Scapula form and locomotion in chimpanzee evolution

A number of primatologists have followed Coolidge (Am. J. Phys. Anthropol. 18:1–57, 1933) in suggesting that 1) there are significant shape differences in scapula form between pygmy and common chimpanzees, 2) scapulae of P. paniscus resemble those of hylobatids more than do those of P. troglodytes, and 3) therefore pygmy chimpanzees may exhibit a greater component of arm-swinging and other arboreal behaviors than common chimpanzees. In this paper I utilize a comparative analysis of ontogenetic allometries of linear dimensions to determine shape differences in the scapulae of adult pygmy and common chimpanzees and to clarify size-related changes in shape resulting from ontogenetic scaling, i.e., the differential extension of common patterns of growth allometry. Results demonstrate that the scapulae of adult P. paniscus are relatively narrower (in a direction approximately perpendicular to the scapula spine) than those of P. troglodytes, supporting Coolidge's original claim. The allometric analysis further demonstrates, however, that the two chimpanzee species exhibit ontogenetic scaling for all proportions of the scapula examined. Thus, adult pygmy chimpanzees have the scapula proportions observed in small adult and subadult P. troglodytes of comparable scapula size. The implications of this finding for past claims concerning differences in locomotor behavior between the species are discussed. This work lends additional support to previous studies that have demonstrated a high frequency of ontogenetic scaling within the genus Pan and a pedomorphic or juvenilized morphology in the pygmy chimpanzee.     

External morphology of limb development in the amphipod <Emphasis Type="Italic">Orchestia cavimana</Emphasis> (Crustacea,Malacostraca, Peracarida)

The external morphology of limb development in Orchestia cavimana is examined by scanning electron microscopy and fluorescence staining from the appearance of the first limb buds until hatching. As other amphipods, O. cavimana undergoes direct development and the degree of segmental differentiation shows a more or less continual decrease in anteroposterior direction. Limbs form ventrally as small buds, which elongate and divide into podomeres early in development. This early subdivision largely corresponds with the limb segmentation of the hatchling. When the post-naupliar limbs start to develop, the germ band begins to split into two halves along the midline, so that the trunk limbs transiently occupy a very dorsolateral position. After the germ band has closed again, the differentiation into the characteristic amphipodan tagmata (cephalothorax, pereon, pleon) takes place and the limb podomeres lose their round-shape. The late embryo is covered by a so-called intermediate cuticle, which is formed after an embryonic moult and shed after hatching. The early development of O. cavimana reveals the Anlage of a vestigial seventh pleonic segment that is assumed to belong to the ground pattern of malacostracans, but is retained as a free, limbless segment only in adult Leptostraca. A transient subdivision of the proximal segment of the pleopods suggests the occurrence of a coxa and a basis in these limbs. The mandible attains its upright, adult position via a characteristic bending process that is strikingly similar to that in Archaeognatha (Insecta).     

Resource partitioning through oceanic segregation of foraging juvenile southern elephant seals (<Emphasis Type="Italic">Mirounga leonina</Emphasis>)

In highly dynamic and unpredictable environments such as the Southern Ocean, species that have evolved behaviors that reduce the effects of intra-specific competition may have a selective advantage. This is particularly true when juveniles face disadvantages when foraging due to morphological or physiological limitation, which is the case for many marine mammals. We tracked the at-sea movements of 48 juvenile southern elephant seals (Mirounga leonina) between the ages of 1 and 4 years from the population at Macquarie Island using locations derived from recorded light levels. There were significant differences in the total amount of the Southern Ocean covered by the different age-groups. The younger seals used a smaller area than the older seals. On average, the younger individuals also made more trips to sea than the older seals and did not travel as far on each trip. Females spent more time at sea than males and there were no significant differences between the total areas used by male and females. In summary, younger seals remained closer to the island at all times, and they spent more time in more northerly regions that older seals. These differences in behavior created temporal and spatial segregation between juveniles of different ages. Therefore, we suggest that these temporal and spatial separations help to avoid intra-specific competition for resources on land, space on beaches, and at-sea foraging areas. Such modifications of haul-out timing and behavior enable them to exploit a patchy and unpredictable environment.     

