Seasonal Variation in the Tubular and Interstitial Areas of the Testes in Sternotherus odoratus L.

Seasonal changes within the tubular and interstitial areas of the testes in Sternotherus odoratus are investigated, histologically and histochemically. Forty specimens were collected in Illinois, Tennessee and Louisiana between May, 1969 and August, 1972. Many of the histological and macroscopic observations made by Risley (1938) on the spermatogenic cycle of S. odoratus in Michigan are confirmed. Contrary to his findings, fluctuations in interstitial cell nuclear diameters are observed during spermatogenesis. Greatest diameters coincide with what Risley has considered . . . period of most active breeding. Sertoli cell nuclear diameters undergo similar fluctuations being greatest during spring breeding and fall steatogenesis. The testes undergo a sequence of well-defined cyclical events. These include a tubular and interstitial lipid cycle correlated with spermatogenesis and a PA/S-glycogenic cycle which can be traced within the Sertoli elements. Roughly, an inverse correlation exists between the two lipid cycles. Lipid concentrations decrease as spermatogenesis advances and accumulate during the interim between cycles. The Sertoli cell is the intratubular locus of lipid accumulation while the interstitial cell is the intertubular locus. Sertoli lipids accumulate more rapidly than do interstitial lipids and are present for a longer time. Whereas interstitial lipids become depleted as secondary spermatocytes are forming, Sertoli lipids remain through the spermatid stage. In the PA/S-gylcogenic cycle, glycogen and carbohydrate materials accumulate within the Sertoli cytoplasm in granular form during the fall and spring. These substrates become depleted during the early stages of spermiogenesis. Latitudinal geographic variation in the timing of spermatogenic, glycogenic and lipid cycles is evident. Spermatogenesis in Illinois is two to three weeks ahead of that found in Michigan, two weeks behind the cycle in Tennessee and five weeks behind in specimens from Louisiana. The PA/S-glycogenic cycle in Illinois is two weeks behind that found in Tennessee and four weeks behind that in Louisiana specimens. Intertubular lipid cycles in Tennessee and Louisiana are similar to those found in Illinois for corresponding spermatogenic stages. The Sertoli lipid cycle follows the same pattern of timing but differs in that lipids are retained for a longer time in turtles from more southerly locations. Spring spermatogenesis accelerates with increasing temperature and photoperiod. Following the summer solstice and despite decreasing photoperiod, the cycle continues unabated. With the onset of cooler temperatures in the fall, the cycle regresses and stops. These facts suggest that temperature is the main environmental factor regulating spermatogenesis once it has started

Weak population structure of the Spot-tail shark Carcharhinus sorrah and the Blacktip shark C. limbatus along the coasts of the Arabian Peninsula, Pakistan, and South Africa.

The increase in demand for shark meat and fins has placed shark populations worldwide under high fishing pressure. In the Arabian region, the spot-tail shark Carcharhinus sorrah and the Blacktip shark Carcharhinus limbatus are among the most exploited species. In this study, we investigated the population genetic structure of C. sorrah (n = 327) along the coasts of the Arabian Peninsula and of C. limbatus (n = 525) along the Arabian coasts, Pakistan, and KwaZulu-Natal, South Africa, using microsatellite markers (15 and 11 loci, respectively). Our findings support weak population structure in both species. Carcharhinus sorrah exhibited a fine structure, subdividing the area into three groups. The first group comprises all samples from Bahrain, the second from the UAE and Yemen, and the third from Oman. Similarly, C. limbatus exhibited population subdivision into three groups. The first group, comprising samples from Bahrain and Kuwait, was highly differentiated from the second and third groups, comprising samples from Oman, Pakistan, the UAE, and Yemen; and South Africa and the Saudi Arabian Red Sea, respectively. Population divisions were supported by pairwise F ST values and discriminant analysis of principal components (DAPC), but not by STRUCTURE. We suggest that the mostly low but significant pairwise F ST values in our study are suggestive of fine population structure, which is possibly attributable to behavioral traits such as residency in C. sorrah and site fidelity and philopatry in C. limbatus. However, for all samples obtained from the northern parts of the Gulf (Bahrain and/or Kuwait) in both species, the higher but significant pairwise F ST values could possibly be a result of founder effects during the Tethys Sea closure. Based on DAPC and F ST results, we suggest each population to be treated as independent management unit, as conservation concerns emerge

