History of Asterias: Asterias is commonly known by the name of starfish. The name starfish is somewhat misleading suggesting an organism to be like a star and fish but as Asterias lacks in both the characteristics, therefore, recently it is renamed as sea star. There occur about species of Asterias all of which have different geographical distribution. The following account will give a general idea about the anatomical organisation of the genus Asterias. Asterias forbesi is found equally abundant on hard, rocky, sandy or soft bottom, while other species have been found to prefer rocky sea bottoms.
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Samples of sea stars were received from several sites along the reported range Table 1 and maintained as described in the section above. Samples of sea stars from these locations were collected under the institutional permits for the collecting institutions. Photographs, body condition scores, and swab samples were taken upon star arrival. The animals were observed daily for mortality and gross signs of disease. Tissue samples were collected from moribund and dead stars and processed as described below for histological examination all stars and for microbiological analysis moribund stars only.
Sample collection and processing Sample collection. For each star with and without clinical signs , two 1. The animal to be sampled was placed in a sterile disposable Petri dish and rinsed three times with 10 mL FASW to remove surface debris. Photographs were taken as described above to document gross morphology of animal. Size, date, water quality from the holding tank, and body condition were recorded.
Using a sterile swab, one 1 cm2 area of ray was swabbed gently, and the swab was rinsed into 1 mL of FASW. If stars showed signs of disease, a swab each was taken from lesions and from an area with no visible lesions.
Tissue clippings 2—3 mm3 were collected from the aboral surface of lesioned and non-lesioned animals, and placed into microcentrifuge tubes with 1 mL of TRIzol Sigma.
Swabs after plating for bacteriological isolation, see below were centrifuged for 10 min at 12, x g at room temperature. Once the supernatant was decanted, 1 mL of TRIzol fixative was added. Histological examination. Fixed tissues were decalcified in a 0.
Cross and longitudinal sections of affected rays and internal organs and sections of central disk and internal organs were sampled from the prepared tissues. Bacterial culture, DNA isolation, and species identification. Bacterial colonies in each of the media plates were classified based on morphology color, shape, and type of growth at 24 and 96 h after plating, and abundance of each colony type in colony forming units CFU per mL was recorded.
Bacterial colonies enriched in diseased animals were resuspended in 5 mL SWT broth and grown for 36 h at room temperature with shaking. Another 1 mL was pipetted into a clean 1. Bacterial challenge experiments One of the potential bacterial pathogens identified based on abundance and predominance in diseased sea stars and a species identity match suggestive of potential pathogenicity was used in challenge experiments.
Stars were monitored twice daily for 10 d, and time to the appearance of clinical signs of SSWD time to morbidity and time to mortality recorded. Cohabitation challenge experiments The purpose of the cohabitation trials was to assess transmission from diseased to healthy-looking stars and to assess the timeline of disease progression.
Time to morbidity and mortality after the initiation of cohabitation were recorded, as well as changes in behavior and physical appearance of stars. Swabs of lesioned areas and tissue samples were collected for quantitative real time PCR analysis; the remaining tissues from selected animals were processed for histological analysis.
All the experiments were performed in flow-through aquaria maintained as described in the Animal Husbandry section above. Records of water quality, temperature, and body condition of cohabitation stars were taken daily for at least 10 d or until all challenged stars were deceased. Cohabitation with diseased Forbes sea stars. Twelve healthy-looking acclimated A. Challenged stars were then monitored for signs of wasting for 10 d. An additional cohabitation trial was performed to collect infected water for immersion challenge experiments see below.
Cohabitation with other diseased echinoderms. Plastic mesh dividers were placed down the middle of the tanks to prevent direct contact between Source and Challenged animals. Three stars that had passed the acclimation phase and were negative for gross SSWD lesions were placed into each of the 4 tanks. Stars were monitored once daily for 3 weeks. Challenge experiments with infected and 0.
All these immersion experiments were performed in aquaria containing FASW to which at least 1 L of water from infected tanks filtered or not was added. Collection and preparation of infected water. An additional cohabitation experiment was performed to test the effect of filtration in challenge experiments. This trial lasted for 40 d October-November , with consistent turnover of diseased stars. Stars were monitored daily for signs of disease. When challenged stars began to show SSWD signs, swab samples were taken for analysis.
Water changes were also performed as needed to maintain water quality. A total of 15 stars were exposed in this way.
To prepare the water for challenge experiments, half of the water collected from infected tanks was filtered through a 0. Most viruses and toxins remain in water that passes through the filter [ 17 , 18 ]. Immersion challenge experiments using filtered infected water. Two filtration challenge experiments were performed, one with freshly collected infected water and one with frozen infected water. Two healthy-looking A. The trial continued for 10 d.
For filtration experiment II, infected water that had been previously frozen was used. Bottles containing frozen infected water were removed from the freezer and placed in an ice bath to thaw 20—30 min. Stars were immersed in antibiotics Enrofloxacin 2.
Treatments, each performed in duplicate, included: 1 control, FASW only; 2 filtered and UV treated frozen infected water, 3 filtered frozen infected water, and 4 frozen infected water. Experimental stars were monitored for an additional 3 weeks for signs of SSWD.
Swab samples were collected for processing before stars entered treatment, when they started to show clinical signs, and at death. Samples were tested in duplicate. For each sample, a volume of Hewson for VP1. Dilutions ten-fold over six orders of magnitude of a plasmid containing the VP1 target region were used as a standard to estimate VP1 concentration.
Hewson Cornell University. Plasmid DNA containing A. Mortality data from the challenge experiments was analyzed using a Keplen Meir survival analysis. Average time to mortality and morbidity was analyzed using a Kruskal-Wallis non-parametrix test. Prior to summer , populations of A.
Within 5 d, all stars showed signs of wasting, including loss of turgor pressure, curled limbs, and lesions that lead to ulceration of the aboral surface and death Fig 2. All stars perished within a week of placing them in the tank. Two major die-off events in A. Reported cases at the New England Aquarium were limited to A.
At the Mystic Aquarium, both A. Samples from Mystic were sent to the Hewson and Breitbart labs for analysis Tuttle, personal communication; [ 8 , 12 ]. In March , echinoderms collected from the field and placed in the touch tank at the Maine State Aquarium quickly showed signs of lethargy, loss of turgor pressure, and lesion development. These echinoderms had experienced temperature stress during transport to the aquarium Ayden-Rodrigues, personal communication.
These clinical signs were also seen in echinoderms cohabitating with the diseased specimens introduced in the tank. Specimens of cohabitating echinoderms showing signs of disease were sent to URI for analysis Table 1.
Tag: asterias forbesi
History[ edit ] The genus Asterias was first created by Carl Linnaeus in the 10th edition of Systema Naturae in when he published A. It was for a time the only species, but by the early s a few dozen taxa had been described in this genus. In Thomas Say listed six species native to the coasts of the Unite States which at the time consisted of the east coast from Maine to Florida, which the US had just formally acquired from Spain a few years earlier. None of these species are accepted or recognised as Asterias today.
Asterias (Starfish): History, Habitat and Development
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