Evaluation of selected plant extracts for in vitro anti-marine leech (Zeylanicobdella arugamensis) activity

The aqueous extracts of thirty-four (34) tropical plants were tested in vitro for potential antimarine leech (Zeylanicobdella arugamensis) activity. The anti-leech activity was determined by exposing 8 adult leeches (Z. arugamensis) (9.3 ± 1.5 mm, aged 15 days) to 20 μl of plant extract (0.5 g/ml) for 5 min in a 24-well plate. After 5 min of exposure, the leeches were rinsed and transferred into seawater, to enable them to revive from the effect of the extract. Leech movements were observed from time to time and the numbers of paralyzed or dead leeches were recorded at 5, 20, 30 and 240 min. The efficacy of the plant extract in killing the adult Z. arugamensis during the 5 min exposure is reflected on the anti-leech property of the extract. The anti-leech property of positive plant extracts was also determined at different exposure time (1, 3, 5 min) and dilutions (1/2 (0.25 g/ml), 1/5 (0.1 g/ml) and 1/10 (0.05 g/ml). The extracts of 4 plants (Melastoma malabathricum, Piper betle, Tetracera indica and Etlingera coccinea) demonstrated anti-leech activity. The effects of M. malabathricum, P. betle and E. coccinea extracts on the leeches were very rapid causing death as early as a few seconds upon exposure. However, all four positive plant extracts were found not effective in killing the leeches at 1/10 dilution (0.05 g/ml). A Scanning Electron Microscopy examination on leeches exposed to the positive plant extracts exhibited effects such as protruding proboscis and shrunken or swollen bodies.

Occurrence of Enterocytozoon hepatopenaei (EHP) infection on Penaeus vannamei in one rearing cycle

The microsporidian parasite Enterocytozoon hepatopenaei (EHP) is an emerging problem in the marine shrimp industry, primarily in Asian countries such as China, Thailand, India, Malaysia, Indonesia, and Vietnam. A screening was conducted to investigate the prevalence of EHP after a fixed period of culturing for 1 rearing cycle in 3 states of Malaysia. The screening stages covered Penaeus vannamei post larvae (PL) and after 14-30, 31-50, 51-70, and 71-90 d of culture in 1 production cycle. A total of 279 samples were amplified using a PCR assay targeting the gene encoding a spore wall protein (SWP) of EHP. The EHP infection was initially detected in the hatchery and increased to 96.6% after the shrimp were transferred to the pond. The positive EHP sequence showed 91 to 100% similarity to sequences from India, Thailand, Vietnam, Indonesia, and Latin America. EHP infection increased throughout 1 rearing cycle due to factors such as the cannibalistic feeding habits of shrimp and the presence of unknown vectors or carriers of EHP in the culture ponds. Hence, the finding from the current study will be fundamental for other studies concerning EHP.

Effect of salinity and temperature on marine leech, Zeylanicobdella arugamensis (De Silva) under laboratory conditions

The high prevalence (80-100%) of the marine leech Zeylanicobdella arugamensis (De Silva) on cage-cultured Asian sea bass Lates calcarifer (Bloch) led us to investigate the percentage of juvenile leeches hatched from deposited cocoons, survival of juvenile and adult marine leeches at different salinity and temperature. The results showed that the hatching percentage of juvenile leeches was highest at salinity of 30 ppt (32.5 ± 2.8%) followed by 20 ppt (18.0 ± 4.3%) and 10 ppt (12.1 ± 1.4%), respectively. It was found that the adult and juvenile leeches could live up to an average range of 4-7 days at salinity ranging from 10 to 40 ppt. The juvenile leeches were able to hatch at temperature ranging from 25 to 35 °C but unable to hatch at 40 °C. The survival period of adult and juvenile leeches ranged from 11 to 16 days at 25 °C, which was comparatively longer than 5-13 days and 10 h--5 days at 27-30 °C and 35-40 °C, respectively. The study provided the information on the physical parameters of salinity and temperature which are most optimal for the marine leech Z. arugamensis to propagate.

Expression profile of immune-related genes in Lates calcarifer infected by Cryptocaryon irritans

