Reproductive Cycle of Nassarius Reticulatus in the Ria De Aveiro, Portugal: Implications for Imposex Studies

1998 ◽  
Vol 78 (4) ◽  
pp. 1233-1246 ◽  
Author(s):  
C.M. Barroso ◽  
M.H. Moreira
Keyword(s):  
Water Temperature ◽  
Reproductive Cycle ◽  
Seasonal Pattern ◽  
Shell Height ◽  
Ria De Aveiro ◽  
North West ◽  
The North ◽  
Nassarius Reticulatus ◽  
Clear Seasonal Pattern ◽  
Penis Length

The reproductive cycle of Nassarius (Hinia) reticulatus was investigated in the Ria de Aveiro on the north-west Portuguese coast during 1992 and 1993. A clear seasonal pattern was observed with the beginning of gametogenesis in August followed by ripening of the gonads in January and February and spawning from February to July. The increase of water temperature above 11°C in February 1993 was associated presumably with the release of gametes. Recruitment inside the Ria of juveniles with 6·5 mm mean shell height was detected in February 1993 and these individuals were spawned in the previous year. Males of N. reticulatus exhibited a considerable variation in length of the penis throughout the reproductive cycle. The accuracy of the use of relative penis length (RPL) index for intersite comparisons of imposex is discussed and the magnitude of the error that might be involved when comparisons are made using populations in different phases of the reproductive cycle is evaluated.

Age and growth of Nassarius reticulatus in the Ria de Aveiro, north-west Portugal

2005 ◽  
Vol 85 (1) ◽  
pp. 151-156 ◽  
Author(s):  
C.M. Barroso ◽  
M.H. Moreira ◽  
C.A. Richardson
Keyword(s):  
Shell Growth ◽  
Shell Height ◽  
Temporal Analysis ◽  
Age And Growth ◽  
Frequency Distributions ◽  
Ria De Aveiro ◽  
North West ◽  
Nassarius Reticulatus ◽  
Average Size ◽  
Age Estimates

Shell growth of the whelk Nassarius (=Hinia) reticulatus was studied in the Ria de Aveiro (north-west Portugal) between 1995 and 1998. Temporal analysis of shell height frequency distributions demonstrated that growth occurs during the first five years of life, whelks attaining a size of 6·7–7·8 mm in the 1st year, 12·1–14·5 mm in the 2nd year, 18–19·5 mm in the 3rd year, 22·7–23·6 mm in the 4th year and by the 5th year males have achieved an average size of ∼25 mm whilst females have reached ∼27 mm. Age estimates from internal microscopic annual growth lines present in the shell lip suggest that large whelks may achieve a longevity of at least 11 years. External annual rings become less discernible as the whelks increase in size and estimates of their age based solely on ring counts can underestimate their age. In males sexual maturation is reached between the 3rd and 4th years whilst in females it is attained between the 4th and 5th years. Imposex was visible in ∼2 year old females and attained maximum development by the 5th year.

Growth, reproductive cycle and penis shedding of Littorina littorea in the Ria de Aveiro (north-west Portugal)

2007 ◽  
Vol 87 (2) ◽  
pp. 547-550 ◽  
Author(s):  
C.M. Barroso ◽  
C. Gonçalves ◽  
M.H. Moreira
Keyword(s):  
Breeding Season ◽  
Reproductive Cycle ◽  
Species Distribution ◽  
Shell Height ◽  
Littorina Littorea ◽  
Von Bertalanffy ◽  
Southern Limit ◽  
Ria De Aveiro ◽  
North West ◽  
Distribution In Europe

The growth and the reproductive cycle of Littorina littorea were investigated in the Ria de Aveiro, Portugal, a country cited as the southern limit of the species distribution in Europe. Littorina littorea growth is well represented by the von Bertalanffy equation SH=24.6[1-e-0.69(t-0.70)] where SH is the shell height (distance from shell apex to the basis of the aperture measured in mm) and t is the number of winters: after periwinkles have reached a mean SH of 4.6 mm in their first winter they grow progressively to about 14.6 mm, 19.6 mm, 22.1 mm and 23.4 mm in the following four years and they attain the asymptotic mean maximum SH of 24.6 mm at the tenth year if they survive. Ripening of the gonads occurred from October to May but was more intense from December to February, whereas spawning extended from January to May in females and November to May in males. There was a seasonal shedding of the male penis at the end of the breeding season (summer) accompanying regression of the testis.

