scholarly journals Population Density, Size Structure, and Reproductive Cycle of the Comestible Sea Urchin Sphaerechinus granularis (Echinodermata: Echinoidea) in the Pagasitikos Gulf (Aegean Sea)

Animals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1506
Author(s):  
Dimitrios Vafidis ◽  
Chryssanthi Antoniadou ◽  
Vassiliki Ioannidi
Keyword(s):  
Population Density ◽  
Reproductive Cycle ◽  
Size Structure ◽  
Aegean Sea ◽  
Paracentrotus Lividus ◽  
Early Spring ◽  
Edible Species ◽  
Sheltered Site ◽  
Baseline Knowledge ◽  
Shell Fragments

Sphaerechinus granularis is a common grazer that lives in various sublittoral habitats, displaying typical covering behavior; i.e., putts shell-fragments, pebbles, and algae on its test. It is an edible species of increasing commercial importance due to the depletion of the common urchin’s, Paracentrotus lividus, stocks. Its biology, however, is not adequately studied over its distributional range. The present study examines population density, size structure, and reproductive biology of S. granularis in the Aegean Sea. Samplings were made with SCUBA-diving (8–10 m) and included: (i) visual census along transects to estimate density, and (ii) random collection of specimens at monthly intervals to assess biometry and gametogenesis. Population density had moderate values that almost doubled when inputted to Distance software. S. granularis had larger dimensions in the sheltered site; size-structures were unimodal (65–70 mm and 70–75 mm, in exposed and sheltered site, respectively). An annual reproductive cycle was evident, according to GSI and gonads’ histology, with a clear spawning peak in early spring. This pattern conforms to previous reports from the Atlantic, but precedes those from the Mediterranean (reproduction in summer). The provided baseline knowledge on the biology of S. granularis is important for the viable management of its developing fishery.

scholarly journals Reproductive Cycle of the Edible Sea Urchin Paracentrotus lividus (Echinodermata: Echinoidae) in the Aegean Sea

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1029 ◽  
Author(s):  
Dimitris Vafidis ◽  
Chryssanthi Antoniadou ◽  
Kyratso Kyriakouli
Keyword(s):  
Reproductive Biology ◽  
Sea Urchin ◽  
Reproductive Cycle ◽  
Sea Urchins ◽  
Reproductive Potential ◽  
Aegean Sea ◽  
Paracentrotus Lividus ◽  
Mediterranean Populations ◽  
Spawning Period ◽  
Gonad Somatic Index

The sustainable management of fisheries resources requires extensive knowledge of their reproductive biology, which is scarcely the case for marine invertebrates. Sea urchins are among the most intensively harvested invertebrates, since their gonads, or “roe”, constitute a highly appreciated gastronomic delicacy, causing a severe decline in natural populations worldwide. In the Mediterranean, the typical commercial echinoid species is Paracentrotus lividus; its biology, however, has not been adequately studied in the Aegean Sea. Within this context, the present study examined the reproductive biology of the edible sea urchin, P. lividus, in the Aegean Sea (Pagasitikos Gulf) over a two-year period. Adult specimens were randomly collected by SCUBA diving (3–5 m) at monthly intervals to determine the gonad-somatic index, fecundity, and gametogenesis through the morphological and histological examination of the gonads. An annual reproductive cycle was defined in both years with a clear spawning peak in early spring, conforming to previous reports from other Mediterranean populations. A discrete secondary spawning period was also detected in early winter, as the species undergoes a second gametogenic event. These results are indicative for the increased reproductive potential of P. lividus in its south distributional range, suggesting a relevant revision of the official fishing season of the species.

Population dynamics, allometric relationships and reproductive status of Microcosmus sabatieri (Tunicata: Ascidiacea) in the Aegean Sea

2008 ◽  
Vol 88 (5) ◽  
pp. 1043-1051 ◽  
Author(s):  
Dimitris Vafidis ◽  
Chryssanthi Antoniadou ◽  
Chariton Chintiroglou
Keyword(s):  
Aegean Sea ◽  
Reproductive Status ◽  
High Plasticity ◽  
Distribution Analysis ◽  
Allometric Relationships ◽  
Length Frequency ◽  
Gonad Somatic Index ◽  
Edible Species ◽  
Strong Relation ◽  
Somatic Index

The Mediterranean ascidian Microcosmus sabatieri is among the conspicuous benthic invertebrates, forming dense populations on moderately inclined cliffs. It is an edible species, commercially harvested at the southern part of the Aegean Sea. Considering that the biology of this species has not been adequately studied, a three-year survey was carried out focusing on population structure, allometric relationships and reproductive status of M. sabatieri stocks in Astypalea Island (Dodecanese, south Aegean). Population density showed insignificant temporal variation and lower values at the steeper station, while the pattern of dispersion was random. All measured biometric characters showed high plasticity, especially those related to siphons. All the examined morphometric relationships follow negative allometry. Ascidian length was a good predictor of biomass, and a strong relation was observed between mantle and tunic characters. Gonad somatic index showed a single spawning season per year, in winter. Length–frequency distribution analysis revealed the presence of one mode of medium sized individuals, implying that M. sabatieri stocks are under moderate fishing pressure in the study area.

