Experiments with the Harbour Seal, Phoca vitulina, a Definitive Host of a Marine Nematode, Porrocaecum decipiens

1953 ◽  
Vol 10 (8) ◽  
pp. 539-547 ◽  
Author(s):  
D. M. Scott
Keyword(s):  
Definitive Host ◽  
Atlantic Cod ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Osmerus Mordax ◽  
Marine Nematode ◽  
The Third ◽  
Males And Females ◽  
Distinct Increase ◽  
Hippoglossoides Platessoides

Infestation experiments carried out in 1947 and 1948 showed that the harbour seal (Phoca vitulina) was a definitive host of a larval nematode found in the flesh of the Atlantic cod (Gadus callarias), smelt (Osmerus mordax), Canadian plaice (Hippoglossoides platessoides) and eelpout (Macrozoarces americanus). Adult worms recovered from experimentally infested seals were identified as Porrocaecum decipiens. Some larval Porrocaecum in the four species of fishes studied were P. decipiens.The worms lost their larval characteristics by moulting between the third and sixth day following introduction into the seal. Sexual maturation proceeded rapidly after the eleventh day and some males and females matured before the twentieth day. Maturation was accompanied by a distinct increase in size.

Experimental Infection of Atlantic Cod with a Larval Marine Nematode from Smelt

1954 ◽  
Vol 11 (6) ◽  
pp. 894-900 ◽  
Author(s):  
D. M. Scott
Keyword(s):  
Experimental Infection ◽  
Atlantic Cod ◽  
Osmerus Mordax ◽  
Marine Nematode ◽  
Intermediate Hosts ◽  
Natural Conditions

Atlantic cod (Gadus callarias) and at least 13 other species of fish in Canadian Atlantic waters are intermediate hosts for a larval nematode (Porrocaecum decipiens). It is pointed out that large cod feed occasionally on infected species of fish and that, as a result, they may become infected. Experiments showed that when larval Porrocaecum from smelt (Osmerus mordax) were fed to cod, some worms passed through the wall of the stomach, crossed the coelom, and penetrated the hypaxonic muscle of the cod. It was concluded that Porrocaecum larvae, under natural conditions, are also able to pass from one species of fish to another.

Incidence of the Ascarid Porrocaecum decipiens in the Stomachs of Three Species of Seals along the Southern Canadian Atlantic Mainland

1958 ◽  
Vol 15 (4) ◽  
pp. 495-516 ◽  
Author(s):  
D. M. Scott ◽  
H. D. Fisher
Keyword(s):  
East Coast ◽  
Atlantic Cod ◽  
Atlantic Coast ◽  
Phoca Vitulina ◽  
The Other ◽  
Harp Seal ◽  
Harbour Seal ◽  
Halichoerus Grypus ◽  
Bay Of Fundy ◽  
Harbour Seals

Identifications were made of ascarids collected from 1948 to 1956 from the stomachs of 318 harbour seals (Phoca vitulina), 812 harp seals (P. groenlandica), and 127 grey seals (Halichoerus grypus) killed in several localities along the Atlantic coast of Canada. Porrocaecum and 2 other genera of ascarids, tentatively identified as Anisakis and Contracaecum, were present in each species of seal. All 112 male Porrocaecum that were identified to species were P. decipiens.Almost all stomachs of harbour and grey seals at all seasons and in all localities contained P. decipiens. Considering all localities, the overall average incidence was about 20 adult P. decipiens in harbour seals and about 100 in grey seals.P. decipiens was normally much rarer in the stomachs of harp seals than in the other seals. It appeared most frequently in harp seals taken around the Magdalen Islands in April and May. The incidence of adult P. decipiens was much lower during the breeding season of the seals and during their southward and northward migrations within the Gulf of St. Lawrence. The incidence of P. decipiens in harp seals from the east coast of Newfoundland was very low.The relative importance of each species of seal as a vector of P. decipiens is as follows. The harbour seal is the most important in the Bay of Fundy and along the southwestern coast of Nova Scotia. Elsewhere harbour and grey seals occur in approximately equal numbers. In such localities the grey seal is probably more important than the harbour seal. The harp seal is about 100 to 200 times as numerous, while in the southwestern Gulf of St. Lawrence, as the combined populations of harbour and grey seals there. Despite this great numerical superiority the harp seal does not appear to be more important than the other seals as a host of P. decipiens.The relation between each species of seal and the incidence of larval P. decipiens in Atlantic cod (Gadus callarias) is discussed.

