Comparative study of gonadal development of Ruditapes philippinarum (Adams and Reeve) and Ruditapes decussatus (L.) (Mollusca: Bivalvia): Influence of temperature

Laboratory experiments were used to study the influence of temperature on the reproductive behaviour of two species of clam, Ruditapes decussatus and Ruditapes philippinarum, during their adaptation to the temperature conditions of Galician coastal waters. In both species the rate of gonadal development was directly related to the increase in temperature. At 14ºC the reproductive behaviour was similar, both species needing over 2 months to mature. At 18ºC, the rate of gonadal development of R. philippinarum was greater than that of R. decussatus. Nevertheless, the results of this study confirm that both species have adapted perfectly to the temperature conditions of the Galician Rias, though certain differences between the reproductive behaviour of these species were detected. R. philippinarum accumulates oocytes prior to their partial or total emission, while in the case of R. decussatus gametes are liberated continuously. In the early phases of its development, the gonad of R. philippinarum is highly heterogeneous in nature, with up to 3 reproductive states being present at the same time, while in R. decussatus gonadal development is much more uniform. Another major difference concerns the phenomenon of reabsorption, common in R. philippinarum but very rare in R. decussatus. These characteristics may well result in a greater reproductive activity in R. philippinarum than in R. decussatus, and a longer reproduction period in the former. They may also represent a certain advantage for the adaptation of the foreign species (R. philippinarum) over the native species (R. decussatus) to the temperature conditions of the Galician Rias.Se llevaron a cabo experiencias de laboratorio para estudiar la influencia de la temperatura en el comportamiento reproductivo de dos especies de almeja, R. philippinarum y R. decussatus, en su adaptación a las condiciones térmicas en las costas de Galicia. En ambas especies la tasa de desarrollo gonadal está directamente relacionada con el incremento de temperatura. A 14ºC el comportamiento reproductivo es similar y ambas especies necesitan cerca de 2 meses para madurar. A 18ºC, la tasa de desarrollo gonadal de R. philippinarum es mayor que en R. decussatus. No obstante, los resultados de este estudio confirman que ambas especies se han adaptado perfectamente a las condiciones térmicas de las rías de Galicia, si bien, se detectan ciertas diferencias en su comportamiento reproductivo. Así, mientras R. philippinarum acumula ovocitos antes de su emisión parcial o total, en el caso e R. decussatus los gametos se liberan continuamente. En las primeras fases de su desarrollo, el aspecto de la gónada de R. philippinarum es muy heterogéneo, presentándose hasta 3 estados reproductivos simultáneamente, mientras que en R. decussatus el desarrollo gonadal es bastante más uniforme. Otra diferencia concierne al fenómeno de la reabsorción, común en R. philippinarum, pero muy raro en R. decussatus. Estas características pueden sustentar una mayor actividad reproductiva en R. philippinarum comparado con R. decussatus, y un mayor periodo reproductivo en el caso de la primera. Ello puede también representar una cierta ventaje adaptativa, de la especie foráneas (R. philippinarum) frente la especie nativa (R. decussatus), a las condiciones térmicas de las rías de Galicia

Comparative study of gonadal development of Ruditapes philippinarum (Adams and Revé) and Ruditapes decussatus (L.) (Mollusca, Bivalvia): Influence of temperature

Laboratory experiments were used to study the influence of temperature on the reproductive behaviour of two species of clam, Ruditapes decussatus and Ruditapes philippinarum, during their adaptation to the temperature conditions of Galician coastal waters. In both species the rate of gonadal development was directly related to the increase in temperature. At 14°C the reproductive behaviour was similar, both species needing over 2 months to mature. At 18°C, the rate of gonadal development of R. philippinarum was greater than that of R. decussatus. Nevertheless, the results of this study confirm that both species have adapted perfectly to the temperature conditions of the Galician Rias, though certain differences between the reproductive behaviour of these species were detected. R. philippinarum accumulates oocytes prior to their partial or total emission, while in the case of R. decussatus gametes are liberated continuously. In the early phases of its development, the gonad of R. philippinarum is highly heterogeneous in nature, with up to 3 reproductive states being present at the same time, while in R. decussatus gonadal development is much more uniform. Another major difference concerns the phenomenon of reabsorption, common in R. philippinarum but very rare in R. decussatus. These characteristics may well result in a greater reproductive activity in R. philippinarum than in R. decussatus, and a longer reproduction period in the former. They may also represent a certain advantage for the adaptation of the foreign species (R. philippinarum) over the native species (R. decussatus) to the temperature conditions of the Galician Rias

