自愿转轮运动对长爪沙鼠身体组成的影响

为研究自愿转轮运动对长爪沙鼠(Meriones unguiculatus)体重的影响,在以前工作的基础上,分析了自愿转轮运动及8周后体重、胴体重和体水,以及心、肝、脾、肺、肾、性腺(睾丸或卵巢)、消化道、腓肠肌、比目鱼肌、肾周脂肪垫和肠系膜脂肪垫等器官及组织的重量变化。结果发现,自愿转轮运动条件下长爪沙鼠胴体湿重、体水和心、肝、脾、肾、腓肠肌、消化道等器官重量增加。自愿转轮运动对比目鱼肌和器官脂肪垫重量的影响存在性别差异。自愿转轮运动使雄性长爪沙鼠器官的脂肪垫重量增加,但雌性降低;对雄性长爪沙鼠比目鱼肌重量没有影响,但雌性增加。以上结果表明,自愿转轮运动促进了长爪沙鼠的体重增长,改变了长爪沙鼠的身体组成。内脏器官和体水重量的增加是体重增加的主要原因。     

Cellularity of organs in mature rams of different breeds

The relative importance of cell number and cell size in determining the mass of 16 organs and tissues in mature rams of six different breeds was studied through estimation of organ deoxyribonucleic acid (DNA) content. The mean fleece-free empty body weight (FFEBW) ranged from 54.6 +/- 0.3 kg for Camden Park Merinos to 76.7 +/- 1.6 kg for Strong Wool Merinos. For all organs, mass increased with FFEBW, but the relationship was significant across all sheep for only eight organs (blood, kidney, liver, abomasum, vastus lateralis muscle, skin, perirenal fat and triceps muscle). There were significant differences between breeds in the mass of 11 organs. With four (heart, rumen reticulum, small intestine and testicular fat) this difference was independent of breed differences in FFEBW, whereas with another four (kidney, abomasum, vastus lateralis muscle and skin), it was closely related to FFEBW. Breed differences in the mass of the remaining three organs (blood, liver and perirenal fat) were partly related to FFEBW and partly breed specific. Blood mass increased with FFEBW across all animals, but, within a breed, it declined as FFEBW increased. The increase in the mass of perirenal fat with FFEBW was significantly greater within a breed than between breeds. Cell number increased significantly with the mass of all organs except blood and brain. There were between-breed differences in the number of cells in seven organs (liver, heart, rumen reticulum, abomasum, small intestine, vastus lateralis muscle and skin), which, except for heart, were attributable to between-breed differences in organ mass. With heart, the increase in cell number with organ mass within a breed was greater than across all breeds. Cell size was significantly related to organ mass only with vastus lateralis muscle, spleen, perirenal fat and liver. The relationship for vastus lateralis muscle and spleen was negative, indicating that cells were smaller in larger organs. There were differences between breeds in cell size for heart, vastus lateralis and triceps muscles. These differences for heart and triceps muscle were breed specific, whereas for vastus lateralis muscle it was attributed to breed differences in organ weight. There was a 30-fold range in mean cell size across organs, with adipose tissue having the largest cells, muscle tissue intermediate and visceral tissues the smallest. In general, organ mass is positively related to FFEBW. Cell number, not cell size, is largely responsible for differences in organ mass between mature sheep of different breeds.     

四川荥经县赤腹松鼠体重及脏器湿重的性别与季节差异

以2015年1月至12月捕自四川荥经县的310只成体赤腹松鼠(Callosciurus erythraeus,雄鼠174只,雌鼠136只)为研究对象,分析了其体重及7种内脏器官湿重的性别和季节差异,以及妊娠对内脏器官湿重的影响。1)雌、雄鼠的体重无性别和季节差异。2)心湿重雌、雄鼠差异显著,春季雄性大于雌性,夏季相反;肝、脾、肺和肾的湿重均无性别差异。3)肝湿重夏、冬季高于春、秋季;脾湿重秋季高于冬季和春季;肺湿重春季最高,夏季最低;肾湿重冬、春季高于夏季;心湿重雄鼠秋季高于夏、冬季,雌鼠夏、秋季高于冬季;睾丸和子宫湿重都在春季最高,秋季最低。4)妊娠鼠肝、肺和肾湿重均高于未妊娠鼠。结果表明,随着季节更替赤腹松鼠的体重维持稳定,雌、雄鼠心湿重差异显著,且器官湿重表现出了一定的弹性,这可能与雌、雄鼠的繁殖状态及季节性环境的多样性变化有关。     

