The effect of salinity and temperature on the larval development of clibanarius vittatus (Bosc) (crustacea: decapoda: diogenidae)

Clibanarius vitatus (Bosc) larvae were reared in twenty combinations of four salinities (15, 20, 25, and 30%) and five temperatures (15, 20, 25, 30 and 35%°C). No development was observed in any salinity at 15°C, but partial development occurred in all other test conditions. Metamorphosis to juvenile crabs was noted only at salinities of 25 and 30A% in combination with temperatures of 25 and 30°C. In general, development times were decreased at higher temperatures; no trend was evidence for salinity. Mortality of zoeae was usually highest at the time of the first molt and greatest overall mortality occurred during the megalopa stage prior to metamorphosis. Previous experiments (unpubl.) have shown that C. vittatus adults can tolerate temperature down to 5°C. It is suggested that geographic distribution of C. vittatus (Virginia, southward) is limited not by adult tolerances but by the inability iof the species to establish a breeding population. Larvae require two months at 25°C or above to metamorphose, and this condition is not met in areas north of Virginia.     

Effect of environmental embryonic temperature on larval development of Macrobrachium rosenbergii (De Man)

Berried females of Macrobrachium rosenbergii (De Man) from Anuenue stock were allowed to incubate their eggs at three different temperatures (25,29, and 31°C). The newborn larvae were reared in the laboratory from hatch through completion of the metamorphosis to postlarva in 30 combinations of temperature (22–34° C) and salinity (0–34 ppt). Survival and stage attainment rates were observed. Multiple linear regression analysis and response surface methodology were used to estimate the response of larvae to these different temperature and salinity combinations. Dissimilarities in the response of zoeae from the three egg incubation temperatures were found. Larvae from eggs incubated at 25° C during embryonic development showed tolerance to a broader range of temperature and salinity conditions than those incubated at 29 or 31 °C. The response also changed with the ontogeny of the larvae. The zoeae are considered to have undergone acclimation during embryonic development, thus eliciting a different response.     

Effects of temperature on growth and efficiency of food utilization in fifth-instar caterpillars of the tobacco hornworm, Manduca sexta

Fifth-instar larvae of Manduca sexta were reared from hatching on artificial diet at 15, 20, 25, 30 and 35°C. Total development time decreased with increasing temperature. Very few larvae (12%) survived at 15°C, so this temperature was not considered further. There was some mortality at 30°C (11%), and at 35°C (50%).The absolute rate of growth in the fifth instar was faster at 25 than at 20°C, but was similar at 25, 30 and 35°C. This was true both for caterpillars that were chronically exposed to experimental temperatures (i.e. since hatching) and for those acutely exposed (i.e. reared up to fifth instar at 25°C).There was a progressive decrease with higher rearing temperatures in both the initial and final sizes of chronically exposed fifth-instar larvae. Acutely exposed caterpillars matched for initial size showed smaller temperature related differences in final size. Because of these size differences there were differences in relative growth rate which did not reflect true differences in absolute growth rate.Total food consumed by chronically exposed caterpillars was greatest at the lowest temperature (20°C), and decreased progressively with increasing temperature. The absolute rate of food consumption increased from 20 to 25°C, but did not vary significantly between 25 and 35°C. Differences in the sizes of the insects at the different temperatures meant that there were differences among relative measures of consumption that did not reflect absolute food consumption.For chronically exposed caterpillars, none of the three usual indices of food conversion efficiency (AD, ECI and ECD) varied significantly with temperature between 20 and 35°C. This implies that the effects of temperature on metabolic costs are closely matched to food consumption.Oxygen consumption increased with temperature between 20 and 25°C but was temperature compensated between 25 and 35°C.These findings are discussed in terms of their implications for the optimal temperature for growth in Manduca.     

