The impact of dietary restriction, intermittent feeding and compensatory growth on reproductive investment and lifespan in a short-lived fish

While dietary restriction usually increases lifespan, an intermittent feeding regime, where periods of deprivation alternate with times when food is available, has been found to reduce lifespan in some studies but prolong it in others. We suggest that these disparities arise because in some situations lifespan is reduced by the costs of catch-up growth (following the deprivation) and reproductive investment, a factor that has rarely been measured in studies of lifespan. Using three-spined sticklebacks, we show for the first time that while animals subjected to an intermittent feeding regime can grow as large as continuously fed controls that receive the same total amount of food, and can maintain reproductive investment, they have a shorter lifespan. Furthermore, we show that this reduction in lifespan is linked to rapid skeletal growth rate and is due to an increase in the instantaneous risk of mortality rather than in the rate of senescence. By contrast, dietary restriction caused a reduction in reproductive investment in females but no corresponding increase in longevity. This suggests that in short-lived species where reproduction is size dependent, selection pressures may lead to an increase in intrinsic mortality risk when resources are diverted from somatic maintenance to both growth and reproductive investment.     

Impacts of differential consumption by the grazing fish, Plecoglossus altivelis, on the benthic algal composition in the Chikuma River, Japan

Grazing effects of ayu, Plecoglossus altivelis Temminck et Schegel, on the benthic algal assemblages were investigated in the Chikuma River, Japan. Comparison of the algal composition on boulders with and without intensively grazed patches indicated that fish grazing decreased the abundance of diatoms and prostrate filamentous cyanobacteria and caused upright filamentous cyanobacteria to predominate. Differential consumption by ayu was estimated by comparing the relative abundance of algae in the stomach contents of ayu and that in the algal assemblages within the grazed patches. The results showed that ayu consumed the prostrate filamentous cyanobacteria proportionally to their abundance, whereas they ingested diatoms and the upright filamentous cyanobacteria in a larger and lower quantity, respectively, than that expected from their abundance. Differential consumption would involve the change in the algal composition toward the predominance of upright filamentous cyanobacteria under fish grazing conditions.     

Indirect effects of the algivorous fish Plecoglossus altivelis altivelis on the growth of two insectivorous benthic fish

1. Animals exploiting different resources may nevertheless interact if one species indirectly alters the abundance and distribution of the food of the other. To analyse this indirect effect, we conducted experiments in artificial pools and in the field to investigate the influence of the algivorous fish Plecoglossus altivelis altivelis (known as the ayu) on two species of insectivorous benthic fish, Pseudogobio esocinus esocinus and the goby Gymnogobius petschiliensis .
2. In the pool experiments, algal biomass was not correlated with the number of ayu, but the percentage of blue-green bacteria rose as the number increased. The number of aquatic macroinvertebrates on the upper surface of ceramic tiles placed in the pool bed decreased as the number of ayu increased.
3. Although ayu and the benthic species did not interact directly, the reduction in invertebrate abundance on the upper surface of tiles in the pool reduced the growth rate of the benthic insectivores.
4. In field experiments, the introduction of ayu into habitats with P. esocinus esocinus or G. petschiliensis reduced the growth rate of these benthic fish. In the field experiment that was carried out over 5 years in the G. petschiliensis habitat, the population density of the goby decreased when ayu were stocked.
5. The ayu is a strong interactor or bioengineer in streams, affecting not only benthic algae but also aquatic invertebrates and fishes. We conclude that to predict the outcome of interspecific interactions amongst fishes in streams with high algal production, possible indirect effects must be considered alongside better known direct effects.     

