Population genetics ofAnisakis simplex (Nematoda: Ascaridoidea) in Atlantic salmon (Salmo salar) and their use as biological indicators of host stocks

Synopsis The extent to which data concerning the population genetics of a parasite — namely larvalAnisakis simplex, may be used as an auxilliary source of information on various aspects of the marine migrations of Atlantic salmon (Salmo salar) is examined.Frequencies of the various acid phosphatase alleles could not be used in distinguishing between or estimating the proportions of North American and European salmon occurring off west Greenland. The genetic structure of larvae from salmon taken in Scotland was different from that taken in Ireland and England confirming an earlier conclusion that the feeding habits of the fish from Scotland were significantly different. In the western Atlantic, salmon from northern Newfoundland and also salmon from the Bay of Fundy had apparently ingested different populations (or different proportions of the same nematode population) than salmon from Miramachi and Chaleur Bay areas. Samples from northern Newfoundland and Labrador were also genetically different. These findings are discussed in relation to the available literature concerning salmon migrations, explanations are put forward and areas of future research suggested.     

Reproductive strategies of coastal marine fishes in the tropics

Synopsis A synthesis of ethnobiological, behavioral and physical oceanographic information leads to the conclusion that temperate zone models of reproductive strategy are inapplicable to many fishes of the coastal tropics. Intense predation appears to exert heavy selection pressure on fishes that spend their adult lives in coral, mangrove or tropical seagrass communities. Many exhibit spawning behaviors and spawn at times and locations that favor the transport of their pelagic eggs and pelagic larvae offshore where predation is reduced. This creates a countervailing selection pressure — the need to return the larvae to shallow water once they are ready to colonize their post-larval habitats. Accordingly, spawning is often concentrated at times of the year when prevailing winds or currents are at their weakest, thereby reducing the transport of larvae long distances from where they originated. Spawning is also concentrated in the vicinity of nearshore gyres which similarly favor the ultimate return of the larvae to their natal area. Among these species, therefore, offshore larval dispersal does not seem to be an adaptation for dispersal of the species, but rather an evolutionary response to intense predation pressure in the adult habitats. Lunar reproductive periodicity is more common among these species than has previously been recognized, and is one of the strategies employed to enhance the offshore flushing of eggs and larvae.This paper forms part of the proceedings of a mini-symposium convened at Cornell University, Ithaca, N. Y. 18–19 May 1976, entitled Patterns of Community Structure in Fishes (G. S. Helfman, ed.).Contribution No. 524, Hawaii Institute of Marine Biology, University of Hawaii, Honolulu.     

Genetic studies among Kanet and Koli of Kinnar district in Himachal Pradesh,India

Data are presented on serological and electrophoretic variants of 18 systems of red cells in 228 individuals belonging to a scheduled tribe (Kanet) and a scheduled caste (Koli) of Kinnar district in Himachal Pradesh, India. Differences in gene frequencies clearly indicate biological distinction in the local population. The possible cause of this genetic heterogeneity is discussed.     

Field observation on death feigning: a unique hunting behavior by the predatory cichlid,Haplochromis livingstoni,of Lake Malawi

Synopsis Haplochromis (=Cyrtocara) livingstoni, one of the predatory cichlids of the sand community of Lake Malawi, Africa, occurs at a density of 1.3 individuals per hectare. They are territorial, defending areas 15 m wide by 40 m long along the interface of sand andVallisneria weed beds. Individuals use a death feigning hunting pattern to capture prey. From a position of lying on their sides semiburied in the sand, these fish attack small cichlids. During four hours of SCUBA observations three successful attacks from this position were seen. After an attack the small cichlids scatter and the predator moves on toward a new aggregation of fish where it again plays dead. Individuals feign death an average of seven times per thirty minutes watch. Death feigning behavior is initiated in two ways. The fish either 1) is stationary with its ventral surface on or close to the sand, and then falls onto its side, or 2) drops from the water colum into `lying on side' position. The initial behavioral actions of the latter method are similar to chafing behavior. But instead of chafing the sand and rising again off the bottom, the fish plows into the sand and remains immobile. These data further add to the evidence that cichlids are remarkably flexible in their feeding behavior.     

Spawning and nesting behavior of the waccamaw darter,Etheostoma perlongum

Synopsis The spawning and nesting behavior ofEtheostoma (Boleosoma) perlongum was investigated in the field and laboratory. Sexual dimorphism is highly developed in such features as genital papillae, first dorsal and paired fins, and nuptial coloration. A reproductive migration from mid-lake to shore occurs in the spring: males precede females to select nest sites under submerged sticks and other debris. The male excavates a depression beneath the submerged object. Gonad analysis indicates a single spawning season extending from March through June. Nests were found from late April to mid-June and were guarded by a single male for periods of 13 to 36 days. Males initiate courtship by lateral display, lead the female to the nest site and show the nest by inverting. The female responds by tail up, tail wag and circle; males also tail wag and circle. Spawning pairs invert, usually in unison, and orient head to head or, less often, head to tail. The female deposits eggs while holding her body in a weak S or J shape with the caudal peduncle held away from the spawning substrate while vibrating.     

