Juvenile Bank Research Articles

The impact of wildlife and environmental factors on hantavirus infection in the host and its translation into human risk.

Identifying factors that drive infection dynamics in reservoir host populations is essential in understanding human risk from wildlife-originated zoonoses. We studied zoonotic Puumala orthohantavirus (PUUV) in the host, the bank vole (Myodes glareolus), populations in relation to the host population, rodent and predator community and environment-related factors and whether these processes are translated into human infection incidence. We used 5-year rodent trapping and bank vole PUUV serology data collected from 30 sites located in 24 municipalities in Finland. We found that PUUV seroprevalence in the host was negatively associated with the abundance of red foxes, but this process did not translate into human disease incidence, which showed no association with PUUV seroprevalence. The abundance of weasels, the proportion of juvenile bank voles in the host populations and rodent species diversity were negatively associated with the abundance index of PUUV positive bank voles, which, in turn, showed a positive association with human disease incidence. Our results suggest certain predators, a high proportion of young bank vole individuals, and a diverse rodent community, may reduce PUUV risk for humans through their negative impacts on the abundance of infected bank voles.

TOTAL SERUM CALCIUM AND EUMELANISM IN JUVENILE BANK MYNA, ACRIDOTHERES GINGINIANUS (LATHAM)

A series of scarce minerals (Ca, Zn, Cu, Fe) obtained from the diet are known to act ascritical regulatory factors in the biosynthesis of eumelanin and phaeomelanin pigments in animals.Juvenile Bank myna is dull brown in colour, whereas adult is bluish grey coloured. A link has beenfound between degree of eumelanism, total serum calcium and bone weight in juvenile Bank mynawith increasing age. Gradual increase in total femur weight was corresponded by increasing degreeof eumelanin pigment and reduction in total serum calcium level.

Mercury exposure to swallows breeding in Canada inferred from feathers grown on breeding and non-breeding grounds.

Aerial insectivorous birds such as swallows have been the steepest declining groups of birds in North America over the last 50 years but whether such declines are linked to contaminants has not been examined. We sampled feathers from five species of swallow at multiple locations to assess total mercury [THg] exposure for adults during the non-breeding season, and for juveniles on the breeding grounds. We assessed Hg exposure to juvenile birds in crop- and grass-dominated landscapes to determine if land-use practices influenced feather [THg]. We assayed feathers for stable isotopes (δ2H, δ13C, δ15N) as proxies for relative habitat use and diet to determine their potential influence on feather [THg]. Feather [THg] was highest in adult bank swallows (Riparia riparia) and purple martins (Progne subis) from Saskatchewan and adult cliff swallows (Petrochelidon pyrrhonota) from western regions, indicating differential exposure to Hg on the non-breeding grounds. Juvenile bank, barn (Hirundo rustica) and tree (Tachycineta bicolor) swallows had lower feather [THg] in crop-dominated landscapes than grass-dominated landscapes in Saskatchewan, potentially resulting from lower use of wetland-derived insects due to wetland drainage and intensive agriculture. Feather [THg] was related to juvenile feather stable isotopes for several species, suggesting complex interactions with diet and environmental factors. Many individuals had feather [THg] values >2 µg/g, a threshold at which deleterious effects may occur. Our findings indicate differential Hg exposure among species of swallow, regions and land-uses and highlight the need for additional research to determine dietary and finer-scale land-use impacts on individual species and populations.

Where does the forest come back from? Soil and litter seed banks and the juvenile bank as sources of vegetation resilience in a semiarid Neotropical forest

AbstractQuestions: The existence of reservoirs from which dominant plants recruit after disturbances is a key factor in ecosystem resilience. With this in mind, we ask the following qestion: where do woody species regenerate from in the semiarid Neotropical Chaco forest? Is land use affecting the floristic composition of biodiversity reservoirs? Are the soil and litter seed banks and the juvenile bank potential sources of resilience of these forests in the face of different land‐use regimes?Location: Chancaní, Northwestern Córdoba, Argentina.Methods: We selected four ecosystem types subjected to increasing long‐term land‐use intensity: primary forest (no land use in the last 50 years), secondary forest (low land‐use intensity), closed species‐rich shrubland (moderate land‐use intensity), and open shrubland (high land‐use intensity). We monitored four sites per ecosystem type where we recorded adults, saplings and seedlings of all woody species. We collected litter and soil samples that were processed in the laboratory for taxonomic identification and germination of seeds. We compared the floristic composition of the soil and litter banks, as well as of the juvenile bank (“biodiversity reservoirs”) with that of established vegetation of the primary forest, considered as the reference ecosystem. We also compared the established vegetation from sites under land use with that of the primary forest.Results: Woody species were scarcely represented in the soil, but very well represented in the litter and the juvenile banks from different ecosystem types. These two reservoirs showed high similarity with the established vegetation of the primary forest. However, as land‐use intensity increased, similarity between the reservoirs and the established vegetation of the primary forest decreased.Conclusion: Litter and juvenile banks, but not the soil bank, are the main reservoirs for the recruitment of new individuals of woody species in the Chaco forest. However, the ability of these reservoirs to act as sources of resilience decreases as land use intensifies.

