Ocean acidification, caused by rising concentrations of carbon dioxide (CO2), is widely considered... more Ocean acidification, caused by rising concentrations of carbon dioxide (CO2), is widely considered to be a major global threat to marine ecosystems. To investigate the potential effects of ocean acidification on the early life stages of a commercially important fish species, European sea bass (Dicentrarchus labrax), 12000 larvae were incubated from hatch through metamorphosis under a matrix of two temperatures (17 and 19◦C) and two seawater pCO2 levels (ambient and 1,000µatm) and sampled regularly for 42 days. Calculated daily mortality was significantly affected by both temperature and pCO2, with both increased temperature and elevated pCO2 associated with lower daily mortality and a significant interaction between these two factors. There was no significant pCO2 effect noted on larval morphology during this period but larvae raised at 19◦C possessed significantly larger eyes and lower carbon:nitrogen ratios at the end of the study compared to those raised under 17◦C. Similarly, when the incubation was continued to post-metamorphic (juvenile) animals (day 67–69), fish raised under a combination of 19◦C and 1000µatm pCO2 were significantly heavier. However, juvenile D. labrax raised under this combination of 19◦C and 1000µatm pCO2 also exhibited lower aerobic scopes than those incubated at 19◦C and ambient pCO2. Most studies investigating the effects of near-future oceanic conditions on the early life stages of marine fish have used incubations of relatively short durations and suggested that these animals are resilient to ocean acidification. Whilst the increased survival and growth observed in this study supports this view, we conclude that more work is required to investigate whether the differences in juvenile physiology observed in this study manifest as negative impacts in adult fish.
It has long been viewed that invertebrates rely exclusively upon a wide variety of innate mechani... more It has long been viewed that invertebrates rely exclusively upon a wide variety of innate mechanisms for protection from disease and parasite invasion and lack any specific acquired immune mechanisms comparable to those of vertebrates. Recent findings, however, suggest certain invertebrates may be able to mount some form of specific immunity, termed 'specific immune priming', although the mechanism of this is not fully understood (see Textbox S1). In our initial experiments, either formalin-inactivated Vibrio harveyi or sterile saline were injected into the main body cavity (haemocoel) of juvenile shrimp (Litopenaeus vannamei). Haemocytes (blood cells) from V. harveyi-injected shrimp were collected 7 days later and incubated with a 1:1 mix of V. harveyi and an unrelated Gram positive bacterium, Bacillus subtilis. Haemocytes from 'vaccinated' shrimp showed elevated levels of phagocytosis of V. harveyi, but not B. subtilis, compared with those from saline-injected (non-immunised) animals. The increased phagocytic activity was characterised by a significant increase in the percentage of phagocytic cells. When shrimp were injected with B. subtilis rather than vibrio, there was no significant increase in the phagocytic activity of haemocytes from these animals in comparison to the non-immunised (saline injected) controls. Whole haemolymph (blood) from either 'immunised' or non-immunised' shrimp was shown to display innate humoral antibacterial activity against V. harveyi that was absent against B. subtilis. However, there was no difference in the potency of antibacterial activity between V. harveyi-injected shrimp and control (saline injected) animals showing that 'vaccination' has no effect on this component of the shrimp's immune system. These results imply that the cellular immune system of shrimp, particularly phagocytosis, is capable of a degree of specificity and shows the phenomenon of 'immune priming' reported by other workers. However, in agreement with other studies, this phenomenon is not universal to all potential pathogens.
Marine reserves (or No-Take Zones) are implemented to protect species and habitats, with the aim ... more Marine reserves (or No-Take Zones) are implemented to protect species and habitats, with the aim of restoring a balanced ecosystem. Although the benefits of marine reserves are commonly monitored, there is a lack of insight into the potential detriments of such highly protected waters. High population densities attained within reserves may induce negative impacts such as unfavourable trophic cascades and disease outbreaks. Hence, we investigated the health of lobster populations in the UK's Marine Conservation Zone (MCZ) at Lundy Island. Comparisons were made between the fished, Refuge Zone (RZ) and the un-fished, No-Take Zone (NTZ; marine reserve). We show ostensibly positive effects such as increased lobster abundance and size within the NTZ; however, we also demonstrate apparent negative effects such as increased injury and shell disease. Our findings suggest that robust cost-benefit analyses of marine reserves could improve marine reserve efficacy and subsequent management strategies.
