Abdominal puncture as a new method to determine sex in tuviras (Gymnotus sp.)

Tuviras (Gymnotus sp.) are a small fish widely used as live bait in sport fishing. Interest in its culture has increased, but there are still several bottlenecks that need to be solved. For example, the process of sexing in tuviras is difficult since they do not present sexual dimorphism. Thus, the aim of this study was to verify if an abdominal puncture could be used as an inexpensive, fast and reliable technique to identify the sex of adult Gymnotus sp. Before performing the abdominal puncture, five individuals were dissected to determine the exact location of the gonads. Based on this information, the abdominal puncture was performed 6 cm away from the tip of the animal's head and 1 cm below the lateral line with an intravenous infusion set connected to a 5 ml syringe. An abdominal puncture was performed on 24 adult animals that were larger than 20 cm in length. Twenty‐two individuals were sexed correctly, and the accuracy degree was 91.66%. The survival rate of the animals 96 hr after the abdominal puncture was 100%. These results indicate that the abdominal puncture is an easy, simple, fast and inexpensive technique that can be performed in a reliable way.     

长翅型与短翅型褐飞虱对杀虫剂的敏感性比较

采用稻苗浸渍法测定了长、短翅型褐飞虱对烯啶虫胺、环氧虫啶、呋虫胺、噻虫嗪、噻虫胺、吡虫啉、毒死蜱、敌敌畏、噻嗪酮、异丙威、吡蚜酮和醚菊酯的敏感性，并对其体内解毒酶活力进行了比较分析。结果表明:长翅型与短翅型褐飞虱若虫对新烟碱类杀虫剂呋虫胺、噻虫嗪、噻虫胺和吡虫啉的敏感性存在显著差异，长翅型比短翅型更敏感；相反，对于有机磷类杀虫剂毒死蜱，短翅型褐飞虱则更敏感；2种生物型对烯啶虫胺、环氧虫啶、敌敌畏、噻嗪酮、异丙威、吡蚜酮和醚菊酯的敏感性无显著差异。解毒酶相对比活力测定结果表明，长翅型褐飞虱若虫酯酶比活力显著高于短翅型，细胞色素P450单加氧酶比活力显著低于短翅型，而谷胱甘肽S-转移酶比活力无显著性差异。本研究结果可为褐飞虱的有效防控提供科学参考。     

稻褐飞虱生物型和翅型分化个体测定的聚类分析

在稻褐飞虱田间种群生物型和翅型分化个体测定的基础上，应用聚类分析法对生物型的个体测定结果进行分析，并比较属于不同生物型个体的翅型分化情况。研究结果表明，稻褐飞虱生物型的个体测定结果可分为3类，分别表现生物型I、生物型Ⅱ、孟加拉型的致害力，即分别属于生物型I、生物型Ⅱ、孟加拉型。属于孟加拉型个体的短翅率显著高于生物型I、生物型Ⅱ的个体，而属于生物型I和生物型Ⅱ的个体则差异不显著。     

Life-history of the flagfin shiner, Pteronotropis signipinnis, from a blackwater stream in southeastern Mississippi

Abstract – Flagfin shiners, Pteronotropis signipinnis , were collected from Sweetwater Creek, a second-order blackwater stream in southeastern Mississippi, during each month of 1996. Analysis of length frequency histograms indicated a life span of 1 to 2 years. Sex ratio was not different from a 1:1 ratio. Adult males were larger and more heavily pigmented near the abdomen than females. Females were reproductive from April to mid-August. All females attained sexual maturity by 27 mm SL and produced multiple clutches of ova. Clutch size varied from 12 to 101 ova and was correlated with SL. Mean mature oocyte diameter was 0.88 mm (range 0.76–0.96). Despite the relationship between clutch size and body size, P. signipinnis may be selected to invest in early reproduction rather than growth. This idea is supported by the small size at maturity in this species and is consistent with an opportunistic life-history strategy. ^Note     