The relationship between organ weights and body weights, facial dimensions, and dental dimensions in a population of olive baboons (Papio cynocephalus anubis)

Questions concerned with the relationship between organ weights and body weight on an intraspecific level are best answered by using a sample of animals collected in the wild from a single locale during a single season. The organ weights and body weights for this study were obtained from the necropsy reports prepared in the field (Athi Plain, Kenya) by H. C. McGill, Jr. on 36 adult animals (18 males and 18 females). Dental and facial measurements were taken by M.I. Siegel. In order to avoid erroneous results produced by statistical treatment of combined sex samples of sexually dimorphic species, data on the sexes were analyzed separately. Means and standard deviations are reported for selected organ weights and body dimensions (heart, lung, liver, spleen, kidney, adrenal, brain, and pancreas weights, crown–rump length, crown–heel length, head circumference, chest circumference, and body weight). All of the above measures were significantly (p<0.05) different between the sexes. Logarithms of these measures were significantly correlated with the logarithm of body weight in males for heart, lung, liver, spleen, kidney, and adrenal weights, crown–heel length, and head and chest circumference, and in females for crown–heel length, heart, liver, and kidney weights. Partial correlational analysis, removing the effects of body size (weight), showed mostly negative correlational relationships between dental and visceral dimensions. Most of the correlations between facial and visceral dimensions were negative. Allometric equations were calculated for the dental, facial, and visceral dimensions versus body weight, and are compared with prior published results.     

The effect of brain size evolution on feeding propensity,digestive efficiency,and juvenile growth

One key hypothesis in the study of brain size evolution is the expensive tissue hypothesis; the idea that increased investment into the brain should be compensated by decreased investment into other costly organs, for instance the gut. Although the hypothesis is supported by both comparative and experimental evidence, little is known about the potential changes in energetic requirements or digestive traits following such evolutionary shifts in brain and gut size. Organisms may meet the greater metabolic requirements of larger brains despite smaller guts via increased food intake or better digestion. But increased investment in the brain may also hamper somatic growth. To test these hypotheses we here used guppy (Poecilia reticulata) brain size selection lines with a pronounced negative association between brain and gut size and investigated feeding propensity, digestive efficiency (DE), and juvenile growth rate. We did not find any difference in feeding propensity or DE between large‐ and small‐brained individuals. Instead, we found that large‐brained females had slower growth during the first 10 weeks after birth. Our study provides experimental support that investment into larger brains at the expense of gut tissue carries costs that are not necessarily compensated by a more efficient digestive system.     

Body burden of hexachlorbenzene in suckling rats and its effects on various organs and on liver porphyrin accumulation.

The hexachlorobenzene (HCB) and porphyrin accumulation in the ograns of 18-day-old Wistar rats, whose mothers were fed a diet containing 80 ppm HCB, were studied. Among the organs examined, the highest HCB residue was in the liver larger than kidney larger than or equal to lung larger than brain larger than spleen larger than heart. The porphyrin level in the liver of the HCB-treated. On the contrary, the weights of the kidney, brain, spleen and heart were significantly reduced. Sex did not influence the organ weight except that of the brain. The results suggested that accumulation of HCB in different organs and porphyrin in the liver of suckling Wistar rats was about equal for the males and females.     

NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase: immunochemical characterization of the lung enzyme from pregnant rabbits

A polyclonal antibody was produced in guinea pig against the lung NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) purified from pregnant rabbits. Western blot analysis demonstrated that the protein identified by this antibody in the 105,000g supernatant fraction of lung tissue from pregnant rabbits had a molecular mass of 30 kDa and comigrated with the purified PGDH. The specific activity of the lung PGDH in pregnant rabbits (25- to 28-day gestations) was 36.7 nmol NADH formed/min/mg protein compared to 0.3 nmol NADH formed/min/mg protein in nonpregnant rabbits. Although the PGDH activity in the lung cytosol of nonpregnant rabbits was inhibited by the anti-lung PGDH antibody, the 30-kDa protein was not detected by Western blot analysis. An examination of this 30-kDa protein during the gestational period indicated that the protein was present after 10 days and the amount of the protein increased from Day 10 to Day 28. This increase in the immunochemically reactive protein correlated with the marked increase in PGDH specific activity between 10 and 28 days. An immunochemically reactive protein also was observed in the ovary of 25- to 28-day pregnant rabbits and the specific activity of the ovary PGDH was 19.3 nmol NADH formed/min/mg protein. Only trace levels of the PGDH activity were detected in the ovaries of nonpregnant rabbits. A 30-kDa protein was not detected by the anti-rabbit lung PGDH in brain, kidney, bladder, uterus, liver, and heart tissue of pregnant or nonpregnant rabbits. When rabbit or human placental cytosol was examined with the anti-rabbit lung PGDH only faint 30-kDa bands were observed by Western blot analysis. A monoclonal antibody prepared against human placental PGDH did not recognize the 30-kDa band in the pregnant rabbit lung. Localization studies indicated a marked increase in immunochemical staining in pulmonary epithelial cells of pregnant rabbits as compared to nonpregnant rabbits. Lung epithelial cells but not endothelial cells were identified as containing the PGDH.     

