Pigmentation of gilthead seabream, Sparus aurata (L. 1875), using Chlorella vulgaris (Chlorophyta, Volvocales) microalga

A feeding experiment was conducted over 9 weeks with seven groups of 30 (fish per group) unpigmented gilthead seabream, Sparus aurata (L. 1875) (initial mean weight = 145.2 ± 12.3 g). Three experimental diets were prepared by adding to a basal diet free of carotenoid (final pigment content of around 40 mg per kg feed): (i) a biomass of the carotenogenic Chlorella vulgaris (Chlorophyta, Volvocales); (ii) a synthetic astaxanthin; and (iii) a mixture (1:1) of microalgal biomass and synthetic astaxanthin. At 3‐week intervals, five fish were sampled from each tank for total carotenoids analysis in skin and muscle. The carotenoid pigments (total amount = 0.4%) identified in the carotenogenic alga were lutein (0.3%), β‐carotene (1.2%), canthaxanthin (36.2%), astaxanthin, free and esterified forms (55.0%), and other pigments (7.3%). Carotenoid pigments were significantly deposited in the four skin zones studied during the feeding trial: the forefront between the eyes, the opercule, along the dorsal fin and in the abdominal area. In the muscle, regardless of the astaxanthin source, the amount of carotenoids measured was very low (less than 1 mg kg^?1) and differences not significant. Moreover, no muscle pigmentation was evident, and there was no variation in the amount of carotenoid analysed in skin tissue, through the trial, for each treatment. It was concluded that supplementing the feed with C. vulgaris would be an acceptable practice in aquaculture to improve the market appeal of the gilthead seabream.     

Myxobolid parasites infecting the gills of the Iberian nase, Chondrostoma polylepis (Steindachner), in Galicia (NW Spain), with a description of Myxobolus gallaicus sp. nov.

Three species of myxobolid parasites were found infecting the gills of the Iberian nase, Chondrostoma polylepis , in the River Ulla (Galicia, NW Spain), Myxobolus leuciscini , M. impressus and M. gallaicus sp. nov., which is described herein. Myxobolus leuciscini locates in the intralamellar space and the plasmodium begins to develop in the endothelium of the capillaries of the secondary lamellae. Myxobolus impressus plasmodia are located in the interlamellar multilayered epithelium. Myxobolus gallaicus plasmodia are elongated and are located exclusively in the central venous sinus of the branchial filament, suggesting that they begin their development in branchial endothelial tissue. We also present data on spore size and morphology, plasmodium and pansporoblast characteristics and pathological effects of the three species in the host branchial tissues.     

Piscine reovirus,but not Jaundice Syndrome,was transmissible to Chinook Salmon,Oncorhynchus tshawytscha (Walbaum), Sockeye Salmon,Oncorhynchus nerka (Walbaum), and Atlantic Salmon,Salmo salar L.

A Jaundice Syndrome occurs sporadically among sea‐pen‐farmed Chinook Salmon in British Columbia, the westernmost province of Canada. Affected salmon are easily identified by a distinctive yellow discolouration of the abdominal and periorbital regions. Through traditional diagnostics, no bacterial or viral agents were cultured from tissues of jaundiced Chinook Salmon; however, piscine reovirus (PRV) was identified via RT‐rPCR in all 10 affected fish sampled. By histopathology, Jaundice Syndrome is an acute to peracute systemic disease, and the time from first clinical signs to death is likely <48 h; renal tubular epithelial cell necrosis is the most consistent lesion. In an infectivity trial, Chinook Salmon, Sockeye Salmon and Atlantic Salmon, intraperitoneally inoculated with a PRV‐positive organ homogenate from jaundiced Chinook Salmon, developed no gross or microscopic evidence of jaundice despite persistence of PRV for the 5‐month holding period. The results from this study demonstrate that the Jaundice Syndrome was not transmissible by injection of material from infected fish and that PRV was not the sole aetiological factor for the condition. Additionally, these findings showed the Pacific coast strain of PRV, while transmissible, was of low pathogenicity for Atlantic Salmon, Chinook Salmon and Sockeye Salmon.     

Henneguya shaharini sp. nov. (Protozoa: Myxozoa), a parasite of marble goby, Oxyeleotns marmoratus (Bleeker)

Abstract. Henneguya shaharini sp. nov. is described from marble goby, Oxyeleotns marmoratus , collected in the State of Selangor, Malaysia. Cysts occurred in the gill filaments. The histopathological examination revealed intralamellar and inter-lamellar forms of infection. A host tissue response against the parasite was seen in some fish.     