Temperature‐dependent development of the double‐spined spruce bark beetle Ips duplicatus (Sahlberg, 1836) (Coleoptera; Curculionidae)

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Temperature and salinity effects on the respiratory metabolism of the first zoeal stage of Macrobrachium holthuisi Genofre & Lobão (decapoda: Palaemonidae)

Oxygen consumption rates of stage I Macrobrachium holthuisi Genofre & Lobão zoeae were measured in 24 different temperature and salinity combinations using Cartesian diver microrespirometers. Metabolic rates varied little with salinity at 15°C while at 20°C a marked elevation occurred in 0 and 35‰ At 25°C, a slight elevation occurred in 0‰; rates remained constant, however, in the other salinities. At 30°C, respiratory rates were similar to those recorded at 25°C except for decreases at 0 and 28‰ salinity. Q₁₀ values in the different salinities were usually highest between 15 and 20°C. Statistical analyses showed that while both temperature, salinity and their interaction significantly influenced larval respiratory rates, temperature had the more pronouced effect. Larval metabolism is salinity independent over the salinity range encountered in the larval biotope (7–21‰) at temperatures of 15–30°C.     

Susceptibility of Heliothis zea larvae to Nomuraea rileyi at various temperatures

Laboratory studies were conducted to determine the susceptibility of various larval instars of Heliothis zea to different spore doses of Nomuraea rileyi at constant and variable temperatures. The fungus was most effective at 20° and 25°C, with a mortality of 80% and 71%, respectively. At 15°C the disease progressed very slowly with larval mortality occurring in 12–28 days post-treatment. Conversely, at temperature ranges above 15°C, the mortality of the larvae occurred in 6–12 days. Three different combinations of variable temperatures included 20–30°, 25–30°, and 20–35°C, but mortality did not exceed 46%. Larvae in the third to fifth instars were more susceptible to infection than were those in the first and second instars.     

The effect of temperature on the population growth potential of Culex annulirostris Skuse (Diptera: Culicidae)

The effect of temperature on the population growth potential of Culex annulirostris was determined by studying larval growth rate and survival at seven temperatures between 10 and 40°C, and adult survival and fecundity at 20, 25 and 30°C. All larvae died at Wand 40°C; survival was greatest at 25°C. The period for complete juvenile development ranged from 8.57 days (35°C) to 37 days (15°C). Development from egg to adult required 196 day-degrees above 9.7°C with incubation temperatures between 15 and 30°C. Population growth potential was positive at 20, 25 and 30°C, greatest at 25°C, but negative at 15°C. The minimum temperature for population growth was estimated as 17.5°C.     

Life table and heat tolerance of Acyrthosiphon pisum (Hemiptera: Aphididae) in subtropical Taiwan

The effect of temperature on the life table of Acyrthosiphon pisum reared on Pisum sativum was evaluated under laboratory conditions using temperatures of 10, 15, 20, 25, 30, and 35°C. The development time of juvenile A. pisum decreased with increasing temperature (from 21.3 days at 10°C to 4.7 days at 35°C). Adult longevity also decreased with increasing temperature (from 53.2 days at 10°C to 2.3 days at 35°C). Interestingly, 70% and 25% of A. pisum nymphs reared at 30°C and 35°C, respectively, successfully developed into adults. These temperatures have previously been considered unsuitable for A. pisum development. However, adult aphids reared at 30°C and 35°C failed to reproduce. Linear regression analysis revealed that the lower development threshold of A. pisum was 153.1 degree‐days above 1.9°C. Maximal average reproductive capability was observed at 10°C for A. pisum adults, with each adult producing more than 120 nymphs. The intrinsic rate of increase (r_m) of A. pisum increased from 0.124/day at 10°C to 0.337/day at 25°C, whereas opposite trends were observed for the net reproductive rate (R₀) and the mean generation time (GT). At 20°C and 25°C, the intrinsic rate of increase of A. pisum was significantly higher than at 10°C and 15°C (P < 0.0001), indicating that 20°C and 25°C are within the optimal range for the growth of A. pisum, and that 30°C is beyond the upper threshold limit for reproduction, which involves a temperature range that is narrower than that of the survival range (upper limit is unknown, but above 35°C).     

Factors influencing the duration and termination of diapause in the Indian-meal moth, Plodia interpunctella

The influence of environmental factors on the duration of diapause in Plodia interpunctella larvae reared in short photoperiods at 20 or 25° C was examined, Diapause terminated most rapidly in long photoperiods at high temperatures. Pupation was more delayed, and mortality was higher, in darkness than in the presence of light. At 20° C, LD 16: 8 hastened diapause termination only slightly in unchilled samples. Chilling for 10 weeks at 10° C greatly reduced the duration of diapause at 20 or 25° C in constant darkness, and rendered LD 16:8 effective in terminating diapause at 20° C. In addition, the quite short duration of diapause under LD 16:8 at 25° C was further shortened by holding for 6–10 weeks at 10° C or below, or by holding in an outbuilding during winter. Holding diapausing larvae at 15 or 20° C proved less effective. Temperature rises from 20 to 25 or 30° C proved effective in terminating diapause. In one stock, the temperature at which diapause was induced influenced its subsequent duration. Lighting conditions during induction had less influence on duration than had temperature, and no difference occurred between pupation times of larvae reared at different population densities, Under all conditions tested, diapause lasted longer in a recently collected field stock than in a laboratory stock.     

