Modelo del efecto de la temperatura sobre los patrones de eclosión y asentamiento de organismos meroplanctónicos: el ejemplo del pulpo

The duration of embryonic development and the planktonic stage of meroplanktonic species is highly temperature dependent and thus the seasonal temperature oscillations of temperate regions greatly affect the patterns of hatching and benthic settlement. Based on data from the literature on embryonic development and planktonic duration of Octopus vulgaris (common octopus) in relation to temperature, and on observed temperature patterns, several models of hatching and settlement patterns were created. There was a good fit between observed settlement patterns and model predictions. Based on these models we concluded that in temperate regions: (1) when temperature is increasing (from early spring to mid summer) the hatching and settlement periods tend to shorten, while when the temperature is decreasing (during autumn) the hatching and settlement periods tend to lengthen; (2) hatching and settlement peaks are narrower and more intense than a spring spawning peak but wider and less intense than an autumn spawning peak; (3) at lower latitudes, hatching and settlement patterns tend to follow the spawning pattern more closely, (4) the periodic temperature pattern of temperate areas has the potential to cause a convergence of hatching during spring.La duración del desarrollo embrionario y de la etapa planctónica de especies mereoplantónicas depende mucho de la temperatura, por lo que las variaciones estacionales de este parámetro afectan considerablemente a los patrones de eclosión y al asentamiento bentónico. Basándose en datos bibliográficos sobre la duración del desarrollo embrionario y del periodo planctónico del pulpo común, Octopus vulgaris, en relación con la temperatura y en las pautas de temperatura observadas, se han desarrollado varios modelos predictivos de los patrones de eclosión y asentamiento de los alevines. Se observó la existencia de un buen ajuste entre los modelos y los datos de campo referentes al desove y al asentamiento. Según estos modelos, y para las regiones templadas, se concluye que: 1º) cuando aumenta la temperatura (desde principios de la primavera hasta mediados del verano) los periodos de eclosión y asentamiento tienden a reducir su duración, mientras que cuando la temperatura desciende (en otoño) los periodos de eclosión y asentamiento tienden a alargarse; 2º) los picos de eclosión y asentamiento son más estrechos e intensos que el pico de desove en la primavera, pero más anchos y menos intensos en el otoño; 3º) en latitudes inferiores, los patrones de eclosión y asentamiento tienden a ajustarse mejor a las pautas de desove; y 4º) el patrón periódico de la temperatura en áreas templadas tiene capacidad para provocar una convergencia de la eclosión en la primavera.

Crecimiento relativo del cangrejo semiterrestre Pachygrapsus marmoratus: un enfoque a partir de la teoría de la información

The patterns of allometric growth of the grapsid crab Pachygrapsus marmoratus were investigated with an information-theoretic approach. This approach is beneficial, more robust, and may reveal more information than the classical approaches (e.g. hypothesis testing). No differentiation in allometric growth was detected between right and left chelar propods in either sex. Significant sexual differentiation in the allometric growth of chelar propods, abdominal somites and telson was found. It was shown that the allometry of chelar propodus width may be used to identify puberty in males, as there is a marked breakpoint at a carapace width of ~16.0 mm. For females, puberty was identified by the breakpoint in the allometry of the third and fourth abdominal somites at a carapace width of ~16.5 mm. In many cases (e.g. in chelar propods of males, or in most abdominal somites and the telson in females) the classic allometric equation log Y = log a + b log X has no essential support and non-linear allometric models between the log-transformed morphometric characters have to be used.Los patrones de crecimiento alométrico del cangrejo gráspido Pachygrapsus marmoratus, fueron investigados mediante un enfoque a partir de la teoría de la información. Esta aproximación es más robusta, completa, y puede revelar más información que los estudios clásicos (como la comprobación de hipótesis). No se detectó diferenciación en el crecimiento alométrico en los quelípedos derecho e izquierdo en ambos sexos. Sí se halló una diferenciación sexual importante entre el crecimiento alométrico de quelípedos, segmentos abdominales y telson. Se demostró que la alometría del ancho de los quelípedos puede utilizarse para identificar la pubertad en los machos, ya que hay un marcado punto de rotura en una anchura de caparazón de ~16.0 mm. En las hembras, la pubertad se identifica por el punto de rotura en la alometría de los segmentos abdominales tercero y cuarto con un ancho de caparazón de ~16.5 mm. En muchos casos (por ejemplo en los quelípedos de los machos o en la mayoría de los segmentos y el telson en las hembras) la ecuación alométrica clásica log Y = log a + b log X no tiene esencialmente ninguna base y deben utilizarse modelos alométricos no lineales entre los caracteres morfométricos trasformados logarítmicamente

