Xavier Chiappa-Carrara

Physiological and Biochemical Variations During the Molt Cycle in Juvenile Litopenaeus Vannamei under Laboratory Conditions

Abstract Biochemical changes, specifically in hemocyanin and glucose concentrations in hemolymph, glycogen in the digestive gland, were studied throughout the molt cycle in juveniles of Litopenaeus vannamei in a high salinity condition (36), and related to variations in the osmotic capacity of organisms. Increasing hemolymph volume before molting modifies circulating glucose and hemocyanin concentrations acting on the osmotic capacity. Variations in glucose concentrations are indicators of differential energy requirements throughout the molt cycle. Hemocyanin was used as an indirect indicator of the energy consumed by shrimp in various molt processes that affect the osmotic capacity. The co-variability of these metabolites is the result of the biochemical adaptations displayed by shrimp to maintain homeostasis. Their relation to changes in the osmotic capacity is given as a model to understand and predict events associated with molting under hypo-osmotic conditions.

Physiological and Biochemical Changes of Wild and Cultivated Juvenile Pink Shrimp Farfantepenaeus Duorarum (Crustacea: Penaeidae) During Molt Cycle

ABSTRACT Changes in metabolite levels in hemolymph and hepatopancreas were used as indicators of physiological status of juvenile wild and cultivated Farfantepenaeus duorarum (Burkenroad, 1939), during hyper-osmoregulatory conditions (salinity 22 ppt, 726 mOsm/kg). We analyzed the relationship between biochemical changes of wild and cultivated shrimp at different molt stages by measurement of osmotic capacity, hemocyanin, acylglycerides, cholesterol, glucose, glycogen and total protein. Biochemical analyses of hemolymph (blood) and hepatopancreas showed a decreasing trend in stages closer to molt and an increasing trend before intermolt. Osmotic capacity and blood proteins indicated a significant effect of the molt stage. Stages A, D1′ and D1′″ showed the greatest effect on the biochemical variables. Higher hemocyanin, cholesterol and glycogen concentrations were observed in wild shrimp than in cultivated shrimp. The effect of the molt cycle was associated with changes in cyclic ions and water balance that produced chemical changes in the hemolymph in both wild and cultivated.

Size-selective foraging behaviour of blue crabs, Callinectes sapidus (Rathbun), when feeding on mobile prey: Active and passive components of predation

Size-selective predation by small (30-50 mm carapace width) and large (90-110 mm) Callinectes sapidus when feeding on three different size classes of Litopenaeus setiferus was investigated. Laboratory experiments using no-choice and multiple-choice designs were carried out. Active and passive components of predation were evaluated by comparing the probability of attacking (active) and capturing (passive) shrimp. Small C. sapidus consumed shrimp of all size classes in similar frequencies during multiple and no-choice experiments, and the probability of attacking and capturing shrimp of all size classes was similar. Large crabs consumed large shrimp with a significantly higher frequency during multiple than during no-choice experiments, and the probability of capturing large shrimp was significantly higher than medium and small ones. Results in the present study suggest that size-specific consumption rates of C. sapidus are mainly the result of a passive mechanism associated with the salience of shrimp to predation. However, an active component of foraging behaviour related to the decision to attack an alternative prey whilst consuming one that has already been captured, helps to explain the differences in shrimp consumption between multiple and no-choice experiments. The complex interaction between active, passive components and satiation is discussed.

Seasonal Variability in Trypsin and α-Amylase Activities Caused by the Molting Cycle and Feeding Habits of Juvenile Pink Shrimp Farfantepenaeus duorarum (Burkenroad, 1939)

ABSTRACT In view of the relationship between shifts in diet composition and the activity of digestive enzymes in penaeid shrimp, the present study focused on the analysis of digestive trypsin and &agr;-amylase activities of wild Farfantepenaeus duorarum (Burkenroad, 1939) juveniles and their changes in phenotypic expression, during the molt cycle as endogenous factor and their changes due to different feeding regimes (exogenous factor) in relation with &dgr;13C and &dgr;15N isotopic signature as an index of food assimilation induced by the seasonal availability of food items in the nursery area. Wild juveniles of F. duorarum were captured from April 2007 to February 2008, in the Celestun coastal lagoon, Yucatan, Mexico. Samplings were carried out considering all quarters of the lunar cycle and in each of the recognized seasons for this region: dry, rainy, and the Nortes (North Wind). Copepods and amphipods were the main source of food for juveniles of F. duorarum. Values of &dgr;13C in the muscular tissue were near -20‰ hence the feeding regime of F. duorarum in the lagoon was composed by material of marine origin. Isotopic signature differences were found between the three annual seasons. It is an opportunist generalist organism that is located in the 4th trophic level. The digestive enzymatic activities of both trypsin and &agr;-amylase in fresh hepatopancreas tissue showed an interaction between season and molt stages (p < 0.05). Activity of the trypsin was highest during the Nortes at molt stage C (140 mU mg-1 HP) and activity of &agr;-amylase was higher in the Nortes at stage B2 (674 mU mg-1 HP). The amylase/trypsin ratio also showed significant interaction between season and molt stages (p < 0.05), with higher values in premolt stages during the rainy and Nortes seasons. Isoforms of these digestive enzymes differed in expression according to the molt stage and also to the season with expression generally being greater at stage C.

