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Many members of the Copepod family Lernaeopodidae are well-known parasites of gadids. This study reports on the occurrence of a lernaeopodid infestation of wild-sourced Gadus morhua sampled from separate inshore (Gilbert Bay, NL) and offshore (Virgin Rocks, NL) populations from Newfoundland, Canada. The majority of the parasites were observed to be associated with the buccal cavity, gill filaments, gill arch, and occasionally near the outer edge of the operculum. Anatomical analysis and detailed redescriptions of the parasite’s functional anatomy (mouth parts, antennae, and bulla complex) using high-resolution SEM indicated that the parasite was most likely of the genus Clavella. New morphological details of the second antennae ornamentation, first maxillae, bulla complex, and the oral cone are provided and discussed with regard to their potential in taxonomic applications.

Two different colours (red and green) of visible implant elastomer (VIE) were used in Nile tilapia (Oreochromis niloticus). The visibility, location and retention of the VIE tags was investigated and any adverse effects on fish survival and growth determined. The use of VIE tags for monitoring individual fish during a bacterial challenge with either Streptococcus agalactiae or S. iniae was also studied. The results showed that VIE treated fish were lighter but not shorter than the non-tagged control fish and that tagging caused no mortality. The retention of tags was better at the base of pectoral fin followed by the nasal area, lower abdomen, upper abdomen and branchiostegal rays inside the operculum. During the bacterial challenge experiment individual animals could be easily identified using the VIE tags. In this preliminary study, VIE tagging appears suitable for Nile tilapia research, as with other fish species, and could be a novel method to identify individual animals during microbial pathogenesis studies.

Summary Here we describe the results of a preliminary study to evaluate the response of the cellular skeleton of the large African barb, Labeobarbus intermedius, to exposure to high levels of the thyroid hormone T3 for 1 and 3 months. We examined the effects in terms of mineral density and mechanical properties of the operculum bone, as well as evaluated and compared the light microscopy features of this bone between the treatment groups and the untreated control group. We found a significant increase in bone mineral density in the treated groups compared to untreated controls, and a tendency towards a corresponding increase of bone material stiffness (Young's modulus). These findings suggest that thyroid hormone enrichment may contribute to improved skeletal properties in pond-raised fish, and help moderate osteomalacia, a commonly seen problem in aquaculture.

In India, oysters, clams, mussels and a few gastropods are local delicacies along the coastal region. Of these total catch, few marine gastropods are not utilized by the people because of lack of awareness about the rich nutritive value of the seafood products. Keeping this in mind, an attempt was made to study the shelf life of the pickled product developed from gastropods such as Chicoreus ramosus and Hemifusus pugilinus for a period of 8 and 6 months at ambient temperature (30 ± 2C). The acceptability of gastropod pickles decreased as free fatty acid, trimethylamine nitrogen, total volatile base nitrogen, total plate count and sensory scores increased (P

Summary The aim of the study was to determine the distribution and relative frequency of Glyptosternon maculatum taste buds (TB) using paraffin sectioning, the HE staining method and light microscopy. TBs were found on a variety of surface body areas (lips, barbels, lateral, ventral and dorsal areas, and the dorsal, pelvic, pectoral, anal and adipose fins), as well as in the oropharyngeal cavity. In the epithelium of histological figures of sampled body parts, TB was pear-shaped from the bottom to the top. The ratio of height/width value of the taste bud was above 1.0, with a range from 1.2 to 2.0. Highest TB frequencies were in the mandibular outer barbel (18.5 ± 3.7 mm−2), mandibular inner barbel (17.1 ± 5.4 mm−2), nasal barbel (16.8 ± 4.2 mm−2) and maxillar barbel (15.9 ± 2.7 mm−2), lips (14.6 ± 3.6 mm−2) and oropharyngeal cavity (13.2 ± 3.5 mm−2). TBs occurred in moderate quantities on the forehead (6.9 ± 2.1 mm−2), anal fin (5.8 ± 2.3 mm−2), and La2 (3.9 ± 1.6 mm−2, between pelvic and anal fins), then decreased to a few in the La1 area (3.4 ± 1.3 mm−2), operculum (2.5 ± 1.3 mm−2) and other examined areas. Type I (elevated), type II (slightly elevated) and type III (not elevated or sunken) TBs were found in the epithelium of various sampling locations. These are the first descriptions of taste buds in G. maculatum.

Summary In order to evaluate the phenotypic plasticity of introduced pikeperch populations in Tunisia, the intra- and interpopulation differentiation was analysed using a biometric approach. Thus, nine meristic counts and 23 morphological measurements were taken from 574 specimens collected from three dams and a hill lake. The univariate (anova) and multivariate analyses (PCA and DFA) showed a low meristic variability between the pikeperch samples and a segregated pikeperch group from the Sidi Salem dam which displayed a high distance between mouth and pectoral fin and a high antedorsal distance. In addition, the Korba hill lake population seemed to have more important values of total length, eye diameter, maximum body height and a higher distance between mouth and operculum than the other populations. However, the most accentuated segregation was found in the Lebna sample where the individuals were characterized by high snout length, body thickness, pectoral fin length, maximum body height and distance between mouth and operculum. This study shows the existence of morphological differentiations between populations derived from a single gene pool that have been isolated in separated sites for several decades although in relatively similar environments.

Summary Age estimates for population analysis must be precise. We assessed the usefulness of pectoral fin rays, sphenoids, opercula, and dorsal scutes of shovelnose sturgeonScaphirhynchus platorynchus (n = 30) as aging structures based on ease of collection, distinctness of annuli, and measures of precision both between and within readers. We also determined how age estimates from paired fin rays of individuals were related (n = 106). Pectoral fin rays generated the highest within-reader precision (100% within 2 years) followed by sphenoids (58%), opercula (56%), and dorsal scutes (49%). Ages estimated by the pectoral fin ray also had higher between-reader agreement (80% within 1 year) than did those from the operculum (60%), sphenoid (59%), or dorsal scute (56%). Likewise, age estimates from pectoral fin rays had the lowest mean coefficient of variation (8.2%) followed by sphenoids (9.9%), opercula (11.3%), and dorsal scutes (11.5%). Only the operculum produced biased estimates between readers. Ages from paired fin rays agreed poorly (36% exact, 30% within 1 year) although no aging bias occurred. The pectoral fin ray is typically used to age shovelnose sturgeon. Because uncertainty about accuracy and precision of age estimates from this structure remains, shovelnose sturgeon management objectives that result from age data should remain conservative.

Triploidy was induced in the fighting fish, Betta splendens Regan, by varying all possible combinations of temperature (37-41°C), time after insemination (2-3min)and shock duration (2-4 min). Heat shock at 39°C for 3 min duration initiated 2-5 min after insemination gave high frequencies of triploids (86%) as assessed from chromosome number and red blood cell nuclear volume. There was no significant difference in the growth rate of triploid and diploid fish. Gonadal development in both sexes was retarded in triploids at 5 months of age. Eggs fertilized with milt from triploids developed to gastrulation. Beyond gastrulation there was increasing mortality associated with abnormalities and none of them hatched. The display frequencies of air gulping, erection of operculum and fins, striking and biting, and undulating movements were fewer in triploids compared to diploids. It appears that triploids are less aggressive than diploids. The aggressive behaviour of fighting fish may be related Io their reproductive activity.