Late Sexual Maturity Research Articles

Molecular characterization of oxytocin receptor gene in water buffalo (Bubalus bubalis).

Buffaloes are known for their productivity as compared to average yielding cows due to higher fat percentage, better feed conversion ability and disease resistance. On the other hand, the reproductive performances of buffaloes are often considered as poor owing to late sexual maturity, weak/silent oestrus, repeat breeder and prolonged intercalving interval. The study of cascade of events during oestrus and oestrous cycle can be useful for the improvement of reproductive efficiency of buffaloes. More precisely, the hormonal changes initiated at the molecular level within the animal determine the reproductive nature of the species. Nucleotide/protein sequence analysis serves as a vital tool in analysing the binding of the hormones for their effect or functions. In this study, we have reported cloning and characterization of the complete coding (cDNA) sequence of oxytocin receptor gene (OXTR) in buffaloes. Buffalo OXTR gene contains an uninterrupted ORF of 1176 nucleotides corresponding to an inferred polypeptide length of 391 amino acids (aa). The molecular weight of the deduced aa sequence was found to be 43kDa with an isoelectric point of 9.253 and 16.328 charge at pH 7.0. The deduced protein sequence consists of 38 strongly basic (+) (K,R), 22 strongly acidic (-) (D,E), 186 hydrophobic (A, I, L, F, W, V) and 95 Polar (N, C, Q, S, T, Y) aa. Results indicated that aspartate (D) at aa position 85 and D, R and C at aa positions 136, 137 and 138, respectively, are conserved in buffaloes. The buffalo OXTR gene shared a per cent similarity ranging from 84.7 to 98.1 and 88.5 to 97.7 at nucleotide and deduced aa sequence levels, respectively, with that of other species. Phylogram constructed on the basis of either nucleotide or deduced aa sequences of buffalo OXTR gene showed that buffalo, cattle and sheep have diverged from human and swine and formed a separate clad. The buffalo sequence has shown maximum similarity and closeness with cattle followed by sheep both at nucleotide and at aa level.

Association of sexual maturation with excess body weight and height in children and adolescents

BackgroundStudies addressing the influence of early sexual maturation on the excess of body weight and height of children and adolescents are scarce. The aim of the study was to analyze the association of sexual maturation with excess body weight and height in children and adolescents.MethodsThis was a cross-sectional study performed in Florianópolis city, Brazil, in 2007, with 2339 school children, aged 8–14 years (1107 males). Selection was based on a probabilistic, cluster-stratified sampling technique. School children were classified according to the presence of excess body weight, using sex- and age-specific body mass index (BMI) cutoff points. Z-scores were calculated from height and BMI data. Sexual maturation was self-assessed according to Tanner stages of development. Subjects were ranked based on tertiles of sexual maturation (early, normal and late) for each stage of development. Poisson and linear regression models were used.ResultsCompared to the reference group (normal sexual maturation), early maturing females had higher prevalence of excess weight (adjusted prevalence ratio: 1.70; 95% CI: 1.24 to 2.33) and increased height-for-age (adjusted β: 0.37; 95% CI: 0.14 to 0.59), while late maturing females had lower prevalence of excess weight (adjusted prevalence ratio: 0.57; 95% CI: 0.37 to 0.87) and decreased height-for-age (adjusted β: −0.38; 95% CI: −0.56 to −0.20). In males, early and late sexual maturation were associated with increased (adjusted β: 0.37; 95% CI: 0.14 to 0.59) and decreased (adjusted β: −0.38; 95% CI: −0.56 to −0.20) height-for-age, respectively.ConclusionEarly sexual maturation is associated with excess body weight in females and with greater height-for-age in both sexes.

Detection of Quantitative Trait Loci (QTL) Related to Grilsing and Late Sexual Maturation in Atlantic Salmon (Salmo salar)