Diel abundance, migration and feeding of fish larvae (Eleotridae) in a floodplain billabong

Eleotrid larvae (2.1–16 mm) were collected from surface waters of a billabong in south-eastern Australia. Estimates of larval density in plankton net samples at night averaged 148.3 larvae per m³ and 16.6 larvae per m³ during the day. In contrast, pump samples provided density estimates of 8.3 larvae per m³ at night and 0.9 larvae per m³ during the day. Larval densities did not differ between open water, snag (fallen tree) and Typha habitats, but Typha habitats yielded larger larvae than other habitats. 32.9% of larvae in pump samples were damaged and unmeasurable, creating a bias favouring larger larvae. The modal length of larvae in net samples at night was 5–6 mm, compared with 3–4 mm during the day, reflecting both greater net avoidance by larger larvae during the daytime and dispersal of smaller larvae from the surface at night. Dispersion patterns of larvae suggest that classes of larvae smaller than, and larger than 5.0 mm exhibit reciprocal diel vertical migration behaviour linked to ontogenetic changes in diet. Larvae less than 5 mm fed only during the day and preyed exclusively on rotifers, whereas larger larvae continued to feed at night and consumed mostly planktonic crustaceans.     

Historical effect in the territoriality of ayu fish

Ayu fish form algae-feeding territories in a river during a non-breeding (growing) season. We build a cost-benefit theory to describe the breakdown and formation of territory. In the early stage of a growing season, all fish hold territories at low densities. Once all territory sites are occupied, excess fish become floaters. When fish density further increases, a phase transition occurs: all the territories suddenly break down and fish form a school. In contrast, when the fish density is decreased, territories are suddenly formed from the school. Both theory and experiments demonstrate that ayu should exhibit a historical effect: the breakdown and formation processes of territory are largely different. In particular, the theory in formation process predicts a specific fish behavior: an “attempted territory holder” that tries to have a small territory emerges just before the formation of territory.     

Growth patterns of the pan‐European freshwater mussel,Anodonta anatina (Linnaeus, 1758) (Bivalvia: Unionidae), vary with sex and mortality in populations

1. Post‐maturation growth leading to indeterminate growth patterns is widespread in nature. However, its adaptive value is unclear. Life history theory suggests this allocation strategy may be favored by temporal pulses in the intensity of mortality and/or the capacity to produce new tissues.
2. Addressing the origin of indeterminate growth and the variability of growth patterns, we studied the growth of duck mussels, Anodonta anatina, a pan‐European unionid, in 18 Polish lakes. For each population, the sex, size, and age of collected mussels were measured to estimate Bertalanffy''s growth curve parameters. We integrated information on A. anatina mortality rates, lake trophy, biofouling by zebra mussels, Dreissena polymorpha, and the prevalence of parasitic trematode larvae to identify selective conditions in lakes.
3. We found two sources of mortality in A. anatina populations, pertaining to adverse effects of zebra mussel biofouling and trophy state on mussel survival. Additionally, populations with heavier biofouling presented a smaller abundance of parasites, indicative of a relationship between filtering intensity and contraction of water‐borne trematode larvae by filtering A. anatina.
4. Consistently for each sex, populations with a greater trophy‐related mortality were characterized in A. anatina by a smaller asymptotic size L_max, indicative of a life history response to mortality risk involving early maturation at a smaller body size. In all populations, females featured higher mortality and larger asymptotic size versus males.
5. Our findings support a theoretical view that adaptive responses to selection involve adjustments in the lifetime resource allocation patterns. These adjustments should be considered drivers of the origin of indeterminate growth strategy in species taking parental care by offspring brooding in body cavities.

     

Relative impacts of Daphnia grazing and direct stimulation by fish on phytoplankton abundance in mesocosm communities