Poblana alchichica: A threatened silverside species?

The status of local endemic species such as Poblana alchichica is difficult to assess, and therefore conservation measures are not efficiently implemented. However, in recent years several methods have helped compare status of different species based on objective criteria. The method to evaluate the extinction risk of Mexican native species (MER), partially based on Gardenfors et al. (2001), considers 4 criteria regarding the taxon: (1) distribution extent in Mexico, (2) habitat condition, (3) intrinsic biological vulnerability, and (4) human impact on the species. Numerical values are assigned to each criterion in ascending risk order. According to Tambutti et al. (2002), each criterion is independent from the others, and the addition comes to be an accumulative evaluation of risk (SEMARNAT 2002). Even if independently evaluating criteria 2 and 4 is difficult, the grade of each criterion is required to obtain the final assessment. The lack of studies on P. alchichica (Pisces: Atherinidae) – and quite probably for many other species – prevents the accurate quantification of 3 of these 4 criteria (except distribution extent) required for the extinction risk assignation. Previous studies on P. alchichica (Fig. 1) are solely taxonomic. De Buen (1945) described the new silverside species collected from Lake Alchichica. Later, Alvarez (1950) and Guerra Magana (1986) considered Alchichica’s silverside to be a subspecies (P. alchichica alchichica). However, Miller (1986), in his study on the origin and geography of the fishes of Central Mexico, and Espinosa et al. (1993), in their list of Mexican freshwater fishes, re-evaluated the specific status of P. alchichica. Our study aimed to provide scientific data to support (a) the actual risk status of P. alchichica by identifying the factors imposing risk to the species through habitat alteration and population status, and (b) to design adequate protection programs for this species.

Threatened fishes of the world: Poblana alchichica (de Buen, 1945) (Atheriniformes: Atherinopsidae)

Common names: Alchichica silverside (English), charal de Alchichica (Spanish). Conservation status: Endangered, NOM-059-ECOL-2001 (SEMARNAT 2002); and critically endangered (CR) (A1ac+2c, B1+2c, C2b) (IUCN 2008). Identification: D 4–5; A 13–15; P 14–15. Gill rakers on the first gill arch, 13–16. Scales 45–56 in a longitudinal series, commonly >50 (De Buen 1945). Size 50–60 mm (SL), maximum 11.5 mm (SL). Abundance: Alcocer et al. (2009) and Arce Uribe (2006) estimated the population abundance between 16, 000 and 21, 000 organisms >1 cm in length. Distribution: Endemic to Lake Alchichica, Puebla, Mexico (19° 24′ N, 97° 24′ W, 2345 m asl) (Alcocer et al. 2009). Habitat and ecology: Lentic, saline (8.5±0.2 g·L) and alkaline (pH=9.0±0.1) water. Inhabits temperate (15.9±1.5°C), well oxygenated (>4 mg·L), clear (euphotic zone 13– 38 m), and oligotrophic water (Adame et al. 2008). Reproduction: Iteroparous, from February to April, and July to September, with a spawning peak in March. The fish spawns entangling eggs with numerous chorionic filaments that adhere to the submersed macrophytes and on the tufa deposits. Feeding: Feeds mainly on benthic macroinvertebrates (chironomid larvae and amphipods). Preys vary according to the seasonal patterns of stratification of Lake Alchichica (Flores Negrete 1998). Threats: The very limited distribution puts the population at risk for rapid or Environ Biol Fish (2009) 85:317–318 DOI 10.1007/s10641-009-9505-4

Variations in the feeding habits of Callinectes rathbunae in Las Palmas lagoon (southern Gulf of Mexico) on three temporal scales