Identification of a novel estrogen-sulfating cytosolic SULT from zebrafish: molecular cloning, expression, characterization, and ontogeny study

By searching the expressed sequence tag database, a zebrafish cDNA encoding a putative cytosolic sulfotransferase (SULT) was identified. Sequence analysis indicated that this zebrafish SULT belongs to the SULT1 cytosolic SULT gene family. The recombinant form of this novel zebrafish SULT, expressed using the pGEX-2TK expression system and purified from transformed BL21 (DE3) Escherichia coli cells, displayed sulfating activities specifically for estrone and 17beta-estradiol among various endogenous compounds tested as substrates. The enzyme also exhibited sulfating activities toward some xenobiotic phenolic compounds. This new zebrafish SULT showed dual pH optima, at 6.5 and 10-10.5, with estrone or n-propyl gallate as substrate. Kinetic constants of the sulfation of estrone, 17beta-estradiol, and n-propyl gallate were determined. Developmental stage-dependent expression experiments revealed a significant level of expression of this novel zebrafish estrogen-sulfating SULT at the beginning of the hatching period during embryogenesis, which continued throughout the larval stage onto maturity.     

Sexual differentiation in three unconventional mammals: spotted hyenas, elephants and tammar wallabies

The present review explores sexual differentiation in three non-conventional species: the spotted hyena, the elephant and the tammar wallaby, selected because of the natural challenges they present for contemporary understanding of sexual differentiation. According to the prevailing view of mammalian sexual differentiation, originally proposed by Alfred Jost, secretion of androgen and anti-Mullerian hormone (AMH) by the fetal testes during critical stages of development accounts for the full range of sexually dimorphic urogenital traits observed at birth. Jost's concept was subsequently expanded to encompass sexual differentiation of the brain and behavior. Although the central focus of this review involves urogenital development, we assume that the novel mechanisms described in this article have potentially significant implications for sexual differentiation of brain and behavior, a transposition with precedent in the history of this field. Contrary to the "specific" requirements of Jost's formulation, female spotted hyenas and elephants initially develop male-type external genitalia prior to gonadal differentiation. In addition, the administration of anti-androgens to pregnant female spotted hyenas does not prevent the formation of a scrotum, pseudoscrotum, penis or penile clitoris in the offspring of treated females, although it is not yet clear whether the creation of masculine genitalia involves other steroids or whether there is a genetic mechanism bypassing a hormonal mediator. Wallabies, where sexual differentiation occurs in the pouch after birth, provide the most conclusive evidence for direct genetic control of sexual dimorphism, with the scrotum developing only in males and the pouch and mammary glands only in females, before differentiation of the gonads. The development of the pouch and mammary gland in females and the scrotum in males is controlled by genes on the X chromosome. In keeping with the "expanded" version of Jost's formulation, secretion of androgens by the fetal testes provides the best current account of a broad array of sex differences in reproductive morphology and endocrinology of the spotted hyena, and androgens are essential for development of the prostate and penis of the wallaby. But the essential circulating androgen in the male wallaby is 5alpha androstanediol, locally converted in target tissues to DHT, while in the pregnant female hyena, androstenedione, secreted by the maternal ovary, is converted by the placenta to testosterone (and estradiol) and transferred to the developing fetus. Testicular testosterone certainly seems to be responsible for the behavioral phenomenon of musth in male elephants. Both spotted hyenas and elephants display matrilineal social organization, and, in both species, female genital morphology requires feminine cooperation for successful copulation. We conclude that not all aspects of sexual differentiation have been delegated to testicular hormones in these mammals. In addition, we suggest that research on urogenital development in these non-traditional species directs attention to processes that may well be operating during the sexual differentiation of morphology and behavior in more common laboratory mammals, albeit in less dramatic fashion.     

Development of prolactin levels in marmoset males: from adult son to first-time father

Previous studies have found a clear relationship between prolactin (prl) and paternal care in various vertebrate taxa. In New World monkeys, it has been demonstrated in several species that fathers have high prolactin levels even during periods without infant rearing. In this study, we followed the reproductive careers of common marmoset males as they transitioned from being an adult son within their native family to fathering their own offspring for the first time. Specifically, we examined the first experience of elevated prolactin levels in marmoset males. Additionally, we investigated the effects of the total number of experienced births as well as of age on prolactin levels. Our results show that common marmoset males did not experience an increase in prolactin secretion after pairing or shortly before birth of their first infants. However, prolactin levels rose more than twofold after the birth of their first infants and had lowered again 2.5 months after this event. We found no correlation between prolactin levels and the number of previous births experienced or age. Our study demonstrates that further work about a possible enhancing effect of prolactin on paternal care, by means of experimentally reducing hormonal levels, should be conducted in common marmosets using first-time fathers before males experience the first paternal increase in prolactin levels.     

