水位对黑斑侧褶蛙蝌蚪形态表型、 白细胞数量和应激反应的影响

为探究水位变化对黑斑侧褶蛙（Pelophylaxnigromaculatus）蝌蚪形态表型、免疫功能和应激反应能力的影响,实验室内测定了水位恒定组以及水位快速、中速和慢速下降组37期蝌蚪发育至变态完成期的变态时长、身体大小和血液中各型白细胞的百分比,以及嗜中性粒细胞与淋巴细胞比值的变化。结果表明,水位快速下降显著缩短了蝌蚪的变态时长（P <0.05）,体长下降明显（P <0.05）,体重和体宽有所降低,但组间差异不显著（P> 0.05）。嗜中性粒细胞的百分比快速下降组显著高于其他处理组,单核细胞的百分比水位恒定组显著高于中速下降组（P <0.05）,嗜酸性粒细胞、嗜碱性粒细胞和淋巴细胞的百分比均无明显的组间差异（P>0.05）;嗜中性粒细胞与淋巴细胞比值快速下降组显著高于其他处理组（P <0.05）。水位加速下降导致登陆后幼蛙的个体变小,由嗜中性粒细胞和单核细胞所代表的天然免疫能力变化趋势不同,应激反应能力增强,可能不利于幼蛙的存活。     

外来捕食者克氏原螯虾对黑斑侧褶蛙不同发育阶段幼体表型与运动能力的影响

外来物种入侵是造成本土无尾两栖类种群下降和灭绝的最严重威胁之一。在中国南部丽水地区,克氏原螯虾(Procambarus clarkiion)是一种捕食本土无尾类蝌蚪的入侵物种。在实验室条件下,通过对黑斑侧褶蛙(Pelophylax nigromaculatus)受精卵和蝌蚪先后进行克氏原螯虾捕食风险的不同处理,检测孵出蝌蚪的形态特征、中期蝌蚪的形态特征、游泳表现及活动水平、变态时间与大小以及幼蛙跳跃表现,评估克氏原螯虾的捕食风险对黑斑侧褶蛙不同生长阶段幼体生长发育、运动能力及行为的综合影响。单因素方差分析表明,捕食者长期存在条件下黑斑侧褶蛙孵出蝌蚪的体长、尾长和尾肌宽均显著短于无捕食者的空白对照组和捕食者仅存在2 d的实验组,后两者处理下的蝌蚪体长差异显著,但尾长和尾肌宽差异不显著。长期捕食者存在条件下黑斑侧褶蛙蝌蚪的游泳总路程和平均游速均显著小于无捕食者和捕食者存在2 d的实验组,而蝌蚪体长、尾长、尾鳍高和尾肌高的组间差异均不显著。有捕食者存在下黑斑侧褶幼蛙的体长和体重均显著大于无捕食者和捕食者存在2 d的实验组的情况,而变态时间和幼蛙跳跃距离组间差异不显著。两因素方差分析表明,测试时间、捕食者设置和两因素的相互作用均显著影响蝌蚪的活动频次。不同实验时间,长期捕食者存在实验组蝌蚪活动频次均小于无捕食者和捕食者存在2 d的实验组。无捕食者实验组蝌蚪的活动频次前期高于捕食者存在2 d的实验组,后期低于捕食者存在2 d的实验组。线性回归分析结果显示,捕食者存在2 d实验组蝌蚪相对活动频次与检测时间相关不显著,长期捕食者存在实验组相对蝌蚪活动频次与检测时间呈显著的正相关。本研究表明了黑斑侧褶蛙蝌蚪能够感知来自入侵捕食者克氏原螯虾的捕食风险,诱导产生较小的孵出个体、蝌蚪较低的活动水平,但这种不足可通过后期补偿生长,不影响进入陆地生境的变态个体的表型与运动能力。     

