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Article Reference Seasonal modifications and morphogenesis of the hypercalcified sponge Petrobiona massiliana (Calcarea, Calcaronea)
The periodicity of sexual elements and soft tissue modifications during the life cycle of the hypercalcified sponge Petrobiona massiliana was investigated monthly from June 2006 to November 2007. Sexual reproduction, likely regulated by seawater temperatures, occurred during more than half of the year (from early April to late October); 70% of the samples appeared reproductively active. Specimens of P. massiliana displayed a high plasticity of tissue organization, allowing modulation and rearrangement of their aquiferous systems in response to life cycle phases and environmental changes. Permanent changes were observed in the basal region of the choanosome in non-reproductive specimens, such as disorganization/ restructuring events leading to remodeling of the aquiferous system. Periodic modifications occurring during sexual reproduction included the transformation of choanocytes from a typical form to hourglass and vespiform shapes, and more global disorganization of the basal region of the choanosome during provisioning of oocytes and embryos, followed by restructuring after release of the larvae. Finally, episodic disorganization/reorganization phenomena occurred in a few specimens after unfavorable environmental conditions (e.g., decreasing seawater temperatures). Histological and ultrastructural observations of storage cells, located in peculiar trabecular tracts, suggest a transdifferentiation capacity that allows such soft tissue dynamics.
Located in Library / RBINS Staff Publications
Article Reference Seasonal variation in concentration, size and settling velocity of muddy marine flocs in the benthic boundary layer
Suspended Particulate Matter (SPM) concentration profiles of the lowest 2 m of the water column and particle size distribution at 2 m above the bed were measured in a coastal turbidity maximum area (southern North Sea) during more than 700 days between 2006 and 2013. The long-term data series of SPM concentration, floc size, and settling velocity have been ensemble averaged according to tidal range, alongshore residual flow direction, and season, in order to investigate the seasonal SPM dynamics and its relation with physical and biological processes. The data show that the SPM is more concentrated in the near-bed layer in summer, whereas in winter, the SPM is better mixed throughout the water column. The decrease of the SPM concentration in the water column during summer is compensated by a higher near- bed concentration indicating that a significant part of the SPM remains in the area during summer rather than being advected out of it. The opposite seasonality between near-bed layer and water column has to our knowledge not yet been presented in literature. Physical effects such as wave heights, wind climate, or storms have a weak correlation with the observed seasonality. The argument to favor microbial activity as main driver of the seasonality lies in the observed variations in floc size and settling velocity. On average, the flocs are larger and thus settling velocities higher in summer than winter.
Located in Library / RBINS Staff Publications
Article Reference application/x-troff-ms Seasonal variation of coastal currents and residual currents in the CAT BA – HA long coastal area (VIET NAM): Results of coherens model
The COHERENS model is used to investigate the temporal and spatial variation of the coastal currents in 2021 at the Cat Ba - Ha Long, northern Vietnam. The findings indicate that tidal oscillation has a notable impact on the current fields in short-term variations (hours to days). Meanwhile, the wind field and river discharge are the decisive factors affecting the seasonal variation of the current fields in Cat Ba - Ha Long coastal area. Furthermore, the characteristics of residual currents are significantly affected by river discharges and wind patterns, which vary across different months and seasons. During the southwest monsoon season (May to August), the residual currents have a prevailing direction towards the sea, from the west and south-southwest towards the east and north-northeast, reaching maximum speeds of approximately 0.1–0.15 m/s. Conversely, in the transitional and northeast monsoon seasons, the directions of residual currents are from the east-northeast to the west-southwest, with peak speed up to 0.2–0.25 m/s. Notably, the residual currents in the bottom and surface layers in the eastern-southwestern area of Cat Ba Island and the north of Ha Long Bay are in opposite directions
Located in Library / RBINS Staff Publications 2024
Article Reference Seasonal variations recorded in cave monitoring results and a 10-year monthly resolved speleothem 18O and 13C record from the Han-sur-Lesse cave, Belgium.