Effect of temperature on germination,growth, and infectivity of the mosquito pathogen Tolypocladium cylindrosporum (deuteromycotina; hyphomycetes)

The mosquito pathogen Tolypocladium cylindrosporum was examined with regard to its response to temperature. Similar temperature ranges were found for growth, germination, and infectivity of blastospores and conidia. Germination occurred at 8° and 33°C but not at 6° and 35°C. Optimal germination and growth was noted between 24° and 27°C for both spore types. Infectivity of blastospores and conidia at different temperatures was examined by exposing L₂Aedes sierrensis larvae to concentrations of 5 × 10⁵ blastospores/ml or 5 × 10⁶ conidia/ml. Larvae were incubated at 12°, 15°, 25°, and 30°C. Infection occurred at all temperatures tested with LT₅₀ values ranging from 22.7 days (12°C) to 5.6 (25°C) days for conidia and 4.7 days (12°C) to 0.6 day (25°C) for blastospores. These results confirmed earlier findings that blastospores infected and killed host larvae more rapidly than conidia and suggested that this difference is largely due to the more rapid germination rate of blastospores. These experiments demonstrated that T. cylindrosporum can be active against mosquito larvae over a broad range of temperatures encompassing both the cold-water habitat of certain temperate mosquito species as well as the habitat of tropical vector species.     

Thermal limits for the establishment and growth of populations of the invasive apple snail <Emphasis Type="Italic">Pomacea canaliculata</Emphasis>

Pomacea canaliculata is a South American freshwater snail considered as one of the world’s worst invasive alien species. A temperature of around 25 °C has usually been considered to be optimal for rearing P. canaliculata. Nevertheless, snails have not been reared under a wide range of temperatures to reveal the optimum for performance in terms of population increase. We investigated the effect of temperature on growth, survival and reproduction, estimating demographic parameters for P. canaliculata in the wide range of temperatures at which these snails are active (15–35 °C). No reproductive activity was evidenced for the snails reared at 15 °C, probably explained by the small sizes attained at this temperature. Temperatures above 25 °C did not promote a significant acceleration in growth so higher temperatures will not result in a reduction in time to reach maturity. In fact, snails from 25 and 30 °C began reproduction at the same age. We report here for the first time a detrimental effect of high temperatures that provoked a significant decrease in the contribution of snails to the next generation: the viability of eggs from the snails reared at 30 °C was very low and the snails exposed to a constant water temperature of 35 °C were unable to produce eggs. Our findings reveal a new environmental constraint that could be a determinant of the range limits of this species in invaded regions, especially during the coming decades, anticipating the scenario predicted from global warming.     

Effects of host stages and temperature on population parameters of Oomyzus sokolowskii, a larval-pupal parasitoid of Plutella xylostella

Oomyzus sokolowskii is alarval-pupal parasitoid of diamondback moth, Plutella xylostella. In a host stage preference test, the parasitoid parasitised all larval and pupal stages, but exhibited a strong preference for larvaeover prepupae or pupae, and did not show a preference among the larval instars. At 25°C, the developmental time, number and sex ratio of offspring per host pupa, and successful parasitism did not differ significantly among parasitoids reared from host larvae of different instars, indicating similar host suitability between larvae of different instars. Mean developmental times from egg to adult at 20, 22.5, 25, 30, 32.5, and 35°C were 26.5,21.0, 16.0, 12.7, 11.9 and 13.4 days, respectively. The favourable temperature range for development, survival, and reproduction of the parasitoid was 20--30°C. However, wasps that developed and emerged at a favourable temperature could parasitise effectively at 32--35°C for 24 hours. Life-fertility table studies at 20, 25, and 30°C showed that each female wasp on average parasitised 3.1, 13.2, 6.8 larvae of diamondback moth and produced 20.5, 92.1, 50.4 offspring, respectively, during her lifetime. The highest intrinsic rate of natural increase (r _m) of 0.263 female/day was reached at 30°C as a result of the short mean generation time at this temperature compared to that at 20 and 25°C, suggesting that the parasitoid had the highest potential for population growth at relatively high temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Proximate control of diel vertical migration in Phyllosoma larvae of the Caribbean spiny lobster Panulirus argus

