Significant Adaptive Changes Research Articles

Adaptive changes in speech perception

The influence of individual characteristics on speech perception was studied in relation to weather conditions. Parameters of emotional and color images for 12 masculine names and 6 vowel sounds were used for experimental models. In the period of 1 February – 7 June 2013, 20 women and 6 men, all residents of St.Petersburg, were filling in a special form, estimating the offered parameters of the emotional image by a 5-score scale and registering their color associations. The data collected during 23 days of the experiment were matched with the indices of local and cosmic weather and compared with individual characteristics: gender, the diurnal chronotype by A.A. Putilov («skylark», «dove», «owl»). Mathematical processing included t-criterion, the Fisher criterion and correlation analysis. Significant and valid adaptive changes in the parameters of images of sounds and names were detected in relation to the part of day, season and weather conditions (p≤0.05÷0.001). Characteristics of the pronunciation of a certain vowel or a name influenced their perception under different environmental conditions. There were significant differences in the studied parameters of speech perception between men and women, which correspond to the higher sensitivity of male organisms to environmental conditions, and between people with different diurnal chronotypes (p≤0,05÷0,001).

Statistical analysis of quiet stance sway in 2-D

Subjects exposed to a rotating environment that perturbs their postural sway show adaptive changes in their voluntary spatially directed postural motion to restore accurate movement paths but do not exhibit any obvious learning during passive stance. We have found, however, that a variable known to characterize the degree of stochasticity in quiet stance can also reveal subtle learning phenomena in passive stance. We extended Chow and Collins (Phys Rev E 52(1):909-912, 1995) one-dimensional pinned-polymer model (PPM) to two dimensions (2-D) and then evaluated the model's ability to make analytical predictions for 2-D quiet stance. To test the model, we tracked center of mass and centers of foot pressures, and compared and contrasted stance sway for the anterior-posterior versus medio-lateral directions before, during, and after exposure to rotation at 10 rpm. Sway of the body during rotation generated Coriolis forces that acted perpendicular to the direction of sway. We found significant adaptive changes for three characteristic features of the mean square displacement (MSD) function: the exponent of the power law defined at short time scales, the proportionality constant of the power law, and the saturation plateau value defined at longer time scales. The exponent of the power law of MSD at a short time scale lies within the bounds predicted by the 2-D PPM. The change in MSD during exposure to rotation also had a power-law exponent in the range predicted by the theoretical model. We discuss the Coriolis force paradigm for studying postural and movement control and the applicability of the PPM model in 2-D for studying postural adaptation.

An Unusual Suspect in Cocaine Addiction

Development of drug addiction is extremely complex, but its initiation can be as simple as the flip-flop of glutamatergic receptor subtypes triggered by an "unusual" type of NMDA receptors, as suggested by Yuan et al. (2013) in this issue of Neuron.

The Social Climate and Peer Interaction on Outdoor Courses

This two-study report investigates achievement goal theory in the social domain to gain greater understanding of how the social climate of outdoor courses relates to peer interactions. In Study 1, we used mixed methods to examine how adolescents experienced the social climate of weeklong outdoor courses and how those perceptions related to peer interactions. In Study 2, a larger sample from longer courses was used to assess perceptions of social climate and how those perceptions relate to peer interactions. Significant adaptive changes in peer interactions were predicted by cohesion and previous experience. Results also indicate the meaningfulness of the instructor role. These studies contribute to knowledge of how the social climate and social motivation interact on outdoor programs.

Reduction of Intestinal Electrogenic Glucose Absorption After Duodenojejunal Bypass in a Mouse Model

The role of intestinal glucose absorption in reducing glycemic levels after duodenojejunal bypass (DJB) is unclear. We hypothesized that DJB surgery decreases intestinal electrogenic glucose absorption by sodium glucose co-transporter 1 (SGLT1), leading to decreased glucose absorption and reduced blood glucose. Six groups of C57/BL6 mice were studied (n = 6 each) 2weeks, 1month, and 2months after DJB or sham surgery. Daily weight and food intake were measured for 1month and an oral glucose tolerance test was performed 2months after surgery. Electrogenic glucose absorption was quantified in an Ussing chamber according to the sodium-dependent increase of short-circuit current (Isc). Intestinal morphology was assessed by hematoxylin and eosin staining. Expression of SGLT1 was determined by quantitative PCR and Western blotting. The DJB mice lost weight compared with the sham group and exhibited significant adaptive changes, with increased villus height, crypt depth, and villus surface area. Oral glucose absorption was significantly reduced in the DJB mice compared with the sham group. Glucose-induced Isc was significantly lower in the DJB mice than in the sham mice 1 and 2months after surgery, indicating that SGLT1 activity was reduced after DJB. Transcript levels and protein abundance of SGLT1 after DJB were also decreased compared with the sham group. DJB surgery reduced intestinal glucose absorption by reducing the activity and expression of the glucose transporter SGLT1, which represents a potential therapeutic target for patients with diabetes.