Multi-element analysis of trace element levels in human autopsy tissues by using inductively coupled atomic emission spectrometry technique (ICP-AES).

Autopsy tissue samples from the brain front lobe, cerebellum, heart, kidney (cortex and medulla), liver, pancreas, spleen and ovary were analysed for AL, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, Sr and Zn in 30 (17 women and 13 men) subjects ranging in age from 17 to 96 years at Haukeland University Hospital in Norway. The tissues were selected from macroscopically normal organs and samples were handled according to guidelines recommended to avoid contamination in the pre-analytical phase. Concentration of the trace elements were determined by the inductively coupled plasma atomic emission spectrometry technique (ICP-AES). In most tissues the concentrations of the essential trace elements followed the order Fe> Zn> Cu> Mn> Se> Cr> Co except in the ovary where Se was higher than Mn. The liver was the major site of deposition for Co, Cu and Mn as well as the spleen for Co, brain front lobe for Cu and pancreas for Mn. Ba, Sr and Ni built up in the ovary foLLowed by the kidney. Older subjects accumulated Ba and Sr in most tissues, whereas Al accumulated in the kidney cortex and Cd in the brain cerebellum. Generally males had higher concentrations of trace elements in the different tissue sampLes than females with the exception of Mn in the brain front lobe and heart and Sr in the liver. ICP-AES is a useful method to assess the concentration and the profiLe of trace elements in human autopsy tissues.     

Ontogenetic shifts and spatial associations in organ positions for snakes

Snakes possess an elongated body form and serial placement of organs which provides the opportunity to explore historic and adaptive mechanisms of organ position. We examined the influence of body size and sex on the position of, and spatial associations between, the heart, liver, small intestine, and right kidney for ten phylogenetically diverse species of snakes that vary in body shape and habitat. Snake snout–vent length explained much of the variation in the position of these four organs. For all ten species, the position of the heart and liver relative to snout–vent length decreased as a function of size. As body size increased from neonate to adult, these two organs shifted anteriorly an average of 4.7% and 5.7% of snout–vent length, respectively. Similarly, the small intestine and right kidney shifted anteriorly with an increase in snout–vent length for seven and five of the species, respectively. The absolute and relative positioning of these organs did not differ between male and female Burmese pythons (Python molurus). However, for diamondback water snakes (Nerodia rhombifer), the liver and small intestine were more anteriorly positioned in females as compared to males, whereas the right kidney was positioned more anteriorly for males. Correlations of residuals of organ position (deviation from predicted position) demonstrated significant spatial associations between organs for nine of the ten species. For seven species, individuals with hearts more anterior (or posterior) than predicted also tended to possess livers that were similarly anteriorly (or posteriorly) placed. Positive associations between liver and small intestine positions and between small intestine and right kidney positions were observed for six species, while spatial associations between the heart and small intestine, heart and right kidney, and liver and right kidney were observed in three or four species. This study demonstrates that size, sex, and spatial associations may have potential interacting effects when testing evolutionary scenarios for the position of snake organs.     

Body and organ mass in agouti and non-agouti deer mice (Peromyscus maniculatus).

