Rabbitfish Siganus Rivulatus Research Articles

Effects of sublethal concentrations of zinc nanoparticles on bioaccumulation and cellular response in the Rabbitfish Siganus rivulatus

Zinc oxide nanoparticles (ZnONP) are increasingly utilized in many products worldwide. Eventual release into the aquatic system poses various environmental hazards and raises concerns for aquatic life and public health. In the present study, the effects of waterborne ZnONP and dissolved Zn+2 (ZnSO4 7H2O) were investigated in Siganus rivulatus through experimental exposure to environmentally relevant concentrations (40, 200, and 400 µg/L) of Zn in both forms. Fish exposed to ZnONP exhibited a higher accumulation of zinc in their muscles, whereas exposure to Zn+2 ions led to elevated zinc levels in the gills and liver. The physiological and histopathological analyses revealed distinct responses between the two experimental groups. ZnONP exposure stimulated the antioxidant system, resulting in a significant elevation (1.7–2 folds) of superoxide dismutase (SOD) and catalase (CAT) enzymes in the gills. On the other hand, Zn+2 ions increased the levels of SOD, CAT, and Glutathione-S-transferase (GST) enzymes 1.5–2.4 times in the liver, along with 1.9–2 folds higher lipid peroxidation (LPO) in both the liver and gills. Histological examination of the gills revealed lamellar fusions, degenerative alterations, and infiltration of melanomacrophagic centers, indicating the impact of both treatments. Similarly, the liver tissue showed cytoplasmic vacuolation and significant infiltration of melanomacrophagic centers engorged with brown spots. These histopathological changes were more severe in fish exposed to all concentrations of Zn+2 and in fish exposed to 400 µg/L of ZnONP. This study concludes that waterborne Zn+2 exhibited higher toxicity in fish liver and gills compared to ZnONP. However, the mechanisms of ZnONP uptake by fish tissues remain unclear and require further investigation.

Stock Status and Management of the Rabbitfish Siganus rivulatus in the Suez Bay, Gulf of Suez, Egypt.

Stock Status and Management of the Rabbitfish Siganus rivulatus in the Suez Bay, Gulf of Suez, Egypt.

The potential role of marine macroalgae Padina pavonica on growth performance, histological status, and resistance of the rabbitfish Siganus rivulatus to Pseudomonas anguilliseptica bacteria

The potential role of marine macroalgae Padina pavonica on growth performance, histological status, and resistance of the rabbitfish Siganus rivulatus to Pseudomonas anguilliseptica bacteria

An invasive herbivorous fish (Siganus rivulatus) influences both benthic and planktonic microbes through defecation and nutrient excretion

Direct and indirect impacts by invasive animals on plants and other animals through predation and competition have been evidenced in many ecosystems. For instance, the rabbitfish Siganus rivulatus, originating from the Red Sea, is now the most abundant species in costal habitats of South-Eastern Mediterranean Sea where it overgrazes algae. However, little is known about its impacts on microbes through release of metabolic wastes and feces. We used a mesocosm experiment to test the effect of S. rivulatus on planktonic and benthic microbial communities. Excretion of dissolved nutrients by fish resulted in higher concentrations of dissolved inorganic nitrogen (NH4, NO2/NO3). This increase in availability of N was associated with higher N content in macroalgae, higher biomass of phytoplankton, higher abundance of bacterioplankton and shift in the structure of planktonic bacterial communities. The feces released mostly under the shelters where the fish rest at night, led to significant increases in diversity of sediment bacterial communities and shifts in their structure. The impact of S. rivulatus on planktonic microbes was related to the indirect bottom-up effect induced by excreted dissolved nutrients while its effect on benthic microbes was due to the direct release of both organic matter and microbes present in feces. Overall, this first evidence of the impacts of invasive species on planktonic and benthic microbes highlights that ongoing changes in fish biodiversity could have ecosystem-wide consequences.