Vitamin A physiology in the precocious harbour seal (Phoca vitulina): a tissue-based biomarker approach

2002 ◽  
Vol 80 (9) ◽  
pp. 1511-1519 ◽  
Author(s):  
Lizzy Mos ◽  
Peter S Ross
Keyword(s):  
Vitamin A ◽  
Marine Mammals ◽  
Relevant Information ◽  
Phoca Vitulina ◽  
Retinyl Palmitate ◽  
Harbour Seal ◽  
Natural Processes ◽  
Reproductive Endocrine ◽  
Positive Correlations ◽  
Free Ranging

Vitamin A is a nutrient essential to all mammals for growth and development, as well as for the maintenance of reproductive, endocrine, and immune systems. Environmental contaminant-related disruption of vitamin A has been observed in many wildlife species and can therefore be used as a biomarker of toxic effects. However, the natural processes regulating vitamin A uptake, storage, and distribution among compartments are poorly understood in marine mammals. In this study, 20 young healthy harbour seals (Phoca vitulina) were captured to establish a compartment-based model providing a foundation for a mechanistic understanding of vitamin A physiology and disruption. Vitamin A (retinol, retinyl palmitate, and (or) retinoic acid) was quantified in blood plasma and in biopsy samples of liver, blubber, and skin. Although the highest concentrations of vitamin A were found in liver, blubber represents a more important storage depot, with an estimated 66% of the total retinoid content of the compartments measured. We suggest that vitamin A physiology in the precocious harbour seal has evolved to deal with high vitamin A availability during a short nursing period and to sustain growth during the postweaning fast. Positive correlations in vitamin A concentrations among liver, blubber, and skin support the use of less invasive biopsy sampling of just blubber or skin, which can provide physiologically relevant information in biomarker studies of free-ranging marine mammals.

scholarly journals Observations on the age and growth of Varicorhinus damascinus (Val.) in Tigris river at Salahuldin province – Iraq

2008 ◽  
Vol 5 (2) ◽  
pp. 243-248
Author(s):  
Baghdad Science Journal
Keyword(s):  
Regression Coefficient ◽  
Age Groups ◽  
Age And Growth ◽  
Gill Nets ◽  
The Third ◽  
Weight Relationship ◽  
Tigris River ◽  
Straight Line ◽  
Males And Females ◽  
Relationship Of

Age and growth of Varicorhinus damascinus (Val.) in Tigris river at Salahuldin province have been investigated. Monthly samples were taken during the period from September 1999 to August 2000, using small-meshed gill nets. The age data showed that there were six age groups and the dominant age groups were (III – IV) for both sexes. The results of the present study revealed that the increment in length of V. damascinus at the sites of study showed a tendency to decrease with the increase in age, after the third year of life in both sexes. The length-weight relationship of males and females were calculated and demonstrated in a straight line logarithmic formula, as follows: Log W = 1.5404 + 2.6885 log L for males r = 0.95 (P > 0.05) Log W = 1.6723 + 2.7877 log L for females r = 0.77 (P > 0.05) The values of the regression coefficient (b) indicated that the growth of both sexes of V. damascinus was allometric..

scholarly journals An Exploration of Teachers' Perspectives towards Cognitive, Affective and Linguistic Teaching Principles while Teaching English as a Foreign Language

2021 ◽  
Vol 13 (1) ◽  
pp. 17-40
Keyword(s):  
Foreign Language ◽  
Teaching English ◽  
Male And Female ◽  
The Third ◽  
Teaching Principles ◽  
Efl Teachers ◽  
Cognitive Principles ◽  
Utmost Care ◽  
Males And Females ◽  
Teachers Perspectives

The study aimed at exploring EFL teachers' perspectives towards cognitive, affective and linguistic teaching principles while teaching English as a foreign language. To conduct the study, the researchers prepared a questionnaire of 30 items that was distributed into three group domains. The first group was the cognitive principles. The second one was the affective principles, and the third group was the linguistic principles. Forty-six male and female EFL teachers responded to the questionnaire's items. Suitable statistical analyses were used to analyze the data. The results of the study pointed out that EFL teachers had positive perspectives towards these teaching principles, as the analysis showed that they looked at these principles positively and they gave them their utmost care and concern. Besides, the analysis showed that the cognitive principles came in the first rank compared with the other two groups (affective and linguistic) as they got the highest mean. Moreover, the results revealed that there were no statistical significant differences, regarding gender, in the participants' perspectives towards the importance of these teaching principles while teaching English as a foreign language as the means of males and females were closer to each other. Keywords: Cognitive Principles, Affective Principles, Linguistic Principles, Foreign language.