Seasonal Migration Patterns of Postlarval and Juvenile Banana Prawns, Penaeus merguiensis de Man, in the Major Rivers of the Gulf of Carpentaria, Australia

1979 ◽  
Vol 30 (2) ◽  
pp. 143 ◽  
Author(s):  
DJ Staples
Keyword(s):  
Seasonal Pattern ◽  
Temporal Distribution ◽  
Major Change ◽  
Seasonal Migration ◽  
Geographical Differences ◽  
Monsoon Period ◽  
Migration Patterns ◽  
North West ◽  
The North ◽  
Two Generations

Samples of juvenile P. merguiensis taken from 20 major rivers around the Gulf of Carpentaria from 1970 to 1973 showed that the Gulf could be divided into four major areas, each characterized by its own seasonal pattern of postlarval immigration and emigration of juveniles. The main nursery areas for the Gulf, however, are the rivers along the east and south-east coasts (Cape Keerweer to Mornington Island) and the majority of prawns migrate from these rivers during the north-west monsoon period (November to February); the main recruitment into the commercial fishery, there- fore, occurs during a relatively confined period each year. Additional sampling in 1976-77 showed that although there have been recent changes in the temporal distribution of adult prawns as a result of increased fishing pressure, no major change in the temporal pattern of postlarval immigration has resulted. An hypothesis is presented in which the observed geographical differences in the seasonal migration patterns are explained with reference to a basic pattern involving two generations of P. merguiensis each year.

scholarly journals Limnological variations of a deep reservoir in periods with distinct rainfall patterns

2013 ◽  
Vol 24 (4) ◽  
pp. 417-426 ◽  
Author(s):  
Ana Maria Geraldes ◽  
Catherine George
Keyword(s):  
Water Temperature ◽  
Total Phosphorus ◽  
Rainfall Intensity ◽  
Seasonal Pattern ◽  
Environmental Parameters ◽  
Early Summer ◽  
Zooplankton Abundance ◽  
Daphnia Longispina ◽  
Wide Range ◽  
Clear Seasonal Pattern

AIM: This study intends to provide information on how precipitation variation may impact environmental parameters (total phosphorus, water temperature, pH, conductivity, dissolved oxygen, Secchi depth, chlorophyll a and Anabaena abundance) and crustacean zooplankton composition and abundance. METHODS: Samples were collected monthly from October 2000 to September 2002 and from October 2007 to September 2009 at one single sampling station located at the deepest point of the reservoir. All data were obtained in the euphotic zone. RESULTS: The highest values of total phosphorous concentrations were reported together with the maximal values of precipitation. Conversely, conductivity decreased during the wet periods. Anabaena presence was only detected between September and December 2001. Daphnia longispina total abundance showed large inter-annual differences. A clear seasonal pattern was inferred for Diaphanosoma brachyurum and Ceriodaphnia pulchella. Both species are thermophilic and begin to be detected in early summer when the water temperature is around 15 ºC. Copidodiaptomus numidicus abundance did not present a clear seasonal pattern. CONCLUSIONS: Some of the observed shifts in environmental parameters (Conductivity, total phosphorus concentrations and Anabaena abundance) resulting in changes in zooplankton abundance are induced by rainfall variation. The most affected species were those with a lack of seasonality (C. numidicus) or species occurring mainly in winter/early summer (Daphnia longispina). However, a wide range of physical, chemical and biotic interactions is likely to influence zooplankton abundance. Therefore, caution is advised when relating the observed variation exclusively with rainfall intensity. In fact, some of the observed shifts were induced by other factors varying subtly in a seasonal or inter-annual pattern, independently of rainfall intensity.

Pronounced seasonal rhythms in plasma somatolactin levels in rainbow trout

1995 ◽  
Vol 146 (1) ◽  
pp. 113-119 ◽  
Author(s):  
M Rand-Weaver ◽  
T G Pottinger ◽  
J P Sumpter
Keyword(s):  
Rainbow Trout ◽  
Water Temperature ◽  
Seasonal Pattern ◽  
Seasonal Cycles ◽  
Plasma Prolactin ◽  
Female Fish ◽  
North West ◽  
Age Related ◽  
Circulating Levels ◽  
Immature Fish

Abstract The aim of this study was to establish whether there are seasonal or age-related changes in circulating levels of somatolactin (SL) in rainbow trout (Onchorhynchus mykiss). SL levels were determined in blood sampled at monthly intervals over a 2-year period from a population of rainbow trout maintained under a natural daylength and temperature regime (North-West England, latitude 54°20′ N). SL levels displayed a distinct circannual cycle, with peak levels in summer (17–20 μg/l) and lowest levels occurring in winter (0·2–2 μg/l). This variation in SL levels was closely correlated with water temperature (P<0·001) but was out of phase with changes in daylength. Plasma SL levels were significantly higher in both mature male and female fish compared with immature fish. Plasma prolactin levels were determined to provide information on a hormone structurally related to SL, and also because mammalian prolactin is known to show distinct seasonal cycles. However, trout prolactin, in contrast to SL, did not show a pronounced seasonal pattern, although prolactin levels were significantly, but inversely, correlated with water temperature (P<0·001). Journal of Endocrinology (1995) 146, 113–119

scholarly journals Effect of precipitation on seasonal variability in cryptosporidiosis recorded by the North West England surveillance system in 1990–1999

