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El presente estudio se desarrolló durante los meses de septiembre y noviembre 2007, en área de la isla Santa Clara. Se establecieron ocho estaciones de muestreo en la zona intermareal de la isla. En cada muestreo se colectaron organismos bentónicos, muestras de sedimento, materia orgánica (MO), así como de las variables ambientales: temperatura, salinidad y pH en el agua de mar. Se aplicaron los índices de diversidad y equidad. El objetivo del presente trabajo es estudiar la comunidad de los poliquetos en la zona intermareal de la isla Santa Clara como bioindicadores de materia orgánica. En el mes de septiembre el valor más alto del índice de diversidad (1,47bits/ind) se ubicó en la estación 4 sitió de menor concentración de MO (1,9%) y el valor más bajo del índice de diversidad (0,21bits/ind) en la estación 7 en el sitio con mayor concentración de MO (9,9%). Mientras que en el mes de noviembre el valor más alto del índice de diversidad (2,01bits/ind) se ubicó en la estación 1 sitio de menor concentración de MO (3,8%) y el valor más bajo del índice de diversidad (1,14bits/ind) en la estación 6 sitio con menor concentración de MO (1,2%) y en la estación 7 sitio con mayor concentración de MO (9,9%) y el valor relativamente mayor de diversidad (1,69 bits/ind). En el mes de septiembre en donde se aplica el índice de equidad, se presenta una distribución de mayor homogeneidad en la estación 4 (0.70), y en la estación con menos homogeneidad fue la No. 7 (0,19). En el mes de noviembre la estación con una distribución más homogénea fue la estación 7, con valor de 0,87 respectivamente. La estación con una distribución menos homogénea fue la estación 4 con valor de 0,52.

Reason for addendum: During the preparation of the original manuscript, a scientific work that dealt precisely with Polychaeta as environmental indicators in Patagonia was not considered. This being the first and only work regarding this subject, it was reasonable and necessary to incorporate this information.

Los poliquetos (Annelida) son organismos en íntimo contacto con el sedimento donde viven y el agua sobrenadante. El estrés ambiental genera rápidas respuestas en estos organismos que se refleja en los individuos y sus poblaciones, por lo que se utilizan como indicadores biológicos de disturbios y de calidad ambiental. Los poliquetos han sido ampliamente utilizados en monitoreo ambiental y en bioensayos, y muchos estudios ecotoxicológicos se realizan con poliquetos. En casi todos los hábitats bentónicos estos organismos juegan un papel muy importante en la organización y estructura de las comunidades bentónicas y redes tróficas. Son un ítem fundamental en la alimentación de otros invertebrados y de aves migratorias y peces. Los poliquetos también tienen importancia económica para la industria farmacéutica, y de alimentos concentrados para especies marinas de cultivo (peces y crustáceos), en el campo médico y en la bioingeniería, además de la recreativa (acuarofilia, carnada) y por supuesto para el consumo humano. Varios de los índices de impacto ambiental y calidad ambiental existentes se basan en las características de tolerancia/sensibilidad de los organismos bentónicos, y muchos de ellos son poliquetos. Existen unos pocos trabajos de revisión de estos organismos como indicadores, pero todos en idioma inglés. Este trabajo muestra una actualización de los datos referidos a Latinoamérica y el Caribe, e incluye una amplia revisión bibliográfica.

Abstract Large predators have disproportionate effects on their underlying food webs. Thus, appropriately assigning trophic positions has important conservation implications both for the predators themselves and for their prey. Large-bodied predators are often referred to as apex predators, implying that they are many trophic levels above primary producers. However, theoretical considerations predict both higher and lower trophic position with increasing body size. Nitrogen stable isotope values (δ 15N) are increasingly replacing stomach contents or behavioral observations to assess trophic position and it is often assumed that ontogenetic dietary shifts result in higher trophic positions. Intraspecific studies based on δ 15N values found a positive relationship between size and inferred trophic position. Here, we use datasets of predatory vertebrate ectotherms (crocodilians, turtles, lizards and fishes) to show that, although there are positive intraspecific relationships between size and δ 15N values, relationships between stomach-content-based trophic level (TPdiet) and size are undetectable or negative. As there is usually no single value for 15N trophic discrimination factor (TDF) applicable to a predator species or its prey, estimates of trophic position based on δ 15N in ectotherm vertebrates with large size ranges, may be inaccurate and biased. We urge a reconsideration of the sole use of δ 15N values to assess trophic position and encourage the combined use of isotopes and stomach contents to assess diet and trophic level.

