The growth of Tilapia mossambica Peters (Pisces: Cichlidae) in Lake Sibaya, South Africa

The scales of Tilapia mossambica Peters * from Lake Sibaya show clear rings formed by broken, widely-spaced circuli in the anterior field. In order to determine the rate and time of scale ring formation, the number of circuli in the marginal increment was determined. Five scales from the pectoral region of 2223 fishes caught at regular intervals over two years were examined. When plotted as histograms, the number of circuli in the marginal increment showed a sharp movement to the left in September–October and again in January, indicating that the rings were formed during these months in the majority of fish examined. Pre- and postbreeding feeding migrations, and increases in condition factor, were associated with scale ring formation. Otoliths and opercula were also examined for age determination. Annual length increments were calculated for 450 T. mossambica collected throughout the year, and growth curves plotted. T. mossambica from Sibaya reach maturity after one year at a standard length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 11–12 cm in females and 17 cm in males. The maximum final size was about 24 cm.     

低龄草鱼鳞片环纹的增长及幼轮和年轮特征的初步研究

幼草鱼鳞片环纹,以孵出后第二个月生长最快,往后生长减慢,冬季停止生长。幼鱼体长一般在47—70毫米形成幼轮。鳞片的“切割相”是区别年轮和幼轮的标志。幼鱼在饥饿时,环片不仅不增长,反而出现环片被吸收的现象。鳞片上各种副轮标记的形成与摄食条件的变化有关。计算了体长与鳞径、环纹数以及鳞径与环纹数的迴归方程,它们之间都呈直线正相关,相关显著性均在99%以上。       

Relationship between scale growth checks, circuli formation rate and somatic growth in Rutilus rutilus (L.) a fish farm-reared cyprinid

Check formation on scales of roach Rutilus rutilus was examined during their production cycle at a fish farm in England through analysis of circuli patterns. Regular check formation was associated with the movement of fish from one type of grow-out facility to another; this resulted in a sudden shift in growth rate and the formation of a new check. As these had the characteristics of annual marks, their formation potentially invalidates their use as structures to determine the age of individuals during recapture events that may follow their introduction to the wild. At low growth rates, the number of circuli was constant throughout the year; this situation changed when fast growth rates were achieved. Five methods of backcalculation were also validated. When the proportionality between the body length and scale radii was weak, backcalculation methods were poor in determining length at check formation.     

Age determination in Pomatoschistus mi nut us (Pallas) and Pomatoschistus microps (Kreyer) (Pisces: Gobiidae) from the upper Tagus estuary, Portugal

The use of scale inspection as a means of age-determination in Pomatoschistus microps and Pomatoschistus minutus in the Tagus estuary is confirmed, but annulus formation pattern is different from that described for P. microps in the area of the British Isles (Miller, 1975). In Britain, two annuli are laid down on the scales each year, but in the Tagus, only one annulus is formed. One possible reason for this difference is the fact that in the Tagus the peak breeding season and the lowest water temperatures coincide. Therefore, the two causes of annulus formation coexist at the same time of year.
Population structure in both species is dominated by the 0-group, which appears earlier (April/May) than reported for other areas. Maximum age seems not to exceed 26 months in P. microps and 32 months in P. minutus .     

Alkaline phosphatase activity in the skin of the Common goby, Pomatoschistus microps (Krøyer), in relation to cycles in scale and body growth

A histochemical study of the distribution of alkaline phosphatase in the skin of the Common goby, Pomatoschistus microps , showed that the enzyme is present in the dermis, not in the epithelium, and is more pronounced around the growing edge of the scale and below the fibrillary plate. The intensity of the enzyme reaction is higher in regenerated scales. In conjunction with the phenology of P. microps , a method was adopted to measure the enzyme activity in the skin, including scales, for successive months over a period of two years. Enzyme activity displayed seasonal fluctuations which were closely related to both body and scale growth. Enzyme activity also reflected other phenological cycles during the life-span of P. microps .     