РЕАКЦИЯ РЫЖИХ ПОЛЁВОК (MYODES GLAREOLUS SCHREBER, 1780) НА ЛОВУШКИ С ЗАПАХОМ СИНАНТРОПНЫХ ДОМОВЫХ МЫШЕЙ (MUS MUSCULUS s.l.) (MAMMALIA: RODENTIA): ПОЛЕВОЙ ЭКСПЕРИМЕНТ

Our hypothesis that the exoanthropic forest rodent species (e.g. bank voles) avoid the urinary odor of the synanthropic house mice was tested in field experiments in August 2016. One count of small mammals was carried out in each of two 4-ha fields by the capture-mark-recapture technique during 12 days. 200 live traps (100 points, 2 traps per point) were exposed and controlled twice a day (early in the morning and in the evening) in each count. One trap in every pair served as a reference, while the second was an experimental one whose foam rubber was applied by 20 μl of the urine of the synanthropic house mice every day. Generally, bank voles chose the odorless trap more often (60.8% vs. 39.2%, χ2 = 3.7, р = 0.054). Adult individuals had a non-significant tendency to avoid the odor-emitting traps. Immature (subadult and juvenile) bank voles reliably avoided the odor-emitting traps (a 2:1 ratio, χ2 = 5.74, р = 0.017). GLM showed an influence of vole age on the choice of the odorless traps. The potential repellent role of sulfur-containing compounds in mouse urine is discussed.

Regeneration of Juvenile Woody Plants after Fire in a Seasonally Dry Tropical Forest of Southern India

AbstractWoody tree species in seasonally dry tropical forests are known to have traits that help them to recover from recurring disturbances such as fire. Two such traits are resprouting and rapid post‐fire growth. We compared survival and growth rates of regenerating small‐sized individuals (juveniles) of woody tree species after dry season fire (February–March) at eight adjacent pairs of burnt and unburnt transects in a seasonally dry tropical forest in southern India. Juveniles were monitored at 3‐mo intervals between August 2009 and August 2010. High juvenile survivorship (>95%) was observed in both burnt and unburnt areas. Growth rates of juveniles, analyzed at the community level as well as for a few species individually (especially fast‐growing ones), were distinctly higher in burnt areas compared to unburnt areas after a fire event, particularly during the pre‐monsoon season immediately after a fire. Rapid growth by juveniles soon after a fire may be due to lowered competition from other vegetative forms such as grasses, possibly aided by the availability of resources stored belowground. Such an adaptation would allow a juvenile bank to be retained in the understory of a dry forest, from where individuals can grow to a possible fire‐tolerant size during favorable conditions.

Reducing Mortality of Shrews in Rodent Live Trapping — a Method Increasing Live-Trap Selectivity with Shrew Exits

Shrews have very high metabolic rates and are often unintentionally starved in rodent live-traps during capture-mark-recapture (CMR) studies. Here, we suggest a shrew exit as a modification to rodent traps. To test whether this modification is (1) saving shrews and (2) not jeopardizing results of rodent captures, we compared captures in Ugglan traps with and without shrew exits, studying bank voles (Myodes glareolus) in a spruce forest in central Finland. Numbers of captured bank voles and body size of smallest juvenile bank voles were not affected by the shrew exit, while the number of captured common shrews (Sorex araneus) was reduced from 31 to 0 individuals per 100 trap nights. However, rare larger shrew species (> 8 g body weight) could not escape through the exit. A shrew exit can, therefore, save smaller shrew species in standard live-trapping of vole-sized rodents without affecting CMR data of the rodent.

