The lakes of Chiloé Island have a high dissolved organic carbon concentration (known as “humic”) and show a connection with brackish water. They also display a high species richness of crustacean zooplankton. The aim of the present study is to characterize the potential factors that explain crustacean species richness in Chiloé Island lakes. To that purpose parameters of the abiotic environment were determined. The results of PCA performed on those data revealed the existence of three lakes with high crustacean species richness that are relatively deep, show high nitrogen concentrations, and are located at relatively high altitude. In contrast, there are two lakes with low species richness, high mineral concentration, and situated at low altitude. One of these lowland lakes gives rise to a river effluent to the sea, and it is connected to the other lake; these observations agree with the results of a performed cluster analysis. Nevertheless, the co-occurrence null model analysis revealed the absence of regulator patterns in species associations, which could be explained to the fact that many of the species occur in most of the lakes. These results are markedly different in comparison to Patagonian lakes of Argentina and Chile that have a low crustacean species number.
Patricio R. De los Ríos Escalante and Fatima Kies
Patricio de los Ríos and Eriko Carreño
The crustacean zooplankton in Chilean coastal lagoons has been poorly studied, and the scarce studies available would indicate the presence of low numbers of species, variable according to the degree of oligotrophy. The aim of the present study was to give a first characterization of crustacean zooplankton communities in a small, shallow coastal lake using Null models, specifically aimed at determining species co-occurrence and niche overlap. The results revealed that species associations are random, which picture originates from the fact that the same species occur many times, while analysis of niche sharing or overlap revealed that there is niche segregation resulting in the absence of competition between species. These results would be similar to earlier observations for mountain lakes and lagoons in northern Patagonia in both Argentina and Chile, and partially similar to the situation in Andean shallow wetlands in northern Chile. More detailed studies will be necessary to fully understand the local population dynamics and overall community dynamics.
Heather Bracken-Grissom, Edith Widder, Sönke Johnsen, Charles Messing and Tamara Frank
Bernd Werding and Alexandra Hiller
A new species of porcellanid crab from the southern Caribbean Sea is described. Pachycheles tuerkayi n. sp. has been confused with P. serratus (Benedict, 1901) since the 1950s because the two species are morphologically and ecologically similar and have overlapping distributions in the southern Caribbean. P. tuerkayi n. sp. is restricted to the coasts of Costa Rica, Panamá and Colombia. P. serratus ranges from Puerto Rico and the Virgin Islands to the coasts of Panamá, Colombia and Venezuela. Genetic differences based on DNA sequences of the mitochondrial 16S rDNA gene from the two species surpassed those estimated for geminate porcellanids on each side of the Isthmus of Panamá. Field observations where P. tuerkayi n. sp. and P. serratus overlap indicated that the two species come into contact when sharing the same substrate. The total number of porcellanid species in the western Atlantic rises to 50.
J. Ohtomi, F. Ahamed, M. Mosaddequr Rahman and H. Fukushima
The pandalid shrimp Plesionika izumiae Omori, 1971 has a wide bathymetric distribution in the coastal waters and the upper continental slope of west Pacific regions. The distribution patterns and population dynamics of P. izumiae were studied in a unique semi-enclosed deep-water bay, Kagoshima Bay, southern Japan, with very steep slopes on both sides. Plesionika izumiae shows a wide spatial distribution in the bay with the majority of the individuals inhabiting the channel area with sediments of almost equal portions of silt and sand, as well as in the bay head with a silty sediment. There were no significant relationships between bottom water temperature or salinity and the distribution patterns of this shrimp, but the sediment characteristics and water depth might appear to influence the distribution patterns of P. izumiae. The distribution patterns with progression of age reveal the dynamics of the P. izumiae population, which was studied by selecting one cohort from each sex and tracing them throughout their life cycle, resulting in similar patterns being shown for both sexes. Juveniles (at the age of 5.7 months) occurred throughout the distribution areas; however, there was a low catch per unit effort (CPUE) even in the main spawning grounds, probably from due to the ongoing recruitment process. The substantial increment in CPUE at the age of 8.4 months throughout the distribution areas likely indicate the stock to be fully recruited by then. A clear shift in CPUE of these cohorts was observed at the ages of 11.6 months and 14.3 months, from the deeper areas towards the shallower areas of the bay, possibly suggesting spawning migration. Individuals approaching their maximum size and longevity were found mostly in the deeper waters. A marked seasonal pattern in CPUE was noted with higher values recorded in summer and lower in winter, which could possibly be related to the life history of the shrimp.