Body, adrenal, brain, heart, liver, kidney, spleen and testis masses were determined for agouti and non-agouti deer mice (Peromyscus maniculatus gracilis) of both sexes. Body mass was highest for non-agouti females and lowest for agouti females; and sex differences in body mass were significant for agouti, but not non-agouti, deer mice. Adrenal, brain and liver masses were similar between color morphs; heart mass was greater in agouti males; and kidney, spleen and testis masses were all significantly greater for non-agouti deer mice. Splenomegaly in non-agouti deer mice was prominent, as spleens of non-agouti deer mice were 50% larger than those of agouti animals. Sex differences varied across organs and color morphs. For both color morphs, males had heavier adrenals and brains, whereas females had heavier livers and spleens. Kidney and heart mass was greater for female non-agouti deer mice, but for agouti animals, heart mass was greater in males and kidney mass differed little between the sexes. For both color morphs, testes and spleen mass was altered by photoperiod in 72 deer mice housed under short- or long-day conditions and the effect was stronger in non-agouti animals. This is the first report of splenomegaly and sex-specific body mass differences associated with the non-agouti allele.     

Cloning of brain aromatase gene and expression of brain and ovarian aromatase genes during sexual differentiation in genetic male and female Nile tilapia Oreochromis niloticus

A brain aromatase gene was identified from the Nile tilapia Oreochromis niloticus. The cDNA sequence of this gene differed from that of the ovarian aromatase gene previously reported from this species. Tissue specific expression for both brain and ovarian aromatase genes was examined in the tissues of adult tilapia. Brain aromatase mRNA was expressed in the brain, kidney, eye, ovary, and testis, but not in the liver and spleen. Ovarian aromatase mRNA was expressed in the brain, spleen, ovary, and testis but not in the eye, kidney, and liver. Differential aromatase gene expression between the sexes was investigated in all-male (XY) and all-female (XX) groups of tilapia fry from fertilisation throughout the sexual differentiation period. Semi-quantitative RT-PCR analysis revealed that the initiation of expression of both aromatase genes lay between 3 and 4 dpf (days post fertilisation) in both sexes. The level of brain aromatase mRNA gradually increased throughout the period studied with little difference between the sexes. This contrasted with marked sexual dimorphism of ovarian aromatase mRNA expression. In females, the expression level was maintained or increased gradually throughout ontogeny, while the level in males was dramatically down-regulated between 15 and 27 dpf. Subsequently, the level of ovarian aromatase mRNA expression fluctuated slightly in both sexes, with the expression in females always being higher than in males. These findings clearly suggest that ovarian aromatase plays a decisive role in sexual differentiation in this species and that this is achieved by down-regulation of the expression of this gene in males. Mol. Reprod. Dev. 59: 359-370, 2001.     

Spontaneous calcification in F344/Slc and F344/JCL rats

F344/Slc and F344/JCL rats 2 years of age were histologically examined for the incidence and distribution of calcification. In the male rats of both strains, calcification was observed in the testis, lung, brain, kidney, heart, aorta, cornea, prostate and seminal vesicle respectively. In the female F344/JCL rats, calcification appeared in the kidney, lung, cornea, brain, stomach, ovary and heart. Among these of both sexes, the lung was one of the most affected organs for calcification. On the other hand, calcification in the kidney was more severe and frequent in the females than in the males, suggesting that the sex may be one of enhancing factors for calcification.     

Fmr1基因敲除小鼠脏器重量和脏器系数的比较分析

目的通过对Fmr1基因敲除小鼠雌雄两性和FVB小鼠的脏器重量和脏器系数进行比较分析,了解其脏器重量的差异,探讨Fmr1基因对动物生长发育等方面的影响。方法分别测定Fmr1基因敲除小鼠雌雄两性和FVB小鼠内脏器官的绝对重量和脏器系数,并进行统计学处理和分析。结果相同年龄的Fmr1基因敲除小鼠雄性的体重、心、肺、肝和肾的绝对重量均极显著的大于雌性（P〈0.01）。雌雄间脏器系数除肾脏（P〈0.05）和脑（P〈0.01）外,其余无显著差异。与FVB小鼠比较,Fmr1基因敲除小鼠心脏较轻（P〈0.01）,肾脏（P〈0.01）、体重和脑较重（P〈0.05）。脏器系数肾脏较大（P〈0.01）,心脏（P〈0.01）、脑和脾（P〈0.05）较小。结论Fmr1基因可影响动物的某些脏器重量和脏器系数。     

Effect in rats of simultaneous prenatal exposure to ochratoxin A and aflatoxin B1. II. Histopathological features of teratological anomalies induced in fetuses