Fine structure and metabolism of multiply innervated fast muscle fibres in teleost fish

Summary Both the fast and slow muscle fibres of advanced teleost fish are multiply innervated. The fraction of slow-fibre volume occupied by mitochondria is 31.3%, 25.5% and 24.6%, respectively, for the myotomal muscles of brook trout (Salvelinus fontinalis), crucian carp (Carassius carassius), and plaice (Pleuronectes platessa), respectively. The corresponding figures for the fast muscles of these species are 9.3%, 4.6% and 2.0%, respectively. Cytochrome-oxidase and citrate-synthetase activities in the fast muscles of 9 species of teleost range from 0.20–0.93 moles substrate utilised, g wet weight muscle^-1 min^-1 (at 15° C) or around 4–17% of that of the corresponding slow fibres. Ultrastructural analyses reveal a marked heterogeneity within the fast-fibre population. For example, the fraction of fibres with <1% or >10% mitochondria is 0,4,42% and 36, 12 and 0%, respectively, for trout, carp and plaice. In general, small fibres (<500 m²) have the highest and large fibres (>1,500 m²) the lowest mitochondrial densities. The complexity of mitochondrial cristae is reduced in fast compared to slow fibres.Hexokinase activities range from 0.4–2.5 in slow and from 0.08–0.7 moles, g wet weight^-1 min^-1 in fast muscles, indicating a wide variation in their capacity for aerobic glucose utilisation. Phosphofructokinase activities are 1.2 to 3.6 times higher in fast than slow muscles indicating a greater glycolytic potential. Lactate dehydrogenase activities are not correlated with either the predicted anaerobic scopes for activity or the anoxic tolerances of the species studied. The results indicate a considerable variation in the aerobic capacities and principal fuels supporting activity among the fast muscles of different species. Brook trout and crucian carp are known to recruit fast fibres at low swimming speeds. For these species the aerobic potential of the fast muscle is probably sufficient to meet the energy requirements of slow swimming.     

Relationship between collagen fibril diameters and body size

Summary Suspensions of collagen fibrils obtained from derma of Elasmobranchia and Actinopterygia of different body sizes and developmental stages were examined by transmission electron microscopy. Fibril diameters were measured and classified into groups comprising a 20 nm diameter interval. Diagrams showing fibril populations of each fish were made. The measurements were averaged and their confidence intervals and standard errors determined. For each species other diagrams were plotted in which the mean diameters were correlated to the body length of each sample. The results show that: 1) a correlation exists between an increase in diameter of collagen fibrils and somatic growth until sexual maturity is reached; 2) fibril populations are subsequently spread over a wider range due to the presence in the derma of classes of newly formed and therefore thinner fibrils. The deposition of new fibrils is possibly influenced by individual factors; 3) no relationship exists between mean fibril diameter and body size; 4) no relationship exists between phylogenetic position and pattern of diameter distribution.Research supported by a grant from C.N.R. Roma (69.02087.0115.1150)     

ABO、MN血型及其与测量体征关系的初步探讨

本文提供了男、女两性共404人ABO、MN血型各表现型的35个体质特征测量数据,对血型和测量体征的关系进行了初步讨论。统计分析表明,不同血型群体的某些单个体征平均值之间有显著差异。对所调查的35个体征作整体分析,可见男性MN系统和女性ABO、MN系统各血型群体平均值之间差异显著。在MN血型系统,MN型群体的测量体征平均值低于M型和N型与MN基因型的杂合状态有密切关系。本文还分析了4个民族的血型资料,表明MN血型在ABO血型系统是随机分布的。     

The performance and distribution of species along soil salinity gradients of mangrove swamps in southeastern Nigeria

Based on periodic soil salinity measurements direct gradient analysis procedures were used to relate the performance and distribution of mangrove swamp species to salinity gradients. Variations in soil salinity were due to distance from the coast, tidal incursions and freshwater inputs. All overstorey species showed statistically significant negative correlations with salinity while most groundlayer species were positively correlated with the same factor. Based on ecological group classification, no species was found to occur on the highest values of soil salinity. There were overlapping range of occurrences and ecological optima for most species along the gradients.     

Occurrence of macro B chromosomes in Astyanax scabripinnis paranae (Pisces,Characiformes, Characidae)

B chromosomes occur in several Neotropical fish species. Cytogenetic analysis of 27 specimens (15 females and 12 males) of Astyanax scabripinnis paranae from the Araquá river (a small headwater tributary of the Tietê river) shows that this population has 2n=50 chromosomes (4M+30 SM+4ST+12A), two chromosome pairs with NORs and conspicuous C-band positive blocks in the terminal position of the long arm of four chromosome pairs. In this population, eight females presented 2n=51 chromosomes and the extra chromosome was a large metacentric similar in size and morphology to the first chromosome pair in the karotype. This accessory chromosome is entirely heterochromatic in C-banded metaphases and shows a late replication pattern evidenced by BrdU incorporation. There was no significant correlation between the presence of B chromosomes and increased NOR activity at the P>0.05 level. Some aspects related to these B chromosomes are discussed.