2012). Triaxial accelerometers tease apart discrete behaviours in the common cuttlefish Sepia off... more 2012). Triaxial accelerometers tease apart discrete behaviours in the common cuttlefish Sepia officinalis.
One of the dogmas of comparative (evolutionary) immunology for the last few decades has been that... more One of the dogmas of comparative (evolutionary) immunology for the last few decades has been that all invertebrates lack any form of immunological memory similar to that found in jawed vertebrates. Vaccinating invertebrates, such as shrimp, should therefore be an ineffective management strategy resulting in no more than short-lived, non-specific immune stimulation. Recent studies in crustaceans and insects, however, suggest a form of immune memory in these animals described variously as ‘immune priming’, ‘specific immune priming’ or ‘line specific immune memory’. Workers have injected various arthropod species with inactivated pathogens and then later challenged them with a dose of the same pathogen capable of killing the host, reporting enhanced survival or increased reproductive fecundity compared with animals vaccinated with an unrelated organism. Interestingly, in some studies this enhanced immunity is trans-generational (i.e. passed on to progeny). This brief review focusses on a mechanistic exploration of ‘specific immune priming’ with particular reference to shrimp culture. Humoral antimicrobial factors, such as antimicrobial peptides and lysozyme, do not possess the required specificity to explain this phenomenon. Instead, recent studies have demonstrated elevated phagocytic activity after “vaccination” that does not result from general (non-specific) stimulation in phagocytosis. This enhanced phagocytic activity is likely linked to specific recognition of determinants on the outside of microbes by the haemocytes of these “vaccinated” animals. In some cases, at least, the mechanism for recognising these determinants appears to rely upon an invertebrate homologue of the Down syndrome cellular adhesion molecule (Dscam) and the ability of the Dscam gene to produce variants of this molecule with specific binding capabilities. Pioneering studies have demonstrated that Dscam is intricately involved in phagocytosis in insects and able to produce pathogen-specific splice form variants after immune challenge or infection. This would enable an animal to tailor an immune response specifically to a pathogen. It should be noted, however, that the phenomenon of immune priming is certainly not universal, possibly because of the much lower numbers of different immune receptors that arthropods are able to produce compared with jawed vertebrates. The review concludes that immune priming in invertebrates should be re-evaluated on an animal to animal and pathogen to pathogen basis. It also notes that whilst there is evidence that vaccinating shrimp against viral and bacterial infections shows promise, the practicality of such processes and their benefit to shrimp requires further evaluation.► Shrimp culture is affected by periodic viral and bacterial diseases. ► These diseases are difficult to control. ► This review examines approaches to ‘vaccination’ of crustaceans such as shrimp. ► Changes in the immune system of shrimp following vaccination are reviewed.
This study reports on an emerging fungal disease of the edible 21 crab, Cancer pagurus. Juvenile ... more This study reports on an emerging fungal disease of the edible 21 crab, Cancer pagurus. Juvenile (pre-recruit) crabs were found to be subject to 22 this disease condition during the months of May to September at two intertidal 23 sites in South Wales, U.K. Histopathology revealed that the fungi overwhelm 24 the host response in the tissues, leading to progressive septicaemia. The 25 causative agent of this infection was isolated and grown in pure culture and 26 was identified as a member of the Ophiocordyceps clade by sequencing of the 27 small subunit of the fungal rDNA. Of the crabs naturally infected with the 28 fungus, 94% had a co-infection with the parasitic dinoflagellate, 29 Hematodinium. To determine if there was any interaction between the two 30 disease-causing agents, apparently fungus-free crabs, both with and without 31 natural Hematodinium infections, were challenged with the fungal isolate. The 32 presence of Hematodinium caused a significant reduction in fungal 33 multiplication in the hemocoel of the crabs in comparison to Hematodinium-34 free individuals. Histopathology of co-infected crabs showed a systemic 35 multiplication of Hematodinium within host tissues, leading to a rapid death; 36 whilst Hematodinium-free crabs experimentally infected with the fungal 37 isolate, died due to fungal sepsis (septicemia) with the same characteristic 38 pathology as seen in natural infections.