The histopathological features of various abnormalities induced by different doses of ochratoxin A (OA), aflatoxin B1 (AFB1), and their combination in rat fetuses were studied. The pregnant Wistar rats were orally treated during 6-15 gestation days with different doses of OA (0.125, 0.25, 0.50, 0.75 mg/kg), AFB1 (0.125, 0.25, 0.50, 1.00 mg/kg), and their combination (0.125+0.125, 0.25+0.50, 0.50+0.25 mg/kg). The fetal sections passing through liver, kidney, brain, heart, and eyes were selected from the fetuses given visceral examination representing each litter. The selected sections were processed for paraffin embedding, stained with H and E, and examined by light microscopy. The histological examination of the fetal organs revealed that OA, AFB1, and their combination treatments caused variable changes in internal organs. In the case of OA, the incidence of pathological lesions liver, kidney, brain, and eye lesions was high, whereas in AFB1 treatment, liver, brain, kidney, and heart were affected. The incidence of heart lesions, especially valvular defects, increased in the combination groups. Bile duct proliferation/new bile duct formation, defective ossification of cranial bones, exposure of the brain to the exterior, hypoplasia of cerebellum, and retinal defects observed in OA treatment and spinal cord defects in addition to liver, kidney, and brain changes observed in AFB1 were less severe in the combination groups. The present study indicates that the occurrence of brain, kidney, and liver lesions in combination treatment was less than in either individual treatment suggesting antagonism of OA-induced teratogenic effects by AFB1. The indication of subtle lesions due to an interference with normal development and arrest of differentiation in various internal organs observed in the present study suggests that microscopic examination of the tissues can provide additional useful information to a developmental toxicity study.     

Generalized accumulation of neutral glycosphingolipids with G M2 ganglioside accumulation in the brain

Analyses have been made of glycosphingolipids from visceral organs and brain of a patient with an unusual lipid storage disorder diagnosed initially as classical Tay-Sachs disease. Levels of the lipids from fresh-frozen sections of gray and white matter, kidney, spleen, liver, and heart from this patient were compared with those of normal juvenile controls, and the fatty acid composition of accumulated glycosphingolipids was compared with reference compounds. This patient was found to have abnormally high concentrations of a globoside in liver, kidney, and spleen, asialo G(M2) ganglioside in brain and liver, and G(M2) ganglioside in the brain. On the basis of these findings along with the clinical manifestations of Tay-Sachs disease with visceral involvement (hepatosplenomegaly) and demonstration of total deficiency of both A and B components of beta-N-acetylhexosaminidase activity, this glycosphingolipidosis is the same as two previously reported cases of G(M2) gangliosidosis with globoside accumulation and total beta-N-acetylhexosaminidase deficiency.     

Mercury 203 distribution in pregnant and nonpregnant rats following systemic infusions with thiol-containing amino acids

Near-term pregnant (gestational day 17) and nonpregnant Long-Evans female rats were continuously infused into the external jugular vein with 0.1 mmole/hour L-cysteine, 0.1 mmole/hour L-leucine, or saline. At 24, 48, and 72 hours, 50 mumole/hour [203Hg]-MeHgCl was administered over 1 hour. Total 203Hg body burden, brain, kidney, liver, and blood 203Hg concentrations were determined at 96 hours by gamma scintillation spectrometry. Despite significantly greater 203Hg whole body retention in the pregnant animals 203Hg concentrations in blood, brain, kidney, and liver were higher in nonpregnant rats. In addition, brain 203Hg concentrations in both pregnant and virgin rats were significantly higher in L-cysteine-treated rats compared with controls. These results suggest that the fetus may act as a "sink" for MeHg, thus decreasing 203Hg concentrations in maternal blood, brain, kidney, and liver. Furthermore, the data indicate that brain uptake of methylmercury in both pregnant and nonpregnant rats is enhanced by chronic L-cysteine infusion, lending support to the hypothesis that methylmercury in the rat may be translocated across the blood-brain barrier by the neutral amino acid carrier transport system.     