Phyllosoma larvae of the spiny lobster Panulirus argus undergo diel vertical migration (DVM), in which they are at depth during the day and nearer the surface at night. This study determined the visual spectral sensitivity of Stage I larvae and investigated whether light plays a proximate role in DVM as an exogenous cue and as an entrainment cue for an endogenous rhythm in vertical migration. Under constant conditions, larvae have a circadian rhythm (24.5-h period) in vertical swimming that resulted in a twilight DVM pattern. The behavioral response spectrum and electroretinogram recording indicated two photoreceptor spectral classes with maxima at 360 and 486 nm. When stimulated in an apparatus that simulated the underwater angular light distribution, dark-adapted larvae showed only positive phototaxis, with a threshold intensity of 1.8 × 10(13) photons m(-2) s(-1) (3.0 × 10(-5) μmoles photons m(-2) s(-1)). They have an avoidance response to predator shadows in which they descend upon sudden decreases in light intensity of more than 69%. When stimulated with relative rates of decrease in light intensity as occur at sunset they ascended, whereas they descended upon relative rates of light intensity increase as occur at sunrise. Thus, the DVM pattern is controlled by both an endogenous circadian rhythm in swimming and behavioral responses to light at sunrise and sunset.     

Inhibition of the accumulation of viral polypeptides in the densonucleosis virus-infected midgut of the silkworm,Bombyx mori,reared at a supraoptimal temperature

Effect of a supraoptimal temperature on the accumulation of viral polypeptides in the midgut was examined by immunoblot analysis in the larvae of the silkworm, Bombyx mori, infected with Bombyx densonucleosis virus type 2. In the larvae reared continuously at 25°C, viral polypeptides were first detected in the midgut at 2 days postinfection (pi) and in the feces at 4 days pi. When the larvae inoculated per os with the virus for 24 hr at 25°C were immediately shifted to 35°C, there were no detectable viral polypeptides in both the midgut and feces throughout the experiment. In the infected larvae shifted from 25° to 35°C at 48 hr pi, viral polypeptides preexisting in the midgut decreased to an undetectable level within 48 hr after the temperature shift, and no viral polypeptides were detected thereafter. Viral polypeptides in the feces of these larvae became detectable at 48 hr (4 days pi) after the temperature shift, as in the larvae at 25°C, and disappeared by 96 hr (6 days pi). These results indicate that a supraoptimal temperature inhibits accumulation of viral polypeptides in the midgut. It is likely that inhibited production of viral polypeptides rather than enhanced discharge of the infected midgut cells is responsible for the inhibited accumulation of viral polypeptides in the midgut at 35°C.     

Influence of temperature on larval survival, development, and respiration inChasmagnathus granulata (Crustacea, Decapoda)