Age-structure and life-span in the Common goby, Pomatoschistus microps

Age-structure and longevity in the euryhaline Common goby, Pomatoschistus microps (Krøyer), has been studied by monthly sampling of estuarine and shore populations in the Isle of Man and in collections from other parts of the British Isles. Age of individuals was determined by examination of caudal peduncle scales, where time of annulus formation was confirmed from monthly changes in mean terminal sclerite width and in frequency of scale-types. After the first winter of life, an annulus of narrow sclerites is produced on resumption of growth in spring and a separate summer annulus, corresponding with a growth retardation during the peak breeding season, is laid down usually in June. Maximum age did not exceed 21–26 months, with most adult fishes dying in the second autumn of life a few months after their first breeding season (within possible age-limits of 12–20 months). Seasonal migration is discussed with reference to the downstream movement of estuarine P. microps when sexually mature after the first winter of life, the winter distribution relative to temperature, and the preference of newly demersal young for less saline parts of the estuary. Cases of mortality from predation and environmental extremes are listed. The question of senescence in relation to life-history pattern and survival in P. microps and some other teleosts is discussed with special reference to gonad maturation and spawning, and the attainment of limiting size.     

Marking zebrafish, Danio rerio (cyprinidae), using scale regeneration

Tagging or marking small laboratory-bred fish species is not an easy task. This also holds for the zebrafish, Danio rerio, which is widely used throughout the world as a model organism for genetics, developmental biology, etc. We present a simple marking technique based on scale regeneration. A comparative morphological study of various types of zebrafish scales indeed shows that regenerated scales are easily distinguishable from nonregenerated ones. We propose to take advantage of this typical morphology to mark a single or several individuals. This technique, based on a natural biological process, is easy to perform and does not enhance fish mortality in laboratory breeding conditions. It permits assembly of several specimens in a single tank with the possibility of identifying each of them by regenerated-scale coding. Nevertheless, a prerequisite is that the species does not lose and regenerate scales in large numbers in laboratory breeding conditions. To check this, 5,200 scales were removed from a large region of the left flank in 100 zebrafish and the number and position of regenerated scales were statistically analysed. Our results indicate that (1) laboratory-bred zebrafish have only a few regenerated scales (7.48%), (2) the probability of finding a regenerated scale is similar whatever its position in a row (antero-posterior axis), but (3) it differs from one row to another (scales from the back are more frequently lost than those from the pectoral region). This paper presents a procedure to mark small breeding colonies of zebrafish using scale regeneration with the number and position of the scales to be removed with high probability of marking success. J. Exp. Zool. 286:297-304, 2000.     

The zebrafish scale as model to study the bone mineralization process

Danio rerio (zebrafish) shows high similarity with humans in terms of bone architecture, bone cells, matrix proteins and molecular signalling. The fish body is covered by elasmoid scales which are part of the dermal skeleton. Since few data have been published about the function of the fish scale cells, we investigated the mineralization pattern of the scale and the role of the episquamal osteoblasts in the neodeposition of the bone tissue. First, we described a specific mineralization pattern and distribution of the bone forming cells in different areas of the scale. We observed along the external circuli that, during the scale growth, the marginal cells migrate and organize in a cord-like structure just before the mineralization process takes place generating a new circulus. These cells exhibit alkaline phosphatase activity, a well known mammalian osteoblastic differentiation marker. The internal circuli are also characterized by new matrix deposition. Thus, zebrafish scale represents a useful model for analyzing the osteoblast behaviour during bone formation and mineralization and it could be useful in physiological studies and pharmacological tests.     

多齿蛇鲻鳞片表面结构的扫描电镜观察

本文对多齿蛇鲻鳞片表面结构进行扫描电镜观祭,描述了鳞纹、年轮形式、齿状粒突、辐射沟、伸缩缝、后区隆突和小棘。鳞纹嵴顶上的齿状粒突,其形态特征和排列方式可作为辅助鉴别疑难种类的依据。鳞纹和后区隆突上的伸缩缝,作者认为对鳞片的伸缩起着柔软缓冲作用。     

