Renin-angiotensin system in elasmobranch fish: A review.

The renin-angiotensin system (RAS) has been identified recently in elasmobranch fish, and the structure of angiotensin II (ANG II) is unusual ([Asp(1),Pro(3),Ile(5)]-ANG II) compared to other vertebrates. Receptors for ANG II have been identified in blood vessels and in a variety of osmoregulatory tissues including the gill, kidney and rectal gland. In addition, there is considerable binding to the interrenal gland and the stimulation of 1alpha-hydroxycorticosterone production in vitro suggests a physiological role in corticosteroidogenesis. ANG II is a potent vasoconstrictor and this effect does not appear to be mediated by sympathetic activation or catecholamine release. Although the RAS may not be involved in maintaining basal blood pressure, it may be important in situations in which blood pressure is reduced. Understanding of the role of ANG II as an osmoregulatory hormone is only just emerging with putative roles in the control of gill, rectal gland and perhaps, drinking. In addition, the stimulation of corticosteroid secretion may provide another means of controlling osmoregulation. J. Exp. Zool. 284:526-534, 1999.     

The status of coral reef ecology research in the Red Sea

The Red Sea has long been recognized as a region of high biodiversity and endemism. Despite this diversity and early history of scientific work, our understanding of the ecology of coral reefs in the Red Sea has lagged behind that of other large coral reef systems. We carried out a quantitative assessment of ISI-listed research published from the Red Sea in eight specific topics (apex predators, connectivity, coral bleaching, coral reproductive biology, herbivory, marine protected areas, non-coral invertebrates and reef-associated bacteria) and compared the amount of research conducted in the Red Sea to that from Australia’s Great Barrier Reef (GBR) and the Caribbean. On average, for these eight topics, the Red Sea had 1/6th the amount of research compared to the GBR and about 1/8th the amount of the Caribbean. Further, more than 50 % of the published research from the Red Sea originated from the Gulf of Aqaba, a small area (<2 % of the area of the Red Sea) in the far northern Red Sea. We summarize the general state of knowledge in these eight topics and highlight the areas of future research priorities for the Red Sea region. Notably, data that could inform science-based management approaches are badly lacking in most Red Sea countries. The Red Sea, as a geologically “young” sea located in one of the warmest regions of the world, has the potential to provide insight into pressing topics such as speciation processes as well as the capacity of reef systems and organisms to adapt to global climate change. As one of the world’s most biodiverse coral reef regions, the Red Sea may yet have a significant role to play in our understanding of coral reef ecology at a global scale.     

A coral reef refuge in the Red Sea

The stability and persistence of coral reefs in the decades to come is uncertain due to global warming and repeated bleaching events that will lead to reduced resilience of these ecological and socio‐economically important ecosystems. Identifying key refugia is potentially important for future conservation actions. We suggest that the Gulf of Aqaba (GoA) (Red Sea) may serve as a reef refugium due to a unique suite of environmental conditions. Our hypothesis is based on experimental detection of an exceptionally high bleaching threshold of northern Red Sea corals and on the potential dispersal of coral planulae larvae through a selective thermal barrier estimated using an ocean model. We propose that millennia of natural selection in the form of a thermal barrier at the southernmost end of the Red Sea have selected coral genotypes that are less susceptible to thermal stress in the northern Red Sea, delaying bleaching events in the GoA by at least a century.     

A new swallow from the Red Sea

A single specimen (Fig. 1), found dead on an islet off Port Sudan in spring 1984 is described as a distinctive new allospecies of African Cliff Swallow Hirundo spilodera.     

Trophic levels of teleost and elasmobranch species in the Persian Gulf and Oman Sea

Knowing the trophic level of marine organisms is essential to understanding their ecological role in the ecosystem and for quantifying the ecosystem effects of fishing to establish effective management of fishing resources. In comparison to other systems, information about the trophic level of marine organisms in the Persian Gulf and Oman Sea is very scarce. Here, the main aim was to estimate trophic level in these areas using all available diet information from different marine species using TrophLab software. The trophic level of 32 fish species was estimated with the available diet data. The trophic level ranged from 2.28 to 4.50. High trophic levels were found for Chorocentrus nudus (TL = 4.7), Saurida tumbil (TL = 4.6), Rhizoprionodon acutus (TL = 4.5), Torpedo sinuspersici (TL=4.5), Gymnura poecilura (TL = 4.5), Sphyraena putnamae (TL = 4.5) and Euthynnus affinis (TL = 4.5). In contrast, lower trophic levels were estimated for Tenualosa ilisha (TL = 2.28) and Sardinella sindensis (TL = 2.92). As expected, a positive correlation was found between the trophic level and body size, indicating changes in the diet due to variations in predatory capacities. The results of this study may be useful in the formulation of trophic indicators and modelling of the ecosystems.     

Synchronous reproduction of corals in the Red Sea

Multi-species synchronous spawning was first described on reefs off the east and west coast of Australia. In contrast, locally abundant species in the northern Red Sea and the central Pacific have little overlap in the time of reproduction. Consequently, the idea developed that high levels of spawning synchrony both within and among species was largely confined to Australian reefs. Here, we show that gamete maturity in colonies of the genus Acropora was highly synchronous in the Red Sea. In early April 2008, at two locations separated by 300 km, 13 of 24 species sampled had mature colonies, and a further 9 species had immature colonies. In late April–early May 2008, all colonies sampled had no oocytes, indicating colonies had spawned a few days after the full moon of 20 April 2008. Similarly, in 2009, 99% of colonies from 17 species at Hurghada were mature in late April, and all were empty in early May. Spawn slicks suggested many of these colonies had released gametes three night prior to the full moon on 8 May 2009. This level of synchrony in gamete maturity is among the highest ever recorded and similar to that typically recorded in Acropora assemblages on Australian reefs. While further work is required to document the night of gamete release, these data strongly suggest that high levels of spawning synchrony are a regular feature of these Red Sea coral assemblages and that multi-species spawning occurs on or around the full moon in April and/or May.     

