Visual acuity in the cathemeral strepsirrhine Eulemur macaco flavifrons

Studies of visual acuity in primates have shown that diurnal haplorhines have higher acuity (30–75 cycles per degree (c/deg)) than most other mammals. However, relatively little is known about visual acuity in non‐haplorhine primates, and published estimates are only available for four strepsirrhine genera (Microcebus, Otolemur, Galago, and Lemur). We present here the first measurements of visual acuity in a cathemeral strepsirrhine species, the blue‐eyed black lemur (Eulemur macaco flavifrons). Acuity in two subjects, a 3‐year‐old male and a 16‐year‐old female, was assessed behaviorally using a two‐alternative forced choice discrimination task. Visual stimuli consisted of high contrast square wave gratings of seven spatial frequencies. Acuity threshold was determined using a 70% correct response criterion. Results indicate a maximum visual acuity of 5.1 c/deg for the female (1718 trials) and 3.8 c/deg for the male (846 trials). These values for E. macaco are slightly lower than those reported for diurnal Lemur catta, and are generally comparable to those reported for nocturnal Microcebus murinus and Otolemur crassicaudatus. To examine ecological sources of variation in primate visual acuity, we also calculated maximum theoretical acuity for Cheirogaleus medius (2.8 c/deg) and Tarsius syrichta (8.9 c/deg) using published data on retinal ganglion cell density and eye morphology. These data suggest that visual acuity in primates may be influenced by activity pattern, diet, and phylogenetic history. In particular, the relatively high acuity of T. syrichta and Galago senegalensis suggests that visual predation may be an important selective factor favoring high visual acuity in primates. Am. J. Primatol. 71:343–352, 2009. © 2009 Wiley‐Liss, Inc.     

Hallucal grasping in Nycticebus coucang: further implications for the functional significance of a large peroneal process

Euprimate grasping feet are characterized by a suite of morphological traits, including an enlarged peroneal process on the base of the first metatarsal, which serves as the insertion site of the peroneus longus muscle. In prosimians, a large process has typically been associated with a powerful hallucal grasp via the contraction of the peroneus longus to adduct the hallux. Recent electromyography (EMG) studies have documented that peroneus longus does not contribute substantially to hallucal grasping in lemurids (Boyer et al., 2007). However, non-lemurid prosimians have a I-V opposable grasp complex that is morphologically different and phylogenetically more primitive than the I-II adductor grasp complex of the lemurids previously studied. Therefore, it is possible that peroneus longus did function during grasping in early euprimates, but lost this function in large-bodied lemurids. The present study tests the hypothesis that a large peroneal process is related to powerful grasping ability in primates displaying the more primitive I-V grasp complex. We use EMG to evaluate the recruitment of peroneus longus, other crural muscles, and adductor hallucis in static and locomotor grasping activities of the slow loris (Nycticebus coucang). Results show that peroneus longus is active during grasping behaviors that require the subject to actively resist inversion of the foot, and likely contributes to a hallucal grasp in these activities. Peroneus longus activity level does not differ between grasping and power grasping activities, nor does it differ between grasping and non-grasping locomotor modes. Conversely, the digital flexors and hallucal adductor are recruited at higher levels during power grasping and grasping locomotor modes. Consequently, we reject the hypothesis that an enlarged peroneal process represents an adaptation specifically to enhance the power of the I-V grasp, but accept that the muscle likely plays a role in adducting the hallux during grasping behaviors that require stabilization of the ankle, and suggest that further work is necessary to determine if this role is sufficient to drive selection for a large peroneal process.     

口服补液减轻40%血容量失血大鼠肠组织缺血性损伤

目的：研究口服葡萄糖-电解质液（GES）对大鼠40%血容量失血时肠组织缺血性损伤的影响。方法：雄性SD大鼠,用氯胺酮-速眠新Ⅱ肌注复合麻醉后,行右颈动脉插管。随机分为3组（n=24）：GES对照组（GES）,失血性休克组（HS）和失血性休克＋口服GES液组（HS＋GES）。GES组：不放血,手术后口服GES;HS和HS＋GES组按全身血容量的40%分两次间隔15min放血制作失血性休克模型。HS＋GES组于失血后0.5h、1h和6h分3次给予3倍失血量的GES灌胃。用激光多谱勒血流仪测定失血后2h、4h和24h肠组织血流量（IBF）后,处死动物后取肠组织检测二胺氧化酶（DAO）和Na^＋-K^＋-ATP酶活性,测定肠组织含水率（WG）,并做病理学检查。结果：HS＋GES组IBF和Na-K-ATP酶活性均显著高于HS组（P〈0.05）,但显著低于GES组（P〈0.05）;失血各组肠WG显著高于GES组（P〈0.05）,24h时HS＋GES组WG显著低于HS组（P〈0.05）;HS＋GES组24hDAO活性均显著高于HS组（P〈0.05）,但显著低于GES组（P〈0.05）;失血后24h病理检查HS＋GES组肠组织水肿和充血改变比HS组明显减轻。结论：口服GES液能显著增加大鼠失血性休克早期IBF,提高Na^＋-K^＋-ATP酶和DAO活性,减轻肠组织水肿和缺血性损伤。     