Marine post-smolt growth and age at maturity of Atlantic salmon

The annual variation in sea-age of maturation for a hatchery dependent stock of Atlantic salmon was compared to variation in post-smolt growth as evidenced by circuli spacing patterns. The proportion of returns of 1-seawinter (1 SW) and 2 SW salmon and the fraction of the smolt year class or cohort that maturated as 1 SW fish, were compared to seasonal growth indices determined from circuli spacing on the scales of smolt class survivors returning as 1 SW and 2 SW spawners. Using image processing techniques, we extracted inter-circuli distances from scales from 2244 recaptured fish. Spacing data for the first year at sea were collected and then expressed as seasonal growth indices for the spring period, when post-smolts first enter the ocean; the summer, when growth appears maximal; and winter, when growth appears to be at a minimum. In general, circuli spacings were wider for 1 SW than for the 2 SW returns of the same smolt cohort. The 1 SW fraction was significantly and positively correlated with late summer growth, suggesting that growth during this season is pivotal in determining the proportion of a smolt class that matures early.     

The histology and calcification of regenerating scales in the blackspotted topminnow, Fundulus olivaceus (Storer)

The regenerating scale and tissues comprising the scale pocket of Fundulus olivaceus were examined microscopically at specific intervals. Scale removal resulted in a thickening of the epidermis which persisted through the early stages of regeneration. This thickening was due in part to the appearance of columnar basal cells which divided producing cells that became mucous cells and squamous cells. The scale regenerated as a relatively large plate of bone which first appeared between layers of scleroblasts on the floor of the scale pocket and then grew producing circuli and radii. By the fourth day of regeneration, calcium was observed in the cytoplasm of the scleroblasts and at randomly distributed foci in the osseous portion of the scale. The osseous layer was completely calcified by 15 days of regeneration.     

Circuli spacing and annulus formation: is there more than meets the eye? The case for sockeye salmon,Oncorhynchus nerka

This study describes a pattern of circulus spacing on the scales of sockeye salmon, Oncorhynchus nerka , which has not been reported previously. The average distance between circuli formed during the second year of ocean growth is much less than that of first year or in subsequent years. This pattern was persistent for fishes of two river systems, six year–classes and two age groups (2.2 and 2.3) and was due to summer growth. Statistical analyses were conducted only on age 2.2 fish because of small sample sizes in four of the six years for age 2.3 fish. There were significant (p < 0.05) differences in the distance between circuli formed in the summer and in the two stocks for various years at sea. No significant variation in average spacing between circuli was explained by oceanic temperatures.
Annuli were formed between November and January. However, oceanic temperatures were declining at this time and do not reach minima until April. Thus, annuli are formed about the time of the equinox and during a declining temperature regime. We hypothesize that the pattern of circuli spacing and annulus formation are responses to photoperiod and food availability which the fish experience during their existence at sea.     

Are scale circuli deposited daily in juvenile weakfish,Cynoscion regalis?

Synopsis Scale circuli of juvenile weakfish,Cynoscion regalis, were counted to determine if deposition was daily. Scale circuli counts were precise with little variation between counts (99% of the two counts from an individual scale were identical, N = 3580). Tetracycline marked juveniles (N = 71) had mean scale circuli deposition rates that were daily up to 24 d after marked. Data from several sources suggest that daily deposition of weakfish scale circuli occurred over a relatively narrow size range, approximately 14.3 to 111.9 mm standard length, however it is during this time that juvenile weakfish occupy estuarine nursery areas, where growth, mortality, and survival may alter subsequent year class strength. The estimated upper size limit at which scale circuli were no longer daily occurred over a wide range (82–142 mm standard length), and additional research is required to further clarify the limits of size and age of daily circuli deposition.     

Weight‐length relationships for five fish species from a temperate coastal lagoon of southern Europe

The weight‐length relationships (WLR) were estimated for five fish species of Ria Formosa, a coastal lagoon in southern Portugal. WLRs for Gobius couchi, Pomatoschistus microps and Parablennius pilicornis were determined for the first time ever and for Gobius cruentatus for the first time for the southern European Atlantic coast.     

大鳞副泥鳅鳞片表面结构的扫描电镜观察

对大鳞副泥鳅的鳞片作了扫描电镜观察。结果表明,大鳞副泥鳅具圆鳞;基区、侧区和顶区均具有辐射沟及环沟,二者交织成网状,将鳞片分割成块状,可增加鳞片的柔软度;次级辐射沟发出部位可作为确定年轮的主要依据。     

Links between patterns of marine growth and survival of Atlantic salmon Salmo salar, L.

