Racial differences in eggs and juveniles of Windermere charr, Salvelinus alpinus

At least four races of charr occur in Windermere, the largest natural lake in England: north basin and south basin autumn spawners, north basin and south basin spring spawners. This study examines racial differences between eggs and juveniles, and relates juvenile size and survival to egg size. There were no major differences between races for egg incubation times and the percentage of eggs hatching successfully, the latter being high (mean values 76–96%) with a negligible proportion of abnormal alevins (<0.8%). Although there were no significant differences in the lengths of the female parents, both eggs and alevins were significantly larger for the autumn spawners than the spring spawners. Size differences in alevins, especially live weight, were positively related to egg size but not female parent size. Mean percentage survival for juveniles attaining the independent feeding stage was higher for the progeny of autumn spawners (32%) than spring spawners (3%). Racial differences in the egg and alevin stages therefore appear to have a significant effect on subsequent survival, and could be ultimately responsible for the relatively small proportion of spring spawners (only 4–6%) in the Windermere population of charr.     

Body condition influences ontogeny of foraging behavior in juvenile southern elephant seals

Ontogeny of diving and foraging behavior in marine top predators is poorly understood despite its importance in population recruitment. This lack of knowledge is partly due to the difficulties of monitoring juveniles in the wild, which is linked to high mortality early in life. Pinnipeds are good models for studying the development of foraging behaviors because juveniles are large enough to robustly carry tracking devices for many months. Moreover, parental assistance is absent after a juvenile departs for its first foraging trip, minimizing confounding effects of parental input on the development of foraging skills. In this study, we tracked 20 newly weaned juvenile southern elephant seals from Kerguelen Islands for up to 338 days during their first trip at sea following weaning. We used a new generation of satellite relay tags, which allow for the transmission of dive, accelerometer, and location data. We also monitored, at the same time, nine adult females from the colony during their post‐breeding trips, in order to compare diving and foraging behaviors. Juveniles showed a gradual improvement through time in their foraging skills. Like adults females, they remarkably adjusted their swimming effort according to temporal changes in buoyancy (i.e., a proxy of their body condition). They also did not appear to exceed their aerobic physiological diving limits, although dives were constrained by their smaller size compared to adults. Changes in buoyancy appeared to also influence their decision to either keep foraging or return to land, alongside the duration of their haul outs and choice of foraging habitat (oceanic vs. plateau). Further studies are thus needed to better understand how patterns in juveniles survival, and therefore elephant seal populations, might be affected by their changes in foraging skills and changes in their environmental conditions.     

Cloning, sequencing, and characterization of CYP1A1 cDNA from leaping mullet (Liza Saliens) liver and implications for the potential functions of its conserved amino acids

A 2,037 bp CYP1A1 cDNA (GenBank AF072899) was cloned through screening of a lambdaZipLox cDNA library constructed from the liver of a leaping mullet (Liza saliens) fish captured from Izmir Bay on the Aegean coast of Turkey using rainbow trout CYP1A1 cDNA as a probe. This clone has a 130 bp 5'-flanking region, a 1,563 bp open reading frame (ORF) encoding a 521-amino acid protein (58,972 Da), and a 344 bp 3'-untranslated region without a poly (A) tail. Alignment of the deduced amino acids of CYP1A1 cDNAs showed 58% and 69-96% identities with human and 12 other fish species, respectively. Southern blot analysis suggested that this CYP1A1 cDNA was from a single-copy gene. Based on the comparison with CYP1A1 genes reported for fish and mammals, the leaping mullet CYP1A1 gene is probably split into 7 exons. The intron insertion sites were predicted. Alignment of the CYP1A1 cDNA encoded amino acids from 13 fish and 7 mammalian species disclosed differences in highly conserved amino acids between aquatic and land vertebrates. The possible associated secondary structure; conserved motifs and substrate-binding sites were discussed. The phylogenetic relationships of CYP1A1s among 13 fish species were analyzed by a distance method.     

饥饿对南方鲇仔稚鱼消化系统的形态和组织学影响

在实验室饲养条件下,对南方鲇仔、稚鱼进行饥饿,观察了消化系统的形态和组织学变化。仔鱼肝脏萎缩,肠管缩短、变细,失去变曲形状。组织学结构与功能明显衰退：肝组织变得疏松,细胞缩小,仔鱼肝细胞内无脂质积累,到饥饿后期,部分细胞核仁解体;稚鱼肝细胞内贮存的脂质迅速消失,细胞由多角形变为圆形。胰脏组织变得致密,腺泡小叶分界不清,腺泡萎缩,其内分泌物减少或消失。消化道上皮细胞的高度下降,微绒毛退化,胃腺下发达     

Thermoregulatory behavior and diel activity of yearling winter flounder,Pseudopleuronectes americanus (Walbaum)

Synopsis Sixteen yearling winter flounder, tested individually for 3-day periods in electronic shuttleboxes, voluntarily occupied an 8–27°C range of temperature, with a modal final thermal preferendum of 18.5°C (mean 18.7°C, median 19°C, midpoint 17.5°C, s.d. 1.9°C, S _k + 0.33). The locomotor activity pattern of the yearling fish in the laboratory was markedly nocturnal, with mean hourly nocturnal activity exceeding mean hourly diurnal activity by a factor of 3.4. Maximum activity occurred at 0300 EST, minimum activity at 1400 EST. While activity generally increased with temperature, a local activity minimum occurred at 18.7°C, coinciding with the 24-hour mean final thermal preferendum. Comparison of these laboratory data with previously published field data suggest that behavioral responses to temperature and light play significant roles in determining age- and size-specific differences in seasonal depth stratification and onshore-offshore distributions in this species.     