In Atlantic salmon aquaculture, early sexual maturation represents a major problem for producers. This is especially true for grilse, which mature after one sea winter before reaching a desirable harvest weight, rather than after two sea winters. Salmon maturing as grilse have a much lower market value than later maturing individuals. For this reason, most companies desire fish that grow fast and mature late. Marker-assisted selection has the potential to improve the efficiency of selection against early maturation and for late sexual maturation; however, studies identifying age of sexual maturation-related genetic markers are lacking for Atlantic salmon. Therefore, we used a 6.5K single-nucleotide polymorphism (SNP) array to genotype five families from the Mainstream Canada broodstock program and search for SNPs associated with early (grilsing) or late sexual maturation. There were 529 SNP loci that were variable across all five families, and this was the set that was used for quantitative trait loci (QTL) analysis. GridQTL identified two chromosomes, Ssa10 and Ssa21, containing QTL related to grilsing. In contrast, only one QTL, on Ssa18, was found linked to late maturation in Atlantic salmon. Our previous work on these five families did not identify genome-wide significant growth-related QTL on Ssa10, Ssa21, or Ssa18. Therefore, taken together, these results suggest that both grilsing and late sexual maturation are controlled independently of one another and also from growth-related traits. The identification of genomic regions associated with grilsing or late sexual maturation provide an opportunity to incorporate this information into selective breeding programs that will enhance Atlantic salmon farming.

Delayed Puberty but Normal Fertility in Mice With Selective Deletion of Insulin Receptors From Kiss1 Cells

Pubertal onset only occurs in a favorable, anabolic hormonal environment. The neuropeptide kisspeptin, encoded by the Kiss1 gene, modifies GnRH neuronal activity to initiate puberty and maintain fertility, but the factors that regulate Kiss1 neurons and permit pubertal maturation remain to be clarified. The anabolic factor insulin may signal nutritional status to these neurons. To determine whether insulin sensing plays an important role in Kiss1 neuron function, we generated mice lacking insulin receptors in Kiss1 neurons (IR(ΔKiss) mice). IR(ΔKiss) females showed a delay in vaginal opening and in first estrus, whereas IR(ΔKiss) males also exhibited late sexual maturation. Correspondingly, LH levels in IR(ΔKiss) mice were reduced in early puberty in both sexes. Adult reproductive capacity, body weight, fat composition, food intake, and glucose regulation were comparable between the 2 groups. These data suggest that impaired insulin sensing by Kiss1 neurons delays the initiation of puberty but does not affect adult fertility. These studies provide insight into the mechanisms regulating pubertal timing in anabolic states.

A checklist of the Chilean Parastacidae (Decapoda, Astacidea)

The family Parastacidae is represented in Chile by the genera Samastacus Riek, 1971, Parastacus Huxley, 1879, and Virilastacus Hobbs, 1991, and includes a total of six species. Its geographical distribution ranges from coastal areas to the Andean mountains, between the river Aconcagua (32°55′S 71°30′W) and the Taitao peninsula (46°30′S 74°30′W). These six species are: Samastacus spinifrons (Philippi, 1882), Parastacus pugnax (Poeppig, 1835), P. nicoleti (Philippi, 1882), Virilastacus araucanius (Faxon, 1914), V. rucapihuelensis Rudolph & Crandall, 2005 and V. retamali Rudolph & Crandall, 2007. All six species are endemic to Chile, with the exception of S. spinifrons which also inhabits Argentina and is the only species that inhabits lentic and lotic waters. The other five species are burrowers, inhabiting underground waters in semi-marshland zones where they build relatively complex burrows of varying depths. Present knowledge on the biology of these parastacids relates to: (a) taxonomy and phylogenetic relationships, (b) type and duration of embryonic and post-embryonic development, and (c) sexual system. Fragmentary studies have also been carried out on: (a) burrow morphology, (b) some physical/chemical parameters of water inside the burrows, (c) reproductive biology, and (d) aquaculture. These species are currently under threat, as a result of strong anthropogenic pressure which causes degradation of their respective habitats and, in some cases, such as S. spinifrons and P. pugnax, due to overexploitation as a human food source. Furthermore, in Chile there is no legislation to regulate the extraction, trade and transport of specimens. Only S. spinifrons is of interest for aquaculture purposes, in view of certain advantageous biological characteristics in comparison to other burrowing species. Nevertheless, certain intrinsic characteristics of parastacids, i.e., low fecundity and growth rate, late sexual maturity, very prolonged ovarian and embryonic development, together with deterioration of respective habitats and, in some species, overexploitation, have resulted in these species being classified as endangered Considering the aforementioned, it is important to study the life history, ecology and behaviour of each of these species, with the aim of compiling information that will permit the proposal and implementation of effective protection measures that, in turn, will ensure their conservation.