黑斑侧褶蛙蝌蚪断尾后的补偿生长和发育研究

动物在经历不利的生长条件或环境后往往出现补偿生长。研究了黑斑侧褶蛙(Pelophylax nigromaculatus)蝌蚪经历来自食蚊鱼(Gambusia affinis)捕食造成断尾损伤后的补偿生长模式、断尾损失对蝌蚪游泳能力以及变态时间与大小的影响。结果表明,经历捕食压力后,全尾组和1/3断尾组蝌蚪的体长显著大于1/2断尾组蝌蚪的体长,全尾组和1/3断尾组之间的蝌蚪体长差异不显著;第19天时,1/2断尾组蝌蚪经过补偿生长后体长显著大于全尾组蝌蚪,1/3断尾组与全尾组和1/2断尾组之间的蝌蚪体长差异均不显著;三个实验组之间蝌蚪尾长差异不显著;全尾组蝌蚪的疾游速显著大于1/2断尾组蝌蚪的疾游速,1/3断尾组蝌蚪的疾游速与全尾组和1/2断尾组之间差异不显著,表明严重断尾对蝌蚪疾游速产生了消极影响。三个实验组蝌蚪的变态时间和变态前后形态差异均不显著。黑斑侧褶蛙蝌蚪能够在变态前调整生长轨迹补偿早期捕食风险造成的生长损失,断尾损失并不影响变态时间与大小,断尾超过一半的蝌蚪经过补偿生长后仍要付出一定的运动代价。     

荧光聚苯乙烯微球对蝌蚪应激水平和免疫功能的影响

为探究纳米塑料对黑斑侧褶蛙(Pelophylax nigromaculatus)37期蝌蚪健康状态的影响,将其暴露于50 nm粒径低、中和高浓度荧光聚苯乙烯微球溶液(fluorescent polystyrene microsphere solution, FPM_S)7 d(7 d时),之后分别移至清水中饲养7 d(14 d时)或14 d(21 d时),以清水组为对照组,测定了每一取样时间点不同浓度组、同一浓度组不同取样时间点的体重与体全长的比值(重长比)、嗜中性粒细胞与淋巴细胞的比值(N/L)和对植物血凝素(phytohemagglutinin, PHA-P)的反应差异。结果表明：重长比只在14 d时清水组显著低于其他浓度组;N/L只在21 d时清水组低于其他浓度组,低、中和高浓度组都从7 d时至21 d时显著增加;7 d时各浓度组蝌蚪对PHA-P的最大反应值出现于注射后3 h或4 h, 14 d时前移至2 h或3 h, 21 d时又恢复至3 h或4 h,只有21 d时高浓度组高于低浓度组和中浓度组;FPMs暴露和初次清除对黑斑侧褶蛙蝌蚪的生长发育有明显的促进作...     

黑斑侧褶蛙消化道重量及长度的性别和季节差异

消化道是联系脊椎动物能量摄入和能量支出之间关系的纽带,其重量和长度对外界环境具有高度的敏感性和弹性(flexibility)。以黑斑侧褶蛙(Pelophylax nigromaculata)为研究对象,测定了山东聊城地区2012年夏季(16只,8♀/8♂)、秋季(19只,9♀/10♂)及翌年春季(17只,8♀/9♂)其体重、体长、胴体湿重和干重系数、总消化道及各段(食道、胃、小肠和大肠)的湿重、干重和长度系数的性别和季节差异(双因素方差分析),对有性别差异的指标,用单因素方差分析分别比较了雌、雄蛙的季节差异。结果显示,1)雌蛙的体重、体长均高于雄蛙,都在秋季最高,春季或夏季最低;雄蛙的胴体湿重系数高于雌蛙,夏季高于秋季;胴体干重系数既无性别差异,也无季节差异。2)除食道湿重系数无性别差异外,雌蛙总消化道及各段的湿重系数均高于雄蛙;除胃湿重系数无季节差异外,春季或秋季的总消化道及各段的湿重系数都高于夏季;雌蛙的总消化道干重和胃干重系数高于雄蛙,食道、小肠和大肠的干重系数无性别差异,所有的干重系数均无季节性差异。3)除雌蛙的大肠长系数高于雄蛙外,总消化道及各段的长度系数均无性别差异,春季和秋季的总消化道长、食道长及胃长系数均高于夏季,小肠长和大肠长系数均无季节性差异。结果表明,随着季节更替,黑斑侧褶蛙消化道各段的重量和长度表现出一定的弹性特征,这与各器官的功能及其生活环境的多样性是相适应的。     

黑斑侧褶蛙的两性异形和雌性繁殖特征

测定了黑斑侧褶蛙成体的体长、体重、头长、头宽、眼径、鼓膜径、前肢长、后肢长等形态指标以及雌体的怀卵数量。黑斑侧褶蛙雌体的体长和体重显著大于雄体。其它局部形态特征指标与体长呈正相关,协方差分析表明,雄体的鼓膜径大于雌体,其余形态指标不存在明显的两性差异。黑斑侧褶蛙雌体怀卵数量与体长和体重皆成正相关关系,表明黑斑侧褶蛙通过增加个体大小增加繁殖输出。     