scholarly journals Trace metal accumulation in hair and skin of the harbour seal, Phoca vitulina

1993 ◽  
Vol 26 (3) ◽  
pp. 152-155 ◽  
Author(s):  
C. Wenzel ◽  
D. Adelung ◽  
H. Kruse ◽  
O. Wassermann
Keyword(s):  
Trace Metal ◽  
Metal Accumulation ◽  
Phoca Vitulina ◽  
Harbour Seal

scholarly journals Deiminated proteins and extracellular vesicles as novel biomarkers in pinnipeds: Grey seal (Halichoerus gryptus) and harbour seal (Phoca vitulina)

Biochimie ◽  
2020 ◽  
Vol 171-172 ◽  
pp. 79-90 ◽  
Author(s):  
Bergljót Magnadóttir ◽  
Pinar Uysal-Onganer ◽  
Igor Kraev ◽  
Vilhjálmur Svansson ◽  
Karl Skírnisson ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Grey Seal ◽  
Novel Biomarkers

Repetition enhances hearing detection thresholds in a harbour seal (Phoca vitulina)

1993 ◽  
Vol 71 (5) ◽  
pp. 926-932 ◽  
Author(s):  
S. D. Turnbull ◽  
J. M. Terhune
Keyword(s):  
White Noise ◽  
Background Noise ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Detection Thresholds ◽  
Noise Masking ◽  
Phoca Groenlandica ◽  
Hearing Thresholds ◽  
Lower Detection ◽  
Pinniped Species

Pure-tone hearing thresholds of a harbour seal (Phoca vitulina) were measured in air and underwater using behavioural psychophysical techniques. A 50-ms sinusoidal pulse was presented in both white-noise masked and unmasked situations at pulse repetition rates of 1, 2, 4, and 10/s. Test frequencies were 0.5, 1.0, 2.0, 4.0, and 8.0 kHz in air and 2.0, 4.0, 8.0, and 16.0 kHz underwater. Relative to 1 pulse/s, mean threshold shifts were −1, −3, and −5 dB at 2, 4, and 10 pulses/s, respectively. The threshold shifts from 1 to 10 pulses/s were significant (F = 12.457, df = 2,36, p < 0.001) and there was no difference in the threshold shifts between the masked and unmasked situations (F = 2.585; df = 1,50; p > 0.10). Broadband masking caused by meteorological or industrial sources will closely resemble the white-noise situation. At high calling rates, the numerous overlapping calls of some species (e.g., harp seal, Phoca groenlandica) present virtually continous "background noise" which also resembles the broadband white-noise masking situation. An implication of lower detection thresholds is that if a seal regularly repeats short vocalizations, the communication range of that call could be increased significantly (80% at 10 pulses/s). This could have important implications during the breeding season should storms or shipping noises occur or when some pinniped species become increasingly vocal and the background noise of conspecifics increases.

Masked and unmasked pure tone detection thresholds of a harbour seal listening in air

1991 ◽  
Vol 69 (8) ◽  
pp. 2059-2066 ◽  
Author(s):  
J. M. Terhune
Keyword(s):  
White Noise ◽  
Pure Tone ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Optimal Conditions ◽  
Vascular Changes ◽  
Detection Thresholds ◽  
Noise Masker ◽  
Auditory Systems ◽  
Tone Detection

In-air pure tone detection thresholds of a harbour seal (Phoca vitulina) were measured using behavioural psychophysical techniques. Thresholds dropped from about 70 dB re 20 μPa at 0.1 kHz to about 35 dB re 20 μ Pa at 4 kHz and then increased to about 45 dB re 20 μPa at 16 kHz. Increased sensitivities at 2 and 8 kHz, which have been reported in other pinnipeds, were not evident. In-air intensity detection thresholds averaged 32 dB above their underwater counterparts (1–16 kHz). Masking studies found the critical ratios at 0.25, 0.5, and 1 kHz to be 24, 15, and 21 dB, respectively (white noise masker). From 0.2 to 1.5 kHz, bandwidths 20 dB below the level of pure tone maskers were 0.16–0.18 kHz. Circumstantial evidence suggests the possibility that blood vascular changes associated with diving might also influence the sensitivity of the auditory systems of seals. Under optimal conditions, a pup's airborne cries may be detected by its mother at ranges of 1 km or more.

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