Ectoparasitic copepods have been reported in a wide range of aquatic animals, including crustacea... more Ectoparasitic copepods have been reported in a wide range of aquatic animals, including crustacean shellfish. However, with the exception of the salmon louse, Lepeophtheirus salmonis, our knowledge of such parasites in commercial species is rudimentary. The current study examines the morphology and pathology of the parasitic copepod, Nicothoë astaci (the ‘lobster louse’) in its host, the European lobster, Homarus gammarus. Lobsters were sampled from waters surrounding Lundy Island (Bristol Channel, UK) and all individuals collected were found to harbour female adult N. astaci in their gills, with a mean of 47·3 parasites/lobster. The majority of N. astaci were found in the basal region of pleurobranch gills. The parasite was found to attach to gill filaments via its oral sucker, maxillae and maxillipeds, and to feed on host haemolymph (blood) through a funnel-like feeding channel. It caused varying degrees of damage to the host gill, including occlusion of gill filaments and disruption to the vascular system in the central axis. Although there was evidence of extensive host response (haemocytic infiltration) to the parasite, it was displaced from the parasite attachment site and thus was observed in the central gill axis below. The region of gill filament immediately underlying the parasite feeding channel was devoid of such activity suggesting that the parasite interferes with the cellular defence and haemostatic mechanisms of the lobster in order to maintain invasion of the host.(Received January 06 2011)(Revised March 18 2011)(Revised April 21 2011)(Accepted May 10 2011)(Online publication July 15 2011)
Ocean acidification, caused by rising concentrations of carbon dioxide (CO2), is widely considered... more Ocean acidification, caused by rising concentrations of carbon dioxide (CO2), is widely considered to be a major global threat to marine ecosystems. To investigate the potential effects of ocean acidification on the early life stages of a commercially important fish species, European sea bass (Dicentrarchus labrax), 12000 larvae were incubated from hatch through metamorphosis under a matrix of two temperatures (17 and 19◦C) and two seawater pCO2 levels (ambient and 1,000µatm) and sampled regularly for 42 days. Calculated daily mortality was significantly affected by both temperature and pCO2, with both increased temperature and elevated pCO2 associated with lower daily mortality and a significant interaction between these two factors. There was no significant pCO2 effect noted on larval morphology during this period but larvae raised at 19◦C possessed significantly larger eyes and lower carbon:nitrogen ratios at the end of the study compared to those raised under 17◦C. Similarly, when the incubation was continued to post-metamorphic (juvenile) animals (day 67–69), fish raised under a combination of 19◦C and 1000µatm pCO2 were significantly heavier. However, juvenile D. labrax raised under this combination of 19◦C and 1000µatm pCO2 also exhibited lower aerobic scopes than those incubated at 19◦C and ambient pCO2. Most studies investigating the effects of near-future oceanic conditions on the early life stages of marine fish have used incubations of relatively short durations and suggested that these animals are resilient to ocean acidification. Whilst the increased survival and growth observed in this study supports this view, we conclude that more work is required to investigate whether the differences in juvenile physiology observed in this study manifest as negative impacts in adult fish.