Experimental evaluation of the energy balance in Octopus vulgaris, fed ad libitum on a high-lipid diet

Abstract A complete energy balance equation was estimated for the common octopus Octopus vulgaris at a constant temperature of 20°C, fed ad libitum on anchovy fillet (Engraulis encrasicolus). Energy used for growth and respiration or lost with faeces and excreted ammonia was estimated, along with total energy consumption through food, for six specimens of O. vulgaris (with masses between 114 and 662 g). The energy balance equation was estimated for the specimens at 10-day intervals. During each 10-day interval, food consumed, body mass increase and quantity of faeces voided were measured. The calorific values of octopus flesh, anchovy flesh and faeces were measured by bomb calorimetry. Oxygen consumption and ammonia excretion rates were monitored for each specimen during three 24-h experiments and daily oxygen consumption and ammonia excretion were estimated. It was found that 58% of the energy consumed was used for respiration. The amount of energy invested in somatic and gonadal growth represented 26% of the total energy budget. The energy discarded through faeces was 13% of consumed energy. The estimated assimilation efficiency (AE) values of O. vulgaris feeding on anchovy (80.9-90.7%) were lower than the AE values estimated for other cephalopod species with different diets of lower lipid content such as crabs or mussels. Specific growth rates (SGR) ranged 0.43-0.95 and were similar to those reported for other high-lipid diets (bogue, sardine) and lower than SGR values found for low-lipid, high-protein diets (squid, crab, natural diet). Ammonia excretion peak (6 h after feeding) followed the one of oxygen consumption (1 h after feeding). The values of atomic oxygen-to-nitrogen (O:N) ratio indicated a protein-dominated metabolism for O. vulgaris

Subtidal littering: Indirect effects on soft substratum macrofauna?

Changes in macrofauna community structure, abundance and species richness were examined both before and one year after the deployment of plastic and glass bottles at littered (litter density: 16 items / 100 m2) and non-littered (control) surfaces at three unimpacted coastal areas of the western Saronikos Gulf (Greece). In parallel, LOI% at the adjacent sediments and changes in the composition of feeding types of the megaepifauna that colonized the litter were examined across treatments. Significant changes in macrofauna community structure were demonstrated between before and after littering. At only one of the sites was there detected a significant difference in macrofauna community structure between control and littered plots after littering. This difference was linked with a significant increase in the abundance of opportunistic polychaete species and LOI% levels in the sediment surface due to the entrapment of macrophytal debris within the littered surface. The study did not show a consistent direct response of macroinfauna community to litter and the associated megafauna. Unlike the megafauna attracted by litter items, soft-substratum macrofauna is less responsive to the addition of novel hard substrates in adjacent sediments. Alternatively, it could be that the impact of littering with small items triggers a macrofauna response detectable in the long-run

Effects of convex surface curvature on heat transfer in turbulent flow

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Effects of convex surface curvature on heat transfer in turbulent flow

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Length, weight and condition factor of acartia clausi (copepoda) in the eastern mediterranean

Cephalothorax length and dry weight of copepodite stages and adults of the planktonic copepod Acartia clausi Giesbrecht in the Saronikos Gulf, Greece, were measured. Length-weight relationships and condition factor were also determined. The results were based on 17 zooplankton samples collected between November 1989 and June 1990, a period in which the abundance of A. clausi is significant. There was an inverse relationship between temperature and length, a pattern shown by many copepods. Temperature had the most significant effect on length, which was also affected by chlorophyll level. This strong temporal variation in length might possibly be considered as an adaptation of A. clausi to a continuously fluctuating environment. Length-weight regressions displayed high coefficients of determination (r2=0.98). Food, expressed as chlorophyll, affected the size and condition factor, and could act as a limiting factor on length and weight of A. clausi in the study area. © 1993, Marine Biological Association of the United Kingdom. All rights reserved

Abundance of Octopus vulgaris on soft sediment

Until now the distribution and abundance of Octopus vulgaris had been investigated in the main fishing areas of the species only by fishing surveys. The catching efficiency of fishing gear is variable and depends on several aspects of the animal's behaviour and life history as well as on the type of the gear and the environmental characteristics of the area surveyed. A good alternative for studying the abundance of octopus is by visual census. The population density of O. vulgaris was measured by visual census with scuba diving. The survey was conducted in coastal areas of Greece and on soft sediment. O. vulgaris density ranged from 0 to 6.88 individuals/1000m2 and the mean density values of this study were much higher than those mentioned in other papers. Octopus density was significantly associated with season. Densities of octopuses lower than 500 g were higher in coarse sediments than in finer ones. The density of large octopuses (> 500 g) increased with depth. Octopuses larger than 200 g tended to dwell deeper during the period of intense thermocline than during the nothermocline period