Recruitment bottlenecks in the rare Australian conifer Wollemia nobilis

Seedling survival plays a critical role in maintaining a supply of potential recruits. We examined seedling recruitment, survival and growth in Wollemia nobilis, a rare, long-lived Australian conifer. Wollemia nobilis seedlings and juveniles were monitored for 16 years (1996–2011). While W. nobilis can recruit from seed and, unlike most conifers, persist through resprouting, seed-based recruitment was the primary focus of this study. Sixty-five per cent of new seedlings died within their first year and only 7 % persisted for the 16-year monitoring period. However, 44 % of established juvenile plants (of unknown age at the beginning of the study) persisted throughout the 16-year monitoring period. Growth of seedlings and juveniles was very slow; growth estimates for most individuals had 95 % confidence intervals that included zero. The recruitment strategy of W. nobilis may be to maintain a slow-growing juvenile bank—a strategy typical of other shade-tolerant rainforest trees, including other Araucariaceae. Seedling recruitment in W. nobilis may act together with resprouting to maintain the population.

Comparing short and long-distance dispersal: modelling and field case studies

Dispersal is a factor of great importance in determining a species spatial distribution. Short distance dispersal (SDD) and long distance dispersal (LDD) strategies yield very different spatial distributions. In this paper we compare spatial spread patterns from SDD and LDD simulations, contrast them with patterns from field data, and assess the significance of biological and population traits. Simulated SDD spread using an exponential function generates a single circular patch with a well-defined invasion front showing a travelling-wave structure. The invasive spread is relatively slow as it is restricted to reproductive individuals occupying the outer zone of the circular patch. As a consequence of this dispersal dynamics, spread is slower than spread generated by LDD. In contrast, the early and fast invasion of the entire habitat mediated by power law LDD not only involves a significantly greater invasion velocity, but also an entirely different habitat occupation. As newly dispersed individuals soon reach very distant portions of the habitat as well as the vicinity of the original dispersal focus, new growing patches are generated while the main patch increases its own growth absorbing the closest patches. As a consequence of both dispersal and lower density dependence, growth of the occupied area is much faster than with SDD. SDD and LDD also differ regarding pattern generation. With SDD, fractal patterns appear only in the border of the invasion front in SDD when competitive interaction with residents is included. In contrast, LDD patterns show fractality both in the spatial arrangements of patches as well as in patch borders. Moreover, values of border fractal dimension inform on the dispersal process in relation with habitat heterogeneity. The distribution of patch size is also scale-free, showing two power laws characteristic of small and large patch sizes directly arising from the dispersal and reproductive dynamics. Ecological factors like habitat heterogeneity are relevant for dispersal, although its importance is greater for SDD, lowering the invasion velocity. Among the life history traits considered, adult mortality, the juvenile bank and mean dispersal distance are the most relevant for SDD. For LDD, habitat heterogeneity and changes in life history traits are not so relevant, causing minor changes in the values of the scale-free parameters. Our work on short and long distance dispersal shows novel theoretical differences between SDD and LDD in invasive systems (mechanisms of pattern formation, fractal and scaling properties, relevance of different life history traits and habitat variables) that correspond closely with field examples and were not analyzed, at least in this degree of detail, by the previously existing models.

Disruption of recruitment in two endemic palms on Lord Howe Island by invasive rats

Invasive species may have negative impacts on many narrow range endemics and species restricted to oceanic islands. Predicting recent impacts of invasive species on long-lived trees is difficult because the presence of adult plants may mask population changes. We examined the impact of introduced black rats (Rattus rattus) on two palm species restricted to cloud forests and endemic to Lord Howe Island, a small oceanic island in the southern Pacific. We combined estimates of the standing size distribution of these palms with the proximal impacts of rats on fruit survival in areas baited to control rats and in unbaited areas. The size distribution of palms with trunks was comparable across baited and unbaited sites. Small juvenile palms lacking a trunk (\50 cm tall) were abundant in baited areas, but rare in unbaited sites for Lepidorrhachis mooreana, and rare or absent in 3 out of 4 unbaited Hedyscepe canterburyana sites. All ripe fruits were lost to rats in the small fruited L. mooreana. Fruit removal was widespread but less (20-54%) in H. canterburyana. Both palms showed evidence of a reduced capacity to maintain a juvenile bank of palms through regular recruitment as a consequence of over 90 years of rat impact. This will limit the ability of these species to take advantage of episodic canopy gaps. Baiting for rat control reduced fruit losses and resulted in the re-establishment of a juvenile palm bank. Conservation of both endemic palms necessitates control (or eradication) of rat populations on the unique cloud forest summits of the island.