Energy balance of mussels Mytilus galloprovincialis: the effect of length and age

Clearance and ingestion rates, absorption efficiencies and respiration rates were measured in mussels Mytilus galloprovincialis Lmk of different lengths (53 to 89 mm) and age (10 to 24 mo) from cultivation rafts in the Ría de Arosa (Galicia, Spain). The experiments were carried out either in the laboratory, using monoalgal food (Isochrysis galbana) with an organic content of 91%, or under natural conditions of food availability in cultivation rafts with seston, the organic content of which ranged from 33 to 69%. Food concentrations ranged from 0.57 to 1.00 mg l-1 of total particulate matter (TPM), a load which is below the threshold for the production of pseudofaeces in Mytilus. These experiments proved that the ingestion rate (IR = mg TPM h-1) of food increases with the size of the mussel (measured as g of soft-tissue dry weight [DW]) according to the power equation IR = 12.661DW0.619, this model accounting for over 90% of the variance of the IR. Behavioural patterns that tended to maintain constant IR regardless of the density of the food were observed. Absorption efficiency (AE) is positively related to the organic content (OC) of the food according to the following hyperbolic equation: AE = 1.015 - 0.163(1/OC) (r = 0.940). AE is independent of mussel size for most of the size range used in this study, but there is a critical length around 85 mm, above which there is a noticeable decrease of AE. Metabolic expenditure, measured in terms of oxygen consumption standarized per unit of dry weight of flesh, tends to increase with the age of the mussel. The results obtained led to the conclusion that physiological traits such as the regulation of ingestion or differences in AE between groups do not explain the differences in growth between mussels of the same age. These differences must therefore be due to the limited food and space available as a result of the large numbers of mussels on the cultivation rafts and the agglomeration of mussels on the cultivation ropes.Versión de editor

Dynamics of biochemical components, lipids classes and energy values on gonadal development of R.philippinarum associated with the temperature and ingestion rate

This study evaluates the effect of temperature, coupled with ingestion rate, on the dynamics of biochemical components and lipid classes in R. philippinarum. The data are discussed with regard to sexual development and energy balance. Experimental protocol developed in the present study used two groups of the clam R. philippinarum: L (temperatures of 14 °C and 18 °C) and H (temperatures of 18 °C and 22 °C). The intra-group ingestion level was similar, although the ingestion level of the clams in the group H was 2.4 times higher than group L. We observed that R. philippinarum conditioned at 18 °C (18L) shows higher protein content, furthermore an important loss of organic weight was observed after 48 days. In such a situation, the clams use their own reserves (carbohydrates and glycogen) for sexual development while in situations without food stress (positive energy balance) and low temperature (14 °C) an accumulation of reserves is produced. Strikingly dissimilar behaviour in biochemical composition was observed for the 18H and 22H treatments, both with a positive energy balance. Despite similar protein content, the highest levels of carbohydrates were observed at the lower temperature (18 °C). Glycogen was also higher for the 18 °C treatment, although the differences were significant only in the males. Although the total lipids in R. philippinarum showed no significant differences in any treatment, they became apparent and related to sex when considering the individual lipid classes. There was no variation in lipid classes in the males between the 14L and 22H treatments despite the large disparity in the degree of sexual development. However, in the females significant differences in lipid classes (phospholipids, triglycerides) were observed. The results of this study show that a positive energy balance permits R. philippinarum gonadal development and accumulation of reserves both in low and high temperature conditions. In low temperature situations, gonadal development is slower and the energy reserves are accumulated in the form of carbohydrates. When the clams are conditioned at high temperatures, gonadal development is fast and complete, carbohydrates are consumed and lipids are accumulated.Publicado

Effects of food rations on gonadal development of the clam Ruditapes decussatus (L., 1758)