Understanding the demographic structure is vital for wildlife research and conservation. For crocodylians, accurately estimating total length and demographic class usually necessitates close observation or capture, often of partially immersed individuals, leading to potential imprecision and risk. Drone technology offers a bias-free, safer alternative for classification. We evaluated the effectiveness of drone photos combined with head length allometric relationships to estimate total length, and propose a standardized method for drone-based crocodylian demographic classification. We evaluated error sources related to drone flight parameters using standardized targets. An allometric framework correlating head to total length for 17 crocodylian species was developed, incorporating confidence intervals to account for imprecision sources (e.g., allometric accuracy, head inclination, observer bias, terrain variability). This method was applied to wild crocodylians through drone photography. Target measurements from drone imagery, across various resolutions and sizes, were consistent with their actual dimensions. Terrain effects were less impactful than Ground-Sample Distance (GSD) errors from photogrammetric software. The allometric framework predicted lengths within ≃11–18% accuracy across species, with natural allometric variation among individuals explaining much of this range. Compared to traditional methods that can be subjective and risky, our drone-based approach is objective, efficient, fast, cheap, non-invasive, and safe. Nonetheless, further refinements are needed to extend survey times and better include smaller size classes.

Abstract: Ecuador is one of the smallest and most densely populated countries in South America. In spite of this, it is also one of the 17 megadiverse countries worldwide and home to the largest number of species per unit area. Most aquatic ecosystems in mainland Ecuador have historically faced strong environmental pressures because the country’s economy has been based on the exploitation and trade of raw materials and agricultural products at a very high environmental cost. In this review, we provide a broad overview of the diversity of freshwater ecosystems and fish in mainland Ecuador. We address broadly current and historical threats to these ecosystems, including pollution due to oil extraction, mining activities, agriculture and the disruption of hydrological connectivity caused by hydroelectric dams. Despite these problems, we show some examples of promising initiatives at the local and national levels to address this situation.

We present data on occurrence of chelonians for the Madeira River (southwestern Amazon, Brazil). Sampling was undertaken along the BR-319 Highway in the Madeira-Purus interfluvium and along a 125‑km stretch of the upper Madeira River. Findings were contrasted with a checklist of species expected to occur in the region according to current distribution maps, and with literature data for the Madeira subbasin. Out of 12 expected species, we recorded five in the Madeira-Purus interfluvium (three other species were registered by other recent voucher-based studies in the region), and eight species in the upper Madeira region. Podocnemis expansa (Schweigger, 1812) and P. unifilis Troschel, 1848 occurred below and inbetween the upper Madeira rapids. Podocnemis sextuberculata Cornalia, 1849 had its range extended by over 700 km, but may be limited upriver by the rapids. Mesoclemmys gibba (Schweigger, 1812) and M. raniceps Gray, 1855 occurred sympatrically along the river. Chelonian diversity along the lower and upper Madeira appears to be complementary.

Although considerable knowledge has been gathered regarding the role of fish in cycling and translocation of nutrients across ecosystem boundaries, little information is available on how the energy obtained from different ecosystems is temporally allocated in fish bodies. Although in theory, limitations on energy budgets promote the existence of a trade-off between energy allocated to reproduction and somatic growth, this trade-off has rarely been found under natural conditions. Combining information on RNA:DNA ratios and carbon and nitrogen stable-isotope analyses we were able to achieve novel insights into the reproductive allocation of diamond mullet (Liza alata), a catadromous, widely distributed herbivorous-detritivorous fish. Although diamond mullet were in better condition during the wet season, most reproductive allocation occurred during the dry season when resources are limited and fish have poorer body condition. We found a strong trade-off between reproductive and somatic investment. Values of δ13C from reproductive and somatic tissues were correlated, probably because δ13C in food resources between dry and wet seasons do not differ markedly. On the other hand, data for δ15N showed that gonads are more correlated to muscle, a slow turnover tissue, suggesting long term synthesis of reproductive tissues. In combination, these lines of evidence suggest that L. alata is a capital breeder which shows temporal uncoupling of resource ingestion, energy storage and later allocation to reproduction.