Growth of the bank voleMyodes glareolusin the non-vegetative period in NE Lithuania

Bank voles (Myodes glareolus) were trapped in north-east Lithuania from October to April in 2004-2008. Investigation of 536 individuals showed that winter growth depression for the species was not strongly expressed, except for the body weight of juveniles in December and January. Only a few skull characters showed stunted growth. The wintering juvenile bank voles attained an average body mass of 14.8 ± 0.07 g and an average body length of 84.3 ± 0.32 mm, while the respective parameters in subadult individuals were 17.0 ± 0.09 g and 86.0 ± 0.37 mm. The successful overwintering of such small bank voles suggests a possible influence of warmer winters.

Manipulation of offspring number and size: benefits of large body size at birth depend upon the rearing environment

Summary 1. Allocation of reproductive effort between the number and size of offspring determines the immediate rearing environment for the growing young. As the number of offspring increases, the amount of parental investment per individual offspring decreases, and the quality of the rearing environment is expected to decrease. This may result in a lower quality of offspring reared in such conditions. 2. We studied the effects of the rearing environment on the quality of juvenile bank voles, Clethrionomys glareolus , with different initial body sizes at birth in a 2 〈 2 factorial experiment. The rearing environment was manipulated by enlarging both the litter size by two extra pups, and mean offspring body size at birth by replacing the original litter with heavier pups from smaller litters. Offspring quality was estimated from body size measurements, parasitic infection with Eimeria spp. and the level of immune response to a novel antigen. 3 The analyses revealed that large body size at birth was an advantage in ‘normal’ rearing environments, but a disadvantage in poor ones. The initially normal sized offspring grown in enlarged litters had a relatively good capacity for growth and high immune function confirming that a poor rearing environment alone does not reduce their quality. 4 Our findings that the benefits of large body size depend on the rearing environment suggest that offspring body size is adjusted in relation to litter size, and thus the evolution of these two traits is combined.

Modelling biological invasions: species traits, species interactions, and habitat heterogeneity

In this paper we explore the integration of different factors to understand, predict and control ecological invasions, through a general cellular automaton model especially developed. The model includes life history traits of several species in a modular structure interacting multiple cellular automata. We performed simulations using field values corresponding to the exotic Gleditsia triacanthos and native co-dominant trees in a montane area. Presence of G. triacanthos juvenile bank was a determinant condition for invasion success. Main parameters influencing invasion velocity were mean seed dispersal distance and minimum reproductive age. Seed production had a small influence on the invasion velocity. Velocities predicted by the model agreed well with estimations from field data. Values of population density predicted matched field values closely. The modular structure of the model, the explicit interaction between the invader and the native species, and the simplicity of parameters and transition rules are novel features of the model.

Species Invasiveness in Biological Invasions: A Modelling Approach

The study of invasiveness, the traits that enable a species to invade a habitat, and invasibility, the habitat characteristics that determine its susceptibility to the establishment and spread of an invasive species, provide a useful conceptual framework to formulate the biological invasion problem in a modelling context. Another important aspect is the complex interaction emerging among the invader species, the noninvader species already present in the habitat, and the habitat itself. Following a modelling approach to the biological invasion problem, we present a spatially explicit cellular automaton model (Interacting Multiple Cellular Automata (IMCA)). We use field parameters from the invader Gleditsia triacanthos and the native Lithraea ternifolia in montane forests of central Argentina as a case study to compare outputs and performance of different models. We use field parameters from another invader, Ligustrum lucidum, and the native Fagara coco from the same system to run the cellular automaton model. We compare model predictions with invasion values from aerial photographs. We discuss in detail the importance of factors affecting species invasiveness, and give some insights into habitat invasibility and the role of interactions between them. Finally, we discuss the relevance of mathematical modelling for studying and predicting biological invasions. The IMCA model provided a suitable context for integrating invasiveness, invasibility, and the interactions. In the invasion system studied, the presence of an invader's juvenile bank not only accelerated the rate of invasion but was essential to ensure invasion. Using the IMCA model, we were able to determine that not only adult survival but particularly longevity of the native species influenced the spread velocity of the invader, at least when a juvenile bank is present. Other factors determining velocity of invasion detected by the IMCA model were seed dispersal distance and age of reproductive maturity. We derived relationships between species' adult survival, fecundity and longevity of both theoretical and applied relevance for biological invasions. Invasion velocities calculated from the aerial photographs agreed well with predictions of the IMCA model.