Influence of food availability on gonadal development of the clam Ruditapes decussatus (L., 1758) was studied. The clams were exposed to three rations (0.1 %, 0.05 % and 0.026 % of the microalgae Isochrysis galbana clone T-ISO) which, respectively, determined situations of positive, null, and negative energetic balances. The degree of sexual maturity was assessed by studying two nonspecific measurements, the dry weight of flesh variable and the condition index parameter, and two measurements specifically referring to the gonada tissue, gonadal occupation index and oocyte maximum diameter. Individuals reached sexual maturity on all of the rations, although both the rate at which the gametogenic development occurred and the volume of gonad generated were strongly influenced by food availability.Se estudió la influencia de la disponibilidad del alimento sobre el desarrollo gonadal de Ruditapes decussatus (L., 1758), para lo que se experimentaron distintas raciones de alimento de la microalga Isochrysis galbana clone T-ISO: 0,1 %, 0,05 % y 0,025 %, que determinaron situaciones de balance energético positivo, cero y negativo, respectivamente. El grado de madurez sexual se evaluó estudiando dos cuantificadores no específicos: el índice de condición y la variable peso seco de la carne; y otros dos cuantificadores referidos expresamente al tejido gonadal: el índice de ocupación gonadal y el diámetro máximo de ovocitos. Con todas las raciones se alcanzó la maduración sexual, si bien la velocidad con que se produjo el desarrollo gametogénico, así como la cantidad de gónada generada, estuvieron condicionadas por la disponibilidad alimenticia.Instituto Español de Oceanografí

Impact of size and food concentration on clearance and ingestion rates in the clam Ruditapes decussates (Linnaeus, 1758)

The impact of food concentration (C) and water flow on the clearance (TA) and ingestion (TI) rates of the clam Ruditapes decussates (Linnaeus, 1758) was studied, using different-sized specimens. We found no relationship between C and TA, whereas there was a significant relationship between C and TI (TI = 24.757 + 0.576 C). The relationship between TA and the clams' live weight (PV) was also significant (TA = 4.292 PV0.683). A close relationship between PV and TI was found only when food availability (AD), a parameter that includes food concentration and flow, was constant. When it was not, the equation TI = 64.089 + 0.015 PV + 0.546 AD appears to explain 96.1% of TI variability.Se estudia el efecto de la concentración de alimento (C) y el flujo sobre las tasas de aclaramiento (TA) e ingestión (TI) de Ruditapes decussatus (Linnaeus, 1758) con ejemplares de diferentes tamaños. En esta especie no se observa relación entre C y TA, mientras que entre TI y C la relación es significativa: TI = 24,757 + 0,576 C. Igualmente es significativa la relación entre TA y el peso vivo (PV): TA = 4,292 PV0,683. PV y TI guardan una estrecha relación sólo en caso de que el alimento disponible (AD), variable que engloba la concentración de alimento y el flujo, se mantenga constante. En caso contrario, se propone la utilización de la ecuación TI = 64,089 + 0,015 PV + 0,546 AD que explica el 96,1 % de la variabilidad de TI.Instituto Español de OceanografíaVersión de editor

Energy balance of the clam Ruditapes decussatus (Linnaeus, 1758)

The effect of food ingestion and clam size on absorption efficiency, absorption rate and oxygen consumption of the clam Ruditapes decussatus (L., 1758) was studied. Absorption efficiency (AE) was related to the ingestion rate (IR) following the non-lineal equation AE = 0.836 + e-0.64/IR (P 0.01; n = 26; r² = 0.321) No significant relationship as found between AE and clam live weight, whereas there was a relationship between absorption rate (AR) and IR, following the expression AR = 0.8248 IR - 0.0344 (P 0.001; n = 26; r² = 0.964) The maintenance food ration for a 2 g (live weight) clam was estimated as 1.528 J/h, equivalent to a daily food ration of 0.08 mg organic matter/g clam live weight.Se estudia el efecto de la ingestión de alimento y el tamaño de las almejas sobre la eficiencia de absorción, la tasa de absorción y el consumo de oxígeno de Ruditapes decussatus (L., 1758). La eficiencia de absorción (EA) se relaciona con la tasa de ingestión (TI) siguiendo el modelo no lineal EA = 0,836 + e-0,64/TI (P 0,01; n = 26; r² = 0,321) Entre EA y el peso vivo de las almejas no existe una relación significativa, mientras que sí la hay entre la tasa de absorción (TA) y TI, y responde a la ecuación TA = 0,8248 TI - 0,0344 (P 0,001; n = 26; r² = 0,964) La ración de mantenimiento de una almeja de 2 g de peso vivo es de 1,528 J/h, que se corresponde con una dieta diaria de 0,08 mg de materia orgánica por gramo de peso vivo.Instituto Español de Oceanografí

