Feeding dynamics of Palaemon peringueyi (Decapoda,Caridea) in the temporarily open/closed Kasouga Estuary,South Africa

The feeding ecology of the caridean shrimp Palaemon peringueyi in the temporarily open/closed Kasouga Estuary, Eastern Cape, was examined during summer and winter employing stomach fullness index (SFI) analysis. Mean SFI values for male and female shrimp during summer ranged from 0.85% to 2.36% and from 0.56% and 2.61% body dry weight, respectively. During winter, SFI values for males and females were lower, and varied between 0.23% and 1.56% and 0.36% and 1.84% body dry weight, respectively. There were no significant differences in the SFI values between males and females during the two seasons. A peak in the feeding activity for both sexes was observed during the daytime during both summer and winter. For both males and females, non-linear regression analysis best explained the change in SFI over time. The gut evacuation rate constants (k) of males and females during summer were estimated at 0.43 h^?1 and 0.30 h^?1, respectively. These values correspond to a daily food intake equivalent to 16.2% body dwt for males and 11.1% body dwt for females. During winter, the gut evacuation rates of the shrimp were estimated at 0.35 h^?1 for males and 0.28 h^?1 for females. The daily ration for adult male and female shrimp during winter was estimated at 6.1% and 6.8% body dwt, respectively. The lower estimates obtained during winter appear largely to reflect the influence of the reduced water temperatures on the metabolic activities of the shrimp.     

Polymorphic microsatellite markers of freshwater prawn Palaemon paucidens (De Haan, 1844) (Crustacea: Palaemonidae)

We report 11 polymorphic microsatellite loci developed from the freshwater prawn Palaemon paucidens. Their genetic characteristics were assessed in 48 individuals selected from six Korean populations. The number of alleles ranged from two to 21, and the observed and expected heterozygosities were between 0.13 and 0.83, and 0.46 and 0.95, respectively. We examined the cross-specific amplification of each locus in three species of palaemonid prawn and one species of atyid prawn.     

Effects of temperature and salinity on the standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi

The standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi to changes in temperature (15-30 °C), salinity (0-45‰) and a combination thereof was investigated. The rate of oxygen consumption of the shrimp was determined using a YSI oxygen meter. At a constant salinity of 35‰ the respiration rate of P. peringueyi increased with an increase in temperature and ranged between 0.260 and 0.982 μl O₂ mg wwt^− 1 h^− 1. The Q₁₀ value over the temperature range 15-25 °C was estimated at 3.13. At a constant temperature of 15 °C the respiration rate of P. peringueyi also increased with an increase in salinity and ranged between 0.231 and 0.860 μl O₂ mg wwt^− 1 h^− 1. For combination experiments the absence of any significant difference in the respiration rate of P. peringueyi at the four temperatures over the salinity range 15-35‰ suggests that the shrimp is well adapted to inhabiting environments characterised by variations in salinity and temperature such as those encountered within the middle and lower reaches of permanently open estuaries with substantial freshwater inflow. On the other hand, the total mortality of the shrimp recorded at salinities < 5‰ at all four temperatures suggests that the upper distribution of the shrimp may reflect physiological constraints. Similarly, the increase in the respiration rate of the shrimp at the four temperatures at salinities > 35‰ suggests that the shrimp may experience osmotic stress in freshwater deprived permanently open and intermittently open estuaries where hypersaline conditions may develop.     

Presence of Palaemon Macrodactylus Rathbun 1902 (Crustacea: Decapoda: Caridea: Palaemonidae) in Mar Del Plata Harbor, Argentina: First Record from Southwestern Atlantic Waters

Adults of the palaemonid prawn Palaemon macrodactylus Rathbun, 1902 were reported for the first time from the southwestern Atlantic waters. Males and ovigerous females were collected in Mar del Plata harbor (38°03′ S; 57°31′ W), Argentina; larvae obtained from one of the collected females were reared in the laboratory until the juvenile stage. The geographical range of P. macrodactylus was previously restricted to the Pacific Ocean: it was originally described in Japan and has been reported as an invasive species in the western coast of USA in the 1950’s and in Australia in the 1970’s. Recently, this prawn has been also reported from European waters.     

Influence d'éclairements brefs, à différentes longeurs d'onde,sur les variations circadiennes des activités enzymatiques digestives chez Palaemon serratus (Crustacea,Natantia)

Abstract

The Influence of Short Periods of Lighting with Different Wavelengths on the Orcadian Changes of the Enzymatic Digestive Activities in Palaemon serratus (Crustacea, Natantia)

The effect of light on the circadian rhythms of digestive activities in the Shrimp Palaemon serratus have been studied.

1. Continuous darkness leads in a few days to a disappearance of the variations of the circadian rhythms of digestive enzymes while these rhythms go on in continuous light.