Genetic divergence and phylogenetic relationship of the rabbitfish Siganus rivulatus inferred from microsatellite and mitochondrial markers

The rabbit fish, Siganus rivulatus, is a Mediterranean non-endogenous species, that has succeeded in migrating to the different coasts of the Mediterranean Sea. The success of this species in the new environment, with different trophic, biotic, and physical conditions, inspired the study of genetic variation between the Rea Sea and Mediterranean Sea populations. The current study aims to use microsatellite (SSR) and mitochondrial DNA sequence (mtDNA) markers to determine the genetic divergence and phylogenetic relationship of S. rivulatus from the Red Sea and the Mediterranean Sea. A total of 200 S. rivulatus samples (42.50 ± 3.89 gm) were collected from the Red Sea and the Mediterranean Sea. Twelve SSR loci were screened to detect genetic differentiation, in addition to those in mtDNA. The results for the SSR markers showed seventy polymorphic alleles, with an average of 5.83 alleles per locus. Additionally, the inter-population genetic diversity was 0.063. The nucleotide composition of the MT-CO1 sequences revealed clear variations between the two studied populations. Phylogenetic analyses indicated that the Red Sea samples were more versatile than the Mediterranean Sea samples. The results indicated that the mtDNA of S. rivulatus is very variable and a species-sensitive marker to detect possible genetic variations, which could be part of the eco-physiological adaptation and key to the success of the migrant S. rivulatus in the Mediterranean Sea.

Right out of the gate: the genomics of Lessepsian invaders in the vicinity of the Suez Canal

Marine organisms that enter the Mediterranean from the Red Sea via the Suez Canal are known as Lessepsian bioinvaders. In general, genetic studies of Lessepsian fishes have shown little structure between Red Sea and Mediterranean populations. Yet notable exceptions suggest the importance of life-history factors that may influence patterns of spatial genetic variation. In this study, by sampling two invasive fishes with different life histories (the rabbitfish Siganus rivulatus and the filefish Stephanolepis diaspros), we looked at evidence of population structure and selection at the boundary between the Red Sea and the Mediterranean (the Suez Canal), using thousands of molecular markers. Results illustrate two divergent patterns of genetic patterns, with little genetic structure in S. rivulatus and strong population structure in S. diaspros, even at such small spatial scale. We discuss differences in ecological characteristics between the two species to account for such differences. In addition, we report that in the face of both high (S. rivulatus) and low (S. diaspros) gene flow, loci under selection were uncovered, and some protein coding genes were identified as being involved with osmoregulation, which seems to be an important feature of individuals crossing the salinity-variable Suez Canal. The presence of genes under selection in populations near the Suez Canal supports the idea that selection may be active and essential for successful invasions right out of the gate.

Biodiversity and Efficiency of fish helminths parasites as a possible bioindicator of water quality in Jazan coastal area, Saudi Arabia

The present study was presented to assess a database about the helminthes parasites species infested marine fish in Jazan coastal area. Thus, the following sites were selected; Jazan Fishing site, Jazan coast near Aramco Company and the coastal area near the sewage treatment station. Emperor fish Lethrinus sp ., rabbitfish Siganus rivulatus, Greasy grouper Epinephelus tauvina, and the marinefish Carangoides orthogrammus were investigated. Water criteria; pH, dissolved oxygen and conductivity were determined for the selected sites. Four trematodes, two nematodes, one acanthocephalan species were detected. Larval stages of trematode, cestode, nematode and acanthocephalan were isolated. A high prevalence of infection was recorded for trematode and nematode parasites in Epinephelus tauvina, Lethrinus nebulosus, and Siganus rivulatus. No significant effect was shown for body weight or sex on the abundance of helminth parasites. Shannon-Wiener diversity index studies demonstrated the highest diversity of helminth parasites for the fishing areas and lowest helminth diversity infected Siganus rivulatus collected from the coastal area near sewage treatment station or Aramco Company. Regression analysis data showed high significant relationship between pH and conductivity on the abundance of trematode, nematode and Acanthocephala and between the dissolved oxygen concentration and the abundance of nematode and Acanthocephala at the three examined sites. Data were discussed to assess the efficiency of helminthes parasites as bioindicator for water quality in the Jazan marine ecosystem.

Hydrolytic bacteria associated with natural helminth infection in the midgut of Red Sea marbled spinefoot rabbit fish Siganus rivulatus