Sexuality and sickle cell disease

For decades, sickle cell disease (SCD) was mainly considered a childhood disease, since until 1973 life expectancy was 14 years(1). However, most children with SCD outlive this barrier(2). Newborn screening, prophylactic penicillin, and effective vaccinations against Haemophilus influenzae type b and Streptococcus pneumonia are some of the factors responsible for this marked decrease in mortality(3-5). Other contributory factors may include chronic transfusion to prevent stroke and the use of hydroxyurea(6,7). However, data from the National Association for Sickle Cell Disease in the USA show that 70% of SCD patients are either partially or totally dependent on financial support(8). Adolescents may be challenged by issues related to body image due to delayed growth and late sexual maturation(9-12), and many adults have difficulty sustaining marital relationships(8,13). The above motifs could explain, but not justify, the fact that sexuality is not a common subject in SCD. There are few reports about this theme in SCD, many of them associated with priapism events(14-16). All these facts reinforce the importance of the paper from Cobo et al. published in this issue(17). Information is a key factor in reported sexual adjustment and satisfaction(8). Cobo et al.(17) observed that individuals with SCD presented a limited knowledge of sexual facts, which may adversely contribute to sexual adjustment and to low self-esteem. These patients need to become independent and responsible adults, with productive and sexually fulfilling lives. There is an urgent necessity of giving adequate and complete information to these individuals and, also, adopting procedures that allow individuals to feel they have some control over their treatment, so that they can improve their self-esteem and achieve a better sexual adjustment. These efforts will help SCD patients to normalize their experiences and increase their chances of having a normal life(8).

Primates

Primates

Fishing groupers towards extinction: a global assessment of threats and extinction risks in a billion dollar fishery

AbstractGroupers are a valuable fishery resource of reef ecosystems and are among those species most vulnerable to fishing pressure because of life history characteristics including longevity, late sexual maturation and aggregation spawning. Despite their economic importance, few grouper fisheries are regularly monitored or managed at the species level, and many are reported to be undergoing declines. To identify major threats to groupers, the International Union for Conservation of Nature (IUCN) Red List criteria were applied to all 163 species. Red List assessments show that 20 species (12%) risk extinction if current trends continue, and an additional 22 species (13%) are considered to be Near Threatened. The Caribbean Sea, coastal Brazil and Southeast Asia contain a disproportionate number of Threatened species, while numerous poorly documented and Near Threatened species occur in many regions. In all, 30% of all species are considered to be Data Deficient. Given that the major threat is overfishing, accompanied by a general absence and/or poor application of fishery management, the prognosis for restoration and successful conservation of Threatened species is poor. We believe that few refuges remain for recovery and that key biological processes (e.g. spawning aggregations) continue to be compromised by uncontrolled fishing. Mariculture, through hatchery‐rearing, increases production of a few species and contributes to satisfying high market demand, but many such operations depend heavily on wild‐caught juveniles with resultant growth and recruitment overfishing. Better management of fishing and other conservation efforts are urgently needed, and we provide examples of possible actions and constraints.

Studies on reproduction of the mullet Mugil platanus Günther, 1880 (Actinopterygii, Mugilidae) from the Mar Chiquita coastal lagoon, Argentina: Similarities and differences with related species

The aim of the present study is to provide the first results on the reproductive biology of Mugil platanus, from the Mar Chiquita coastal lagoon (Argentina). To address this topic, we employed mainly female gonads, at both microscopic and macroscopic levels. The following stages of oocyte development were observed: (A) oogonias, (B) primary growth oocyte, (C) cortical alveolus stage, (D) yolked oocytes, and (E) atretic follicle. Also five of the seven stages of gonad maturity were macro and microscopically stated. The potential fecundity ranged between 1,002,026 and 2,548,769 yolked oocytes, with a mean of around 1,800,000 oocytes. The length at first maturity (L50) was 450.6 total length (TL) and 367.7 standard length (SL) for females, 436.3 TL and 354.9 SL for males, showing a late sexual maturity for both sexes. Seasonal changes in gonadosomatic index (GSI) of females were observed. The mean GSI was ≤1 during six months of the year (January, June–October). Two modes in the ovarian maturation were observed, the most important in April–May and a secondary one in November–December. Both modes, correlated with the CPUE values, are indicative of the mullet migration from the coastal lagoon towards the sea for spawning. Differences and similarities have been found between Mugil platanus and other mugilid species (Mugil cephalus, Mugil curema, Liza aurata, Liza abu, Liza argentea, Myxus elongatus, and Valamugil cunnesius), from the reproductive point of view. The length at first maturity obtained for M. platanus is higher than in other mugilid species and when a relationship between maximum length and L50 is established the percentage corresponding to Mugil platanus is 75%, while the others range between 50 and 61%.