2. Short (1 or 2 hrs) and low intensity flashes of white light are effective in bringing on the reappearance of rhythmic variations in darkness.

3. We have been able to establish an isoquantic spectrum of action of the light. Two values of wavelength appears to account for a maximum sensibility of the shrimp: one in ultraviolet light and an other one, more important, in the green (λ=544 nm).

4. In green light it is possible to obtain the same effect of light by decreasing the time of stimulation to 5 or 10 mn and in increasing the total quantity of energy. Significant responses are obtained with total energy greater than 10000 pE. cm^‐2.

     

Physiological responses of the early zoeal stages of Palaemon pandaliformis Stimpson and Palaemon northropi (Rankin) to salinity variation

The effect of salinity variation (0, 7, 14, 21, 28 and 35S) on survival, moulting and respiratory metabolism of the early zoeal stages of the shrimps Palaemon pandaliformis and P. northropi from the northern coast of the State of São Paulo, Brazil is investigated. Freshly hatched larvae were maintained at 20 °C, in each salinity for a maximum of seven days. Oxygen consumption measurements were made at 20 °C for each salinity using Cartesian diver microrespirometers. In 0S, all P. northropi zoeae died after 24 h while 24% of the P. pandaliformis zoeae survived until 4 days. Zoeae of both species survived poorly in 7S, the best survival for the two species (90%) being registered in 28%.S. Palaemon northropi zoeae did not survive 35S while 45% survival was recorded for P. pandaliformis zoeae in this medium after seven days. Moulting did not occur in zoeae of either species in 0%.S, nor in P. northropi in 7S. The metabolism-salinity curve for P. pandaliformis zoea I is very stable over the range 0–21S while that for P. northropi exhibits complete salinity independence from 21–35 S. Thus, while the early zoeal stages, at least, are conspecific, both developing in the same environment as part of the coastal zooplankton community, they clearly maintain distinct physiological characteristics. The data presented possibly reflect genetic adaptations to the adult biotope already manifested in the first zoeae.     

杭州湾北部安氏白虾的繁殖生物学特征

采用2017年4月至2018年3月张网逐月采样数据分析杭州湾北部安氏白虾（Palaemon annandalei）的繁殖生物学特征。结果显示,安氏白虾体平均体长（32.0 ± 5.4）mm（14 ~ 51 mm,n = 3 210）,抱卵群体平均体长（36.3 ± 3.4）mm（27 ~ 51 mm,n = 375）。体重分布范围为0.016 ~ 1.700 g,n = 3 210,平均体重（0.565 ± 0.282）g,抱卵群体体重分布范围为0.400 ~ 1.700 g,n = 375,平均体重（0.868 ± 0.225）g。雌、雄个体间平均体长和平均体重都具有显著性差异（P < 0.01）;雌雄性比为1.27︰1,雌性个体数显著多于雄性个体数（P < 0.01）。繁殖期从4月下旬一直持续至10月下旬,6月和8月为两个繁殖旺期,抱卵率（B）和性比（S）具有显著线性相关关系（P < 0.05）,关系式为B = 41.80S﹣21.06（R2 = 73.9）。绝对繁殖力为17 ~ 179粒,平均绝对繁殖力（60 ± 26）粒,平均相对繁殖力（70 ± 24）粒/g,n = 375。绝对繁殖力（FA,单位粒）与体长（L,单位mm）、体重（W,单位g）均呈二次函数显著相关（P < 0.01）,关系式分别为FA = 0.29L2﹣18.52L + 342.67（R2 = 76.8）和FA = 97.32W2 ﹣100.75W + 71.66（R2 = 94.5）。卵长径分布范围为1.090 ~ 2.688 mm,平均长径（1.599 ± 0.158）mm,短径分布范围0.807 ~ 1.992 mm,平均短径（1.141 ± 0.118）mm,n = 2 787。研究表明,与20世纪80年代相比,安氏白虾个体朝小型化方向发展,繁殖周期延长,繁殖旺期由单峰型变为双峰型,这可能是生态环境持续恶化和高强度捕捞压力所致。     

Ecdysteroids and meiotic reinitiation in Palaemon serratus (Crustacea Decapoda Natantia) and in Locusta migratoria (Insecta orthoptera). A comparative study

Summary

Meiotic reinitiation has been studied in Locusta migratoria and Palaemon serratus in relation to the titre of free ecdysteroids present in the maturing oocyte. In both species meiotic reinitiation is characterized by two meiotic arrests, in prophase I and in metaphase I, and the first meiotic resumption which leads to germinal vesicle breakdown (GVBD) is correlated with increasing titres of ecdysteroids in the oocyte. Meiotic reinitiation has been successfully triggered in the oocytes of both species by incubation with physiological doses of ecdysteroids.