黑斑侧褶蛙肥满度及脏器重量的性别和季节差异

内脏器官的大小能反映动物的生长发育情况和生理生态状况,可作为动物对环境适应的近似指标。以黑斑侧褶蛙Pelophylax nigromaculata为研究对象,测定了2012年夏季、秋季及2013年春季其体重、体长、含水量、肥满度及脏器重量的性别和季节差异。结果显示:1)雌蛙的体重和体长均高于雄蛙,两性都在秋季最高;胴体湿重和干重无性别差异,胴体湿重夏季最高,胴体干重无季节差异。2)含水量和肥满度无性别差异,前者夏季和春季高于秋季,后者秋季高于春季;躯体肥满度和干体肥满度雄蛙均高于雌蛙,雄蛙无季节差异,雌蛙夏季最高,春季最低。体重与体长的比值(K WL)雌蛙高于雄蛙,两性都在秋季最高,春季最低。3)除肺干重雄蛙大于雌蛙,肾脏干重雌蛙大于雄蛙外,其他内脏器官的湿重和干重均无性别差异。肺湿重春季高于夏季和秋季,肾脏湿重无季节性差异;雄蛙的肺干重春季高于夏季,肾干重秋季高于夏季和春季,雌蛙均无季节差异。心脏和脾脏湿重都在夏季最高,秋季或春季最低,但干重均无季节差异。脂肪体和肝脏及卵巢和输卵管的湿重和干重均在秋季最高,春季或夏季最低。精巢的湿重及干重均无季节差异。结果表明,K WL可较好地反映成年黑斑侧褶蛙整体水平的营养和生理状况,多种器官重量有季节性的可塑性,这可能与雌、雄蛙的繁殖状态有关。     

密度对大树蛙蝌蚪生长发育和存活率的影响

种群密度效应主要表现在影响和调节种群的死亡率、发育速率、繁殖率以及扩散、迁移等反应种群数量动态的重要参数。分析密度对大树蛙蝌蚪生长发育和存活率的影响,有助于探究外界环境因子导致大树蛙种群密度迅速下降的作用机制。设置了15、20、25只/L和30只/L 4个密度组,测量大树蛙蝌蚪的尾长、体长、发育时间和存活率。结果表明,在15—30只/L范围内,密度升高显著降低了大树蛙蝌蚪尾长和体长的生长速率,减小其变态期的尾长和体长大小,其中与15只/L相比,20、25只/L和30只/L 3组蝌蚪的尾长分别降低了11.6%、11.8%和13.9%,体长分别降低了11.1%、9.5%和12.9%;随着密度的升高,大树蛙蝌蚪发育至跗蹠部伸长期和前肢伸出期的所需时间显著延长;大树蛙蝌蚪生长后期的存活率随密度升高显著降低,但密度对蝌蚪生长早期的存活率影响不显著。因此,密度升高可显著减小大树蛙蝌蚪的尾长和体长、延长发育时间和降低其生长后期的存活率,可能影响大树蛙蝌蚪变态后的适合度。     

中国林蛙生长发育盐效应的研究进展

本文对中国林蛙受精卵、蝌蚪和幼蛙等不同发育阶段生长发育的盐效应进行了综述。盐度对不同发育阶段的中国林蛙均有影响。中国林蛙受精卵孵化的最适盐浓度范围为0~5 g/L,孵化率超过80%;在2~3 g/L盐浓度下孵化的中国林蛙雌性个体超过90%,孵化后中国林蛙蝌蚪的存活率没有显著变化;中国林蛙蝌蚪和变态幼蛙的安全盐度上限分别为2 g/L和1.5 g/L。这些研究结果为中国林蛙野生资源的保护和人工养殖提供了一定的理论基础。     

