Number Of Fin Rays Research Articles

Taxonomic status ofBathysolea profundicola andB. polli (Soleidae; Pleuronectiformes) with notes on the genus

The objectives of this study were to i) clarify the taxonomic status and provide redescriptions of the deepsea soleid speciesBathysolea profundicola andB. polli (Pleuronectiformes), ii) discuss the taxonomic status ofB. lactea andB. lagarderae and iii) examine the monophyletic status of the genus. One hundred and fifteen specimens including most available type material were examined.B. profundicola andB. polli can be differentiated by their dorsal fin pterygiophore complex over the cranium, number of dorsal fin rays, angle between the dorsal and ventral branches of the urohyal and relative length of the posteriormost ray of the dorsal fin. Both species also share a unique diagnostic combination of traits among soleids and are hypothesized to be sister species. This study confirmed thatCapartella longisquamis andSolea greeni are junior synonyms ofBathysolea profundicola. Bathysolea lactea, known only from the description of the lost holotype, remains valid pending the capture of more specimens from Cabo Verde Islands. Two apomorphic characters define the genus as monophyletic: the filamentous structure of the pectoral fins and the presence of dark pigmentation inside the abdominal and branchial cavities. However, contradictory evidence from a study of the supracranial dorsal fin pterygiophore complex indicated that B. lagarderae, a deep-sea species endemic to the coasts of Madagascar, and the eastern Atlantic clade,B. profundicola-B. polli, might be more closely related to other soleid taxa than to each other. Until a revision of the family Soleidae is completed, it is preferable to maintain all of the abovementioned species withinBathysolea. An identification key to species in the genus is provided.

Postglacial genetic differentiation of reproductive ecotypes of kokanee Oncorhynchus nerka in Okanagan Lake, British Columbia.

Okanagan Lake, south-central interior of BC, contains two reproductive ecotypes of kokanee Oncorhynchus nerka; individuals spawn in tributary streams ('stream-spawners') as well as on shoreline gravel areas ('beach-spawners'). We tested the hypothesis that these sympatric ecotypes comprise a single panmictic population by assaying variation in morphological traits and at allozyme, mitochondrial and minisatellite DNA loci in fish collected from three stream-spawning and two beach-spawning sites. No morphological traits consistently distinguished the reproductive ecotypes with the exception of the number of anal fin rays which was greater in stream-spawning kokanee. Four of 18 allozyme loci screened were polymorphic, but no significant allele frequency differences were detected among populations within ecotypes or between ecotypes. Similarly, allele frequencies at two minisatellite DNA loci were not significantly different among populations or between ecotypes. By contrast, significant differences in the frequencies of mitochondrial DNA restriction fragment length polymorphism (mtDNA RFLP) haplo-types were detected between stream- and beach-spawners, but not among populations within ecotypes. Further, two RFLPs that distinguished stream- and beach-spawning adults were found in juvenile kokanee sampled from the limnetic zone of Okanagan Lake. The two mtDNA RFLPs and a d-loop sequence variant appear to be unique to Okanagan Lake Kokanee because we did not observe these haplotypes in sockeye salmon and kokanee sampled outside of Okanagan Lake. Our data suggest that: (i) there is restricted female-mediated gene flow between stream- and beach-spawning kokanee in Okanagan Lake, (ii) the forms have diverged within the lake basin since the retreat of the Wisconsinian glaciers (< approximately equal to 11 000 years ago), and (iii) distinct reproductive niches may promote divergence in north temperate freshwater fish faunas.