Use of single-cell detritus (SCD) produced from Laminaria saccharina (L.) Lamouroux in feeding Ruditapes decussatus (L., 1758) seed clam

A production technique for single cell detritus (SCD) from Laminaria saccharina (L.) Lamouroux was developed based on the sequential action of two enzymes, endoglucanases and cellulases, and two bacteria isolated in our laboratories: CECT-5255 and CECT-5256, which have high levels of cellobiosic, proteolytic and alginolytic activity. Using this technique, L. saccharina meal is transformed into a suspension of algal cells and detritus of less than 20 m in diameter, which can easily be filtered and digested by bivalve molluscs. A feeding trial carried out with Ruditapes decussatus (L., 1758) seed clams showed that L. saccharina SCD, when used as their sole diet, got 40 % of the seed growth achieved with a microalgal diet (control diet). When the SCD was used in a mixed diet, it could substitute up to 90 % of the microalgae, with comparable or even higher growth rates than exclusive microalgal diets.En este estudio se desarrolla una técnica de producción de biotransformados de Laminaria saccharina (L.) Lamouroux basada en la acción secuencial de enzimas (endoglucanasas y celulasas) y dos bacterias aisladas en laboratorios del Instituto Español de Oceanografía: las cepas códigos CECT-5255 y CECT-5256 de la CECT, que presentan una alta actividad celobiósica, proteolítica y alginolítica. Con dicha técnica, la harina de L. saccharina se transforma en una suspensión de células libres y detritos algales de tamaño inferior a 20 m, perfectamente capturables y digeribles por los moluscos bivalvos. Los diversos ensayos realizados en la alimentación de semilla de la almeja Ruditapes decussatus (L., 1758) ponen de manifiesto que con este biotransformado de L. saccharina, utilizado como único alimento, se obtienen crecimientos de alrededor del 40 % del logrado con fitoplancton. Si se mezcla con fitoplancton, puede sustituir hasta el 90 % del alimento vivo obteniéndose crecimientos equivalentes, incluso superiores, a los de las dietas algales puras.Instituto Español de Oceanografí

Efecto de la restauración post-minería de la comunidad vegetal de matorral xerófilo, en Nuevo León, México

Background and Aims: Restoration strategies promote the recovery of disturbed ecosystems in order to renew their natural structure and function. Our research evaluated the abundance, dominance, frequency, and diversity of species in three areas of Tamaulipan thornscrub.Methods: Two areas were subject to opencast limestone mining over the course of seven years from 2000 to 2006. Restoration techniques were applied in one of the excavated areas, whereas this was not done in other. The third one, an undisturbed area, was used as the reference community. In 2013, we recorded ecological attributes of established plant communities in 36 preselected 100 m2 (10 m × 10 m) sampling sites, 12 per site.Key results: The area without restoration did not register regeneration within the vegetation. Species richness (S), Margalef index (DMg) and Shannon index (H’) showed significant differences (mean values S 4.75 and 8.25, DMg 0.87 and 1.80, H’ 0.7 and 1.54, respectively) between the restored and reference area while the variables of density, crown area, and Pretzsch index (A) were similar.Conclusions: Based on the similarity in the density and crown area with a reference area, we conclude that active restoration techniques, involving deposition of rock and soil materials and exclusion of industrial activities, generate favorable conditions for the reestablishment of vegetation communities in Tamaulipan thornscrub in seven years.Antecedentes y Objetivos: Las estrategias de restauración tienen como objetivo favorecer la recuperación de los ecosistemas alterados, para lograr el restablecimiento de su estructura y funcionamiento naturales. La presente investigación evaluó la abundancia, dominancia, frecuencia y diversidad de especies en tres áreas de matorral espinoso tamaulipeco.Métodos: Dos áreas fueron sometidas durante siete años (2000-2006) a procesos de aprovechamiento a cielo abierto. A una se le aplicaron técnicas de restauración y a la otra no, y se compararon con un área en la que no se tiene perturbación registrada llamada área referencia. En el año 2013 se establecieron 36 sitios de muestreo, 12 por cada una de las áreas cuyas dimensiones fueron de 100 m2 (10 × 10 m), en las que se registraron los atributos ecológicos de las comunidades vegetales establecidas.Resultados clave: En el área sin restaurar no se registró regeneración de la comunidad vegetal. La riqueza específica (S), índice de Margalef (DMg) e índice de Shannon (H´) mostraron diferencias significativas entre el área restaurada y la de referencia (Valores medios S 4.75 y 8.25, DMg 0.87 y 1.80, H´ 0.7 y 1.54, respectivamente), mientras que las variables de densidad, área de copa e índice de Pretzsch (A) no mostraron diferencias.Conclusiones: Se concluye que la técnica de restauración activa, la cual consiste en el depósito de material rocoso y edáfico en el área, y su exclusión de actividades productivas, generan condiciones favorables para que la comunidad vegetal del matorral espinoso tamaulipeco se establezca teniendo similitud en la densidad y área de copa a un área de referencia en siete años