• 1 Planktivorous fish were hypothesised to influence the abundance of algal biomass in lakes by changing zooplankton grazing, affecting zooplankton nutrient recycling and by direct recycling of nutrients to phytoplankton. The relative roles of direct fish effects vs. zooplankton grazing were tested in mesocosm experiments by adding to natural communities large grazing zooplankton (Daphnia carinata) and small planktivorous fish (mosquitofish or juveniles of Australian golden perch).
• 2 The addition of Daphnia to natural communities reduced the numbers of all phytoplankton less than 30 µm in size, but did not affect total biomass of phytoplankton as large Volvox colonies predominated.
• 3 The addition of Daphnia also reduced the abundance of some small (Moina, Bosmina, Keratella) and large (adult Boeckella) zooplankton, suggesting competitive interactions within zooplankton.
• 4 The addition of mosquitofish to communities containing Daphnia further reduced the abundance of some small zooplankton (Moina, Keratella), but increased the numbers of Daphnia and adult Boeckella. In spite of the likely increase in grazing due to Daphnia, the abundance of total phytoplankton and dominant alga Volvox did not decline in the presence of mosquitofish but was maintained at a significantly higher level than in control.
• 5 The addition of juveniles of golden perch to communities containing Daphnia reduced the abundance of small zooplankton (Moina), increased the abundance of large zooplankton (adult Boeckella) but had no significant effect on Daphnia and total phytoplankton abundance.
• 6 The results of the present study suggest that some planktivorous fish can promote the growth of phytoplankton in a direct way, probably by recycling nutrients, and even in the presence of large grazers. However, the manifestation of the direct effect of fish can vary with fish species.

     

Effect of the removal of cleaner fish on the abundance and species composition of reef fish

The ecological significance of cleaner fish on coral reefs was investigated. I removed all cleaner fish, Labroides dimidiatus, from eight small reefs, measured the subsequent effect on the abundance and species composition of all reef fish after 3 and 6 months, and compared it with eight control reefs with cleaner fish. The removal of cleaner fish had no detectable effect on the total abundance of fish on reefs and the total number of fish species at both times. Multivariate analysis by non-metric multidimensional scaling and ANOSIM pairwise tests based on 191 fish species revealed no effect of cleaners on the community structure of fish. Similar results were obtained using principal components analysis on subsets of the data using the 33 most common fish species and the 15 most abundant species (≥5 individuals per reef ) with both log10 (x + 1) transformed data and with fish numbers standardized for abundance. This study demonstrates that the removal of cleaner fish for 6 months did not result in fish suffering increased mortality nor in fish leaving reefs to seek cleaning elsewhere. Received: 28 October 1996 / Accepted: 7 February 1997     

The influence of prey abundance on the feeding ecology of two piscivorous species of coral reef fish

Despite the potential importance of predation as a process structuring coral reef fish communities, few studies have examined how the diet of piscivorous fish responds to fluctuations in the abundance of their prey. This study focused on two species of rock-cod, Cephalopholis cyanostigma (Valenciennes, 1828) and Cephalopholis boenak (Bloch, 1790) (Serranidae), and monitored their diet in two different habitats (patch and contiguous reef) at Lizard Island on the northern Great Barrier Reef, Australia, over a 2-year period. The abundance of the rock-cods and the abundance and family composition of their prey were monitored at the same time. Dietary information was largely collected from regurgitated samples, which represented approximately 60% of the prey consumed and were unbiased in composition. A laboratory experiment showed that fish were digested approximately four times faster than crustaceans, leading to gross overestimation of the importance of crustaceans in the diet. When this was taken into account fish were found to make up over 90% of the diet of both species. Prey fish of the family Apogonidae, followed by Pomacentridae and Clupeidae, dominated the diet of both species of rock-cod. The interacting effect of fluctuations in prey abundance and patterns of prey selection caused dietary composition to vary both temporally and spatially. Mid-water schooling prey belonging to the families Clupeidae and to a lesser extent Caesionidae were selected for over other families. In the absence of these types of prey, apogonids were selected for over the more reef-associated pomacentrids. A laboratory experiment supported the hypothesis that such patterns were mainly due to prey behaviour. Feeding rates of both species of rock-cod were much higher in summer than in winter, and in summer they concentrated on small recruit sized fish. However, there was little variation in feeding rates between habitats, despite apparent differences in prey abundance. In summary, our observations of how the feeding ecology of predatory fish responded to variation in prey abundance provide potential mechanisms for how predation may affect the community structure of coral reef fishes.     