Origin of variation in isogenic, gynogenetic, and androgenetic strains of common carp,Cyprinus carpio

After androgenetic or gynogenetic reproduction, a large expansion of phenotypic variance is generally observed. Within one homozygous family, this expansion is the result of increased environmental variance, since genetic variance does not increase. We consider three types of environmental variance (VE) within homozygous offspring: (1) “true” VE (inter-individual variance), (2) VE, due to developmental instability (DI, intra-individual variance) and (3) VE originating from embryonic damage (ED) caused by the chromosome manipulation treatment. We examined the importance of these three types of VE. It is thought that homozygous individuals show high levels of true VE and DI. Therefore, in the first experiment we compared three F1-isogenic and one partly outbred strain of common carp, Cyprinus carpio, in true VE of length, body weight, and number of dorsal fin rays. The isogenic strains varied in degree of homozygosity (coefficient of inbreeding F: 0 to 0.99). DI was determined by measuring fluctuating asymmetry (FA) of five bilateral symmetric characteristics. We found the strain with the highest F to display the lowest true VE. FA was equal in all isogenic strains but highest in the partly outbred strain. In a second experiment, similar observations were performed on gynogenetic and androgenetic offspring from parents with identical genotypes. Homozygous (endomitosis, EM: F = 1) and partly heterozygous (2pb-gynogenesis: F = 0.74) gynogenetic groups were produced. Normal fertilizations (F = 0.75) served as controls. The androgenetic groups showed highest FA and variations caused by ED, followed by 2pb- and EM-gynogenetic groups, respectively. We conclude that increased variation within gynogenetic or androgenetic of offspring is the result of ED, caused by the chromosome manipulation treatment. J. Exp. Zool. 277:72–79, 1997. © 1997 Wiley-Liss, Inc.

Juveniles of two sillaginids,Sillago aeolus andS. sihama, occurring in a surf zone in the Philippines

Sillaginid juveniles collected from the surf zone at Tigbauan, Iloilo, Philippines, between May 1986 and September 1987 were identified asSillago aeolus (n=702, 8.9–26.0 mm SL) andS. sihama (n=3414, 8.6–22.9 mm SL), based on the numbers of dorsal and anal soft fin rays and vertebrae. The two species were easily distinguishable by the pattern of melanophores distributed on the caudal fin base,S. aeolus having a triangular-shaped cluster, whereas the melanophores formed a vertical line inS. sihama. The ratios of pre-anal and caudal peduncle lengths to SL also differed between the species, both being higher inS. aeolus. The occurrence ofS. aeolus was limited to the dry season, from January to March. On the other hand,S. sihama occurred year-round, although a peak was observed in the dry season, from November to April.

Description of the early ontogeny of the Atlantic salmon, Salmo salar, with a novel system of interval (state) identification

The sequence of morphological changes through intervals from the time of egg insemination until the time of completed yolk absorption was investigated. The studied time span was divided into more than 100 morphologically discrete states. For this purpose, some quantitative characters, such as number of cells, somite pairs, or caudal fin rays, extent of epiboly, or vascularisation, were selected as key characters, since they seem to provide the most adequate picture of the dynamic developmental process. Descriptions and drawings of 41 states (out of the more than 100) were chosen for the present study to illustrate the embryo and alevin periods. The time it takes to form one somite pair (τS) was used as the unit of relative age and duration of the early ontogenetic states. The morphological description of each state was supplemented by the estimation of the relative age of the embryo or alevin at this state as the value of N/τS, where N is the time elapsed from egg insemination up to any given state at a given constant temperature. It was determined that the developmental rate of Atlantic salmon embryos depends on the incubation temperature according to the equation: Ig Nt = Ig No + (−0.0967 + 0.00207t)t, where NO and Nt are values of τS at temperatures of 0 and t (°C), respectively, taking into account that the values of τS and the duration of the entire embryogenesis vary proportionally within the temperature range tolerated by the species. The methods used here to identify states of embryogenesis and to estimate the relative age of S. salar embryos and alevins might also be applied to other fish species.