Use of mixed feeding schedules in fish culture: field trials on catla, Catla catla (Hamilton-Buchanan), rohu, Labeo rohita (Hamilton), and common carp, Cyprinus carpio L.

Abstract. The applicability of mixed feeding schedules using low-and high-protein diets was evaluated by three on-farm field trials conducted in fertilized earthen ponds. Rohu, Labeo rohita (Hamilton), and common carp, Cyprinus carpio L., were used in the first two trials, and catla. Catla catla (Hamilton-Buchanan), was also included in the third trial. The concept of a mixed feeding schedule was tested using a 1:1 rice bran-groundnut meal cake mixture, a commonly used feed in Indian carp culture.
In a mixed feeding schedule, two feeds are used alternately, each for a predetermined number of days. In the present study, one of three such mixed feeding schedules was used in conjunction with one of two control diets. The control diets were rice bran (diet A) or a mixture of rice bran-groundnut meal cake (diet B). The mixed feeding schedules tested were: 1A/1B, 1A/2B and 1A/3B (numerals indicate number of days diet A or B was offered continuously). Diet A (rice bran only) induced significantly poor growth in all treatments. Interestingly, growth in the mixed feeding schedules was generally equal or superior to that when fish were fed with diet B. Growth efficiency indicators such as SGR. FCR and PER were found to be good for fish maintained on certain mixed schedules. Savings of 15–31% protein and 10–20% of the feed cost were achieved with the various schedules, the highest saving being achieved with the 1A/1B schedule. Nitrogen retention was higher in fish treated with mixed schedules. The results demonstrated the usefulness of mixed schedules in reducing nitrogen input, output and feed costs.     

Preferred temperature of grass carp, Ctenopharyngodon idella (Valenciennes), and brema carp, Megalobrama amblycephala (Yih), (Pisces, Cyprinidae) in horizontal and vertical gradients

The preferred temperatures of grass carp, Ctenopharyngodon idella (Valenciennes), and brema carp, Megalobrama amblycephala (Yih), were determined individually and together in both horizontal and vertical gradients. No significant difference was found by two methods between the preferred temperatures in either species of carp (28.0-28.5 ^oC) when the fish were placed individually. However, when the two species of carp were placed together, C. idella was displaced thermally, preferring a temperature of 23.5 ^oC, which was significantly lower than that obtained when it was held separately. This suggests that, if both species of carp are placed in ponds forming part of a Chinese polyculture system, C. idella will seek out a lower temperature as a mechanism to avoid competition, and therefore, the growth of this species will be reduced.     

Incidence of Psorospermium sp. in Several Cultivated Populations of Crayfishes, Procambarus spp. (Decapoda, Cambaridae), in Southern Louisiana

An organism tentatively classified as Psorospermium haeckeli was found in red swamp crayfish Procambarus clarkii at four culture sites in southwestern (3) and southeastern Louisiana (1) and in white river crayfish Procambarus zonangulus ( =P. acutus acutus ) at three culture sites in southwestern Louisiana. Incidence was about 70% in P. clarkii and 25% in P. zonangulus. Psorospermium haeckeli was present in all individual populations of P. clarkii sampled, but not in all P. zonangulus populations. Overall abundance was considerably lower than that observed in the European astacid crayfish Astacus astacus . Furthermore, the organism differed in shape, being longer and narrower than the organism found in A. astacus .     

Description of Vavraia parastacida sp. nov. (Microspora: Pleistophoridae) from marron, Cherax tenuimanus (Smith), (Decapoda: Parastacidae)

Abstract. A plcistophorid microsporidian is described from marron, Cherax tenuimanus (Smith). The parasite is polysporous, forming eight, 16, 32 or 64 ovoid spores in persistent, two-layered mcrontogcnctic sporophorous vesicles. Nuclei remain isolated throughout merogony and sporogony. The sporophorous vesicle forms from the amorphous coat surrounding meronts, which thickens and condenses into two layers during sporogony. The parasite is placed in Vavraia Weiser, 1977, and named Vavraia parastacida sp. nov.     

Cardiac myxosporiosis of pearl-spot, Etroplus suratensis (Bloch), due to Myxobolus etropli sp. nov

A new myxosporean, Myxobolus etropli sp. nov., was found to infect the bulbus arteriosus of Etroplus suratensis (Bloch) from brackishwater lagoons of Muttukkadu, Chennai coast, India. A survey from May 1993 to October 1994 revealed a prevalence rate of 33.7% of this parasite. Macroscopic discoloured foci/cysts were seen in the bulbus arteriosus of the fish. The parasite showed strict host and site specificity. Histopathology showed that the infection was restricted to the bulbus. This is the first report of a myxosporean from E. suratensis.