Prey selection of the least weasel Mustela nivalis in the laboratory

Prey individuals representing the bank vole Clethrionomys glareolus and the field vole Microtus agrestiswere presented in pair to male and female least weasels Mustela nivalis Linnaeus, 1766 in the laboratory. The voles were placed in two radomly selected boxes out of 8 boxes, which were connected to an arena housing the weasel. For each trial we recorded the finding, killing and eating order of the two prey individuals. Male weasels tended to kill bank voles before field voles, and female weasels preffered to eat the bank vole first. Both sexes selected juvenile bank voles as the first prey to eat.

Effect of differential photoperiod treatment on Leydig cell ultrastructure in the bank vole ( Clethrionomys glareolus, S.)

Juvenile bank voles (18–22 days of age) born and reared in a stimulatory long photoperiod (18L:6D, lights on 0600–2400 hr) were subjected either to a long photoperiod (18L:6D, Group L) or to a short photoperiod (6L: 18D, lights on 0800–1400 hr, Group S) for 6 to 8 weeks whereafter the animals were killed by decapitation. Possible photoperiod-induced changes in Leydig cell ultrastructure were studied by conventional transmission electron microscopy and stereological methods. Striking differences in Leydig cell ultrastructure between the experimental groups were encountered. Light deprivation induced a marked decrease in the cytoplasmic and nuclear volume as well as in the amounts of smooth endoplasmic reticulum (SER), rough endoplasmic reticulum, mitochondria, and lipid inclusions in the Leydig cells. The number of myelin bodies and dense bodies seemed to be somewhat higher in the regressive Group S Leydig cells. These results are in good agreement with our previous histological and biochemical studies on the effects of photoperiod on Leydig cell function and suggest that in the bank vole the volume of mitochondria and SER in particular correlates positively with the steroidogenic capacity (the activity of C 20α22-C 27 desmolase, 17α-hydroxylase, and C 17–20 lyase in particular) of the Leydig cell.

Photoperiodic modulation of testicular LH receptors in the bank vole (Clethrionomys glareolus).

The temporal changes in testicular binding of 125I-labelled hCG in juvenile bank voles (18 days of age, born and reared in a 18L:6D photoperiod) exposed to a long (18L:6D, Group L) or short (6L:18D, Group S) photoperiod for 0, 3, 7, 14 and 42-56 days were investigated. During testicular maturation, in Group L, there was a slight initial decrease in LH receptor numbers per testis followed by a marked prepubertal rise during the initial phase of rapid testicular growth after which a decrease took place. In Group S, during testicular regression, the temporal changes in LH receptor numbers per testis resembled those of Group L except that the corresponding increase in hCG binding during the initial week was considerably less marked and the receptor numbers remained thereafter at a significantly lower level than in Group L. Leydig cell count indicated that the observed changes in LH receptors per testis were due to changes in the number of Leydig cells as well as in LH receptors per Leydig cell. The present results indicate, that (1) photoperiod is an important modulator of testicular LH receptor numbers in this species, (2) photoperiod or age has no significant effect on the binding affinity of LH receptors, (3) short photoperiods arrest the induction of LH receptors as well as the increase in Leydig cell numbers associated with normal testicular maturation, and (4) changes in LH receptor numbers per testis correlate well with the photoperiod-induced changes in androgen biosynthesis, spermatogenesis and Leydig cell morphology observed in our previous studies.

Testicular steroid metabolism in juvenile bank voles ( Clethrionomys glareolus schreber) exposed to different photoperiods: An in vitro study

Juvenile male bank voles (18–22 days of age) were either sacrificed immediately (Group C) or subjected first to a long (18L:6D, lights on 0600–2400; Group L) or a short (6L:18D, lights on 0800–1400; Group S) photoperiod for 1 week. The animals were killed by decapitation, the gonads were excised, and minced, and the conversion of [4- 14C]pregnenolone (Δ 5P) and [4- 14C]dehydroepiandrosterone (DHA) to metabolites was studied in vitro. The radioactive steroids formed were separated and identified by thin-layer chromatography (TLC). The conversion of Δ 5P to C 19-steroids increased markedly from 35 (Group C) to 86% (Group L) during the first week in the long photoperiod whereas in the short photoperiod a decrease to 14.42% (Group S) was observed. The reduced production of C 19-steroids in the more inactive testes was accompanied by the accumulation of progesterone (Δ 4P) (52.98% Group S and 24.9% Group C) and small amounts of 17α-hydroxyprogesterone (17α-OH-Δ 4P) (2.5 and 4.5%, respectively), whereas in Group L only trace amounts of these metabolites were encountered. No marked differences in the metabolism of [4- 14C]DHA between the photoperiodic groups were observed. These results seem to indicate that at least in vitro marked changes in C 17-C 20-lyase and/or 17α-hydroxylase activities occur in this seasonally breeding species during testicular maturation and photoperiodically induced regression.