Fahmida Wazed Tina, Mullica Jaroensutasinee, Krisanadej Jaroensutasinee and Anantanit Chumsri
We examined the effects of mudballs around burrows and of sex on burrow characteristics (shape, diameter, length, depth and volume) in an underground mating fiddler crab species, Austruca annulipes (H. Milne Edwards, 1837). We investigated 35 burrows with mudballs (males: 20; females: 15) and 34 burrows without mudballs (males: 16; females: 18), and measured their burrow characteristics. Results showed that burrow characteristics did not differ between burrows with and without mudballs. Males built larger-sized burrows with greater volumes, and had more mudballs than females. Crabs built J-, I-, L-, S- and U-shaped burrows, with higher numbers of J-shaped burrows in males, and higher numbers of I-shaped burrows in females. J-shaped burrows were larger with greater volumes, and had more mudballs than I-shaped burrows. For burrows with mudballs, mudball numbers were positively associated with burrow characteristics. This indicates that fiddler crab burrow characteristics are affected by sex, not by the production and presence of mudballs.
Juan Barile, Manuel Escudero and Patricio De los Ríos-Escalante
Youhui Huang, Ye Liang, Yiming Li, Mingqi Cai, Qichen Jiang, Daming Li, Xianyun Wang and Yunlong Zhao
Cladocerans have been widely used as bioassay organisms to evaluate the impact of toxic substances. In this study, the activities of selected immunological enzymes and MDA level were investigated to characterize Daphnia similoides’ immune response to ammonia stress. The activity of ACP and CAT showed no significant change during the test. The activity of AKP was significantly increased in the 0.19 and 0.38 mg/l NH3-N exposure groups after 6 h. After 24 h, a significant depression occurred in the high concentrations. After 24 h, significant decreases in SOD activity were observed at the concentrations of 0.38, 0.57 and 0.76 mg/l NH3-N. After 24 h, a significant change in MDA was also observed in 0.57 and 0.76 mg/l. These results suggest that changes in whole-body immune parameters of Daphnia similoides are effective to predict sub-lethal ammonia toxicity and useful as an early warning tool in monitoring studies of natural environments.
Xiu Li, Fengying Zhang, Keji Jiang, Weihong Zhao, Ming Zhao, Wei Song and Lingbo Ma
The oriental river prawn, Macrobrachium nipponense, is one of the important commercial shrimp species. Recently a severe problem of precocious maturation has greatly hampered this shrimp aquaculture industry. Bisphenol A (BPA), a high-production-volume chemical substance used in the plastic manufacturing industry, has been thought of as an endocrine disruptor on the developmental processes of animals. In this study, we investigated the effect of BPA exposure on the expressions of five ovary development related genes such as Mago nashi, Tsunagi, Gustavus, Ubc9, and Von Willebrand factor D-Kazal in M. nipponense. Five concentration gradients (5.01, 7.76, 12.06, 18.62 and 28.84 mg/l) of BPA were set and the ovaries of exposed prawns were collected at different time points for expression analysis. Compared with the control group at day 19, BPA had a two-phase effect: a stimulating effect under low concentrations from 5.01 to 12.06 mg/l, whereas a negative effect was noted at high concentrations from 12.06 to 28.84 mg/l. The expression profiles under different BPA concentrations significantly changed along with the extension of exposure time. The medium concentration of BPA (12.06 mg/l) had a persistent influence on the expressions of the transcripts, while the effect was transient under the lowest concentration (5.01 mg/l). It is suggested that the concentration under 5.01 mg/l might be safe for the development of M. nipponense, but exceeding 12.06 mg/l may be harmful. When exposed to clean fresh water without BPA, the gene expressions rebounded a little. This may indicate that the biological damage of BPA was partly reversible after the prawns had been placed in the fresh water without BPA. So the BPA pollutant concentration should be controlled at secure levels in order to ensure safety in aquaculture, in this respect. This study provides fundamental data for the relationship between BPA and precocious maturation of the prawn, and will most probably contribute to the understanding of the sexual maturation process in crustaceans.
Alessandra Augusto, Andressa C. Ramaglia and Paulo V. Mantoan
Climate changes are altering the chemistry of the oceans, and knowing their effects on the biology of animals is urgent. Since the physiological responses of crustaceans may be different given the seasons of the year, this work evaluated the synergistic effect of ocean acidification and seasonality on the physiology of the sea-bob shrimp, Xiphopenaeus kroyeri. Experimental groups were exposed for 5 days to two levels of pH, representing present-day mean ambient conditions (pH 8.0) and distant-future conditions (pH 7.3) during the summer and winter. Metabolism, nitrogen excretion, energy type and storage were determined, respectively, by oxygen consumption, ammonia excretion, atomic ratio O/N and hepatosomatic index. The reduction of pH resulted in a decrease of about 30% in the X. kroyeri metabolism during the summer and winter. Nitrogen excretion (reduction of 40%) and hepatosomatic index (increase of 120%) showed to be altered in animals exposed to reduced pH only throughout summer. Regardless of pH and seasons of the year, animals use mainly proteins as energy substrate and they do not show mortality. The increase of the hepatosomatic index, indicator of the accumulation of energy reserves, associated with metabolism reduction, suggests the suppression of activities that demand energy expenditure. The consequences of the physiological alterations observed may include decreases in growth and reproduction rate and displacement of populations to more appropriate conditions. The results might be associated with a set of factors resulting from the exposure to reduced pH, the synergy between pH and temperature, but also with a pattern of different physiological responses that may occur according to seasonality.