Effects of dietary n-6:n-3 ratio on immune and reproductive systems of pullet chicks

The objective of this study was to examine the effects of dietary n-6:n-3 ratio on immune and reproduction systems of Leghorn pullet chicks. A total of 216 Hy-Line W-36 pullet chicks (1 d old) were randomly assigned to 3 diets (n-6:n-3 ratios of 10, 6, and 2) until 22 wk of age. The Optomega-50 (Optivite International Ltd., Nottinghamshire, UK) containing 50% salmon fish oil was used as an n-3 source. Pullets were injected with SRBC suspension at 6 and 9 wk and anti-SRBC titers were measured 7 and 14 d after each immunization. The antibody (Ab) titers for Newcastle disease (ND), avian influenza, infectious bronchitis (IB), and infectious bursal disease (IBD) were determined at 4, 6, 10, 14, and 18 wk of age. Pullets fed diet with the n-6:n-3 ratio of 2 had higher feed consumption and lower BW gain (P < 0.05) compared those fed diets with the ratios of 6 and 10. The results demonstrated that the different dietary n-6:n-3 ratios did not have a significant effect on the anti-SRBC titers in pullets serum (P > 0.05). The Ab production against avian influenza vaccine was increased in pullets fed diet containing the n-6:n-3 ratio of 10 at wk 10 and 14 and increased for ND at only 14 wk (P < 0.05). On the other hand, the Ab response to IBD (14 wk) and IB (14 wk) vaccines was increased when pullets were fed diet containing a ratio of 6 (P < 0.05). The pullets fed diet with the n-6:n-3 ratio of 2 showed lower egg production and late sexual maturity (P > 0.05) whereas ovary weight (P = 0.01) and number of large yellow follicles (P = 0.049) were significantly decreased at first oviposition. Our results revealed that the supplementation of Optomega-50 as a source of n-3 to decrease the n-6:n-3 ratio in diet significantly increased Ab production for ND, IB, and IBD in pullet chicks with slight reduction in reproductive organs weight at early production.

AFLP reveals no sex-specific markers in Persian sturgeon (Acipenser persicus) or beluga sturgeon (Huso huso) from the southern Caspian Sea, Iran

The late sexual maturity in sturgeon and the absence of morphological differences between males and females makes sex discrimination difficult. Identification of sex at an early life stage is of high interest in caviar production because it allows efficient selection of females. In this study, the genome of 10 mature male and 10 mature female specimens of Persian sturgeon (Acipenser persicus) and beluga sturgeon (Huso huso) were screened using AFLP and 100 primer combinations. Results showed a total of 3771 and 3779 scoreable bands in A. persicus and H. huso, respectively. Approximately 30% of markers in A. persicus and 29.6% H. huso were polymorphic. No sex specific makers were identified. The results of the present study suggest that the sex chromosomes are not extensively differentiated in sturgeon species, or possibly the methods utilized were not sufficiently sensitive to recognize them. © 2011 Progress in Biological Sciences, Vol 1, No.1, 55-60

Modeling population dynamics and conservation of arapaima in the Amazon

To promote understanding of fish population dynamics in tropical river-floodplains, we have synthesized existing information by developing a largely empirical population model for arapaima (Arapaima sp.). Arapaima are characterized by very large bodies, relatively late sexual maturity, small clutches, and large parental investment per offspring, and their populations are overexploited and even declining due to overfishing. We used unparalleled time series data on growth, reproduction, catch-at-age, and size-class abundance estimates for a population that has increased several-fold and undergone drastic changes in fishing practices in the Amazon, Brazil. Model population numbers were close to observed numbers, with generally low mean absolute percentage errors for juveniles (16%), adults (30%), and catch (18%). In using the model to test ecological hypotheses and to investigate management strategies, we found the following: (1) Annual recruitment is directly and positively related to spawner abundance, and it appears to be density-compensatory following a Beverton–Holt relation (R 2 = 0.85). (2) Fishing-selectivity of arapaima caused by use of harpoons and gillnets can lower yield potentials dramatically through removal of the faster-growing individuals of the population. That is in part because fewer individuals live long enough to reproduce and survivors take longer to reach reproductive age. (3) Arapaima populations can sustain annual catches of up to 25% of the number of adults in the population the previous year if minimum size (1.5 m) and closed season (December–May) limits are met. (4) When 25% of the number of adults in the population the previous year is harvested under a 1.6 m minimum size limit of catch, catches are slightly smaller but abundance of adults in the population is considerably greater than under a 1.5 m limit. These findings can be used in ongoing management initiatives, but caution is needed because of present biological and ecological uncertainty about these fishes.