Sensitive stages during embryonic development of wolffish,Anarhichas lupusL. determining the final numbers of rays in unpaired fins and skeletal abnormalities

Larvae of common wolYsh (Anarhichas lupus L.) obtained from eggs incubated at a constant temperature of 7.0)C had mean numbers of rays in the dorsal, anal, and caudal fins of 74.5, 46.4, and 23.8 respectively; those incubated at 11.0)C had 53.8, 25.7, and 25.2 rays, respectively. Several skeletal abnormalities, including fusion of parts and abnormal structure of neural arches in the pre-urostyle area, accompanied the reduction in numbers of dorsal and anal fin rays at 11)C. To test which period of embryonic development was critical for determining the final numbers of unpaired fin rays and skeletal abnormalities, the eggs were transferred from 7) Ct o 11 )C and back at diVerent stages. Determination of the final numbers of rays in the dorsal and anal fins and most of skeletal abnormalities occurred mainly between 50% vascularization of the yolk sac and the beginning of formation of rays in the caudal and pectoral fins. The final number of caudal fin rays was determined between the latter stage and formation of rays in the dorsal and anal fins. To reduce the egg incubation period and still obtain larvae without skeletal abnormalities, a temperature regime during embryonic development is suggested. ? 1996 International Council for the Exploration of the Sea

Development of wolffish eggs at different temperature regimes

Embryonic development of common wolffish (Anarhichas lupus L.) was studied at constant temperatures 5.0, 7.0, 9.0, 11.0, 13.0 and 15.0°C. Duration of development from egg activation to several morphological stages including 50% hatching was determined. At 5.0–11.0°C, the survival rate of eggs to hatching ranged from 51 to 88% with a tendency to increase at 5.0 and 7.0°C. Morphological anomalies, bacterial contamination and large mortalities were observed in eggs incubated at 13.0 and 15.0°C. The period of hatching lasted from 10 to 50 d in different egg groups. Embryo length and yolk sac volume at identical morphological stages of development showed only slight relation to temperature. At lower temperatures newly hatched larvae were longer and at more advanced stages of ontogeny. Normal numbers of fin rays in larvae (mean values 74 for dorsal fin and 46 for anal fin) were observed at 5.0 and 7.0°C and in most larvae at 9.0°C. At 11.0 and 13.0°C, many rays were absent, with mean values for dorsal fin 60 and 39 respectively and for anal fin 28 and 4 respectively. The approximate upper limit for normal development of fin rays appeared to be 9.0 °C.

Morphometric Comparison of Pupfish Populations, Cyprinodon nevadensis, at Shoshone and Tecopa, California

Shoshone Spring by Taylor et al. (1988). Shoshone Spring is at the northern-most head of the pluvial Amargosa River in the Death Valley system. It is tributary to the Amargosa River approximately 21 km N (upstream) of Tecopa, Inyo Co., California. The elevation of Shoshone Spring is 518 m, dropping to approximately 487 m at the outflow creek. Elevation of Tecopa Bore is approximately 390 m, an elevational drop of approximately 128 m. The elevation of the Amargosa River decreases significantly as it enters and flows through the Amargosa Canyon south of Tecopa. During periods of heavy rainfall and flash flooding, the area may briefly have fastmoving water flowing downstream throughout the entire system. During his 1939 visit to Shoshone and Tecopa, Miller (1948) found no water in the Amargosa River at Shoshone and found two permanent flows occurring in the lower Amargosa River. One began shortly above Tecopa and continued through the Amargosa Canyon about 11 km to Sperry. The other flow was round in Death Valley, northwest of Saratoga Springs and approximately 32 km downstream from Sperry. Taylor et al. (1988) found water in the Amargosa River at Shoshone, although approximately 11 km of the 21 km of streambed be w en Shoshone and tecopa were dry. In a meristic analysis, Taylor et al. (1988) concluded that the rediscovered population at Shoshone most closely resembled C. n. shoshone as described by Miller (1948). The Shoshone population resembled C. n. shoshone and differed from the Tecopa popultion by having lower mean numbers of pelvic, dorsal, and caudal fin rays (Taylor et al., 1988). In this paper we present a morphometric analysis as a supplement to the meristic data reported by Taylor et al. (1988) for C. n. shoshone. We compare the results with similar data for C. n. amargosae from Tecopa Bore. We also compare our results for the two subspecies with those presented by Miller (1948). Sixty specimens from both Shoshone and Tecopa Bore were collected with seines, traps, and dipnets on 31 July 1986 (Taylor et al., 1988). All specimens were cataloged (catalog numbers F-1957; F-1959) at the Marjorie Barrick Museum of Natural History, University of Nevada, Las Vegas. Following Miller (1948), each specimen was characterized for head width, body width, caudal peduncle length, depressed dorsal fin length, depressed anal fin length, pelvic-fin length, and snout length. The Shoshone population differed from the Tecopa population by having smaller means for head width, body width, and pelvic fin length in