Larvae of an estuarine grapsid crabChasmagnathus granulata Dana 1851, from temperate and subtropical regions of South America, were reared in seawater (32/%.) at five different constant temperatures (12, 15, 18, 21, 24 °C). Complete larval development from hatching (Zoea I) to metamorphosis (Crab I) occurred in a range from 15 to 24 °C. Highest survival (60% to the first juvenile stage) was observed at 18 °C, while all larvae reared at 12 °C died before metamorphosis. The duration of development (D) decreased with increasing temperature (T). This relationship is described for all larval stages as a power function (linear regressions after logarithmic transformation of bothD andT). The temperature-dependence of the instantaneous developmental rate (D ⁻¹) is compared among larval stages and temperatures using the Q₁₀ coefficient (van't Hoff's equation). Through all four zoeal stages, this index tends to increase during development and to decrease with increasingT (comparing ranges 12–18, 15–21, 18–24 °C). In the Megalopa, low Q₁₀ values were found in the range from 15 to 24 °C. In another series of experiments, larvae were reared at constant 18 °C, and their dry weight (W) and respiratory response to changes inT were measured in all successive stages during the intermoult period (stage C) of the moulting cycle. Both individual and weight-specific respiration (R, QO ₂) increased exponentially with increasingT. At each temperature,R increased significantly during growth and development through successive larval stages. No significantly differentQO ₂ values were found in the first three zoeal stages, while a significant decrease with increasingW occurred in the Zoea IV and Megalopa. As in the temperature-dependence ofD, the respiratory response to changes in temperature (Q₁₀) depends on both the temperature range and the developmental stage, however, with different patterns. In the zoeal stages, the respiratory Q₁₀ was minimum (1.7–2.2) at low temperatures (12–18 °C), but maximum (2.2–3.0) at 18–24 °C. The Megalopa, in contrast, showed a stronger metabolic response in the lower than in the upper temperature range (Q₁₀=2.8 and 1.7, respectively). We interpret this pattern as an adaptation to a sequence of temperature conditions that should typically be encountered byC. granulata larvae during their ontogenetic migrations: hatching in and subsequent export from shallow estuarine lagoons, zoeal development in coastal marine waters, which are on average cooler, return in the Megalopa stage to warm lagoons. We thus propose that high metabolic sensitivity to changes in temperature may serve as a signal stimulating larval migration, so that the zoeae should tend to leave warm estuaries and lagoons, whereas the Megalopa should avoid remaining in the cooler marine waters and initiate its migration to wards shallow coastal lagoons.     

Contribution to the biology of the citrus bud mite, Aceria sheldoni (Ewing) (Acarina: Eriophyidae)*

In laboratory studies mites of Aceria sheldoni were reared on citrus fruit peels, beneath coloured cellophane hoods, to cater for their thigmotaxis and sensitivity to light of particular wave lengths. Hatching was most successful at 25°C and 98% r.h. but was reduced by low humidities (35–40% r.h.), when abnormal dwarf larvae emerged. The eggs hatched in 3–14 days; the length of a generation (egg to egg) was 12–33 days. The threshold of embryonic development was 9 °C and that for completion of the life cycle, egg to egg, was 12.5 °C. The average number of eggs laid per female was six (4–8). It increased to twelve (5–19) if the mite, during its larval stages, had been fed on buds. The vitality of both the eggs and the mature mites was tested by exposure to extreme low and high temperatures (below 0 °C, 39 °C): 50% of mites died after 30 min at 30 °C; 50% died after 30 min at –15 °C or lower.     

Black soldier fly (Diptera: Stratiomyidae) larval heat generation and management

Mass production of black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), larvae results in massive heat generation, which impacts facility management, waste conversion, and larval production. We tested daily substrate temperatures with different population densities (i.e., 0, 500, 1000, 5000, and 10 000 larvae/pan), different population sizes (i.e., 166, 1000, and 10 000 larvae at a fixed feed ratio) and air temperatures (i.e., 20 and 30 °C) on various production parameters. Impacts of shifting larvae from 30 to 20 °C on either day 9 or 11 were also determined. Larval activity increased substrate temperatures significantly (i.e., at least 10 °C above air temperatures). Low air temperature favored growth with the higher population sizes while high temperature favored growth with low population sizes. The greatest average individual larval weights (e.g., 0.126 and 0.124 g) and feed conversion ratios (e.g., 1.92 and 2.08 g/g) were recorded for either 10 000 larvae reared at 20 °C or 100 larvae reared at 30 °C. Shifting temperatures from high (30 °C) to low (20 °C) in between (∼10-d-old larvae) impacted larval production weights (16% increases) and feed conversion ratios (increased 14%). Facilities should consider the impact of larval density, population size, and air temperature during black soldier fly mass production as these factors impact overall larval production.     

Adaptive significance of hatching rhythms and dispersal patterns of estuarine crab larvae: avoidance of physiological stress by larval export?