Antihemophilic Globulin (Factor VIII) Activity of Human Fibrinogen *

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75567/1/j.1423-0410.1966.tb04212.x.pd

Extensive use of mesopelagic waters by a Scalloped hammerhead shark (Sphyrna lewini) in the Red Sea

Background: Despite being frequently landed in fish markets along the Saudi Arabian Red Sea coast, information regarding fundamental biology of the Scalloped hammerhead shark (Sphyrna lewini) in this region is scarce. Satellite telemetry studies can generate important data on life history, describe critical habitats, and ultimately redefine management strategies for sharks. To better understand the horizontal and vertical habitat use of S. lewini in the Red Sea and to aid with potential future development of zoning and management plans for key habitats, we deployed a pop-up satellite archival transmitting tag to track a single female specimen (240 cm total length) for a tracking period of 182 days. Results: The tag was physically recovered after a deployment period of 6 months, thus providing the complete archived dataset of more than one million depth and temperature records. Based on a reconstructed, most probable track, the shark travelled a circular distance of approximately 1000 km from the central Saudi Arabian Red Sea southeastward into Sudanese waters, returning to the tagging location toward the end of the tracking period. Mesopelagic excursions to depths between 650 and 971 m occurred on 174 of the 182 days of the tracking period. Intervals between such excursions were characterized by constant oscillatory diving in the upper 100 m of the water column. Conclusions: This study provides evidence that mesopelagic habitats might be more commonly used by S. lewini than previously suggested. We identified deep diving behavior throughout the 24-h cycle over the entire 6-month tracking period. In addition to expected nightly vertical habitat use, the shark exhibited frequent mesopelagic excursions during daytime. Deep diving throughout the diel cycle has not been reported before and, while dive functionality remains unconfirmed, our study suggests that mesopelagic excursions may represent foraging events within and below deep scattering layers. Additional research aimed at resolving potential ecological, physiological and behavioral mechanisms underpinning vertical movement patterns of S. lewini will help to determine if the single individual reported here is representative of S. lewini populations in the Red Sea

Population genetics of four heavily exploited shark species around the Arabian Peninsula.

The northwestern Indian Ocean harbors a number of larger marine vertebrate taxa that warrant the investigation of genetic population structure given remarkable spatial heterogeneity in biological characteristics such as distribution, behavior, and morphology. Here, we investigate the genetic population structure of four commercially exploited shark species with different biological characteristics (Carcharhinus limbatus, Carcharhinus sorrah, Rhizoprionodon acutus, and Sphyrna lewini) between the Red Sea and all other water bodies surrounding the Arabian Peninsula. To assess intraspecific patterns of connectivity, we constructed statistical parsimony networks among haplotypes and estimated (1) population structure; and (2) time of most recent population expansion, based on mitochondrial control region DNA and a total of 20 microsatellites. Our analysis indicates that, even in smaller, less vagile shark species, there are no contemporary barriers to gene flow across the study region, while historical events, for example, Pleistocene glacial cycles, may have affected connectivity in C. sorrah and R. acutus. A parsimony network analysis provided evidence that Arabian S. lewini may represent a population segment that is distinct from other known stocks in the Indian Ocean, raising a new layer of conservation concern. Our results call for urgent regional cooperation to ensure the sustainable exploitation of sharks in the Arabian region

Environmental conditions are poor predictors of immature white shark Carcharodon carcharias occurrences on coastal beaches of eastern Australia

Understanding and predicting the distribution of organisms in heterogeneous environments is a fundamental ecological question and a requirement for sound management. To implement effective conservation strategies for white shark Carcharodon carcharias populations, it is imperative to define drivers of their movement and occurrence patterns and to protect critical habitats. Here, we acoustically tagged 444 immature white sharks and monitored their presence in relation to environmental factors over a 3 yr period (2016-2019) using an array of 21 iridium satellite-linked (VR4G) receivers spread along the coast of New South Wales, Australia. Results of generalized additive models showed that all tested predictors (month, time of day, water temperature, tidal height, swell height, lunar phase) had a significant effect on shark occurrence. However, collectively, these predictors only explained 1.8% of deviance, suggesting that statistical significance may be rooted in the large sample size rather than biological importance. On the other hand, receiver location, which captures geographic fidelity and local conditions not captured by the aforementioned environmental variables, explained a sizeable 17.3% of deviance. Sharks tracked in this study hence appear to be tolerant to episodic changes in environmental conditions, and movement patterns are likely related to currently undetermined, location-specific habitat characteristics or biological components, such as local currents, prey availability or competition. Importantly, we show that performance of VR4G receivers can be strongly affected by local environmental conditions, and provide an example of how a lack of range test controls can lead to misinterpretation and erroneous conclusions of acoustic detection data.</jats:p