日本七鳃鳗冬季两性形态及个体生殖力研究

采用SPSS13.0软件的t检验、回归检验和因子分析等方法,对2006年12月于黑龙江中下游萝北江段捕到的日本七鳃鳗(Lampetra japonica)的两性形态及个体生殖力进行了研究。结果表明:日本七鳃鳗雌雄个体的体长、体重、净体重和肥满度等指标在繁殖前没有显著差异,而性腺重和成熟系数两性差异显著。日本七鳃鳗的个体绝对生殖力平均为(101959.47±23259.82)粒,体长的相对生殖力(FL)平均为(2219.36±496.84)粒/cm,净体重的相对生殖力(FW)平均为(964.1±260.9)粒/g。体长绝对生殖力、体长相对生殖力(FL)和净体重相对生殖力(FW)均与卵巢重和成熟系数显著正相关。卵巢重、成熟系数、绝对生殖力、体长相对生殖力(FL)和净体重相对生殖力(FW)是与个体生殖力密切相关的主要因子,而体长、体重、净体重和肥满度可以间接地反映个体生殖力的大小。     

Sexual dimorphism in the African legless skink subfamily Acontiinae (Reptilia: Scincidae)

The extent to which sexual dimorphism in snout–vent length, tail length and head shape (length, width and height) manifests itself in the legless fossorial skink subfamily Acontiinae was investigated in representatives of all four of its genera, Acontias, Microacontias, Acontophiops and Typhlosaurus. Where data were available fecundity selection and diet partitioning (ecological causation) were tested as possible proximate causes for dimorphisms found. The possibility of a relationship between head shape and microhabitat density was also investigated. The data showed that significant sexual dimorphism in snout–vent length and head shape was present in only a minority of taxa and that it was absent with respect to tail length. There are indications of a relationship between head shape and microhabitat density, and head shape seems to become increasingly more pointed as SVL increases. A serious impediment to placing the findings of this study into a firm evolutionary context is the general lack of information about the ecology, social organization and behaviour of the taxa.     

The effect of feed supply rate on growth of juvenile perch (Perca fluviatilis)

This study investigates the effect of the feed supply rate within a meal on growth of juvenile perch (Perca fluviatilis). Groups of PIT-tagged, feed-trained juvenile perch (12 g) were held in 100-L tanks at 18 °C, under a 24L:0D photoperiod and fed five meals per day in excess. Feed was applied at rates of 1.2 (Low), 4.2 (Medium) and 14.3 (High) pellets fish⁻¹ min⁻¹ during two periods, each of 50 days. Cumulative meal-time per day ranged from 10 to 225 min. Specific growth rates (SGR) in the two periods were positively correlated, indicating a consistent individual growth performance. There was growth dimorphism between the sexes. Females grew about 20% faster than males, resulting in final mean weights of ≈ 87 and 58 g respectively. Autopsy revealed differences in sex ratios between treatments and the effect of feeding rate was analysed according to sex. There was a tendency for fish fed at the lowest rate to have a higher SGR than fish in other treatments, both for females (L = 1.98 ± 0.0, M = 1.84 ± 0.08, H = 1.88 ± 0.19% bw day⁻¹) and males (L = 1.68 ± 0.01, M = 1.55 ± 0.16, H = 1.57 ± 0.02% bw day⁻¹). Fish fed at the lowest rate also tended to have the lowest feed conversion ratio (L = 0.88 ± 0.05, M = 1.02 ± 0.11, H = 1.04 ± 0.10) but the effects were not significant. These results suggest that juvenile perch can feed efficiently under a range of conditions.     