Age,growth, reproduction and status of resource development of Ptychidio jordani,a critically endangered freshwater fish in the Hongshui River,China

The age, growth, reproduction and resource development status of Ptychidio jordani, as a critically endangered freshwater fish in the Hongshui River, China, was studied in this work. A total of 525 specimens were collected monthly using the cages and gillnets from October 2021 to September 2022 in the Hongshui River. The scale was used for age determination, and the maximum age for both female and male was estimated to be 5 years and 3 years, respectively. Female and male P. jordani showed different growth patterns, which were expressed as L_t = 261.3 (1-e^{−0.4885(t−0.1476)}) and L_t = 251.2 (1-e^{−0.4758(t+0.9643)}), respectively. The overall sex ratio was 1:0.47 (female:male). Female attained sex maturity at 2.34 years (192 mm body length). Month variation of the gonad somatic index indicated that the spawning period occurred from April to October. The absolute fecundity was estimated at 9046 ± 3434 eggs per individual, and the relative fecundity was 38.08 ± 15.77 eggs per gram. The exploitation rate of female and male was 0.233 and 0.495, which indicated that P. jordani was not overfishing. This study provided data on the key life-history traits of P. jordani, which has not been known previously and is essential for conservation strategy and policy development.     

Distribution of two sympatric amphidromous grazing fish Plecoglossus altivelis Temminck & Schlegel and Sicyopterus japonicus (Tanaka) along the course of a temperate river

Densities of two sympatric amphidromous grazing fishes, Plecoglossus altivelis and Sicyopterus japonicus, and gross primary production of benthic algae were investigated at the second, third and fourth-order sites located, respectively, 7.0, 6.7 and 3.6 km from the mouth of the Choshi River, Japan. Gross primary production estimated by multiplying gross photosynthetic rates by hours of insolation on the streambed increased downstream with decreasing canopy cover by valley walls and trees standing along the river. Density of P. altivelis was greatest at the fourth-order site with the higher primary production, while the distribution pattern of S. japonicus differed between adult (> ca. 7 cm in total length) and young individuals. Density of adult of S. japonicus was greater at the third-order site, although the young were more abundant at the fourth-order site. Aggressive acts against conspecifics and different species were observed only by adults of S. japonicus and most frequently observed at the third-order site. The upstream shift in the distribution of the adults of S. japonicus would mitigate interference competition with P. altivelis and contribute to their coexistence in the river. Handling editor: K. Martens     

Non-breeding territoriality and the effect of territory size on aggression in the weakly electric fish,Gymnotus omarorum

acta ethologica - Agonistic behavior involves the displays that arise when conspecifics compete for valuable resources such as territory. After conflict resolution, dominants obtain priority access...     

Genetic characteristics of the amphidromous fish Ayu Plecoglossus altivelis altivelis (Osmeriformes: Plecoglossidae) on Yaku-shima Island in Japan,the southernmost population of the subspecies

Genetica - The Ayu (Plecoglossus altivelis altivelis) population on Yaku-shima Island, Kagoshima Prefecture, Japan represents the southernmost population of the subspecies and is considered to be...     

长江上游特有种长鳍吻鮈种群数量和资源利用评估

长鳍吻鮈(Rhinogobio ventralis)为长江上游特有种, 由于过度捕捞和大坝建设, 其种群生存受到极大威胁。为了解三峡工程蓄水后、金沙江一期工程蓄水前该物种的种群动态, 作者利用2007-2009年长江上游江津和宜宾江段调查获取的体长频率数据, 评估了其生长和死亡参数、种群数量及资源利用情况。结果表明, 长江上游长鳍吻鮈渔获群体体长范围为52-250 mm, 体重范围为2.7-307.2 g, 平均体长为150.8 ± 40.7 mm, 平均体重为72.3 ± 49.7 g。江津江段长鳍吻鮈平均体长(168.6 ± 29.5 mm)显著大于宜宾江段(125.6 ± 41.2 mm)。长鳍吻鮈体长-体重关系为: W = 6.06 × 10^-6L^3.20 (R² = 0.98, P < 0.01, n = 436)。由体长频率法拟合出渐近体长(L_∞)为338 mm, 生长系数(k)为0.24/yr。由Pauly公式、Gunderson和Dygert公式、Jensen公式等3种方法估算出其平均自然死亡系数为0.43。由长度转渔获物曲线估算出江津和宜宾江段长鳍吻鮈的总死亡系数分别为2.26和2.09。江津和宜宾江段长鳍吻鮈资源开发率分别为0.81和0.79, 已超过由Beverton-Holt动态综合模型估算出的最大开发率0.57和0.62。由体长实际种群分析估算出2007、2008和2009年江津江段长鳍吻鮈种群数量分别为68,247、67,432和176,266尾, 平均为103,982尾; 宜宾江段种群数量分别为22,953尾、46,340尾和34,021尾, 平均为34,438尾, 表明江津江段种群数量高于宜宾江段。长鳍吻鮈资源已被过度开发, 建议加强种群动态监测, 延长禁渔期及开展栖息地修复等措施保护这一特有物种。     