Indications of phenotypic plasticity in moulting birds: captive geese reveal adaptive changes in mineralisation of their long bones during wing moult

Bone is continually undergoing cycles of apposition and resorption referred to as adaptive remodelling. We tested the hypothesis that captive moulting Barnacle Geese (Branta leucopsis) would show adaptive bone mineralisation during the flightless period of their annual flight feather moult, despite having never flown. The three leg bones showed selective changes in mineralisation in terms of mass and mineral content, while the wing bones did not change in mass or mineral content. The tibia/fibula was the only bone to also undergo significant changes in mass, increasing as moult progressed then decreasing significantly towards the end of moult. This was not a response to changing body mass. Instead, we propose that this is a response to the requirement for increased strength brought about by the significant increase in the force producing muscles that attach to the tibia. The femur and tarsometarsus showed the opposite trend, with mineral content decreasing significantly during mid-moult before increasing again at the end. These changes were also independent of changing body mass, suggesting instead that the calcium, or rather calcium derivatives, were mobilised for feather regrowth. This study demonstrates significant and selective adaptive natural changes in bone mass and mineralization that have not been previously demonstrated. That they should also occur in captive birds which show a decrease in locomotion during the wing moult period, suggests a high endogenous capacity for these changes.

Decreased reuptake of dopamine in the dorsal striatum in the absence of alpha-synuclein

The presynaptic protein alpha-synuclein (α-syn) plays a role in dopaminergic neurotransmission in the nigrostriatal dopaminergic system. Mutations in this protein have been linked to pathogenesis of Parkinson's disease. However, the details of regulation of dopamine homeostasis by α-syn and its molecular targets are generally unknown. We investigated the effect of α-syn deletion on striatal dopaminergic homeostasis. Two α-syn deficient mouse lines, one carrying a spontaneous deletion of α-syn locus and the other a transgenic α-syn knockout, were used in the study. Stimulated and basal extracellular dopamine levels were determined in the dorsal striatum by in vivo voltammetry and in vivo microdialysis, respectively. Dopamine transporter expression was studied by immunohistochemistry. Stimulated dopamine overflow and basal extracellular dopamine levels were higher in mice lacking α-syn with a concomitant decrease in dopamine transporter expression and reuptake in the dorsal striatum. We show that α-syn deletion produces significant adaptive changes in the striatal dopaminergic system via modulation of reuptake.

The influence of nutrients, biliary-pancreatic secretions, and systemic trophic hormones on intestinal adaptation in a Roux-en-Y bypass model

Purpose The signals that govern the upregulation of nutrient absorption (adaptation) after intestinal resection are not well understood. A Gastric Roux-en-Y bypass (GRYB) model was used to isolate the relative contributions of direct mucosal stimulation by nutrients, biliary-pancreatic secretions, and systemic enteric hormones on intestinal adaptation in short bowel syndrome. Methods Male rats (350-400 g; n = 8/group) underwent sham or GRYB with pair feeding and were observed for 14 days. Weight and serum hormonal levels (glucagon-like peptide-2 [GLP-2], PYY) were quantified. Adaptation was assessed by intestinal morphology and crypt cell kinetics in each intestinal limb of the bypass and the equivalent points in the sham intestine. Mucosal growth factors and expression of transporter proteins were measured in each limb of the model. Results The GRYB animals lost weight compared to controls and exhibited significant adaptive changes with increased bowel width, villus height, crypt depth, and proliferation indices in the alimentary and common intestinal limbs. Although the biliary limb did not adapt at the mucosa, it did show an increased bowel width and crypt cell proliferation rate. The bypass animals had elevated levels of systemic PYY and GLP-2. At the mucosal level, insulin-like growth factor-1 (IGF-1) and basic fibroblast growth factor (bFGF) increased in all limbs of the bypass animals, whereas keratinocyte growth factor (KGF) and epidermal growth factor (EGF) had variable responses. The expression of the passive transporter of glucose, GLUT-2, expression was increased, whereas GLUT-5 was unchanged in all limbs of the bypass groups. Expression of the active mucosal transporter of glucose, SGLT-1 was decreased in the alimentary limb. Conclusions Adaptation occurred maximally in intestinal segments stimulated by nutrients. Partial adaptation in the biliary limb may reflect the effects of systemic hormones. Mucosal content of IGF-1, bFGF, and EGF appear to be stimulated by systemic hormones, potentially GLP-2, whereas KGF may be locally regulated. Further studies to examine the relationships between the factors controlling nutrient-induced adaptation are suggested. Direct contact with nutrients appears to be the most potent factor in inducing mucosal adaptation.