Length–weight relationships for 10 elasmobranch species from the Oman Sea

Length–weight relationships (LWRs) were estimated for ten elasmobranch species from Iranian waters of the Oman Sea. All specimens were collected by bottom trawl (mesh size 80 mm in the cod end) between May and December 2014. A total of 509 individuals (107 Torpedo sinuspersici, 68 Rhinobatos punctifer, 63 Chaenogaleus macrostoma, 72 Himantura walga, 80 Himantura gerrardi, 58 Gymnura poecilura, 4 Himantura uarnak, 4 Rhinoptera javanica, 14 Aetobatus flagellum, and 39 Pastinachus sephen) were sampled and studied. Results showed that most species had positive allometric or isometric growth but that more studies were needed for final decisions on growth patterns. Both the disk length‐body weight (DL/BW) and disk width‐body weight (DW/BW) relationships also showed a good fit, reinforcing the credibility of the data in relation to the LWRs. This study is the first report of LWRs for these elasmobranchs in the northern Oman Sea.     

Opisthobranch molluscs of the Sudanese Red Sea

Eighteen opisthobranch species are described and illustrated from the Sudanese Red Sea, including seven new species, one new subspecies and three species for which this is the first Red Sea record. Eleven bullomorphs, four pleurobranchomorphs, four sacoglossans and four phyllidiid mudibranchs are now known from the Red Sea.
There appears to be a high percentage of endemic species in the Red Sea. This is what one might expect, in view of the conditions of near isolation, low temperatures and high salinity that prevailed in this sea 13000 23000 years ago.
Of the groups discussed in this paper, one Red Sea species has invaded the Mediterranean Sea, and one Mediterranean species has invaded the Red Sea, since the opening of the Suez Canal in 1867.
Many Red Sea species are very colourful, in comparison to Mediterranean ones. This could perhaps be because Red Sea waters are cleaner, thereby favouring the evolution of greater precision in colour markings.     

Opisthobranch molluscs of the Sudanese Red Sea

Eighteen opisthobranch species are described and illustrated from the Sudanese Red Sea, including seven new species, one new subspecies and three species for which this is the first Red Sea record. Eleven bullomorphs, four pleurobranchomorphs, four sacoglossans and four phyllidiid mudibranchs are now known from the Red Sea. There appears to be a high percentage of endemic species in the Red Sea. This is what one might expect, in view of the conditions of near isolation, low temperatures and high salinity that prevailed in this sea 13000 23000 years ago. Of the groups discussed in this paper, one Red Sea species has invaded the Mediterranean Sea, and one Mediterranean species has invaded the Red Sea, since the opening of the Suez Canal in 1867. Many Red Sea species are very colourful, in comparison to Mediterranean ones. This could perhaps be because Red Sea waters are cleaner, thereby favouring the evolution of greater precision in colour markings.     

Discrimination of coral reflectance spectra in the Red Sea

Benthic populations can potentially be mapped from remotely acquired spectral imagery, provided that they have distinctive reflectance signatures. We examined the spectral reflectance characteristics of 14 genera of Red Sea coral using a submersible spectroradiometer. Coral spectra varied quantitatively and qualitatively over the depth interval 5-20 m. Tissue pigment content had a larger effect on reflectance than colony morphology. Ten coral genera could be discriminated with a statistical probability of 52% on the basis of their absolute reflectance. Six groups of two to three coral genera could be discriminated with a probability of 60% on the basis of their rates of change in reflectance at specific wavelengths. All coral genera could be discriminated with a minimum probability of 59% on the basis of their proportionate reflectance at one wavelength as compared with another. Ratio analysis holds significant potential for interpretation of remotely sensed imagery because measurement of reflectance at six wavelengths generates 15 different parameters that can be used to identify and discriminate the component classes. The method distinguishes spectra on the basis of their shape rather than their amplitude, which helps to factor out light-induced variation in pigment concentration, exposing taxon-specific differences in pigment composition and morphology.     

月光花素的研究

月光花素(calonyctin)是从月光花的茎叶中提取的一种天然植物生长调节物。其化学结构是由11-羟基十六-烷酸及十四烷酸乙酯和2-羟基-3-甲基-丁酸与四个鼠李糖所组成的糖苷。月光花素在十几种农作物上均有很强的生理活性;特别是对植物愈伤组织的生长和分化有显著的调节作用。     

中国沿海的赤潮问题

统计了中国沿海１９７２～１９９８年的赤潮事件３６０起（香港、台湾省未统计在内）,系统介绍了中国赤潮研究概况和研究机构与组织。对中国沿海的赤潮进行分海区分析。根据海洋学特征,中国赤潮可分为：近岸型（河口和内湾型）、外海型（外洋型）、外来型（外源型）、养殖区型赤潮。根据中国近十多年来发生赤潮的现状,可归纳为４个特点：①频率增高;②持续时间长、范围广和危害增大;③新记录和有毒种类增多;④“双相型”赤潮有上升趋势、类型多样等。