Estuarine crabs commonly display two larval dispersal patterns in which larvae are either exported from or retained within estuaries. The semiterrestrial fiddler crab Uca minax (LeConte, 1855) hatches on nocturnal spring high tides in the upper estuary and larvae are rapidly transported downstream. The mud crab Rhithropanopeus harrisii (Gould, 1841) hatches on nocturnal high tides of any amplitude and larvae are retained behaviorally in the upper estuary throughout development. If larvae are exported from the estuary to avoid environmental stress, then exported larvae should be less tolerant of high temperatures and low salinities than retained larvae. Larvae of these two species of estuarine crabs were hatched at 20‰ and 25 °C and subjected to salinities of 0, 5, 10,20, and 30‰, temperatures of 25 and 35 °C, and exposure times of 2, 6, 12, and 48 h. Larvae of both species reared at 30 or 20‰ survived well, while those reared in fresh water all died within 2 h regardless of temperature. Mud crab larvae reared at 5 and 10‰ survived better at the lower temperature (25 °C), higher salinity, and shorter exposure times. There was no significant effect of temperature or salinity on the survival of fiddler crab larvae, although survival decreased with increasing exposure time. Thus, the hypothesis that fiddler crab larvae are exported into stable coastal waters to reduce physiological stress is not supported. However, fiddler crab larvae may have evolved to be very tolerant of extreme temperature and salinity stress because they, unlike mud crabs, often release their larvae into shallow creeks. Most fiddler crab larvae are released on nocturnal spring high tides, which facilitates dispersal from tidal creeks. However, freshwater runoff and heat transferred from the marsh surface to flooding waters may still create stressful conditions for larvae soon after they are released. Larval release on spring high tides may facilitate dispersal from tidal creeks.     

Temperature-dependent age-specific demography of grapevine moth (Lobesia botrana) (Lepidoptera: Tortricidae): jackknife vs. bootstrap techniques

Grapevine moth, Lobesia botrana (Lep. Tortricidae) is a key pest of grape in Iran and other vineyards of the world. In this study, eight constant rearing temperatures (5, 10, 15, 20, 25, 30, 32 and 35 ± 1 °C) along with 60 ± 10% RH and a 16:8 (L:D) h photoperiod were chosen for demographic studies of the grapevine moth. Immature stages were unable to develop when reared at 5 and 35 °C, and the progeny moths were unable to successfully mate at 10, 15 and 32 °C. The overall developmental time of juveniles decreased at 30 °C (from 320.7 ± 3.4 d at 10 °C to 34.2 ± 0.2 d) followed by an increase to 42.5 ± 0.6 d at 32 °C. Based on values of the stable population growth parameters, the temperature of 25 °C was found to be optimal for propagation of grapevine moth. The highest values of the intrinsic rate of increase, gross and net reproductive rates were 0.0719 d?^?1, 55.5 and 23 females per generation, respectively, at 25 °C. Since jackknife and bootstrap estimates of mean and standard error were mainly similar, both methods may equally be used for uncertainty estimates. Our data suggest that cold storage of grapes will help to control grapevine moth infestations and damage. In many grape growing regions of Iran, the first generation is expected to cause damage. It is expected since our reproductive life table analysis suggests that the hot summer temperatures may restrict pest development during subsequent generations.     

Seed germination temperatures of eight Mexican Agave species with economic importance

The genetic diversity of Agave plants is threatened by clonal commercial reproduction and climatic change. Sexual reproduction is uncommon and research on seed germination is scarce. The present study evaluated the seed germination of Agave lechuguilla, Agave striata, Agave americana var. marginata, Agave asperrima, Agave cupreata, Agave duranguesis, Agave angustifolia ssp. tequilana and Agave salmiana at constant temperatures (10, 15, 20, 25, 30, 35 and 40°C). Initial imbibition (after the first 12 h) was significantly variable among species, positively correlated with seed weight (r = 0.6560, P < 0.001) and increased with temperature (from 35% at 10°C to 66% at 40°C). Temperature affected maximum imbibition (83–150%) for A. asperrima, A. lechuguilla, A. salmiana and A. striata; other species averaged 110%. Most germination kinetics best fitted a logistic model, whereas only a few treatments fit a Weibull model. The time to germination onset diminished (P < 0.05) from 125–173 h at 15°C to 68–84 h at 25°C, and then ascended to 84–196 h at 35°C. The mean germination rate and seed germination percentage after 312 h peaked at 25°C (0.50–0.95% seeds/h and 85–99%, respectively) and fell (P < 0.05) to near zero at 10 and 40°C. Temperatures of 10, 35 and 40°C were partially lethal to A. asperrima, A. duranguensis and A. salmiana seeds. The time to germination onset, seed germination percentage after 312 h and mean germination rate are best described by a Gaussian distribution, with its optimum at approximately 25°C. Thus, optimum temperatures are related to the ecological characteristics of each species area.