Microcephalin coordinates mitosis in the syncytialDrosophilaembryo

Microcephalin (MCPH1) is mutated in primary microcephaly, an autosomal recessive human disorder of reduced brain size. It encodes a protein with three BRCT domains that has established roles in DNA damage signalling and the cell cycle, regulating chromosome condensation. Significant adaptive evolutionary changes in primate MCPH1 sequence suggest that changes in this gene could have contributed to the evolution of the human brain. To understand the developmental role of microcephalin we have studied its function in Drosophila. We report here that Drosophila MCPH1 is cyclically localised during the cell cycle, co-localising with DNA during interphase, but not with mitotic chromosomes. mcph1 mutant flies have a maternal effect lethal phenotype, due to mitotic arrest occurring in early syncytial cell cycles. Mitotic entry is slowed from the very first mitosis in such embryos, with prolonged prophase and metaphase stages; and frequent premature separation as well as detachment of centrosomes. As a consequence, centrosome and nuclear cycles become uncoordinated, resulting in arrested embryonic development. Phenotypic similarities with abnormal spindle (asp) and centrosomin (cnn) mutants (whose human orthologues are also mutated in primary microcephaly), suggest that further studies in the Drosophila embryo may establish a common developmental and cellular pathway underlying the human primary microcephaly phenotype.

Horizontal Smooth Pursuit Adaptation in Macaques After Muscimol Inactivation of the Dorsolateral Pontine Nucleus (DLPN)

The smooth pursuit (SP) system can adapt its response to developmental changes, injury, and behavioral context. Previous lesion and single-unit recording studies show that the macaque cerebellum plays a role in SP initiation, maintenance, and adaptation. The aim of this study was to determine the potential role of the DLPN in SP adaptation. The DLPN receives inputs from the cortical SP system and delivers eye and visual motion information to the dorsal/ventral paraflocculus and vermis of the cerebellum. We studied SP adaptation in two juvenile rhesus monkeys (Macaca mulatta), using double steps of target speed that step- up (10-30 degrees/s) or step-down (25-5 degrees/s). We used microinjection of muscimol (<or=2%; 0.15 microl) to reversibly inactivate the DLPN, unilaterally. After DLPN inactivation, initial ipsilesional SP acceleration (first 100 ms) was significantly reduced by 47-74% (P < 0.01; unpaired t-test) of control values in the single-speed step-ramp paradigm. Similarly, ipsilesional steady-state SP velocity was also reduced by 59-78% (P < 0.01; unpaired t-test) of control values. Contralesional SP was not impaired after DLPN inactivation. Control testing showed significant adaptive changes of initial SP eye acceleration after 100 trials in either step-up or step-down paradigms. After inactivation, during ipsilesional SP, adaptation was impaired in the step-up but not in the step-down paradigm. In contrast, during contralesional tracking, adaptive capability remained in the step-down but not in the step-up paradigm. Therefore SP adaptation could depend, in part, on direction sensitive eye/visual motion information provided by DLPN neurons to cerebellum.