黑斑蛙变态过程中甲状腺发育及甲状腺激素分泌

系统研究了我国本土两栖动物种黑斑蛙（Rana nigromaculata）变态发育过程中甲状腺组织学和甲状腺激素水平的变化,为甲状腺生物学和甲状腺干扰研究提供基础数据。黑斑蛙蝌蚪发育的形态变化: 第26-40阶段,后腿芽生长并逐渐分化出五趾结构;42阶段,开始进入变态高峰期,前肢展开,尾吸收,蝌蚪身体发生巨大形变;46阶段,蝌蚪完全变态成小蛙。随着形态学的变化,甲状腺的组织结构也发生明显的变化: 26-37阶段,甲状腺体积较小,增长缓慢;38阶段甲状腺体积迅速膨大,进入高峰期,甲状腺的发育达到顶峰;随着变态完成,甲状腺又逐渐缩小。甲状腺组织学变化的同时,甲状腺激素水平也相应发生变化: 在变态前期,下颌中3,3',5-三碘代-L-甲腺原氨酸（T3）水平增长缓慢,进入变态期后,T3含量迅速升高,在变态高峰期达到峰值,随后下降。以上结果表明,黑斑蛙发育过程中甲状腺组织学的变化与甲状腺激素水平的波动相吻合。对黑斑蛙甲状腺系统的研究,可为日后使用黑斑蛙开展甲状腺干扰作用的研究提供基础。       

Trait Performance Correlations across Life Stages under Environmental Stress Conditions in the Common Frog,Rana temporaria

If an organism''s juvenile and adult life stages inhabit different environments, certain traits may need to be independently adapted to each environment. In many organisms, a move to a different environment during ontogeny is accompanied by metamorphosis. In such organisms phenotypic induction early in ontogeny can affect later phenotypes. In laboratory experiments we first investigated correlations between body morphology and the locomotor performance traits expressed in different life stages of the common frog, Rana temporaria: swimming speed and acceleration in tadpoles; and jump-distance in froglets. We then tested for correlations between these performances across life stages. We also subjected tadpoles to unchanging or decreasing water levels to explore whether decreasing water levels might induce any carry-over effects. Body morphology and performance were correlated in tadpoles; morphology and performance were correlated in froglets: hence body shape and morphology affect performance within each life stage. However, performance was decoupled across life stages, as there was no correlation between performance in tadpoles and performance in froglets. While size did not influence tadpole performance, it was correlated with performance of the metamorphosed froglets. Experiencing decreasing water levels accelerated development time, which resulted in smaller tadpoles and froglets, i.e., a carry-over effect. Interestingly, decreasing water levels positively affected the performance of tadpoles, but negatively affected froglet performance. Our results suggest that performance does not necessarily have to be correlated between life stages. However, froglet performance is size dependent and carried over from the tadpole stage, suggesting that some important size-dependent characters cannot be decoupled via metamorphosis.     

Effects of Transgenic cry1Ca Rice on the Development of Xenopus laevis

In fields of genetically modified, insect-resistant rice expressing Bacillus thuringiensis (Bt) proteins, frogs are exposed to Bt Cry proteins by consuming both target and non-target insects, and through their highly permeable skin. In the present study, we assessed the potential risk posed by transgenic cry1Ca rice (T1C-19) on the development of a frog species by adding purified Cry1Ca protein or T1C-19 rice straw into the rearing water of Xenopus laevis tadpoles, and by feeding X. laevis froglets diets containing rice grains of T1C-19 or its non-transformed counterpart MH63. Our results showed that there were no significant differences among groups receiving 100 μg L^–1 or 10 μg L^–1 Cry1Ca and the blank control in terms of time to completed metamorphosis, survival rate, body weight, body length, organ weight and liver enzyme activity after being exposed to the Cry1Ca (P > 0.05). Although some detection indices in the rice straw groups were significantly different from those of the blank control group (P < 0.05), there was no significant difference between the T1C-19 and MH63 rice straw groups. Moreover, there were no significant differences in the mortality rate, body weight, daily weight gain, liver and fat body weight of the froglets between the T1C-19 and MH63 dietary groups after 90 days, and there were no abnormal pathological changes in the stomach, intestines, livers, spleens and gonads. Thus, we conclude that the planting of transgenic cry1Ca rice will not adversely affect frog development.     

Evolutionary reduction of developmental plasticity in desert spadefoot toads

Organisms vary their rates of growth and development in response to environmental inputs. Such developmental plasticity may be adaptive and positively correlate with environmental heterogeneity. However, the evolution of developmental plasticity among closely related taxa is not well understood. To determine the evolutionary pattern of plasticity, we compared plasticity in time to and size at metamorphosis in response to water desiccation in tadpoles among spadefoot species that differ in breeding pond and larval period durations. Like most tadpoles, spadefoot tadpoles possess the remarkable ability to accelerate development in response to pond drying to avoid desiccation. Here, we hypothesize that desert spadefoot tadpoles have evolved reduced plasticity to avoid desiccation in ephemeral desert pools compared to their nondesert relatives that breed in long-duration ponds. We recorded time to and size at metamorphosis following experimental manipulation of water levels and found that desert-adapted species had much less plasticity in larval period and size at metamorphosis than nondesert species, which retain the hypothetical ancestral state of plasticity. Furthermore, we observed a correlation between degree of plasticity and fat body content that may provide mechanistic insights into the evolution of developmental plasticity in amphibians.     