Fish infected with intestinal helminths or pathogenic bacteria can pose a serious risk of foodborne disease, threatening human and animal health, and require high attention. The current study investigates the diversity and composition of the microbiota in the midgut of rabbit fish Siganus rivulatus naturally infected with helminths. Six species of helminth parasites, including the digeneans Hexangium sigani and Gyliauchen volubilis, the acanthocephalans Sclerocollum rubrimaris and Neorhadinorhynchus macrospinosus, and the nematodes Procammalanus elatensis, and Ascaridoid larvae were recorded in the fish intestine. P. elatensis had the highest prevalence, occurring in 65% of infected fish; 72.2% of infected fish had concurrent infection with two or more helminth species. The total count of aerobic bacteria ranged from 1 to 305 colony-forming units (CFU)/g midgut contents. Four hydrolytic bacteria were recovered from the infected samples: Escherichia coli (ASU 31), Bacillus cereus (ASU 36) MN955553, Bacillus thuringiensis (ASU 34) MN955550, and Novosphingobium aromaticivorans (ASU 35) MN955552, which were identified using 16S rRNA genes. Bacterial richness was significantly correlated with concurrent parasitic infection and high content of extracellular hydrolytic amylases, proteases, cellulases, and lipases. The present results showed that the composition of the microbiota was affected by natural helminth infections in Siganus rivulatus, and the significant interaction between parasitic load and intestinal pathogenic bacteria, which may be primary in fish diseases etiology.

Variation in the Reproductive Biology of Female Rabbitfish Siganus rivulatus with Histological and Ultrastructural Evidence

Variation in the Reproductive Biology of Female Rabbitfish Siganus rivulatus with Histological and Ultrastructural Evidence

Neoechinorhynchus macrospinosus (Acanthocephala: Neoechinorhynchidae) in Rabbit fish Siganus rivulatus (Siganidae): morphology and phylogeny.

Siganids are the most important marine fish distributed along the African coast. Therefore, the current study aimed to investigate parasite fauna infects one of the most important mariculture fish species in the Red Sea, the Rabbit fish Siganus rivulatus. One acanthocephalan species has been isolated from the posterior region of fish intestine, belonging to the Neoechinorhynchidae family, and named as Neoechinorhynchus macrospinosus Amin & Nahhas, 1994 based on its morphological and morphometric features. In order to determine the accurate taxonomic position of this acanthocephalan species, molecular phylogenetic analysis was carried out based on the partial sequences of 18S rDNA gene region. The obtained data revealed that this species was associated with a close identity ˃71% for other species belonging to the Neoechinorhynchidae family. In addition, the recovered species deeply embedded in the Neoechinorhynchus genus, closely related to the previously described Neoechinorhynchus sp., N. mexicoensis, and N. golvani with identity percent of 95.14, 93.59, 93.59%, respectively. Therefore, the present study provide a better understanding about the taxonomic status of N. macrospinosus based on 18S rDNA that can be useful for achieving a proper assessment of biodiversity.

Embryonic development of the rabbit fish Siganus rivulatus and allometric growth patterns during yolk sac larvae stage produced by hormone-induced broodstock

Embryonic development of the rabbit fish Siganus rivulatus and allometric growth patterns during yolk sac larvae stage produced by hormone-induced broodstock

Stock assessment and management of the rabbitfish Siganus rivulatus from the Southern Red Sea, Egypt

Stock assessment and management of the rabbitfish Siganus rivulatus from the Southern Red Sea, Egypt

Habitat utilization by an invasive herbivorous fish (Siganus rivulatus) in its native and invaded range

Movement is essential for understanding the distribution and abundance of animals. While it has been suggested that invasion success can be facilitated by species’ ability to adapt to novel environments, direct comparisons of movement patterns between native and invaded ranges of animals in their natural habitat are rare. The rivulated rabbitfish Siganus rivulatus was introduced from the Red Sea into the Mediterranean, where it is now found in extremely high abundances, and has overgrazed the coastal marine ecosystem in many locations. Through a continuous acoustic tracking system, we found that the movement of S. rivulatus individuals at a Mediterranean site differed substantially from those at a Red Sea site, with individuals in the Mediterranean having larger overall home ranges and lower site fidelity. However, no variation between sites was found in daily home range sizes. Results show that at the Mediterranean site S. rivulatus individuals have a larger spatial footprint, which may contribute to their impact and ability to expand their distribution. This study demonstrates a potential shift in individual movement of a marine invasive species between its native and invaded range, and highlights the role of movement in understanding biological invasions.