Genetic Gain for Growth and Delayed Sexual Maturation Using a Feral Strain of Anadromous Brook Trout

AbstractA selective breeding program was initiated with a wild population of anadromous brook trout Salvelinus fontinalis from the Laval River, Quebec. The objective was to develop a new strain characterized by improved growth and reduced precocious sexual maturation. A control line was maintained by use of random within‐family selection. Length and weight were measured and sexual maturity (mature or not mature) was determined at the end of the second year of growth (22 months of age). In the selected line, phenotypic variance, additive genetic variance, and heritability for weight within the selected families were reduced. A comparison between generations showed that fish weight at 22 months in the selected line increased by 23.1% from the F1 to the F2 generation and by 32.1% from the F2 to the F3 generation. The control line increased similarly in weight from the F1 to the F2 generation (34.7%) but not thereafter; this result was probably due to the domestication effect in the first generation after captivity. The proportion of fish that were immature at 22 months was 32.2% in the F1 generation and increased to 61.4% by the F3 generation in the selected line; the proportion immature did not change significantly after two generations in the control line (27.5%). Our results show that simultaneous selection for growth and late sexual maturation are compatible goals for brook trout breeding programs.Received April 29, 2009; accepted August 9, 2010

Cryptic diversity and species assignment of large lantern sharks of the Etmopterus spinax clade from the Southern Hemisphere (Squaliformes, Etmopteridae)

Straube, N., Kriwet, J. &amp; Schliewen, U. K. (2010). Cryptic diversity and species assignment of large lantern sharks of the Etmopterus spinax clade from the Southern Hemisphere (Squaliformes, Etmopteridae). —Zoologica Scripta, 40, 61–75.Many species of the speciose deep‐sea shark family Etmopteridae (lantern sharks) are a regular by‐catch component of deepwater trawl and longline commercial fisheries. As for many elasmobranchs, the low fecundity, late sexual maturation and extreme longevity of the lantern sharks increase their susceptibility to overfishing. However, the taxonomic uncertainty within etmopterids and the poorly known patterns of dispersal of these shark species hampers the establishment of reasonable monitoring efforts. Here, we present the first molecular approach to clarify the taxonomy and distribution of a morphologically uniform group of lantern sharks comprising Etmopterus granulosus and closely related congeners by using nucleotide sequence data from the mitochondrial DNA cytochrome oxidase I gene and amplified fragment length polymorphisms. Samples were collected from several locations in the Southern Hemisphere, where the species occur. Our analyses reveal a high level of cryptic diversity. E. granulosus is not endemic to Chile, but instead has a widespread distribution in the Southern Hemisphere being synonymous to New Zealand Etmopterus baxteri. Conversely, specimens previously assigned to E. baxteri from off South Africa apparently represent a distinct species. Our results provide the basis for the re‐description of E. granulosus and E. baxteri which will help in the establishment of useful monitoring and management strategies.