Food availability determines the response to pond desiccation in anuran tadpoles

Food availability and pond desiccation are two of the most studied factors that condition amphibian metamorphosis. It is well known that, when food is abundant, organisms undergo metamorphosis early and when they are relatively large. The capability of anurans to accelerate their developmental rate in response to desiccation is also common knowledge. These two variables must act together in nature, since we know that, as a pond dries, the per capita resources decrease. We conduct an experiment to evaluate the effects of desiccation and food availability separately and in combination in tadpoles of the painted frog (Discoglossus pictus). We demonstrate that food deprivation leads to slow growth rates, which delay metamorphosis and produce smaller size and weight. The capability to accelerate metamorphosis when facing a drying pond is also confirmed, but, nevertheless, with factor interaction (when the pool is drying and resources are scarce) the capacity to respond to desiccation is lost. In addition, slow drying rates are shown to be stressful situations, but not enough to provoke a shortening of the larval period; in fact, the larval period becomes longer. We also demonstrate that the interaction of these factors changes the allometric relationship of different parts of the hind limb, which has implications for the biomechanics of jumping. Due to low mortality rates and an adequate response to both environmental factors, we expect D. pictus to have a great invasive potential in its new Mediterranean distribution area, where lots of temporary and ephemeral ponds are present.     

浙江丽水中华大蟾蜍和黑眶蟾蜍蝌蚪对水位变化的表型响应

全球气候变暖引发栖息地干涸将对生活在水中的无尾类幼体提出了挑战。通过浙江丽水中华大蟾蜍(Bufo gargarizans)和黑眶蟾蜍(Duttaphrynus melanosticus)蝌蚪在实验条件下对不同水位变化的表型响应,检测表型可塑性的遗传性和环境近因性影响。结果表明,水位变化对中华大蟾蜍蝌蚪早期发育历期、头宽和体重影响不显著,对体长影响显著,其中逐减水位最大、恒低水位最小,慢波、恒高与快波、逐增水位依次减少;水位变化对黑眶蟾蜍蝌蚪早期发育历期、体长、头宽和体重影响均显著;发育历期以恒高水位最大,恒低水位最小;体长以逐减水位最大,恒低、快波和慢波水位显著偏小,逐增和快波水位居中;头宽以恒低水位最小,逐增水位居中,其余较大;体重以恒低水位最小、恒高水位最大,其余居中。水位变化对中华大蟾蜍蝌蚪的变态时间、体长、头宽和体重影响均不显著;水位变化对黑眶蟾蜍蝌蚪的变态时间、体长和体重影响均显著,对头宽影响不显著;恒低水位的变态时间最长,恒高水位的变态时间最短,其他水位变化之间差异不显著;恒高水位的体长最大,恒低和快波水位最小,其他居中;逐增和快波水位的体重最大,恒低水位最小。研究结果表明,繁殖季节不同的中华大蟾蜍和黑眶蟾蜍蝌蚪响应水位变化的表型可塑性差异显著,长期在容易发生干旱和水位变化的冬季繁殖的中华大蟾蜍蝌蚪的表型可塑性低,在雨水充沛的春季繁殖的黑眶蟾蜍蝌蚪的表型可塑性高,表现出表型可塑性的种间差异和遗传性;在早期发育过程中,两种蝌蚪体长的共同的表型变异与缺乏遗传基础的环境近因性影响有关;黑眶蟾蜍蝌蚪对低水位或水位下降作出减速分化的消极响应,响应程度与环境信号的强弱直接相关。     

Survival, development, and gonadal differentiation in Rana dalmatina chronically exposed to chlorpyrifos