It has long been viewed that invertebrates rely exclusively upon a wide variety of innate mechani... more It has long been viewed that invertebrates rely exclusively upon a wide variety of innate mechanisms for protection from disease and parasite invasion and lack any specific acquired immune mechanisms comparable to those of vertebrates. Recent findings, however, suggest certain invertebrates may be able to mount some form of specific immunity, termed 'specific immune priming', although the mechanism of this is not fully understood (see Textbox S1). In our initial experiments, either formalin-inactivated Vibrio harveyi or sterile saline were injected into the main body cavity (haemocoel) of juvenile shrimp (Litopenaeus vannamei). Haemocytes (blood cells) from V. harveyi-injected shrimp were collected 7 days later and incubated with a 1:1 mix of V. harveyi and an unrelated Gram positive bacterium, Bacillus subtilis. Haemocytes from 'vaccinated' shrimp showed elevated levels of phagocytosis of V. harveyi, but not B. subtilis, compared with those from saline-injected (non-immunised) animals. The increased phagocytic activity was characterised by a significant increase in the percentage of phagocytic cells. When shrimp were injected with B. subtilis rather than vibrio, there was no significant increase in the phagocytic activity of haemocytes from these animals in comparison to the non-immunised (saline injected) controls. Whole haemolymph (blood) from either 'immunised' or non-immunised' shrimp was shown to display innate humoral antibacterial activity against V. harveyi that was absent against B. subtilis. However, there was no difference in the potency of antibacterial activity between V. harveyi-injected shrimp and control (saline injected) animals showing that 'vaccination' has no effect on this component of the shrimp's immune system. These results imply that the cellular immune system of shrimp, particularly phagocytosis, is capable of a degree of specificity and shows the phenomenon of 'immune priming' reported by other workers. However, in agreement with other studies, this phenomenon is not universal to all potential pathogens.
Marine reserves (or No-Take Zones) are implemented to protect species and habitats, with the aim ... more Marine reserves (or No-Take Zones) are implemented to protect species and habitats, with the aim of restoring a balanced ecosystem. Although the benefits of marine reserves are commonly monitored, there is a lack of insight into the potential detriments of such highly protected waters. High population densities attained within reserves may induce negative impacts such as unfavourable trophic cascades and disease outbreaks. Hence, we investigated the health of lobster populations in the UK's Marine Conservation Zone (MCZ) at Lundy Island. Comparisons were made between the fished, Refuge Zone (RZ) and the un-fished, No-Take Zone (NTZ; marine reserve). We show ostensibly positive effects such as increased lobster abundance and size within the NTZ; however, we also demonstrate apparent negative effects such as increased injury and shell disease. Our findings suggest that robust cost-benefit analyses of marine reserves could improve marine reserve efficacy and subsequent management strategies.
2012). Triaxial accelerometers tease apart discrete behaviours in the common cuttlefish Sepia off... more 2012). Triaxial accelerometers tease apart discrete behaviours in the common cuttlefish Sepia officinalis.
One of the dogmas of comparative (evolutionary) immunology for the last few decades has been that... more One of the dogmas of comparative (evolutionary) immunology for the last few decades has been that all invertebrates lack any form of immunological memory similar to that found in jawed vertebrates. Vaccinating invertebrates, such as shrimp, should therefore be an ineffective management strategy resulting in no more than short-lived, non-specific immune stimulation. Recent studies in crustaceans and insects, however, suggest a form of immune memory in these animals described variously as ‘immune priming’, ‘specific immune priming’ or ‘line specific immune memory’. Workers have injected various arthropod species with inactivated pathogens and then later challenged them with a dose of the same pathogen capable of killing the host, reporting enhanced survival or increased reproductive fecundity compared with animals vaccinated with an unrelated organism. Interestingly, in some studies this enhanced immunity is trans-generational (i.e. passed on to progeny). This brief review focusses on a mechanistic exploration of ‘specific immune priming’ with particular reference to shrimp culture. Humoral antimicrobial factors, such as antimicrobial peptides and lysozyme, do not possess the required specificity to explain this phenomenon. Instead, recent studies have demonstrated elevated phagocytic activity after “vaccination” that does not result from general (non-specific) stimulation in phagocytosis. This enhanced phagocytic activity is likely linked to specific recognition of determinants on the outside of microbes by the haemocytes of these “vaccinated” animals. In some cases, at least, the mechanism for recognising these determinants appears to rely upon an invertebrate homologue of the Down syndrome cellular adhesion molecule (Dscam) and the ability of the Dscam gene to produce variants of this molecule with specific binding capabilities. Pioneering studies have demonstrated that Dscam is intricately involved in phagocytosis in insects and able to produce pathogen-specific splice form variants after immune challenge or infection. This would enable an animal to tailor an immune response specifically to a pathogen. It should be noted, however, that the phenomenon of immune priming is certainly not universal, possibly because of the much lower numbers of different immune receptors that arthropods are able to produce compared with jawed vertebrates. The review concludes that immune priming in invertebrates should be re-evaluated on an animal to animal and pathogen to pathogen basis. It also notes that whilst there is evidence that vaccinating shrimp against viral and bacterial infections shows promise, the practicality of such processes and their benefit to shrimp requires further evaluation.► Shrimp culture is affected by periodic viral and bacterial diseases. ► These diseases are difficult to control. ► This review examines approaches to ‘vaccination’ of crustaceans such as shrimp. ► Changes in the immune system of shrimp following vaccination are reviewed.