The reproductive cycle of the viviparous seaperch, Cymatogaster aggregata Gibbons

1968 ◽  
Vol 46 (6) ◽  
pp. 1221-1234 ◽  
Author(s):  
John P. Wiebe
Keyword(s):  
Oocyte Maturation ◽  
Reproductive Cycle ◽  
Sertoli Cells ◽  
Reproductive Behavior ◽  
Seasonal Changes ◽  
Environmental Temperature ◽  
Interstitial Cells ◽  
Early Spring ◽  
Seminiferous Tubules ◽  
Male And Female

The natural reproductive cycle of male and female Cymatogaster aggregata is described with reference to gametogenesis, development of secondary sex structures, reproductive behavior, and gestation. Spermatocytogenesis starts in early spring and by June or July clusters of spermatozoa fill the seminiferous tubules. Concurrently the Sertoli cells and interstitial cells of Leydig increase in size and secondary sex structures develop on the male anal fin. When the sexes mingle in summer, the males perform very elaborate reproductive behavior. Fertilization occurs about mid-December—5 months after mating—and the ovary is then modified to maintain the young embryos until parturition in mid-summer. Oocyte formation is highest in July and August, just after parturition, while vitellogenesis and oocyte maturation occur mainiy from October to December. These seasonal changes are discussed in relation to changes in environmental temperature and photoperiod.

Pituitary gonadotropin contents and ultrastructure of the gonadotrops in the African catfish Clarias gariepinus during the annual cycle in a natural habitat

1986 ◽  
Vol 64 (8) ◽  
pp. 1718-1726 ◽  
Author(s):  
J. Peute ◽  
M. A. Zandbergen ◽  
H. J. Th. Goos ◽  
R. de Leeuw ◽  
R. Pinkas ◽  
...  
Keyword(s):  
Reproductive Cycle ◽  
Secretory Granules ◽  
Natural Habitat ◽  
Clarias Gariepinus ◽  
Early Spring ◽  
Late Winter ◽  
Breeding Period ◽  
African Catfish ◽  
Pituitary Gonadotropin ◽  
Gonadal Recrudescence

Over a period of 1 year, male and female specimens of a natural population of African catfish, Clarias gariepinus, were collected monthly at locations in northern Israel. Both the ultrastructural appearance of the gonadotrops and the pituitary gonadotropin content in males and females showed cyclical changes, which paralleled alterations in the reproductive cycle. In summer, during the breeding period, the gonadotrops were large and fully granulated, and pituitary gonadotropin reached maximum levels. After spawning, the resting period begins, with an increasing number of fusion products of secretory granules and globules in the gonadotrops, probably indicating a breakdown of hormone storage. This was followed by the appearance of residual bodies, cell shrinkage, and a considerable drop in pituitary gonadotropin content. In late winter and early spring, during gonadal recrudescence, the gonadotrops redeveloped, i.e., they increased in size and granulation, and at the same time the pituitary gonadotropin content augmented. This reproductive cycle will permit induced spawning and artificial propagation of African catfish from March till September. However, keeping the catfish at favourable feeding and temperature conditions may also permit the gonadotrops to produce gonadotropin continuously, thus providing the possibility of complete gametogenesis and of obtaining viable eggs and healthy larvae throughout the year.

scholarly journals Sea urchin response to rising pCO2 shows ocean acidification may fundamentally alter the chemistry of marine skeletons

2014 ◽  
Vol 15 (3) ◽  
pp. 510 ◽  
Author(s):  
L. BRAY ◽  
M.A. PANCUCCI-PAPADOPOULOU ◽  
J. M. HALL-SPENCER
Keyword(s):  
Ocean Acidification ◽  
Species Interactions ◽  
Sea Urchins ◽  
Marine Ecosystem ◽  
Aegean Sea ◽  
Paracentrotus Lividus ◽  
Low Ph ◽  
Reference Sites ◽  
Coastal Systems ◽  
Arbacia Lixula