Dietary arachidonic acid affects immune function and fatty acid composition in cultured rabbitfish Siganus rivulatus

The marbled spinefoot rabbitfish (Siganus rivulatus) is an economically valuable fish species that has potential for commercial production in aquaculture. To overcome challenges in its sustainable production, a formulated diet is required for imparting health and robustness. This study evaluates the effect of dietary supplementation with arachidonic acid (ARA; 20:4n-6) on growth, survival, immune function and fatty acid composition of red blood cells (RBCs) in rabbitfish. We conducted two feeding trials using juvenile fish (to evaluate growth and survival) and adults (to evaluate immune function and fatty acid incorporation). Fish were fed diets supplemented with three different levels of ARA (in % of total fatty acids): 0.6 (unsupplemented control), 2.6 (moderate) and 4.7 (high). The fish fed with moderate ARA levels exhibited improved (p < 0.05) growth over the control and the high ARA level groups. During an outbreak of Streptococcus iniae, fish fed with moderate ARA survived significantly (p < 0.05) better (89%) than the control and the high ARA groups (59% and 48%, respectively). Moderate ARA supplementation resulted in elevated lysozyme and complement levels in the plasma of rabbitfish. A significant increase in the total serum immunoglobulin levels was observed in both the medium and the high ARA level groups; however, a decrease in antiprotease activity was recorded in the supplemented groups as compared to the control.Fatty acid analysis in fish red blood cells revealed a significant (p < 0.05) increase in the proportion of ARA of total fatty acids in the groups fed with the medium and the high ARA level diets (9.5% and 11.2%, respectively, compared to 7.1% in the control). Concomitantly, there was a decrease in the proportion of eicosapentaenoic acid (EPA; 20:5n-3), dihomo-γ linolenic acid (DGLA; 20:3n-6) and several 18-carbon unsaturated fatty acids in these groups.In conclusion, ARA in rabbitfish feeds improved growth, survival as well as innate and acquired humoral immune functions. Thus ARA supplementation in the diet of this species could be a valuable step towards establishing the commercial culture of rabbitfish.

A novel marine bioinvasion vector: Ichthyochory, live passage through fish

AbstractMany species of Indo‐Pacific holobenthic foraminifera have been introduced and successfully established sustainable populations in the Mediterranean Sea over the past few decades. However, known natural and anthropogenic vectors do not explain how these species were introduced long distances from their origin. We present evidence for a novel marine bioinvasion vector explaining this long‐distance transport and introduction using both contemporary field and historical analyses. In 2015–2016, we found living specimens of 29 foraminiferal species in the fecal pellets of two Red Sea herbivorous rabbitfish—Siganus rivulatus and Siganus luridus in the Mediterranean. In our historical analysis, we found 34 foraminiferal species in preserved Red Sea rabbitfish specimens, dating between 1967 and 1975. In addition, we found congruent propagation patterns of the non‐indigenous rabbitfish and foraminifera, lagging 4–11 yrs between discoveries, respectively. Predation of marine benthos by non‐indigenous fish, followed by incomplete digestion and defecation of viable individuals, comprise the main introduction vector of these organisms into novel environments.

Effect of feeding frequency and feeding time on growth performance, feed utilization efficiency and body chemical composition on Rabbitfish Siganus rivulatus fry and juvenile under laboratory condition

The present study consisted of two trials that conducted to evaluate the feeding frequency and the feeding time on growth performance, feed efficiency and body composition of rabbitfish Siganus rivulatus, the fish fed on one diet (35% crude protein). The first trial was conducted on rabbitfish fry (initial weight 0.18 g ± 0.012) and consisted of different three treatments of feeding frequency, the first treatment the daily meal divided into two times, the second treatment the daily meal divided into three times and the third treatment, the meal was divided into four times. The second trial was conducted on rabbitfish juvenile (initial weight 0.948 g ± 0.124) and consisted of different four treatments of feeding time. fish fed in two times the first treatment fed at 9am and 11am, the second treatment fish fed at 11am and 1pm, the third treatment fish fed 1pm and 4pm and the fourth treatment fish fed at 9am and 4pm. The statistical analysis of results indicated that, feeding frequency feeding time appeared significantly differences between the treatments in growth performance and feed utilization parameters. The total gain in weight and feed conversion ratio were affected by feeding frequency and feeding time. The results affirmed that, the third treatment (four time feeding /day) in the first trial and both the first and second treatments in the second trial were the best of the growth performance and feed utilization parameters.