2005 ◽  
Vol 3 (2) ◽  
pp. 185-196 ◽  
Author(s):  
Elena N. Naumova ◽  
John Christodouleas ◽  
Paul R. Hunter ◽  
Qutub Syed
Keyword(s):  
Spatial Variability ◽  
Seasonal Pattern ◽  
North West ◽  
Multiple Exposures ◽  
The North ◽  
West Region ◽  
Health Authorities ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial

The goal of this study was to examine temporal and spatial variability of reported cryptosporidiosis in 15 health authorities in the North West of England using regression modelling. We also examined the role of precipitation as a driving factor for seasonal variation. We separated the time series of the reported cryptosporidiosis into two processes: an endemic process and an epidemic process, and examined the spatial variability of each of these processes. In the North West region of England we observed a strong seasonal pattern that consists of two waves, spring and autumn, during which the weekly rates exceeded the endemic level 3.5 and 3 times, respectively. Health authorities with the high endemic cryptosporidiosis incidence and well-pronounced seasonal patterns exhibited a significant increase in rates of cryptosporidiosis associated with increased precipitation. The endemic level and the magnitude of epidemic peaks were inversely related, which might be indicative of multiple exposures to the pathogen in these localities and the development of some partial immunity.

scholarly journals Seasonal and sex-related variations in serum steroid hormone levels in wild and farmed brown trout Salmo trutta L. in the north-west of Spain

2013 ◽  
Vol 11 (4) ◽  
pp. 720-728 ◽  
Author(s):  
Juan M. Fregeneda-Grandes ◽  
Salvador Hernández-Navarro ◽  
Ignacio A. Fernandez-Coppel ◽  
Adriana Correa-Guimaraes ◽  
Norlan Ruíz-Potosme ◽  
...  
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Seasonal Pattern ◽  
Serum Cortisol ◽  
Mature Female ◽  
North West ◽  
The North ◽  
Steroid Profiles ◽  
Brown Trout Salmo Trutta ◽  
Wild Trout

Serum steroid profiles were investigated in order to evaluate the potential use of circulating sex steroid levels as a tool for sex identification in brown trout. Changes in the serum concentrations of testosterone (T), progesterone (P), 17-β-estradiol (E2), and cortisol (F) in wild and farmed mature female and male brown trout, Salmo trutta L., were measured in each season (January, May, July, and October) in six rivers and four hatcheries located in the north-west of Spain. Serum cortisol levels in farmed brown trout were significantly higher and showed a seasonal pattern opposite to that found in wild trout. Because levels of the hormones under study can be affected by disruptive factors such as exposure to phytoestrogens (which alters the hypothalamic–pituitary–gonadal axis) and infection with Saprolegnia parasitica (which alters the hypothalamic–pituitary–adrenal axis), both factors are taken into account.

SEM and TEM observations of sperm development in the testis of the freshwater fish Oreochromis mossambicus

1990 ◽  
Vol 48 (3) ◽  
pp. 58-59
Author(s):  
Daryl A. Cornish ◽  
George L. Smit
Keyword(s):  
Morphological Characteristics ◽  
Oreochromis Mossambicus ◽  
Breeding Cycle ◽  
Limited Information ◽  
North West ◽  
The North ◽  
Sem And Tem ◽  
Sperm Development ◽  
Ultrastructural Characteristics ◽  
The University

Oreochromis mossambicus is currently receiving much attention as a candidater species for aquaculture programs within Southern Africa. This has stimulated interest in its breeding cycle as well as the morphological characteristics of the gonads. Limited information is available on SEM and TEM observations of the male gonads. It is known that the testis of O. mossambicus is a paired, intra-abdominal structure of the lobular type, although further details of its characteristics are not known. Current investigations have shown that spermatids reach full maturity some two months after the female becomes gravid. Throughout the year, the testes contain spermatids at various stages of development although spermiogenesis appears to be maximal during November when spawning occurs. This paper describes the morphological and ultrastructural characteristics of the testes and spermatids.Specimens of this fish were collected at Syferkuil Dam, 8 km north- west of the University of the North over a twelve month period, sacrificed and the testes excised.

The North West Passage

2014 ◽  
Author(s):  
Roald Amundsen ◽  
Godfred Hansen
Keyword(s):  
North West ◽  
The North
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