Effect of thyroid hormones on morphogenesis and growth of larvae and fry of telescopic-eye black goldfish, Carassius auratus

Three-day-old larvae of telescopic-eye black moor goldfish, Carassius auratus, were treated with different concentrations of Eltroxin (L-thyroxine-sodium, T 4) by immersion (0.01, 0.02, 0.05 and 0.10 ppm). The hormone treatment significantly accelerated the differentiation and growth of all the fins. The number of dorsal and anal fin rays was significantly higher in hormone-treated groups than in controls after 15 days of treatment. The highest dose of 0.10 ppm T 4 resulted in abnormalities especially in the vertebral column and pectoral fins. At the end of 25 days when the experiment was terminated, the eyes were still not telescopic and the body not yet black in any of the treatments, but the larvae exposed to 0.02 ppm and 0.05 ppm were significantly larger than controls. In another experiment, 30-day-old fry were treated with T 4 (0.02, 0.05 and 0.10 ppm) and triiodothyronine (T 3; 0.01 and 0.02 ppm). The hormone treatments accelerated scale formation: after 5 days the body was completely covered with scales, whereas in controls only a few scales were found. After 40 days of treatment, the number of black fish was greater after hormone treatment compared to controls. The number of melanophores on the scales was significantly greater after exposure to 0.10 ppm T 4 and 0.02 ppm T 3 than in controls. T 4 and T 3 treatments also accelerated the telescoping of eyes (exophthalmia). Among the different treatments used, only 0.05 ppm and 0.10 ppm T 4 and 0.01 ppm T 3 significantly accelerated the growth of fry over controls.

Supernumerary median fin-rays in teleostean fishes

Supernumerary fin-rays in the dorsal and anal fins are those that articulate directly with the head of the first proximal radial; they lie in front of the ray serially associated with the first radial. The argument presented here is that just as the number of fin-rays per dorsal and anal radial has decreased in actinopterygian history, so the number of dorsal and anal supernumeraries has decreased in teleosts. It is proposed that D > 3 and A > 3 (more than three dorsal and anal supernumeraries) is the condition primitive for teleosts, and that D2 and A3 are primitive for acanthomorphs.

Analysis of Meristic Characters and Genetic Differentiation in Greenland Halibut (Reinhardtius hippoglossoides) in the Northwest Atlantic

A stock identification study of Greenland halibut (Reinhardtius hippoglossoides) in the Northwest Atlantic was carried out based on samples from off eastern Newfoundland, Davis Strait, three West Greenland fjords and Denmark Strait. Meristic characters and frequencies of electrophoretically detectable alleles of protein loci were analyzed. Mean number of vertebrae showed significant heterogeneity among areas, while fin-ray numbers showed no difference. Offshore areas were very alike in terms of mean numbers of vertebrae, while those from the inshore areas of West Greenland differed both among themselves and from those of the offshore areas. The genetic variation between samples was small. In all samples the phenotypic distribution of four polymorphic loci was in accordance with the expectation from the Hardy-Weinberg proportions. Pair comparisons of the allelic distributions between samples showed that more than one breeding stock must exist. Although the Denmark Strait stock could not be separated from the stock in the area between West Greenland and Canada, results support the conclusion that at least two spawning stocks exist in the Northwest Atlantic. Results are consistent with the prevailing theory that Greenland halibut form a single, interbreeding stock in the offshore area between Canada and West Greenland, but also agree with other evidence that Greenland halibut in West Greenland fjords are partially isolated from the offshore stock.