Located in Library / RBINS Staff Publications
Article Reference Seasonality and microdistribution of the non-marine ostracods of Lake Zwai (Ethiopia) (Crustacea, Ostracoda)
Located in Library / RBINS Staff Publications
Article Reference Seasonality of floc strength in the southern North Sea
The suspended particulate matter (SPM) concentration in the high turbidity zones of the south- ern North Sea is inversely correlated with chlorophyll (Chl) concentration. During winter, SPM concentration is high and Chl concentration is low and vice versa during summer. This seasonality has often been associated with the seasonal pattern in wind forcing. However, the decrease in SPM concentration corresponds well with the spring algal bloom. Does the decrease of SPM concentration caused by changing wind conditions cause the start of algae bloom, or does the algae bloom decrease SPM concentrations through enhanced floccula- tion and deposition? To answer the question, measurements from 2011 of particle size distribution (PSD), SPM, and Chl concentrations from the southern North Sea have been analyzed. The results indicate that the frequency of occurrence of macroflocs has a seasonal signal, while seasonality has little impact upon floc size. The data from a highly turbid coastal zone suggest that the maximum size of the macroflocs is controlled by turbulence and the available flocculation time during a tidal cycle, but the strength of the macroflocs is con- trolled by the availability of sticky organic substances associated with enhanced primary production during spring and summer. The results highlight the shift from mainly microflocs and flocculi in winter toward more muddy marine snow with larger amounts of macroflocs in spring and summer. The macroflocs will reduce the SPM concentrations in the turbidity maximum area as they settle faster. Consequently, the SPM concen- tration decreases and the light condition increases in the surface layer enhancing algae growth further.
Located in Library / RBINS Staff Publications
Article Reference Seasonality only works in certain parts of the year: The reconstruction of fishing seasons through otolith analysis
Seasonality estimations using incremental data usually suffer from small sample sizes and from the lack of comparison with sufficiently large modern samples. The present contribution reports on incremental studies carried out on large assemblages of plaice (Pleuronectes platessa) and haddock (Melanogrammus aeglefinus) from a late medieval fishing village (Raversijde, Belgium) on the North Sea coast. In an attempt to refine previous seasonality estimates made for this site, and to expand conclusions concerning general methodology, extensive monthly samples of modern otoliths of these species, caught within the North Sea, have also been investigated. The modern material shows that the timing of the seasonal changes in the edge type (hyaline or opaque) of the otoliths is extremely variable and that it is dependent on the fishing ground, the year considered, and the age of the fish. It also appears that the increase of the marginal increment thickness is highly variable, to such an extent that the thickness of the last increment of a single otolith is mostly useless for seasonality estimation. Where large archaeological otolith assemblages can be studied, preferably from single depositional events, seasonality determination becomes possible on the condition, however, that the archaeological assemblage corresponds to fish that were captured during their period of fast growth. The growth ring study on the otoliths from Raversijde shows that plaice fishing took place in spring and that it was preceded by a haddock fishing season, probably in late winter/early spring.
Located in Library / RBINS Staff Publications
Article Reference Second Record and DNA Barcode of the Ant Tyrannomyrmex rex Fernández (Hymenoptera: Formicidae: Myrmicinae)
Located in Library / RBINS Staff Publications
Article Reference Secondary sex estimation using morphological traits from the cranium and mandible: application to two Merovingian populations from Belgium
It is generally accepted that the coxal bone is the most reliable bone for estimating the sex of adult subjects. When the coxal bone is not usable, researchers generally turn to methods based on the skull (cranium and mandible). However, these methods are less reliable, because they are largely based on an estimate of the robusticity, which can be influenced by characteristics independent of the sex of the subject. In the context of primary sex estimation, skull-based methods should therefore be avoided. However, by using morphological traits of the cranium and the mandible as part of a secondary sex estimation, we were able to estimate the sex of a relatively large number of individuals with a minimum reliability of 95%. Our study thus illustrates the value of using morphological characteristics of the skull for a secondary sex estimation conducted with a reliable statistical method.
Located in Library / RBINS Staff Publications 2024
Article Reference Secrets of de Selys Longchamps archives: one watercolour and two records of nineteenth century observations of the grasshopper species Psophus stridulus (Linnaeus, 1758) and Locusta migratoria (Linnaeus, 1758) in Belgium (Orthoptera: Acrididae)
Next to voucher specimens in entomological collections, also historical archives and historical illustrations can contain valuable taxonomical as well as ecological and faunistic data. We report here faunistic data for two currently extinct Belgian grasshopper species from the year 1862, deduced from a letter accompanied by a watercolour. The letter and watercolour are stored in the archives of Edmond de Selys Longchamps at the Royal Belgian Institute for Natural Sciences (RBINS). Both the watercolour and the letter are discussed, focusing on the observations of Psophus stridulus (Linnaeus, 1758) and Locusta migratoria (Linnaeus, 1758) (Orthoptera) at Lanaken in 1862. Two voucher specimens of these observations and their original labels, that are stored in the RBINS collections, were studied. We can conclude that Egide Fologne was the first to observe P. stridulus in Belgium. He reported this in a letter to Edmond de Selys Longchamps and supplied the watercolour depicting the specimen he collected and donated to Selys for his collection.
Located in Library / RBINS Staff Publications 2017