Estructura y diversidad del matorral submontano contiguo al área metropolitana de Monterrey, Nuevo León, México

In this study the structure and diversity of the piedmont scrub that abuts the western portion of the metropolitan area of Monterrey, Mexico, were examined. Vegetation composition and diversity were assessed by sampling vegetation in 41 plots of 100 m2 each. All trees and shrubs with a basal diameter (d0.10) ≥0.5 cm were counted, including succulents. In addition, the crown diameter (dcrown) for each species was recorded. Species richness was assessed by means of the Margalef index (DMg), while Shannon’s index (H’) was used to assess species diversity. A total of 45 species, 39 genera and 18 families were recorded. Fabaceae was the most important family with the highest species richness (12), followed by Cactaceae (5), Euphorbiacae, Rhamnaceae, Rutaceae and Verbenaceae (3); these families accounted for 64.44% of the entire flora recorded in the area. As for dominance (Dr), Fabaceae, Rutaceae, Asteraceae and Verbenaceae accounted for 64.08% of the Importance Value Index (IVI) in the community. The scrub presented a density of 3629 ind./ha-1 and a total crown cover of 6629 m2/ha-1. Acacia amentacea and Zanthoxylum fagara were the most important species, since they accounted for 25.87% of the IVI values in the locality. The rank/abundance curve for species fitted best to a log-normal function, which is characteristic of mature communities. The present study shows that the studied community is characterized by a high diversity and species richness in comparison to other arid and semi-arid climate vegetation in Northeast Mexico. Structural and diversity attributes documented in this study indicated that the piedmont scrub neighboring Monterrey is a well-preserved community in a mature successional stage; hence, it is urgent to develop strategies aimed at its conservation.En este estudio se evaluaron la estructura y la diversidad del matorral submontano limítrofe con la porción occidental del área metropolitana de Monterrey, México. Se determinó la composición y la diversidad de la vegetación mediante el establecimiento de 41 parcelas de 100 m2 cada una. Se censaron todos los árboles y arbustos con un diámetro basal (d0.10) ≥0.5 cm, incluyendo a las plantas suculentas; además, se midió el diámetro de copa (dcopa), para cada especie. Se calcularon los índices de Margalef (DMg) y de Shannon (H´) para determinar la riqueza y la diversidad de especies, respectivamente. Se registraron 45 especies, 39 géneros y 18 familias. La familia Fabaceae fue la que presentó más taxones (12), seguida de Cactaceae (5), Euphorbiacae, Rhamnaceae, Rutaceae y Verbenaceae (3), las cuales constituyen en conjunto 64.44% de la flora registrada para la zona de estudio. En cuanto a la dominancia (Dr); las Fabaceae, Rutaceae, Asteraceae y Verbenaceae sumaron 64.08% de los valores del Índice de Valor de Importancia (IVI) en la comunidad. Este matorral presenta una densidad de 3629 ind./ha-1 y una cobertura de copas de 6629 m2/ha-1. Acacia amentacea y Zanthoxylum fagara fueron las más importantes al acumular entre ellas 25.87% de los valores del IVI en la localidad. La curva de rango/abundancia de especies se ajustó a una función log-normal, característica de la vegetación madura. La comunidad estudiada presenta una alta diversidad y riqueza de especies en comparación con otras asociaciones vegetales de climas áridos y semiáridos del noreste de México. Los atributos de estructura y diversidad documentados en este estudio indican que el matorral submontano contiguo a la ciudad de Monterrey está bien conservado y en una fase de sucesión madura, por lo que es urgente proponer estrategias para su conservación