This study reports on an emerging fungal disease of the edible 21 crab, Cancer pagurus. Juvenile ... more This study reports on an emerging fungal disease of the edible 21 crab, Cancer pagurus. Juvenile (pre-recruit) crabs were found to be subject to 22 this disease condition during the months of May to September at two intertidal 23 sites in South Wales, U.K. Histopathology revealed that the fungi overwhelm 24 the host response in the tissues, leading to progressive septicaemia. The 25 causative agent of this infection was isolated and grown in pure culture and 26 was identified as a member of the Ophiocordyceps clade by sequencing of the 27 small subunit of the fungal rDNA. Of the crabs naturally infected with the 28 fungus, 94% had a co-infection with the parasitic dinoflagellate, 29 Hematodinium. To determine if there was any interaction between the two 30 disease-causing agents, apparently fungus-free crabs, both with and without 31 natural Hematodinium infections, were challenged with the fungal isolate. The 32 presence of Hematodinium caused a significant reduction in fungal 33 multiplication in the hemocoel of the crabs in comparison to Hematodinium-34 free individuals. Histopathology of co-infected crabs showed a systemic 35 multiplication of Hematodinium within host tissues, leading to a rapid death; 36 whilst Hematodinium-free crabs experimentally infected with the fungal 37 isolate, died due to fungal sepsis (septicemia) with the same characteristic 38 pathology as seen in natural infections.
Ectoparasitic copepods have been reported in a wide range of aquatic animals, including crustacea... more Ectoparasitic copepods have been reported in a wide range of aquatic animals, including crustacean shellfish. However, with the exception of the salmon louse, Lepeophtheirus salmonis, our knowledge of such parasites in commercial species is rudimentary. The current study examines the morphology and pathology of the parasitic copepod, Nicothoë astaci (the ‘lobster louse’) in its host, the European lobster, Homarus gammarus. Lobsters were sampled from waters surrounding Lundy Island (Bristol Channel, UK) and all individuals collected were found to harbour female adult N. astaci in their gills, with a mean of 47·3 parasites/lobster. The majority of N. astaci were found in the basal region of pleurobranch gills. The parasite was found to attach to gill filaments via its oral sucker, maxillae and maxillipeds, and to feed on host haemolymph (blood) through a funnel-like feeding channel. It caused varying degrees of damage to the host gill, including occlusion of gill filaments and disruption to the vascular system in the central axis. Although there was evidence of extensive host response (haemocytic infiltration) to the parasite, it was displaced from the parasite attachment site and thus was observed in the central gill axis below. The region of gill filament immediately underlying the parasite feeding channel was devoid of such activity suggesting that the parasite interferes with the cellular defence and haemostatic mechanisms of the lobster in order to maintain invasion of the host.(Received January 06 2011)(Revised March 18 2011)(Revised April 21 2011)(Accepted May 10 2011)(Online publication July 15 2011)
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