The hypothesis that marine survival of Atlantic salmon Salmo Salar is linked to marine growth was explored by using inter-circuli distances and total numbers of circuli existing on scales from a population monitored over nearly four decades. The results suggest that marine growth controls survival, particularly during the late summer and early winter of the first year at sea. Recruitment is strongly linked to growth, described as the total number of circuli, but not to inter-circuli distances. This highlights the potential of patterns of circuli number to be considered as proxies for growth. Indications that hatchery populations might be subject to other mortality events, in addition to those experienced by wild populations, are also presented.     

Consistency of elemental and isotope‐ratio patterns across multiple scales from individual fish

Assays of elemental and stable‐isotope ratios across growth increments of scales have the potential to provide a non‐lethal alternative to otolith chemistry for identifying migration and ontogenetic trophic shifts. A central assumption when employing scales as otolith analogues is that any scale from an individual will provide equivalent information about the chemical history of that fish. This assumption was investigated with multiple scales from wild and captive euryhaline Atlantic tarpon Megalops atlanticus from the north‐west Gulf of Mexico. Elemental (Sr:Ca) and isotope‐ratio (δ¹³C and δ¹⁵N) life‐history profiles were compared among multiple scales from each fish. All three chemical proxies showed highly consistent patterns among non‐regenerated scales, while patterns in regenerated scales diverged, indicating rapid regrowth of interior scale material at the onset of regeneration. Patterns of Sr:Ca and δ¹³C covaried, supporting their use as salinity proxies, while δ¹⁵N patterns were consistent with ontogenetic diet shifts. Water samples taken from aquaria holding captive fish were used to calculate partition coefficients for a suite of elements in M. atlanticus scales for future quantification of migratory movements in the region. Together, these results support the assumption that non‐regenerated scales from individual M. atlanticus provide equivalent chemical histories, further validating their use as a viable non‐lethal alternative to otoliths.     

Callus formation and plant regeneration in various <Emphasis Type="Italic">Lilium</Emphasis> species and cultivars

Summary In researching the application of genetic transformation to lily breeding, callus formation from cultured explants and plant regeneration from induced calluses were examined in 33 Lilium genotypes, 21 species, three Asiatic hybrids, two LA hybrids, two Longiflorum hybrids, three Oriental hybrids, and two Trumpet hybrids. Seed, bulb scale, leaf, or filament explants were placed on a medium containing 4.1 μM 4-amino-3,5,6-trichloropicolinic acid (picloram; PIC) and cultured in the dark. After 2 mo., callus formation was observed in 30 genotypes, and a formation frequency of more than 50% was obtained in 24 genotypes. Bulb scale and filament explants showed great ability to form calluses, whereas seeds had poor ability. Most of the induced calluses were yellow and had a nodular appearance. When subcultured onto the same fresh medium, twofold or more increases in callus mass were obtained in 1 mo. for 15 genotypes. Callus lines showing sustained growth 1 yr after the initiation of subculture were examined for their ability to produce shoots on a medium without plant growth regulators (PGRs) and a medium containing 22 μM 6-benzyladenine (BA). Shoot regeneration was observed in all genotypes examined, and a regeneration frequency of over 80% was obtained in 20 genotypes. Initial explants used for callus induction and callus type (nodular or friable) had no effect on shoot regeneration. Most of the regenerated shoots developed into complete plantlets following their transfer to a PGR-free medium.     

Scale surface micro-structures of British freshwater cyprinidae

The scales of the roach (Rutilus rutilus L.), rudd (Scardinus erythropthalmus L.) and Crucian carp (Carassius carassius L.) Cyprinidae, Teleostei, were examined by scanning electron microscopy. The circuli in the overlapped areas of the scales were found to be denticulated. Inter-specific variation of denticular morphology, height and spacing was revealed when circuli of comparable ontogenetic age were investigated. The osseus material forming the circuli is reduced in thickness or absent at the scale radii. On the basis of the results of this study it is considered that the term micro-structure should be used in preference to ‘ornamentation’ to describe scale surface characteristics.