5 mm) y el incremento de la temperatura en los océanos, vienen generando perturbaciones en la vida marina, que se pueden relacionar con alteraciones en el metabolismo de organismos filtradores, como los mitílidos. Objetivo: Se evalúa el efecto de diferentes temperaturas y concentraciones de MPs sobre la tasa de filtración (TF) de Semimytilus algosus. Métodos: Una muestra de organismos (N = 72) fue expuesta a cuatro temperaturas (17, 20, 23 y 26 °C), y un testigo sin microplásticos (MPs0) y dos concentraciones de MPs (< 125 µm) de 0.125 mg/l (MPs1) y 0.250 mg/l (MPs2), todos en combinación con la microalga Isochrysis galbana (1x106 cel/ml/día) por 21 días. Resultados: A medida que aumentó la concentración de MPs, se redujo la TF de S. algosus. Respecto a la temperatura, durante el día 7 se observó una mayor TF a 23 °C en todos los tratamientos, y para los días 14 y 21 se obtuvieron los menores valores de TF a 23 y 26 °C. La acción conjunta del incremento de temperatura y MPs, afectó negativamente la TF de S. algosus, donde ambos factores ocasionaron el descenso de la TF para todos los tiempos de evaluación. No se registró mortalidad a 17 °C para ningún tratamiento, y en el caso de mitílidos expuestos a MPs1 y temperaturas de 20 y 26 °C se presentó la mayor mortalidad (67 %). Conclusiones: El estudio demuestra el efecto adverso del incremento de temperatura y MPs sobre la TF de S. algosus.

Energetic trade-offs: Implications for selection between two bivalve prey species by a carnivorous muricid gastropod

Active predators obtain energy and nutrients from prey through complex processes in which the energy gained must exceed the energy invested in finding and ingesting the prey. In addition, the amount of energy available will vary with the prey that are selected for consumption. The muricid gastropod Acanthina monodon inhabits rocky shores, where it routinely feeds on the mytilids Semimytilus algosus and Perumytilus purpuratus. In this study, S. algosus was highly preferred by the predator (over 90% were eaten) versus P. purpuratus (only 9% were eaten) when offered a mixed diet. The energetic cost of attacking one S. algosus individual was 91 J bivalve-1 while for P. purpuratus it was slightly higher: 95 J bivalve-1. Also, whereas A. monodon required on average 19 h to consume S. algosus, successful attacks on P. purpuratus required about 32% more time (25 h). In addition, a longer resting time was needed by the predator after preying on P. purpuratus before it initiated another attack. Moreover, the active metabolic costs associated with successfully attacking the prey increased 3.2 times over the basal metabolic costs when attacking S. algosus, but only by 2.5 times when attacking P. purpuratus. The calculations associated with preying on each species showed that the energetic gain per unit time likely accounts for the predator’s preference for attacking S. algosus, even though predation on both species provided net energy gains for the predator. However, as S. algosus occurs seasonally at our study site, P. purpuratus would probably also be consumed due to its constant availability throughout the whole year.

Microplastic ingestion and feeding ecology in three intertidal mollusk species from Lima, Peru

Microplastics (< 5 mm) are ubiquitous contaminants in the marine environment. The aims of the present study were to report the incidence of microplastic pollution in three mollusk species from the coast of Lima and to investigate the relationship between microplastic ingestion and feeding ecology. Specimens of three mollusk species Semimytilus algosus, Tegula atra and Chiton granosus were sampled from the intertidal rocky zone. For microplastic isolation, soft tissues were digested in 10% KOH, vacuum filtrated and analyzed under a microscope. Rigorous contamination prevention measures were taken into account. C. granosus was the most contaminated mollusk (6.92 ± 2.13 particles g-1). Red fibers were the overall most abundant microplastic. The feeding behavior of T. atra promotes microplastic exposure to C. granosus. More research is needed to fully understand the microplastic effects on mollusk species.