CYANOPHYTE AND CYANELLE DNA: A SEARCH FOR THE ORIGINS OF PLASTIDS1

Cyanophyte-like prokaryotes are widely presumed to be the progenitors of eukaryote plastids. A few rare protistan species bearing cyanophyte-like cyanelles may represent intermediate stages in the evolution of true organelles. Cyanophyte DNA disposition in the cell, so far as is known from electron microscopy, seems uniform within the group and distinctly different from the several known arrangements of DNA in plastids. Therefore a survey of representative cyanophytes and protistan cyanelles was undertaken to determine whether forms reminiscent of plastids could be found. DNA-specific fluorochromes were utilized, along with epifluorescent microscopy, to study the DNA arrangement in situ in whole cells. Only the endospore (baeocyte)-forming Cyanophyta contained more than one, centrally located DNA skein per cell, and then only for the period just preceding visible baeocyte formation. Such forms might, with modification, presage the “scattered nucleoid” DNA disposition found in plastids of several groups, including Rhodophytes, Cryptophytes, Chlorophytes and higher plants. The DNA arrangement in cyanelles of two protists, Cyanophora and Glaucocystis, appear different from each other and possibly related to, respectively, the cyanophytes Gloeobacter and Synechococcus. Cyanelles of the third protist, Glaucosphaera, like the cells of the unique prokaryote Prochloron, appear to have multiple sites of DNA, somewhat similar to those of the “scattered nucleoid” line of plastid evolution. No obvious precursor of the “ring nucleoid” or other types of plastid DNA conformation was found.     

An evaluation of the influence of environment and biogeography on community structure: the case of Holarctic mammals

Aim To evaluate the influence of environment and biogeographical region, as a proxy for historical influence, on the ecological structure of Holarctic communities from similar environments. It is assumed that similarities among communities from similar environments in different realms are the result of convergence, whereas their differences are interpreted as being due to different historical processes. Location Holarctic realm, North America and Eurasia above 25° N. Methods Checklists of mammalian species occurring in 96 Holarctic localities were collected from published sources. Species were assigned to one of 20 functional groups defined by diet, body size and three‐dimensional use of space. The matrix composed of the frequencies of functional groups in the 96 localities is used as input data in a correspondence analysis (CA). The localities are classified into nine groups according to Bailey's ecoregions (used as a surrogate of regional climate), and the positions of the communities in the dimensions of the CA are compared in relation to ecoregion and realm. Partial regression was used to test for the relative influence of ecoregion and realm over each dimension and to evaluate the effect of biogeographical realm on the variation in the factor scores of the communities of the same ecoregion. Results In some cases, mammalian communities from areas with similar regional climates exhibit convergence in community structure, irrespective of the biogeographical realm where they are located. However, all of them are clearly subdivided into Nearctic and Palearctic subsets. Differences in the composition of the regional pools only partially explain differences in local communities between realms. Main conclusions Holarctic mammalian communities from regions with widely different climates differ in ecological structure irrespective of their biogeographical location. On the other hand, the structures of Nearctic and Palearctic communities from regions of similar climate radically differ in some features. Thus, although present climatic conditions influence community structure, contingent historic processes associated with each region also play a major role in determining community structure.     

Numbers of pink sugarcane mealy bug, Saccharicoccus sacchari (Cockerell) (Hemiptera: Pseudococcidae), differ within seasons and among regions and stages of the sugarcane crop cycle

Abstract  The pink sugarcane mealy bug (PSMB; Saccharicoccus sacchari ) is widespread on sugarcane globally. PSMB infest above-ground storage tissue as it develops, feeding on phloem and producing exudate. It is not known, however, whether the level of infestations is the same in different sugar growing regions, or how population size varies year to year within a region. Field surveys of the number of nodes infested were conducted over five seasons in three mill-regions in northern Australia (Macknade, Kalamia and Marian) on plant and ratoon crops. The pattern of infestation was very similar across seasons (only in 1 year of very low rainfall was the increase in population delayed). In all three regions the proportion of nodes infested was similar but reached the maximum 1 month later in the Marian region compared with the Kalamia and Macknade regions. The Kalamia region was distinguished by the rapid decline in the number of nodes infested down to a very low level by March. In the Macknade region mealy bugs persisted at higher levels than the other two regions. The PSMB infestation started earlier and was much greater in ratoon crops than plant crops throughout the sampling period. The differences were more pronounced in the Macknade and Marian districts. These observations provide a firm basis from which future strategies to control PSMB can be developed.     

Evolution of eye size and shape in primates

Strepsirrhine and haplorhine primates exhibit highly derived features of the visual system that distinguish them from most other mammals. Comparative data link the evolution of these visual specializations to the sequential acquisition of nocturnal visual predation in the primate stem lineage and diurnal visual predation in the anthropoid stem lineage. However, it is unclear to what extent these shifts in primate visual ecology were accompanied by changes in eye size and shape. Here we investigate the evolution of primate eye morphology using a comparative study of a large sample of mammalian eyes. Our analysis shows that primates differ from other mammals in having large eyes relative to body size and that anthropoids exhibit unusually small corneas relative to eye size and body size. The large eyes of basal primates probably evolved to improve visual acuity while maintaining high sensitivity in a nocturnal context. The reduced corneal sizes of anthropoids reflect reductions in the size of the dioptric apparatus as a means of increasing posterior nodal distance to improve visual acuity. These data support the conclusion that the origin of anthropoids was associated with a change in eye shape to improve visual acuity in the context of a diurnal predatory habitus.