Cryptocaryon irritans causes Cyptocaryonosis or white spot disease in a wide range of marine fish including Lates calcarifer (Asian seabass). However, the immune response of this fish to the parasite is still poorly understood. In this study, quantitative polymerase chain reaction (qPCR) was performed to assess the expression profile of immune-related genes in L. calcarifer infected by C. irritans. A total of 21 immune-related genes encoding various functions in the fish immune system were utilized for the qPCR analysis. The experiment was initiated with the infection of juvenile fish by exposure to theronts from 200 C. irritans cysts, and non-infected juvenile fish were used as controls. Spleen, liver, gills and kidney tissues were harvested at three days post-infection from control and infected fish. In addition, organs were also harvested on day-10 post-infection from fish that had been allowed to recover from day-4 up to day-10 post-infection. L. calcarifer exhibited pathological changes on day-3 post-infection with the characteristic presence of white spots on the entire fish body, excessive mucus production and formation of a flap over the fish eye. High quality total RNA was extracted from all tissues and qPCR was performed. The qPCR analysis on the cohort of 21 immune-related genes of the various organs harvested on day-3 post-infection demonstrated that most genes were induced significantly (p < 0.05) in all tissues, particularly liver (11/21 genes) and kidney (11/21). The expression profile demonstrated that induction of the MHC Class IIα gene was the highest compared to the other genes followed by serum amyloid A, CC chemokine and hepcidin-2 precursor genes. In fish that were allowed to recover from the C. irritans infection (10 days post-infection), expression of the immune-related genes was down-regulated to levels similar to the control fish. These results provide insights into the interaction between C. irritans and L. calcarifer and suggest that the innate immune system plays an important role in early defence against parasite infection allowing the fish to eventually recover from the infection.

Cryptocaryon irritans infection induces the acute phase response in Lates calcarifer: a transcriptomic perspective

Cryptocaryoniasis (also known as marine white spot disease) is mediated by Cryptocaryon irritans. This obligate ectoparasitic protozoan infects virtually all marine teleosts, which includes Lates calcarifer, a highly valuable aquaculture species. Little is known about L. calcarifer-C. irritans interactions. This study was undertaken to gain an informative snapshot of the L. calcarifer transcriptomic response over the course of C. irritans infection. An in-house fabricated cDNA microarray slides containing 3872 probes from L. calcarifer liver and spleen cDNA libraries were used as a tool to investigate the response of L. calcarifer to C. irritans infection. Juvenile fish were infected with parasites for four days, and total RNA was extracted from liver tissue, which was harvested daily. We compared the transcriptomes of C. irritans-infected liver to uninfected liver over an infection period of four days; the comparison was used to identify the genes with altered expression levels in response to C. irritans infection. The greatest number of infection-modulated genes was recorded at 2 and 3 days post-infection. These genes were mainly associated with the immune response and were associated in particular with the acute phase response. Acute phase proteins such as hepcidin, C-type lectin and serum amyloid A are among the highly modulated genes. Our results indicate that an induced acute phase response in L. calcarifer toward C. irritans infection is similar to the responses observed in bacterial infections of teleosts. This response demonstrates the importance of first line defenses in teleost innate immune responses against ectoparasite infection.

Infestation of gill copepod Lernanthropus latis (Copepoda: Lernanthropidae) and its effect on cage-cultured Asian sea bass Lates calcarifer

Twenty Asian sea bass Lates calcarifer from a floating cage in Bt. Tambun, Penang were examined for the presence of parasitic gill copepod, Lernanthropus latis. The prevalence of L. latis was 100% with the intensity of infection ranging from 1 to 18 parasites per host or 3.75 of mean intensity. Female parasites having oblong cephalothorax and egg-strings were seen mainly on the entire gill of examined Asian sea bass. The infected gill of Asian sea bass was pale and had eccessive mucus production. Under light and scanning electron microscopies (SEM), L. latis was seen grasping or holding tightly to the gill filament using their antenna, maxilla and maxilliped. These structures are characteristically prehensile and uncinate for the parasite to attach onto the host tissue. The damage was clearly seen under SEM as the hooked end of the antenna was embedded into the gill filament. The parasite also has the mandible which is styliform with eight teeth on the inner margin. The pathological effects such as erosion, haemorrhages, hyperplasia and necrosis along the secondary lamellae of gill filaments were seen and more severe at the attachment site. The combined actions of the antenna, maxilla and maxilliped together with the mandible resulted in extensive damage as L. latis attached and fed on the host tissues.

Optimal protein extraction methods from diverse sample types for protein profiling by using Two-Dimensional Electrophoresis (2DE)

There is a great diversity of protein samples types and origins, therefore the optimal procedure for each sample type must be determined empirically. In order to obtain a reproducible and complete sample presentation which view as many proteins as possible on the desired 2DE gel, it is critical to perform additional sample preparation steps to improve the quality of the final results, yet without selectively losing the proteins. To address this, we developed a general method that is suitable for diverse sample types based on phenolchloroform extraction method (represented by TRI reagent). This method was found to yield good results when used to analyze human breast cancer cell line (MCF-7), Vibrio cholerae, Cryptocaryon irritans cyst and liver abscess fat tissue. These types represent cell line, bacteria, parasite cyst and pus respectively. For each type of samples, several attempts were made to methodically compare protein isolation methods using TRI-reagent Kit, EasyBlue Kit, PRO-PREP™ Protein Extraction Solution and lysis buffer. The most useful protocol allows the extraction and separation of a wide diversity of protein samples that is reproducible among repeated experiments. Our results demonstrated that the modified TRI-reagent Kit had the highest protein yield as well as the greatest number of total proteins spots count for all type of samples. Distinctive differences in spot patterns were also observed in the 2DE gel of different extraction methods used for each type of sample.