Photorhabdus luminescens LN2转座突变菌株的研究

发光杆菌属Photorhabdus细菌与异小杆属Heterorhabditis昆虫病原线虫的共生关系是这类生物杀虫剂产业化生产和田间应用的基础。本文采用Tn5转座方法构建了共生细菌P. luminescens LN2突变体库;从中筛选出一个对其共生线虫H. indica LN2的生长繁殖有显著促进作用的突变菌株（LN2-M2716）;测定了该突变菌株的菌落特征、对大蜡螟Galleria mellonella及非特异共生线虫H. bacteriophora H06的毒性、对线虫产量的影响。结果显示,LN2-M2716菌株在菌落形态、色素分泌、过氧化氢酶反应、荧光、食物信息作用以及对大蜡螟毒力等方面与野生型菌株差异不明显;但对非特异共生线虫H. bacteriophora H06的毒性及对特异共生线虫H. indica LN2生长繁殖的促进作用方面均明显高于野生型菌株。论文结果为构建支持线虫高产的菌株提供了关键技术。     

Trophic shift in young‐of‐the‐year Mugilidae during salt‐marsh colonization

This study investigated the trophic shift of young‐of‐the‐year (YOY) thinlip grey mullet Liza ramada and golden grey mullet Liza aurata during their recruitment in a salt marsh located on the European Atlantic Ocean coast. Stable‐isotope signatures (δ¹³C and δ¹⁵N) of the fishes followed a pattern, having enrichments in ¹³C and ¹⁵N with increasing fork length (L_F): δ¹³C in fishes < 30 mm ranged from ?19.5 to ?15.0‰, whereas in fishes > 30 mm δ¹³C ranged from ?15.8 to ?12.7‰, closer to the level in salt‐marsh food resources. Large differences between the δ¹⁵N values of mugilids and those of food sources (6·0‰ on average) showed that YOY are secondary consumers, similar to older individuals, when feeding in the salt marsh. YOY mugilids shift from browsing on pelagic prey to grazing on benthic resources from the salt marsh before reaching 30 mm L_F. The results highlight the role of European salt marshes as nurseries for juvenile mugilids.     

Cranial and appendicular ontogeny of Bactrosaurus johnsoni,a hadrosauroid dinosaur from the Late Cretaceous of northern China

Abstract: The juvenile anatomy of various cranial and appendicular elements of the hadrosauroid dinosaur Bactrosaurus johnsoni is described in detail. Growth changes are documented from juvenile to adult stages for each skeletal element available. In the studied skull, ontogenetic trends consist of: development of features on the ventral surface of the frontal; reduction in the slope of the posteromedial process of the premaxilla; a posterior shift of the dorsal process of the maxilla; development of concavities on the medial surface of the prefrontal; increased robustness and development of the ventral flange of the jugal; decreased curvature of the long axis of the quadrate; increased ventral deflection of the dentary; and changes in the length/width proportions and depth of the anterior surface of the predentary. In the appendicular skeleton, the majority of ontogenetic variation from juvenile to adult occurs in the limb bones, including increased robustness of the deltopectoral crest of the humerus; relative shortening of the ulna; increased development of the fourth trochanter and mediolateral widening of the distal end of the femur; increased expansion of the cnemial crest of the tibia; and the increased prominence of articular protuberances and flanges of the metatarsals. A survey of the phylogenetically informative characters present in B. johnsoni indicates that several characters concerning the frontal, maxilla, jugal, quadrate, predentary, dentary, scapula, humerus and ilium are affected by ontogeny. Nevertheless, the majority of phylogenetic characters are not ontogenetically variable, suggesting that a substantial amount of the information provided by juvenile and subadult specimens for phylogenetic inference is reliable in basal hadrosauroids.     

Molecular Characterization of a Xiphinema hunaniense Population with Morphometric Data of all Four Juvenile Stages

A population of Xiphinema hunaniense Wang and Wu, 1992 with all four juvenile stages was found in the rhizosphere of Pinus sp. in Hangzhou, Zhejiang, China. Morphometrics of 18 females and 35 juveniles of this population are given herein. Detailed morphology and morphometrics of the four juvenile stages are provided. Further comparisons based on morphometrics of the population with previous studies of the females and the first-stage juveniles of X. hunaniense with X. radicicola are given, and morphological variation in X. hunaniense populations are discussed. A revised polytomous key code of Loof and Luc (1990) for X. hunaniense identification is provided, i.e., A1- B4- C4- D4/5- E1- F2(3)- G2- H2-I3- J4- K2- L1. In addition, the sequence of the D2 and D3 expansion region of the 28S rRNA gene was analyzed and compared with sequences of closely related species downloaded from the NCBI database. Cluster analysis of sequences confirmed and supported the species identifications.