Reproductive cycles of buffalo

The domestic water buffalo ( Bubalus bubalis) has an important role in the agricultural economy of many developing countries in Asia, providing milk, meat and draught power. It is also used in some Mediterranean and Latin American countries as a source of milk and meat for specialized markets. Although the buffalo can adapt to harsh environments and live poor quality forage, reproductive efficiency is often compromised by such conditions, resulting in late sexual maturity, long postpartum anoestrus, poor expression of oestrus, poor conception rates and long calving intervals. The age at puberty is influenced by genotype, nutrition, management and climate, and under favourable conditions occurs at 15–18 months in river buffalo and 21–24 months in swamp buffalo. The ovaries are smaller than in cattle and contain fewer primordial follicles. Buffalo are capable of breeding throughout the year, but in many countries a seasonal pattern of ovarian activity occurs. This is attributed in tropical regions to changes in rainfall resulting in feed availability or to temperature stress resulting in elevated prolactin secretion, and in temperate regions to changes in photoperiod and melatonin secretion. The mean length of the oestrous cycle is 21 days, with greater variation than observed in cattle. The signs of oestrus in buffalo are less overt than in cattle and homosexual behaviour between females is rare. The duration of oestrus is 5–27 h, with ovulation occurring 24–48 h (mean 34 h) after the onset of oestrus. The hormonal changes occurring in peripheral circulation are similar to those observed in cattle, but the peak concentrations of progesterone and oestradiol-17β are less. The number of follicular waves during an oestrous cycle varies from one to three and influences the length of the luteal phase as well as the inter-ovulatory interval. Under optimal conditions, dairy types managed with limited or no suckling resume oestrus cyclicity by 30–60 days after calving, while swamp types with free suckling do so at 60–90 days. However, in many farming systems prolonged postpartum anoestrus is a major problem, and the causes include poor nutrition and body condition, and stress due to harsh climates and improper management. Synchronization of time or induction of oestrus can be done using the same regimens as applied in cattle, using various combinations of prostaglandins, progesterone releasing devices, GnRH and eCG, but success rate is poor when treatment is done during the periods of marginal breeding activity or seasonal anoestrus.

MicroRNAs, the epigenetic memory and climatic adaptation in Norway spruce

*Norway spruce expresses a temperature-dependent epigenetic memory from the time of embryo development, which thereafter influences the timing bud phenology. MicroRNAs (miRNAs)are endogenous small RNAs, exerting epigenetic gene regulatory impacts. We have tested for their presence and differential expression. *We prepared concatemerized small RNA libraries from seedlings of two full-sib families, originated from seeds developed in a cold and warm environment. One family expressed distinct epigenetic effects while the other not. We used available plant miRNA query sequences to search for conserved miRNAs and from the sequencing we found novel ones; the miRNAs were monitored using relative real time-PCR. *Sequencing identified 24 novel and four conserved miRNAs. Further screening of the conserved miRNAs confirmed the presence of 16 additional miRNAs. Most of the miRNAs were targeted to unknown genes. The expression of seven conserved and nine novel miRNAs showed significant differences in transcript levels in the full-sib family showing distinct epigenetic difference in bud set, but not in the nonresponding full-sib family. Putative miRNA targets were studied. *Norway spruce contains a set of conserved miRNAs as well as a large proportion of novel nonconserved miRNAs. The differentially expression of specific miRNAs indicate their putative participation in the epigenetic regulation.

Threatened fishes of the world: Acipenser schrenckii Brandt, 1869 (Acipenseridae)

Common name: Amur sturgeon (English). Conservation status: Endangered—IUCN Red List, Classified under Appendix II of CITES, Endangered—China Species Red List. Identification: D 35–54, A 19–33, P 35, V 25. Five rows of scutes: D 11–19, L 30–47, V 4–11. Gill rakers: 31–48 (Zhang 1995). Triangular head, inferior and small mouth elongated and depressed snout, two pairs of barbels (Yue and Chen 1998). There are two distinct morphs of Amur sturgeon: brown and grey (Krykhtin and Svirskii 1997). Figure from Wei et al. (1997). Distribution: The species is distributed throughout the Amur River basin, as well as the Ussuri and Sungari (Songhuajiang) rivers, and also can be found in Japan due to the possibility of anadromous migration (Shmigirilov et al. 2007). Abundance: Declining dramatically from the 1930s, with natural stock unknown as yet. Habitat and ecology: A typical benthic feeder. Feeds on bottom invertebrates and mollusks, as well as small fishes (Shmigirilov et al. 2007). Dwells in the middle to lower layers of deep eddy currents. Reproduction: Late sexual maturity (7–24 years). Spawning period from late May to early July. Fecundity ranges from 114 000 to 1 292 000 with mean of 385 000 (Zhang 1995). Threats: Stock has been destroyed by illegal poaching and overfishing (Yue and Chen 1998). Contamination of the Amur River and its tributaries is also a potential threat. Conservation action: Local regulations for the protection, enacted in the 1950s and renewed in 1982, and conservation efforts by China in 1998 were insufficient to prevent stock decline. Collaboration and cooperation between China and Russia play a crucial role in Amur sturgeon conservation. Conservation recommendations: Fishing regulations must be strictly implemented, with emphasis on fishing prohibition period and areas. Artificial hatching and releasing of raised young Amur sturgeons into rivers should be considered.