Las Palmas lagoon is a part of the hydrographic system of Pom-Atasta-Puerto Rico, NE of Laguna de Terminos, southern Gulf of Mexico. Swimming crabs of the genus Callinectes abound in this area and play an important role in the complex trophic dynamics of the macrobenthos. We analysed the feeding habits of Callinectes rathbunae and its variations on three temporal scales. Sampling was carried out from August 1999 through July 2000, both on a monthly basis (9:00-13:00 h) at new moon, and for each season (every 6 h during 24 h) with a small shrimp trawl net. Samples of epiand infauna were simultaneously taken. The stomachs of all C. rathbunae collected were dissected and the dietary components identified to the lowest taxonomic level possible. Percentage frequency of occurrence (%F) of each taxon was calculated, together with the normalized Levins index (Ba) for each (a) season, (b) size class (20 mm intervals), and (c) day- and night-time period in each season. While the trophic niche breadth of this species does not vary significantly with season, crab size, or time of day, diet components differed among seasons and crab size classes. Results indicate that ontogenic differences in the feeding strategies of this species contribute most importantly to overall variations in diet. La laguna de Las Palmas forma parte del sistema hidrografico Pom-Atasta-Puerto Rico, ubicado al NE de Laguna de Terminos, en el sur del Golfo de Mexico. Las jaibas del genero Callinectes son abundantes en esta zona, y juegan un papel preponderante en la compleja dinamica trofica del macrobenthos. Se analizaron los habitos alimenticios de Callinectes rathbunae, y sus variaciones en tres escalas temporales. Se realizaron muestreos mensuales de agosto 1999 a julio 2000 (9:00-13:00 h en luna nueva), y estacionales (cada 6 h durante 24 h), utilizando una red de prueba camaronera. Simultaneamente, se tomaron muestras de la epi y meiofauna. Los estomagos de todos los C. rathbunae capturados fueron disecados, y se identificaron los componentes del contenido estomacal hasta grupos taxonomicos mayores. Se calcularon los valores de porcentaje de frecuencia de ocurrencia (%F) de cada componente, asi como los valores de del indice normalizado de Levins (Ba) por (a) epocas del ano, (b) por intervalo de talla (20 mm), y (c) para el dia y la noche en cada epoca del ano. En tanto que la amplitud del nicho trofico no vario significativamente entre epocas del ano, talla u hora del dia, se registraron diferencias en los componentes de la dieta a lo largo del ano y entre jaibas de diferente tamano. Los resultados indican que las diferencias ontogenicas en las estrategias alimenticias de esta especie contribuyen de manera importante en la variacion general de la dieta.

Pacific Coast of Mexico

Abstract The Pacific coast of Mexico has 68% of the country’s coastline. It comprises several distinct ecoregions and a wide variety of habitats, a great diversity of coastal types and marine diversity, and several endemic or flagship species that live there permanently or transiently. This natural richness offers many opportunities for development and also provides a great challenge for conservation, since the influence of events acting at different scales, including global warming, urban population growth, industrial development, contamination, and overfishing, is evident clearly. The increasing economic activities enhance population growth in some coastal municipalities. Growing urban areas require new resources, magnifying pressures on the environment that manifest themselves through habitat destruction, greater waste production, and soaring pollution. The coasts of the Mexican Pacific are environments vulnerable not only to a variety of natural phenomena but to human activities whose catastrophic effects on natural communities are unequivocally obvious. This review shows that the Mexican Pacific is a region with serious sustainability challenges. A prominent need is to prioritize factors promoting wellness; previously economic growth has been the main and almost only driver without taking into consideration environmental conservations. The need is for diversifying activities that trigger economic growth, reduce socioeconomic inequality, modernize the infrastructure, and improve public security. At the same time, actions to protect critical socio-ecosystems, with the services that they provide, and to conserve the unique biological diversity they support, must be implemented to address the complex challenges that this region of the world is experiencing.

Estimating geographic patterns of ophidism risk in Ecuador

Abstract The species richness of venomous snakes in Ecuador (~39 species) is among the highest in the world. However, until now no information exists regarding geographic patterns of ophidism. In this study, we present a detailed spatial snakebite risk map which was built by stacking weighted ecological niche models of the 19 snake species responsible for the majority of Ecuador’s envenomation cases. Our weights were based on the proportion of cases reported for each species on local epidemiological studies. Based on our analyses, we identify 184 densely populated rural communities with high snakebite risk that should be monitored by health organizations. We also identified three densely populated rural locations (Palora Metzera, Sangay and Shell) that may require special attention because they had much higher snakebite risk values than the rest.

Wetland plant species improve performance when inoculated with arbuscular mycorrhizal fungi: a meta-analysis of experimental pot studies

The presence of arbuscular mycorrhizal fungi (AMF) in wetlands is widespread. Wetlands are transition ecosystems between aquatic and terrestrial systems, where shallow water stands or moves over the land surface. The presence of AMF in wetlands suggests that they are ecologically significant; however, their function is not yet clearly understood. With the aim of determining the overall magnitude and direction of AMF effect on wetland plants associated with them in pot assays, we conducted a meta-analysis of data extracted from 48 published studies. The AMF effect on their wetland hosts was estimated through different plant attributes reported in the studies including nutrient acquisition, photosynthetic activity, biomass production, and saline stress reduction. As the common metric, we calculated the standardized unbiased mean difference (Hedges’ d) of wetland plant performance attributes in AMF-inoculated plants versus non-AMF-inoculated plants. Also, we examined a series of moderator variables regarding symbiont identity and experimental procedures that could influence the magnitude and direction of an AMF effect. Response patterns indicate that wetland plants significantly benefit from their association with AMF, even under flooded conditions. The beneficial AMF effect differed in magnitude depending on the plant attribute selected to estimate it in the published studies. The nature of these benefits depends on the identity of the host plant, phosphorus addition, and water availability in the soil where both symbionts develop. Our meta-analysis synthetizes the relationship of AMF with wetland plants in pot assays and suggests that AMF may be of comparable importance to wetland plants as to terrestrial plants.