Exercise Associated Genes in Rat Colon Mucosa: Upregulation of Ornithin Decarboxylase-1

Epidemiology has revealed that physical activity is an important lifestyle factor that reduces the risk of colon cancer. However, the underlying mechanisms of this protective effect have so far not been defined. The aim of this study was to identify molecular targets of physical activity in rat colon mucosa by employing our voluntary exercise model. Twenty male rats underwent a 12-week exercise program, with 9 additional rats serving as a control group. Running distances, body weights and heart weights as measures of physical adaptations were recorded, and changes in mRNA steady-state levels of marker genes involved in vascularization (VEGF, HIF-1 alpha, ODC-1), apoptosis (Bcl-2, PPAR gamma) and prostaglandin synthesis (COX-2) were determined by qRT-PCR. The four housekeeping genes GAPDH, beta-actin, 18S and ALDA served as reference genes. Recorded running distances showed great inter-individual differences resulting in three different groups of low (L-EX, < 2629 m/night; n=5), moderate (M-EX, 3003 - 7458 m/night; n=10) and high (H-EX, > 8314 m/night; n=5) physical activity. The M-EX and H-EX group revealed significant (p<0.05) adaptive changes with an increase in heart mass per kg body weight and a decrease in mean body weight. Amongst the marker genes studied by mRNA expression analysis only ODC-1 appears to be differentially expressed. Its 1.8-fold increased steady-state mRNA level in the H-EX group suggests that synthesis of polyamines may be increased by physical activity. This new finding could provide a link between extensive physical activity and its protective effects on colon cancer development.

Adaptive changes of bifidobacteria in the presence of 5-fluorouracil

To observe the characteristics for the adaptive changes of bifidobacteria under the influence of 5-fluorouracil (5-FU). METHODS: The growth and morphological characteristics of bifidobacteria in the presence of 5-FU were acquired by drug-sensitivity test, gram stain and atomic force microscopic scan- ning as well as the identification of the 5-FU- resitant isolates.. RESULTS: In the presence of 5-FU, bifidobac- teria were lengthened with fewer ruptures, becoming filament-like, with a length of more than 10 μm. The bifidobacteria were ramose at both ends and the relative height was about 1 μm. The 5-FU-resistent bifidobacteria were also found within the inhibition zone. Given the normal growth conditions, the filament-like bifi - dobacteria restored to the normal growth again. CONCLUSION: 5-FU can directly influence the growth of bifidobacteria, whereas bifidobacteria exhibit significant adaptive changes to the action of 5-FU.

Self-Triggered Functional Electrical Stimulation During Swallowing

Hyolaryngeal elevation is essential for airway protection during swallowing and is mainly a reflexive response to oropharyngeal sensory stimulation. Targeted intramuscular electrical stimulation can elevate the resting larynx and, if applied during swallowing, may improve airway protection in dysphagic patients with inadequate hyolaryngeal motion. To be beneficial, patients must synchronize functional electrical stimulation (FES) with their reflexive swallowing and not adapt to FES by reducing the amplitude or duration of their own muscle activity. We evaluated the ability of nine healthy adults to manually synchronize FES with hyolaryngeal muscle activity during discrete swallows, and tested for motor adaptation. Hooked-wire electrodes were placed into the mylo- and thyrohyoid muscles to record electromyographic activity from one side of the neck and deliver monopolar FES for hyolaryngeal elevation to the other side. After performing baseline swallows, volunteers were instructed to trigger FES with a thumb switch in synchrony with their swallows for a series of trials. An experimenter surreptitiously disabled the thumb switch during the final attempt, creating a foil. From the outset, volunteers synchronized FES with the onset of swallow-related thyrohyoid activity (approximately 225 ms after mylohyoid activity onset), preserving the normal sequence of muscle activation. A comparison between average baseline and foil swallows failed to show significant adaptive changes in the amplitude, duration, or relative timing of activity for either muscle, indicating that the central pattern generator for hyolaryngeal elevation is immutable with short term stimulation that augments laryngeal elevation during the reflexive, pharyngeal phase of swallowing.