The influence of territoriality and mating system on the evolution of male care: a phylogenetic study on fish

Evolution of male care is still poorly understood. Using phylogenetically matched-pairs comparisons we tested for effects of territoriality and mating system on male care evolution in fish. All origins of male care were found in pair-spawning species (with or without additional males such as sneakers) and none were found in group-spawning species. However, excluding group spawners, male care originated equally often in pair-spawning species with additional males as in strict pair-spawning species. Evolution of male care was also significantly related to territoriality. Yet, most pair-spawning taxa with male care are also territorial, making their relative influence difficult to separate. Furthermore, territoriality also occurs in group-spawning species. Hence, territoriality is not sufficient for male care to evolve. Rather, we argue that it is the combination of territoriality and pair spawning with sequential polygyny that favours the evolution of male care, and we discuss our results in relation to paternity assurance and sexual selection.     

Effects of large herbivore grazing on grasshopper behaviour and abundance in a meadow steppe

1. Adaptive phenotypic plasticity has been a major subject in evolutionary ecology, but how a species' behaviour may respond to certain environmental change is still not clear. In grasslands worldwide, large herbivores are increasingly used as a tool for grazing management, and occur to interact with grasshoppers that dominate grassland insect communities. Previous studies have been well-documented about grazing effects on diversity and abundance of grasshoppers. Yet, how grazing may alter grasshopper behaviour, and potential effects on their abundance remains elusive. 2. We conducted a field experiment by manipulating grazing using sheep, cattle, and their mix to examine the behavioural responses and abundance of the grasshoppers (Euchorthippus unicolor) to grazing in a Leymus chinensis-dominated grassland. 3. Results showed that the grasshoppers spent less time on feeding and resting on grasses, but more time on switching and resting on forbs under cattle grazing and mixed grazing with cattle and sheep. In contrast, the grasshoppers spent more time on feeding but less time on switching and resting on forbs under sheep grazing. The behavioural changes were also potentially linked to grasshopper abundance in the context of grazing management. 4. The responses of grasshopper behaviour and abundance to grazing may be largely triggered by altered vegetation and microclimates. Such behavioural flexibility of grasshoppers must be considered when large herbivores are recognised as a management tool for influencing grasshopper abundance, and grazer species should be paid more attention both individually and jointly for better grassland conservation.     

Conserved ontogeny and allometric scaling of resource acquisition and allocation in the Daphniidae

Life histories vary widely among taxa, but within phylogenetic groups there may be a fundamental framework around which trait variation is organized, perhaps as a consequence of lineage-specific developmental constraints. In organisms with indeterminate growth, there is an ongoing problem of optimally allocating resources between growth and reproduction, and that allocation decision may manifest itself through allometric scaling. Previous work on freshwater zooplankton has shown that the ontogenetic pattern of resource allocation can be described by simple mathematical functions. An important component of understanding how such functions can explain life-history variation is to discover which parameters in these functions are robust, with respect to both resource availability and evolutionary diversification, and which parameters exhibit interspecific allometry. To shed light on these issues, detailed life table experiments were conducted on eight species in the family Daphniidae (Crustacea) at high and low levels of resources. Using data on growth, reproduction, and instar duration, the ontogeny of resource allocation to growth and reproduction could be described as functions that plateau at or shortly after the onset of maturity. To be sure that the results were not an artifact of phylogenetic structure, the parameters were tested in a phylogenetically controlled fashion. The results suggest a simple set of resource allocation rules for daphniids, whereby all species exhibit a similar form of ontogenetic change in allocation, and reach a plateau where approximately 94% of available resources are allocated to reproduction. The asymptotically maximal rate of net resources incorporated in growth and reproduction was positively related to size at maturity, whereas the rates of approach to plateaus (for both net resource assimilation and proportional allocation to reproduction) were negatively related to body size. Per-offspring investment was positively related to the square root of size at maturity. Using this approach, a wide range of interspecific variation in life-history features can be related to a single underlying trait, the size at first reproductive investment.     