Avaliação da predação de Podocnemis expansa e Podocnemis unifilis (Testudines, Podocnemididae) no rio Javaés, Tocantins

Podocnemis expansa e P. unifilis são animais de vida longa, com uma demorada maturação sexual, o que influencia uma baixa taxa de substituição de indivíduos. Suas populações são caracterizadas por uma pequena mortalidade dos animais adultos, mas alta taxa de mortalidade de filhotes e embriões. Sendo a predação natural de ninhos e filhotes um dos fatores mais importantes do baixo sucesso de eclosão dessas espécies. No rio Javaés, os ovos e recém-eclodidos podem ser predados por uma grande diversidade de animais: dentre as aves, urubus (Coragyps atratus e Cathartes aura), carcará (Polyborus plancus), jaburu (Jabiru mycteria); lagartos (Tupinambis teguixin) e mamíferos de pequeno porte, coati (Nasua nasua) e cachorro-do-mato (Cerdocyon thous). Do total anual de desovas de P. unifilis em média 65,98% são predadas, sendo 41,68% de forma total e 24,30% parcialmente. Enquanto que apenas 5,31% das ninhadas de P. expansa são sempre parcialmente predadas. Dentre os predadores aquáticos existem diversos peixes, principalmente piranhas (Serrasalmus nattereri) e jacarés (Melanosuchus niger e Caimam crocodilus). Os predadores das fêmeas de P. unifilis são: jacaré-açu (Melanosuchus niger), onça-pintada (Panthera onca) e onça-parda (Puma concolor). Enquanto que as fêmeas de P. expansa em postura, somente são predadas por P. onca. As fêmeas de P. unifilis em postura são predadas num total médio de 3,93% anualmente, enquanto que para P. expansa a média anual é 5,66% das fêmeas.

The role of chromosomal rearrangement in mammalian speciation with special reference to Cetacea and Pinnipedia

The karyotypes of 17 cetaceans and 18 pinnipeds are surveyed. Within the Cetacea only two different chromosome numbers have been found, viz. 2n = 42 and 2n = 44. Within the Pinnipedia three different chromosome numbers have been described, viz. 2n = 32, 2n = 34 and 2n = 36. The material indicates that the orders Cetacea and Pinnipedia are characterized by a remarkable stability of their karyotypic patterns. Factors cooperating towards karyotypic stability may be sought in the reproductive biology of these animals — late sexual maturity and small progeny — as well as in their ecology — good mobility in an environment without distinct niches. In such animals, the main mode of speciation should be a allopatric. The orders Insectivora and Rodentia on the other hand which both display great karyotype variability would accordingly represent a different mode of speciation. The species belonging to these orders have early sexual maturity and large progeny; their mobility is often limited and the distribution discontinuous. Consequently, in Insectivora and Rodentia stasipatric speciation should be frequent.

The population dynamics of the longnose skate, Raja rhina, in the northeast Pacific Ocean

The longnose skate, Raja rhina, is the most commonly landed skate species in the northeast Pacific Ocean. It also dominates survey catches in the area. Existing knowledge on skate biology and fisheries suggests that large skate species with late sexual maturation, like the longnose skate, are extremely vulnerable to overfishing, and if overfished they are slow to recover. Historically, in the US Pacific Coast skates have not supported directed fisheries, but have been taken as bycatch in other commercially important fisheries. For the past 13 years, landed catches of skates in waters off Washington, Oregon and California have significantly increased. Using the Stock Synthesis 2 modeling framework, a population model for the longnose skate was developed to assess the current state of the stock and reconstruct its past dynamics. Model results indicate that the longnose skate spawning biomass has slowly declined since 1915; the current stock biomass is estimated as 66% of its unexploited level. Uncertainty in regards to fishery-dependent data and female maturity parameters was explored through sensitivity analyses. The model results indicate that it is important to conduct species-specific identification in the fishery and monitor discard of longnose skate to improve the accuracy of fishery catch data and make assessment conclusions more robust.