Exposure to Intermittent High Altitude Induces Different Changes in Adenylyl Cyclase Activity in Hearts of Young and Adult Wistar Rats

This study investigates changes of adenylyl cyclase activity in the heart of young and adult Wistar rats exposed to experimental conditions simulating high altitude hypoxia as a model for interpretation of some adaptive changes of adenylyl cyclase observed in human. The exposure of rats to intermittent high altitude (IHA) hypoxia (5000 m) showed significant adaptive changes. The right ventricular weight and the ratio of right/left ventricular weights of adult rats exposed to IHA were significantly increased when compared to appropriate controls; adaptive changes of cardiac adenylyl cyclase being dependent on the age of the animals. The isoprenaline‐stimulated activity was higher in the left than in the right ventricle, and in both ventricles it was higher in young rats than in adult rats. When compared to controls, isoprenaline stimulation was decreased in the right ventricles of adapted young rats and, by contrast, it was increased in the left ventricles of adapted adult rats. This decrease and increase of adenylyl cyclase activity evoked by isoprenaline was paralleled by forskolin‐induced adenylyl cyclase activity in these experimental groups. It seems therefore that the changes in the pattern of total adenylyl cyclase activity observed under IHA hypoxia may at least be partially explained by the changes of beta‐adrenergic receptor susceptibility following IHA hypoxia.

Thickness of the articular soft tissue of the temporal component in temporomandibular joints with and without disk displacement

Objective. The purpose of this investigation was to test the hypothesis that temporomandibular joint disk displacement is associated with significant functional adaptive changes of the articular soft tissue of the articular eminence. Study Design. Thirteen temporomandibular joint autopsy specimens with normal superior disk position and 12 with complete anterior disk displacement were cryosectioned, and sections were stained and photographed. At a magnification of ×20 the soft tissue was measured (1) at the inflection point, (2) on the posterior slope, (3) at the apex, and (4) on the anterior slope of the articular eminence. Results. Displacement of a deformed or nondeformed temporomandibular joint disk without perforation of the posterior disk attachment was associated with significantly increased thickness of the articulating soft tissue at the apex and on the posterior and anterior slopes of the articulating eminence. When disk displacement was associated with a perforation of the posterior disk attachment, the soft tissue was not significantly thicker than in joints with normal superior disk position. Conclusions. Increase in articulating soft tissue thickness is interpreted as an adaptive mechanism to maintain the condyle path and withstand excessive loading at interposition of the temporomandibular joint components. When the plasticity of the tissues is surpassed, the adaptation will be thwarted and replaced by tissue breakdown. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:20-26)

Changes in Intervertebral Disc Cross-Sectional Area With Bed Rest and Space Flight

We measured the cross-sectional area of the intervertebral discs of normal volunteers after an overnight rest; before, during, and after 5 or 17 weeks of bed rest; and before and after 8 days of weightlessness. This study sought to determine the degree of expansion of the lumbar discs resulting from bed rest and space flight. Weightlessness and bed rest, an analog for weightlessness, reduce the mechanical loading on the musculoskeletal system. When unloaded, intervertebral discs will expand, increasing the nutritional diffusion distance and altering the mechanical properties of the spine. Magnetic resonance imaging was used to measure the cross-sectional area and transverse relaxation time (T2) of the intervertebral discs. Overnight or longer bed rest causes expansion of the disc area, which reaches an equilibrium value of about 22% (range 10-40%) above baseline within 4 days. Increases in disc area were associated with modest increases in disc T2. During bed rest, disc height increased approximately 1 mm, about one-half of previous estimates based on body height measurements. After 5 weeks of bed rest, disc area returned to baseline within a few days of ambulation, whereas after 17 weeks, disc area remained above baseline 6 weeks after reambulation. After 8 days of weightlessness, T2, disc area, and lumbar length were not significantly different from baseline values 24 hours after landing. Significant adaptive changes in the intervertebral discs can be expected during weightlessness. These changes, which are rapidly reversible after short-duration flights, may be an important factor during and after long-duration missions.

Post-transcriptional control of plastid mRNA accumulation during adaptation of chloroplasts to different light quality environments.