Temporal changes in testicular histology and steroidogenesis in juvenile bank voles (Clethrionomys glareolus, Schreber) subjected to different photoperiods.

The temporal relationships of testicular steroidogenesis, gametogenesis, and interstitial cell histo0logy during testicular maturation and regression induced by photoperiod were investigated. Juvenile bank voles (18–22 days old) were killed immediately or after exposure to either a long [18-h light-6-h dark (18L:6D)] or a short (6L:18D) photoperiod for 1, 2, 4, and 6 weeks. Testicular pregnenolone (Δ5-P), progesterone (Δ4-P), 17αa-hydroxyprogesterone (17-Δ4-P) and testosterone (T) concentrations were determined, and the histological state of the Leydig cells and seminiferous epithelium were evaluated. After 2 weeks of exposure to the short photoperiod, marked histological changes were evident in both testicular compartments, and a decline in the testicular T level was observed. The intratesticular concentrations of Δ5-P remained low and that of 17-Δ4-P declined during the first 2 weeks of exposure to the short photoperiod. After 4 and 6 weeks in the short photoperiod, spermatogenesis was virtually absent and the mean concentrations of all four steroids were very low, indicating a marked suppression of T synthesis. In voles subjected to the long photoperiod, there was an increase in Δ5-P, Δ4-P, and T levels as the testes developed. Despite considerable individual variation in testicular steroid concentrations, the relative amounts of the various steroids were similar after 4–6 weeks of exposure to long days, Δ5-P and 17-Δ4-P concentrations being lower than those of Δ4-P and T. These findings indicate that the enzymes catalyzing cholesterol side chain cleavage, C17-C20-lyase and/or 17αhydroxylase, may be rate limiting in the biosynthesis of T in this species. The results suggest that short photoperiods inhibit androgen synthesis in the bank vole by modifying cholesterol side chain cleavage, and possibly C17-C20-lyase and/or 17αhydroxylase activities in the testis.

Effect of photoperiod on the testicular steroidogenesis of the bank vole ( Clethrionomys glareolus, schreber): An in vitro study

Testicular minces from juvenile bank voles subjected to short (6L:18D, light on 0800 to 1400, Group S) and long (18L:6D, 0600–2400, Group L) photoperiods for 6 to 9 weeks were incubated (1 hr) with [4- 14C]pregnenolone (Δ 5P) and [4- 14C]dehydroepiandrosterone (DHA). The main metabolites formed were identified by thin-layer chromatography (TLC). In the presence of exogenous cofactors (NADPH/NADP 1.3 mmol/liter) [4- 14C]Δ 5P was almost totally metabolized in Group L testes and was mainly converted to androstenedione (Δ 4A; 36.9%), testosterone (T; 29.5%), and DHA (6.7%). In similar incubations with Group S testes no C 19-steroids were formed from [4- 14C]Δ 5P which was predominantly converted to progesterone (60.7%). A substantial portion (32.1%) of the substrate was not metabolized. When [4- 14C]DHA was incubated with exogenous cofactors it was mainly converted to Δ 4A (41.4%, Group S and 53.5%, Group L), T (37.7%, Group S and 36.1%, Group L), and dihydrotestosterone (DHT) (2.5%, Group L4 only). In Group S testes the substrate (DHA) was not utilized as effectively as in Group L (15.5 and 2.3% unmetabolized substrate, respectively). When exogenous cofactors were not added there was a marked decrease in substrate utilization in both groups. The results indicate that at least in vitro the testes of voles subjected to short photoperiods have a drastically reduced ability to synthesize such potent androgens as Δ 4A and T from exogenous [4- 14C]Δ 5P and that this incapability is largely due to a C 17-C 20-lyase and/or 17α-hydroxylase deficiency.