Ocean acidification caused by an increase in pCO2 is expected to drastically affect marine ecosystem composition, yet there is much uncertainty about the mechanisms through which ecosystems may be affected. Here we studied sea urchins that are common and important grazers in the Mediterranean (Paracentrotus lividus and Arbacia lixula). Our study included a natural CO2 seep plus reference sites in the Aegean Sea off Greece. The distribution of A. lixula was unaffected by the low pH environment, whereas densities of P. lividus were much reduced. There was skeletal degradation in both species living in acidified waters compared to reference sites and remarkable increases in skeletal manganese levels (P. lividus had a 541% increase, A. lixula a 243% increase), presumably due to changes in mineral crystalline structure. Levels of strontium and zinc were also altered. It is not yet known whether such dramatic changes in skeletal chemistry will affect coastal systems but our study reveals a mechanism that may alter inter-species interactions.

scholarly journals Population structure and reproductive cycle of the commercial sea cucumber Holothuria mexicana in Belize

2018 ◽  
Vol 66 (4) ◽  
Author(s):  
Arlenie Rogers ◽  
Jean-François Hamel ◽  
Annie Mercier
Keyword(s):  
Sex Ratio ◽  
Protected Areas ◽  
Reproductive Cycle ◽  
Sexual Maturity ◽  
Sea Cucumber ◽  
Size Structure ◽  
Natural Populations ◽  
Gonad Index ◽  
Size At Sexual Maturity ◽  
Spawning Periods

The population and reproductive biology of the commercial sea cucumber Holothuria mexicana (Ludwig, 1875) was studied in Southern Belize (Caribbean Sea), including the sex ratio, size at sexual maturity and reproductive cycle, as well as the size structure among habitats located inside and outside protected areas. Individuals found inside marine protected areas were consistently larger than individuals found outside these boundaries. The male:female sex ratio was 1.1:1.0 with a unimodal size distribution composed mainly of sexually mature individuals (87 %). Size at sexual maturity was established to be ~10 cm based on measures of gamogenetically mature individuals during the peak of the gametogenic maturity period. Juveniles and small adults measuring ≤ 15 cm (13 %), were collected exclusively in sandy and muddy areas of seagrass habitats associated with mangroves. Larger adults were commonly found on hard substrates in both seagrass-associated and coral-reef-associated habitats. Based on histology and gonad indices, the first sign of early gametogenesis was detected in August in both sexes. Gametes developed and matured throughout the colder months between November and February. Decreases in gonad index in both years suggest annual spawning, starting in March-April 2014 (single major event) and March-April and July-August 2015 (two smaller events) for both males and females. The spawning periods were correlated with warmer or increasing temperatures, low rainfall and increasing or high chlorophyll-a concentrations. These data will hopefully guide management and protection of the natural populations of H. mexicana, which are already suffering from overfishing in Belize and neighboring countries. 

scholarly journals Assessment of a daily defecation rate of fallow deer upon a closed population study

2012 ◽  
Vol 60 (6) ◽  
pp. 173-180 ◽  
Author(s):  
Antonín Košnář ◽  
Romana Rajnyšová
Keyword(s):  
Population Density ◽  
Fallow Deer ◽  
Early Spring ◽  
Summer Season ◽  
Accurate Assessment ◽  
Indirect Methods ◽  
Defecation Rate ◽  
Closed Population ◽  
Deer Population ◽  
Precise Knowledge

Many indirect methods of counting even-toed ungulates are based on the principle of accumulating dung in a known area per a unit of time. In order to provide the most accurate assessment of the population size, these methods require the knowledge of daily defecation of the monitored species. The main objective of the study submitted is the assessment of a daily defecation rate of fallow deer based on the monitoring of its closed population. A partial objective is the assessment of the distribution of fallow deer in an enclosed area with a view to biotopes represented. A fallow deer population was studied for the period of three years (2009–2011) in a fenced-in area (8 ha). During this period, dung heaps were counted in forty sites with the total area of 0.8 ha in all seasons of the year. In each season, the sites were cleared, and the dung was counted after a seven-day exposure. This counting was performed twice in each season. Thanks to the precise knowledge of the number of monitored animals, daily defecation rates (DDR) were derived upon the dung found, using a formula for the calculation of population density. Subsequently, the determined DDRs were verified by direct observation. The highest average DDR value calculated from the formula (21.11 ± 0.32 S.E.) was obtained in the summer season. The lowest defecation of fallow deer was established to be in winter (12.34 ± 0.25 S.E.) and early spring (10.61 ± 0.24 S.E.).

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