Developmental stability, heterozygosity, and genetic analysis of morphological variation in pink salmon (Oncorhynchus gorbuscha)

Heterozygosity of 26 pink salmon (Oncorhynchus gorbuscha) families was compared with family survival rates up to 410 d after fry emergence and also with asymmetry of pectoral and pelvic fin ray numbers. There was no significant association between heterozygosity calculated at six electrophoretic loci and either survival rate or asymmetry in fin ray number at any time during the 410-d rearing period. More heterozygous families did not have higher survival rates than less heterozygous families, and they did not have less asymmetry in the fin ray characters. Heritabilities of 11 morphometric characters were, on average, lower than the heritabilities of the 2 meristic characters examined. There is no evidence yet to indicate that increased heterozygosity results in increased canalization of morphology in pink salmon.

A New Clingfish (Teleostei: Gobiesocidae) from the Mangroves of Costa Rica, with Notes on Its Ecology and Early Development

Tomicodon abuelorum is described from the Gulf of Nicoya, Costa Rica. It is characterized by high numbers of fin rays, relatively forward placement of the dorsal fin, and the lack of a dermal flap on the anterior nostril. Adults and juveniles are common associates of Rhizophora prop roots, from which they feed on small molluscs and crustaceans at high tide. Postflexion larvae are often found attached to floating mangrove leaves, and may use them as a dispersal mechanism into mangrove root systems. Reproduction appears to be year-round. The development of the pigment pattern from the postflexion larva to adult is described. Tomicodon abuelorum most closely resembles T. prodomus from the Gulf of Guayaquil, Ecuador.

Sexual selection is stabilizing selection in pupfish (Cyprinodon pecosensis)

One of the predictions of the ‘good genes’ model of sexual selection is that reproductively successful males with well-developed indicator traits should show smaller variances for non-indicator traits, that are not directly associated with mating success, when compared to non-breeding males and females. Thus sexual selection should reinforce stabilizing natural selection in reducing the variance in quantitative traits. This prediction is tested by analysing variation in eight morphological traits of breeding males, non-breeding males, and females of pupfish (Cyprinodon pecosensis). Breeding males tended to be less variable than non-breeding males for all principal component factors, and for all morphological traits except for depth, although these differences were statistically significant only for PC2, and PC5 and for pelvic fin length, number of pelvic fin rays and number of preopercular and preorbital pores. Similarly, breeding males tended to be less variable than females for all principal component factors and for all morphological traits except for number of preopercular pores. These differences were statistically significant for PC2, and for depth, pelvic fin length, number of preorbital pores and pectoral fin rays. The overall pattern of reduced variability in independent traits of breeding males revealed by principal component analysis is very consistent and highly significant (P<105). These results support the prediction of the ‘good genes’ model and show that reproductively active males are subject to more severe stabilizing selection for several quantitative traits than non-breeding males and females. Thus sexual selection, through male-male competition, female choice, or an interaction of both selective processes, results in stabilizing selection on quantitative morphological traits.

Lack of congruence between genetic and morphological stock structure of the southern African anglerfishLophius vomerinus

Meristic and morphometric variation and isozyme population markers were used to study the geographic stock structure of the southern African anglerfish Lophius vomerinus. Analysis of variance (ANOVA) revealed that the numbers of vertebrae and left pectoral fin rays differed significantly among areas. ANOVA of size-free estimates of morphometric variables showed that the length of the second dorsal fin spine, the head width and the snout width differed significantly among areas. A size-free principal component analysis (PCA) revealed that head characters and dorsal spine lengths covaried. A discriminant function based on meristic and morphometric characters correctly classified 36 and 51 per cent of the individuals respectively. A total of 24 protein-encoding loci was examined for Mendelian variation with starch-gel electrophoresis. Average heterozygosity (H) was 12,6 per cent, larger than that for most other marine fishes. There were no significant differences in allele-frequency among areas for nine polymorphic loci. A gene-diversity analysis showed that most of the genetic variation was contained within areas (99,62%), and that only a fraction of the total (0,38%) could be attributable to geographic differences among locations. Combining the data shows that the slight morphological differentiation among areas does not have a genetic basis. A conservative management policy, however, would be to set separate harvesting quotas for Namibia, for the South African west coast and for the South African south coast.