The adaptation of germinating spinach seedlings to yellow and red light was studied and compared with plants grown in white light. Spinach chloroplasts isolated from cotyledons and leaves of yellow and white light-grown plants showed similar membrane structures and compositions, while chloroplasts from plants grown in red light have significant adaptive changes. Based on an equal amount of chlorophyll, these changes include a reduction in the number of photosystem I complexes, an increase of photosystem II antenna size, and an increased ratio of stacked to unstacked membranes in red light-adapted chloroplasts. The decrease in the number of photosystem I complexes per unit of chlorophyll in these chloroplasts was qualitatively correlated with an approximately 10-fold decrease in the level of the psaA mRNA encoding the photosystem I 65-kilodalton to 70-kilodalton chlorophyll apoprotein, as well as with a differential decrease in mRNA levels of other photosynthetic proteins. Light quality adaptations do not significantly affect the plastid to nuclear DNA ratio or the overall chloroplast transcription activity. The relative transcriptional activities of 10 plastid genes, as determined by run-on transcription assays, are similar in chloroplasts from cotyledons and leaves of plants grown under the three light qualities. Only the psaA gene shows a 30% to 40% decrease in transcription activity in chloroplasts of plants adapted to red light. This decrease in psaA transcription activity, however, cannot fully account for the decrease of its mRNA level. We conclude, therefore, that post-transcriptional mechanisms are primarily responsible for the control of differential chloroplast mRNA accumulation in light quality adaptations.

Indirect thermal selection in Drosophila melanogaster and adaptive consequences

Short-term indirect selection in Drosophila melanogaster for heat-sensitivity and heat resistance resulted in two strains, one heat sensitive and another heat resistant, and correlated responses were found for the rate of heat shock protein synthesis, behavioral patterns (asymmetrical sexual isolation) and fitness components (fecundity, fertility, viability, developmental time), as well as for several enzyme activities (MDH, G-6-PDH, ADH, ACHE). These responses associated with temperature selection may reflect the effects of differential inbreeding depression caused by homozygosity of temperature sensitive mutations with different pleiotropic effects. Selection even of a very short duration can induce significant adaptive and evolutionary changes.

Gastric stapling for morbid obesity: gastrointestinal response in a rat model

The adaptive response of the gastrointestinal tract to gastric stapling was studied in a Zucker (fafa) genetically obese rat model. The effects of gastric stapling in rats with a Roux-en-Y gastrojejunostomy were compared to Roux-en-Y and intact controls. Rats (225 to 275 g) were divided into three groups: group I (GI), Roux-en-Y, stapled, ad libitum fed; group II, Roux-en-Y, unstapled; and group III, intact (laparotomy only). Groups II and III were further subdivided into group IIA (GIIA) and group IIIA (GIIIA), pair-fed to GI; and group IIB (GIIB) and Group IIIB (GIIIB), fed ad libitum. All rats were fed a diet of liquid rat formula and rat food (50:50 cal ratio). After 2 wk rats were killed and the liver, pancreas, and stomach removed, weighed, and tissue taken for histology. The intestine was divided into three segments corresponding to the excluded segment (1, duodenum), transposed segment (2, jejunum), and ileal segment (3), with tissue taken for histology. Liver lipid, pancreatic amylase, serum amylase and gastrin, and intestinal mucosal protein and DNA were measured. Weight gain, g/14 days, was: GI, 24.1 ± 7.8; GIIA, 17.0 ± 2.0; GIIB, 42.6 ± 4.8; GIIIA, 17.6 ± 4.7; GIIIB, 54.6 ± 8.9. All rats were in positive N balance. Liver weight and lipid were similar in all groups. Pancreatic mass was significantly increased in all Roux-en-Y animals, while amylase activity per g tissue was significantly less than in intact animals. Stapled rats had atrophy of the glandular portion of the stomach, decreased stomach mucosal weight, and lower serum gastrin concentration compared with all other rats (p < 0.01). In stapled rats, segment weight and mucosal weight were lower in the excluded segment, and higher in the transposed segment, compared to all other rats. Tissue pathology was found only in stapled rats: gastric atrophy, focal fibrosis of gastric wall, peritonitis, minimal to mild multifocal hepatitis, and mild periductal fibrosis of the pancreas. There are significant early adaptive and pathological changes after gastric stapling in the rat.

Role of polyploidy in the evolution of fishes.

Polyploidy is not generally believed to have played a major role in the evolution of animals. This view has been fostered principally by G. L. Stebbins and M. J. D. White, both of whom as early as the 1940’s advocated that Polyploidy at best has played a secondary role in evolution; neither of them has substantially altered this view in recent years (1,2). Some of the arguments against the importance of Polyploidy are: (a) that the large amount of gene duplication in polyploids dilutes the effects of new mutations so significant adaptive changes are unlikely, (b) that Polyploidy in animals is restricted mainly to asexual forms which are evolutionary dead ends, and (c) the number of polyploid animals relative to diploids is small.