Operational protocols for the use of drones in marine animal research

The use of drones to study marine animals shows promise for the examination of numerous aspects of their ecology, behaviour, health and movement patterns. However, the responses of some marine phyla to the presence of drones varies broadly, as do the general operational protocols used to study them. Inconsistent methodological approaches could lead to difficulties comparing studies and can call into question the repeatability of research. This review draws on current literature and researchers with a wealth of practical experience to outline the idiosyncrasies of studying various marine taxa with drones. We also outline current best practice for drone operation in marine environments based on the literature and our practical experience in the field. The protocols outlined herein will be of use to researchers interested in incorporating drones as a tool into their research on marine animals and will help form consistent approaches for drone-based studies in the future

‘Solo datasets’: unexpected behavioural patterns uncovered by acoustic monitoring of single individuals

A holistic understanding of the life-history strategies of marine populations is often hindered by complex population dynamics, exacerbated by an intricate movement ecology across their life history (Nathan et al. 2008; Parsons et al. 2008; Jeltsch et al. 2013). Movement patterns and spatial ecology can vary spatially and temporally for different reasons, mainly related to the organism’s life history and environmental variability (Abecasis et al. 2009, 2013; Afonso et al. 2009). Changes in spatial use and movement can occur daily when visiting feeding grounds or avoiding predators, or seasonally, when sexually mature individuals migrate to spawning/breeding grounds (Kozakiewicz 1995; Sundström et al. 2001). However, observed shifts in spatial use and movement patterns, as a result of behavioural plasticity, may also vary greatly from one individual to another of the same species and/or population (Afonso et al. 2009). Further, ontogeny can also play an important role and explain a possible change in individual spatial variation. Noticeable differences in the behaviour and movements of mature and immature individuals have been documented in various marine organisms (Lowe et al. 1996; Lecchini and Galzin 2005). Permanent habitat shifts have been associated with ontogenesis in pigeye sharks (Carcharhinus amboinensis), moving from inshore to offshore areas after reaching maturity (Knip et al. 2011).This research was partially funded by the EU LIFE-BIOMARES Project (LIFE06 NAT/P/000192).info:eu-repo/semantics/publishedVersio

Repeated observations of cetaceans and carcharhiniformes associations in the Red Sea

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Troubled waters: Threats and extinction risk of the sharks, rays and chimaeras of the Arabian Sea and adjacent waters

The extinction risk of sharks, rays and chimaeras is higher than that for most other vertebrates due to low intrinsic population growth rates of many species and the fishing intensity they face. The Arabian Sea and adjacent waters border some of the most important chondrichthyan fishing and trading nations globally, yet there has been no previous attempt to assess the conservation status of species occurring here. Using IUCN Red List of Threatened Species Categories and Criteria and their guidelines for application at the regional level, we present the first assessment of extinction risk for 153 species of sharks, rays and chimaeras. Results indicate that this region, home to 15% of described chondrichthyans including 30 endemic species, has some of the most threatened chondrichthyan populations in the world. Seventy‐eight species (50.9%) were assessed as threatened (Critically Endangered, Endangered or Vulnerable), and 27 species (17.6%) as Near Threatened. Twenty‐nine species (19%) were Data Deficient with insufficient information to assess their status. Chondrichthyan populations have significantly declined due to largely uncontrolled and unregulated fisheries combined with habitat degradation. Further, there is limited political will and national and regional capacities to assess, manage, conserve or rebuild stocks. Outside the few deepsea locations that are lightly exploited, the prognosis for the recovery of most species is poor in the near‐absence of management. Concerted national and regional management measures are urgently needed to ensure extinctions are avoided, the sustainability of more productive species is secured, and to avoid the continued thinning of the regional food security portfolio