A taxonomic reappraisal of the Atlanto‐Mediterranean soles Solea solea, S. senegalensis and S. lascaris

Examination of morphometric characters of Solea aegyptiaca shows that it cannot be separated from Solea solea. Diagnostic characters are given to separate this species from S. senegalensis. The available data show that Solea impar and S. nasuta are junior synonyms of S. lascaris. Meristic characters of S. solea and S. lascaris vary greatly according to the geographical origin of the examined fishes, indicating the influence of temperature on the number of vertebrae and fin rays. A key is provided for the identification of the four species of the genus Solea known in the Atlanto‐Mediterranean region.

Diaphus pallidus sp.n., a new lanternfish from the Gulf of Aden (Pisces, Myctophidae)

A new myctophid species, Diaphus pallidus sp.n., was captured in the Gulf of Aden. The species can be distinguished from most of its congeners by the high number of dorsal fin rays and low number of gill rakers. It can be distinguished from D. lucidus (Goode &amp; Bean) by the form of the operculum and by the situation of some of the body photophores.

Adaptive, genetically based differences in life history between estuary and freshwater threespine sticklebacks (Gasterosteus aculeatus L.)

Life history theory predicts that migratory fishes should delay reproduction, be larger at maturity, and have higher fecundities than nonmigrants. We tested this hypothesis by comparing life histories of laboratory-reared estuary and freshwater threespine sticklebacks (Gasterosteus aculeatus L.) from the Navarro River, California. We also estimated phenotypic correlations and genetic variance (broad-sense heritabilities) for reproductive characteristics of these fish. The more migratory estuary sticklebacks delayed reproduction, were larger at first reproduction, and had higher fecundities than the freshwater fish. We found no significant differences in interclutch interval or average size of eggs. The body size – fecundity relationship did not differ among these populations, unlike the findings in previous reports comparing anadromous and freshwater threespine sticklebacks. We found significant levels of genetic variance for age and size at first reproduction in both populations, and for fecundity in the freshwater population. The estuary and freshwater sticklebacks did not differ in average number of fin rays, gill rakers, or lateral plates, indicating that differentiation in life history has not been accompanied by significant changes in these characteristics. These results provide evidence of genetic divergence between these populations with respect to life histories, and the nature of these differences suggests that adaptation to different migratory life-styles has occurred.

Responses of meristic characters in chum salmon (Oncorhynchus keta) to temperature changes during development

Variability in the number of dorsal, anal, caudal, pectoral, and pelvic fin rays, vertebrae, and gill rakers was examined in four populations of chum salmon (Oncorhynchus keta) transferred from 8 to 2 °C at various stages of embryonic development. Late transfers at complete eye pigmentation produced more gill rakers than transfers earlier in development. Transfers at completion of epiboly and initial eye pigmentation produced fewer vertebrae than earlier or later transfers. Stage of transfer had no significant effect on fin ray counts. Vertebral responses differed among families. Genotype–environment interactions produce meristic phenotypes that are presently difficult to predict.

Spawning and development ofLesueurigobius sanzoioff northern namibia

The presence of the gobiid Lesueurigobius sanzoi in the Benguela upwelling region was recorded for the first time from the capture of five adult specimens in 1980. This paper presents evidence that this region can be included in the species distribution range. It also presents the first description of the larval series and juveniles, together with a morphometric study of the larval stages and a comparative study of the characters differentiating larvae of this species from those of Nematogobius bibarbatus, the dominant gobiid in the region. The smallest stages of the larvae of these two species are distinguished by their pigmentation patterns, the larger stages by the number of fin rays. Information on the geographical and depth distribution of Lesueurigobius sanzoi larvae is also included. This species spawns on the northernmost part of the Namibian continental shelf in autumm. The larval distribution area is associated with the warmer waters of the Angola Current.