Effect of stocking density and water exchange period on growth performance, feed utilization and body chemical composition on Rabbitfish Siganus rivulatus juvenile under laboratory condition

Effect of stocking density and water exchange period on growth performance, feed utilization and body chemical composition on Rabbitfish Siganus rivulatus juvenile under laboratory condition

Herbivorous fishes Siganus rivulatus (Siganidae) and Zebrasoma desjardinii (Acanthuridae) feed on Ctenophora and Scyphozoa in the Red Sea

Individuals of the rabbitfish Siganus rivulatus (Siganidae) and surgeonfish Zebrasoma desjardinii (Acanthuridae) were observed feeding on ctenophores and scyphozoans in the northern Red Sea during late spring and early summer seasons between 2010 and 2015. Siganus rivulatus and Z. desjardinii, considered nominally herbivorous, preyed on relatively large ctenophores until disintegration, and on the moon jellyfish Aurelia aurita (Scyphozoa) until they sank to the bottom. Siganus rivulatus was the most dominant predatory fish feeding on gelatinous zooplankton (37 % of attacks on ctenophores and 51 % of attacks on A. aurita). Furthermore, prey individuals were usually approached by two or more fish simultaneously. Eleven additional fish species fed on gelatinous zooplankton, with Chaetodon fasciatus (Chaetodontidae) accounting for 27 and 12 % of the attacks on ctenophores and A. aurita, respectively, and Z. desjardinii for 17 and 24 % of the attacks. Other fishes attacked gelatinous zooplankton in ≤6 % of the observations. This study constitutes the first record of S. rivulatus and Z. desjardinii preying on ctenophores and also confirms preliminary observations of S. rivulatus feeding on scyphozoans. Although herbivorous fishes may accidentally ingest small invertebrates while feeding on algae, the deliberate feeding on gelatinous zooplankton observed for S. rivulatus and Z. desjardinii suggests that their trophic role should be reevaluated.

Effect of Dietary Protein Level on Growth Performance and Blood Parameters of Marbled Spinefoot Siganus rivulatus

The present study evaluated the effect of dietary protein levels on growth performance and blood parameters of juvenile marbled spinefoot (Siganus rivulatus). Five semipurified, isoenergetic (14.2 MJ digestible energy/kg; 84 g lipids/kg) diets were formulated to contain 30, 35, 40, 45, and 50 g crude protein (CP)/100 g diet. Groups of 15 juvenile fish (7.4 g individual weight) were randomly assigned in triplicate to each of the five treatments and offered the test diets three times daily ad libitum for 9 weeks. Total erythrocyte and differential leukocyte counts, hematocrit, hemoglobin, blood glucose, protein, and serum aspartate aminotransferase and alanine aminotransferase were evaluated. Survival was greater than 95% in all treatments. Maximum growth was observed in fish offered the diet containing 40 g CP/100 g diet crude protein. Differences in dietary protein level had no effect on the hepatosomatic and viscerosomatic indices of the fish, but whole body composition was influenced by diet. Blood parameters showed no physiological or metabolic dysfunctions among fish offered any of the five diets. Findings of the present work strongly suggest that diets containing 40 g CP/100 g and 14.2 MJ digestible energy/kg are suitable for good growth of juvenile spinefoot rabbitfish Siganus rivulatus and do not affect hematological parameters.

Infections by Lactic Acid Bacteria in Marine Fish from Southern Israel (Red Sea): New Records

Gram-positive chain-forming bacteria were isolated from the spleen, kidney, and blood of dead wild Red Sea fish (broomtail wrasse Cheilinus lunulatus, grouper Epinephelus fasciatus, goatfish Parupeneus sp.) that washed ashore on the Eilat Nature Reserve beach (Israel, Red Sea). Gram-positive bacteria were similarly isolated from rabbitfish Siganus rivulatus, white grouper Epinephelus aeneus, and grey mullet Mugil cephalus cultured in the Israel Oceanographic and Limnological Research, National Center for Mariculture, Eilat. On the basis of their phenotypical characteristics and 16S rRNA gene partial sequence analyses, the bacteria were identified as Streptococcus parauberis (from C. lunulatus), Lactococcus lactis (from E. aeneus and M. cephalus), Streptococcus iniae (from E. fasciatus, Parupeneus sp. and S. rivulatus), Streptococcus agalactiae (from M. cephalus), and Carnobacterium sp. (from E. aeneus). These lactic acid bacteria, isolated between 2009 and 2011, are added to the growing list of bacterial pathogens detected in wild or farmed marine fish in the Gulf of Eilat in recent years, suggesting a rising trend in areas subjected to intense anthropogenic impact (including aquaculture), where newly emerging pathogens and previously unexposed host populations are brought together.