Digestive and metabolic flexibility allows female degus to cope with lactation costs

Lactation is the most energetically demanding period in the life cycle of female mammals, and its effects on digestive flexibility and the size of internal organs have been extensively studied in laboratory mice and rats since the early 1900s. However, there have been only two studies on this topic for wild rodent species. Here, we analyzed digestive flexibility--that is, changes in gut content, activity of digestive enzymes, and gut morphology--during lactation in the caviomorph rodent Octodon degus. In addition, we evaluated changes in the size of other internal organs and analyzed their relationship with the resting metabolic rate. We found that gut content, the dry masses of digestive chambers, the dry mass of liver, and resting metabolic rate were greater in lactating than in nonbreeding control females. In contrast, fat stores were higher in control subjects. Maltase and aminopeptidase-N specific activity did not change with lactation, and both enzymes had greater activity values in the middle portion of the small intestine. Thus, our data indicate that the previously reported increase in food assimilation that occurs during lactation in O. degus is related to a mass increase in several central organs, leading, in turn, to higher energetic costs. Fat stores may help to mitigate these costs, but, as expected for small animals, to a limited extent. Our study reveals a complex interplay among energy acquisition, storage, and expenditure processes that ultimately determine an organism's fitness.     

Covariation between brain size and immunity in birds: implications for brain size evolution

Parasitism can negatively affect learning and cognition, setting the scene for coevolution between brain and immunity. Greater susceptibility to parasitism by males may impair their cognitive ability, and relatively greater male investment in immunity could compensate for greater susceptibility to parasites, in particular when males have a relatively large brain. We analysed covariation between relative size of immune defence organs and brain in juvenile and adult birds. The relative size of the bursa of Fabricius and the spleen in adults covaried positively with relative brain size across bird species. The relative size of these two immune defence organs covaried with sex differences in relative size of the brain, indicating that the relationship between immune defence and brain size was stronger for males. In contrast, liver and heart size or sexual size dimorphism in size did not covary with immune defence. Thus, species in which males have relatively large brains also have relatively large immune defence organs.     

Impact of Obstructive Sleep Apnea on Liver Fat Accumulation According to Sex and Visceral Obesity

Rationale

Associations between obstructive sleep apnea (OSA) and liver fat accumulation have been frequently investigated because both morbidities are common. Visceral fat was reported to be closely related to OSA and liver fat accumulation. Recently, sex differences in the association between OSA and mortality have gained much attention.

Objectives

To investigate the associations among OSA, liver fat accumulation as determined by computed tomography, and visceral fat area and their sex differences.

Methods

Studied were 188 males and 62 females who consecutively underwent polysomnography and computed tomography.

Results

Although the apnea-hypopnea index was positively correlated with liver fat accumulation in the total males, none of the OSA-related factors was independently associated with liver fat accumulation in either the total male or female participants in the multivariate analyses. When performing subanalyses using a specific definition for Japanese of obesity or visceral obesity (body mass index (BMI) ≥25 kg/m² or visceral fat area ≥100 cm²), in only males without visceral obesity, percent sleep time with oxygen saturation <90%, in addition to BMI, insulin resistance, and serum triglyceride values, was independently correlated with liver fat accumulation (R² = 15.1%, P<0.001). In males, percent sleep time of oxygen saturation <90% was also a determining factor for alanine aminotransferase values regardless of visceral fat area. In contrast, OSA was not associated with liver fat accumulation or alanine aminotransferase values in females whether or not visceral obesity was absent.

Conclusions

Sex differences in the visceral fat-dependent impact of OSA on liver fat accumulation existed. Although the mechanisms are not known and ethnic differences may exist in addition to the specific criteria of visceral obesity in Japan, the treatment of male patients with OSA might be favorable from the viewpoint of preventing liver fat accumulation and liver dysfunction even in patients without obvious visceral fat accumulation.     

Comparative support for the expensive tissue hypothesis: Big brains are correlated with smaller gut and greater parental investment in Lake Tanganyika cichlids

The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the energetic requirements of encephalization are suggested to impose considerable constraints on brain size evolution. Three main hypotheses concerning how energetic constraints might affect brain evolution predict covariation between brain investment and (1) investment into other costly tissues, (2) overall metabolic rate, and (3) reproductive investment. To date, these hypotheses have mainly been tested in homeothermic animals and the existing data are inconclusive. However, there are good reasons to believe that energetic limitations might play a role in large-scale patterns of brain size evolution also in ectothermic vertebrates. Here, we test these hypotheses in a group of ectothermic vertebrates, the Lake Tanganyika cichlid fishes. After controlling for the effect of shared ancestry and confounding ecological variables, we find a negative association between brain size and gut size. Furthermore, we find that the evolution of a larger brain is accompanied by increased reproductive investment into egg size and parental care. Our results indicate that the energetic costs of encephalization may be an important general factor involved in the evolution of brain size also in ectothermic vertebrates.