饲喂黄顶菊对黄粉虫生长发育及繁殖的影响

【背景】黄顶菊是近年来人侵我国的一种有害杂草,其竞争力强,给自然界造成了严重危害,同时也产生了大量的生物质资源。作为一种杂食性昆虫,黄粉虫易于饲养,可以用于多种生物质资源的转化处理。【方法】本研究分别以黄顶菊、小白菜和西瓜皮作为青料,与麦麸等配制成人工饲料后,对黄粉虫进行定期饲喂,研究其对黄粉虫幼虫、成虫生长发育及繁殖的影响。【结果】黄粉虫幼虫饲料中添加一定比例的黄顶菊与添加小白菜相比,虫体生物量增长率较低,饲料利用率和死亡率较高;成虫饲料中添加黄顶菊与添加西瓜皮相比,黄粉虫平均寿命延长,单雌产卵量减少,且差异均显著,体长略有减小。【结论与意义】本研究对利用黄粉虫转化处理黄顶菊的效果做出了初步评价,即黄粉虫能够取食黄顶菊,但转化处理效果不太理想。     

Spatial variation in relative abundance of a widespread, numerically dominant fish species and its effect on fish assemblage structure

Collections of fish assemblages from streams in the midwestern United States were used to examine assemblage-level effects of spatial variation in relative abundance of the red shiner, Cyprinella lutrensis, a widespread and highly abundant minnow species. This species has been widely introduced outside its native range and is suspected to have impacted local assemblages where it has become established. Given its overall dominance of midwest fish assemblages, and its suspected impact on assemblage structure, we asked if structure of the residual fish assemblages (red shiners excluded) was a function of the relative abundance of red shiners throughout the native range of C. lutrensis in the USA. Although red shiner ranked first in abundance in half of the assemblages and numerically dominated 28% of the assemblages, red shiner relative abundance in an assemblage had no detectable effect on richness, diversity, evenness, or complexity of other (residual) species in the assemblage. Relative abundance of red shiners did have a positive effect on the abundance of benthic minnows in the residual assemblage, but not on water column minnows that are ecologically most like red shiners. Environmental factors did not explain a significant amount of the variation in relative abundance of red shiners, but did explain some variation in residual assemblage structure. Although widespread and numerically dominant at many localities, red shiners do not appear to have a strong impact on local fish assemblage structure within their native range. This is in sharp contrast to the reported negative effects of red shiners on fish assemblages where they have been introduced outside their native range.     

食料对烟草甲共生菌数量和生长发育的影响

烟草甲Lasioderma serricorne(Fabricius)消化道内含有一种类酵母共生菌,其在烟草甲的营养需求和对外源物质的解毒过程中有重要作用。以麦粒、烟叶、麦片、甘草和面粉为食料饲养烟草甲,研究了食料对烟草甲共生菌数量和发育历期的影响,发现:烟草甲5龄幼虫体内的共生菌数量最多,蛹次之;食料对共生菌的数量有显著的影响,尤其在5龄幼虫期;麦粒饲养的烟草甲发育历期最短、体内的共生菌数量最多,而甘草饲养的烟草甲发育历期最长、体内的共生菌数量最少;共生菌的数量与烟草甲的生长发育历期之间存在着明显的负相关关系。