Chlorpyrifos is an organophosphate pesticide among the most widely used in the world, which is suspected to be an endocrine-disrupting compound. To determine the capacity of chlorpyrifos to affect gonadal differentiation in Rana dalmatina, tadpoles were exposed to this pesticide during larval development until completion of metamorphosis at ecologically relevant concentrations (0.025 and 0.05 mg/L). No effects of chlorpyrifos exposure on survival, development, or metamorphosis were observed. After a 1 month metamorphosis, the gonadal phenotype was determined by gross morphology and histological examination. Morphological and histological analysis revealed normal ovaries or testes in froglets belonging to control group, whereas testes from several froglets exposed to chlorpyrifos were interspersed with testicular oocytes in histological sections. Chlorpyrifos exposure during the entire larval period did not affect sex ratio, but reduced the percentage of males with histologically normal testes. The findings suggest that chlorpyrifos exposure has significant effects on gonadal differentiation in some animals by inducing an intersex condition and alterations to testicular morphology, and that R. dalmatina is sensitive to endocrine disruption. Thereby, this study provides evidence that the ecologically relevant concentrations of chlorpyrifos, although not adversely affect the survival, development, or metamorphosis, may interfere with sex differentiation and reproductive development of R. dalmatina via endocrine-disrupting mechanisms.     

葡萄糖和维生素C对镇海林蛙蝌蚪生长 及其三种酶活性的影响

营养源对动物生长发育具有重要作用。本文采用静水实验浸泡法探究葡萄糖和维生素C对镇海林蛙(Rana zhenhaiensis)蝌蚪生长及其苹果酸脱氢酶、乳酸脱氢酶及淀粉酶活性的影响。在葡萄糖实验组共分为0.5、1.0和2.0 g/L三个浓度组,维生素C实验组共分为10.0、20.0和30.0 mg/L浓度组,另设1组加曝气水作为对照组。在葡萄糖实验组中,蝌蚪存活率在不同实验组间的差异不显著(P0.05)。变态时间在0.5 g/L和1.0 g/L实验组最短,分别为(43.0±4.0)d和(43.0±3.4)d,2.0 g/L实验组最长,为(46.2±5.4)d,且实验组间差异显著(P 0.05)。变态时,0.5 g/L实验组的体重和体全长最大,且各实验组间的体重差异显著(P 0.01),但体全长差异不显著(P 0.05)。增重率在0.5 g/L实验组最高,为(9.67±1.71)mg/d,对照组最低,为(7.54±1.22)mg/d,且各实验组之间差异显著(P0.05)。维生素C实验组中,存活率在各实验组间差异不显著(P 0.05)。所有实验组蝌蚪的发育历期在实验第7、14、21和28天时均大于对照组。变态时间在所有的实验组相似,为43 d左右(P 0.05)。变态时,蝌蚪的体重(P 0.05)和体全长(P 0.05)在20.0 mg/L实验组和30.0 mg/L实验组最大,对照组最小,但各实验组间差异不显著。蝌蚪的增重率在20.0 mg/L和30.0 mg/L实验组最高,10.0 mg/L实验组最低,但不同实验组间差异不显著(P 0.05)。生化酶活性检测中,苹果酸脱氢酶(MDH)活性在葡萄糖实验组和维生素C实验组中均随实验浓度的增加而增加。乳酸脱氢酶(LDH)和淀粉酶(AMS)活性分别在葡萄糖的1.0 g/L实验组和维生素C的10.0 mg/L实验组达到最高。本研究结果表明,10.0mg/L维生素C或1.0g/L葡萄糖为镇海林蛙蝌蚪的最适外源物添加浓度,能促进蝌蚪的生长和体内酶活性。该研究结果将为镇海林蛙的养殖提供一定的理论参考数据。     

The ontogeny of Pseudis platensis (Anura,Hylidae): Heterochrony and the effects of larval development on postmetamorphic life

Recent studies have described the giant tadpole, delayed metamorphic transformations, and absence of postmetamorphic growth of the skeleton of Pseudis Platensis. These features address questions about derived patterns of life cycles and the role of the heterochrony during the metamorphosis in anurans. Using anatomical methods, we provide new data on the development of reproductive, digestive and integument systems, and age inference obtained from ontogenetic series of Pseudis platensis. Our results indicate that at the end of metamorphosis, the adult skin is completely differentiated, including the calcified dermal layer; the testis has seminiferous tubules with spermatogonia, spermatocytes, and spermatids; ovarian sacs present previtellogenic ova; and the adult digestive tract is fully formed. The froglets differ from adults only in being unable to reproduce. The entire life cycle of P. platensis can occur in 4 years. In the first year, larval development, growth to adult size, and gonad differentiation are completed. Long larval development rather than size of the tadpoles seems to be involved in the absence of juvenile stages. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.