昭觉林蛙的食性与两性异形

对采自1998年5月至2003年10月的昭觉林蛙Rana chaochiaoensis解剖428只(♀202,♂184,亚成体42只)分析食性,测量体长大于40 mm的成体151只(♀81,♂70)作两性异形研究。解剖结果表明,昭觉林蛙以动物性食物为主,两性的食性无显著性差异,食性不是影响两性异形分化的原因。t检验结果表明,昭觉林蛙成年雌雄个体在前臂宽/前臂长存在极显著差异。协方差分析结果显示,昭觉林蛙雌雄个体头宽、吻长、鼓膜直径、眼径、前臂长、前臂宽、手长、后肢全长、胫长和足长存在显著差异。两性异形主要系性选择压力的结果。昭觉林蛙属于成年雌雄个体大小无显著差异的类型。雄性昭觉林蛙的前臂明显比雌性的粗壮,第一指基部具有发达的婚垫,表面具细密角质刺,以加大拥抱摩擦,增强拥抱能力,避免雌蛙逃脱。雄性昭觉林蛙没有声囊,但后肢较长和具有较雌性发达的蹼,有利于提高自身追逐雌性的能力,以提高繁殖成功机率;而雌蛙发达的后肢则有利于提高跳跃能力,快速躲避干扰和威胁。表2参29     

罗氏沼虾性成熟前后形态性状对体质量的通径分析

为探明罗氏沼虾(Macrobrachium rosenbergii)养殖群体在性成熟前后表型性状间的相互关系,本研究随机选取人工养殖的罗氏沼虾1106尾,对其体质量、全长、体长等15个性状进行测量,并采用相关分析和通径分析阐明形态性状对体质量的影响。结果表明：在性成熟前后及同一阶段雌雄群体之间,影响体质量的关键指标以及所构建的关键表型性状多元回归方程是截然不同的;在性成熟后,雌雄个体呈现出明显的性二态现象,除第二步足长和第二步足重雄性极显著大于雌性(P<0.01),雌性全长、体长、额剑长、头胸甲宽、头胸甲高、腹长、腹宽、腹高和腹部重极显著大于雄性(P<0.01),这可能与雌性为提升其繁殖能力有关。统计结果显示被保留的性状与体质量的复相关系数大于0.85,表明本研究已确定影响各群体体质量的主要性状。因此在选育过程中,建议将罗氏沼虾的性成熟状态和雌雄群体的优良表型作为选育依据,并有效利用影响体质量的关键性状指标。本研究可以为罗氏沼虾的良种选育提供参考依据。     

Ecology of Wahlberg’s velvet gecko,Homopholis wahlbergii,in southern Africa

We examined 170 museum specimens of the southern African gekkonid lizard Homopholis wahlbergii, to quantify sexual dimorphism, male and female reproductive cycles and diet. The largest male and female we recorded were 116 and 119 mm snout–vent length (SVL) respectively. We compared SVL, tail length, head length, head width and eye diameter and found no evidence of sexual dimorphism in any of these characters. The smallest female with thickened muscular oviducts and follicles, indicating sexual maturity, was 59 mm SVL, but the smallest female we found with fully developed eggs was 85mmSVL. Virtually all females larger than 59 mm appeared to be in some stage of reproduction, suggesting that females reproduce every year once they reach sexual maturity. Egg size ranged from 17–19mm long. Egg size was not correlated with maternal SVL. We found adult females with ready-to-lay eggs during the warmer months of the year, but not during winter and spring. The smallest sexually mature male was 72 mm SVL. Virtually all males larger than this size displayed at least semi-turgid testes and most adult male testes were at least semi-turgid for much of the year. The only significant decrease in testicular activity was in mid-winter (June–August), thus, spermatogenesis is closely tied to female follicular development and ovulation. Velvet geckos are largely insectivorous (92%) and feed on a broad spectrum of prey. Their diet was dominated both numerically (34%) and volumetrically (22%) by beetles. Lepidoptera were the next most important prey category, suggesting that they exploit both terrestrial and flying invertebrates. They are unusual among lizards because they feed on millipedes. Males and females had very similar diets which may be explained by their lack of sexual dimorphism, although females tended to eat a greater volume of prey. Interestingly, less than half (37%) of the lizards examined contained prey items, suggesting that most individuals were not in positive energy balance. We also found evidence of prey size selection as a function of gape size, such that larger geckos took advantage of larger prey items.