The importance of life-history stage and individual variation in the allorecognition system of a marine sponge

In marine invertebrates with complex life cycles, it may often be the case that trade-offs and behaviors differ between adult and larval stages. In this study, I examined the effects of life-history stage on allorecognition system function in the sponge, Haliclona sp. For sedentary marine invertebrates, allorecognition systems allow individuals to distinguish between genetically similar and distinct tissue they may encounter and are thought to reduce costly tissue fusion with individuals other than self or kin. Although it was found that sessile adults fused preferentially with self-tissue and exhibited a functioning allorecognition system, free-swimming larvae fused equally with sibling and non-sibling larvae resulting in swimming chimeras capable of successful metamorphosis, suggesting a stage-activated allorecognition system. In addition, adult sponges differed significantly in the propensity of their larvae to fuse suggesting variation in parental strategies. Analysis of larval swimming behavior indicated that larvae aggregate and are capable of increasing their encounters with other larvae and perhaps their probability of fusing in nature. The pursuit of fusion at this motile stage, along with evidence of a functioning adult allorecognition system, suggests that larvae may not express a recognition system, or that factors other than relatedness such as benefits to larval or adult chimeras, are involved in larval fusion and a stage-activated allorecognition system. In addition, this study demonstrates the presence of variation among individuals in the allorecognition system's ontogeny in the sponge Haliclona sp.     

Hair Cells – Beyond the Transducer

Overview This review considers the “tween twixt and twain” of hair cell physiology, specifically the signaling elements and membrane conductances which underpin forward and reverse transduction at the input stage of hair cell function and neurotransmitter release at the output stage. Other sections of this review series outline the advances which have been made in understanding the molecular physiology of mechanoelectrical transduction and outer hair cell electromotility. Here we outline the contributions of a considerable array of ion channels and receptor signaling pathways that define the biophysical status of the sensory hair cells, contributing to hair cell development and subsequently defining the operational condition of the hair cells across the broad dynamic range of physiological function.     

Review Article – A System for Analysing Features in Studies Integrating Ecology, Development, and Evolution

Ecology is being introduced to Evolutionary Developmental Biology to enhance organism-, population-, species-, and higher-taxon-level studies. This exciting, bourgeoning troika will revolutionise how investigators consider relationships among environment, ontogeny, and phylogeny. Features are studied (and even defined) differently in ecology, development, and evolution. Form is central to development and evolution but peripheral to ecology. Congruence (i.e., homology) is applied at different hierarchical levels in the three disciplines. Function is central to ecology but peripheral to development. Herein, the supercategories form (‘isomorphic’ or ‘allomorphic’), congruence (‘homologous’ or ‘homoplastic’), and function (‘adaptive’ or ‘nonadaptive’) are combined with two developmental mode (i.e., growth) categories (‘conformational’ or ‘nonconformational’) to provide a 16-class system for analysing features in studies in which ecology, development, and evolution are integrated.     

Development and maturation of thymic dendritic cells during human ontogeny

Thymic dendritic cells (TDC) are dendritic cells situated mainly in the cortico-medullary zone and in the medullary region of the thymus. However, the phenotype of TDC during ontogeny is poorly documented. The aim of this study has been to investigate the development and maturation of TDC during human ontogeny. Immunohistochemical analyses and immunoelectron-microscopic investigation of 21 human thymus specimens have been performed to detect the subtypes of TDC by using various DC-related and DC-development-related markers. TDC express a Langerhans-cell-like phenotype during human ontogeny. Cells expressing thymic stromal lymphopoietin receptor have been observed in Hassal’s corpuscles of the thymus. Granulocyte/macrophage colony-stimulating factor (GM-CSF) is also expressed in thymic epithelial cells (TEC) localized in Hassal’s corpuscles. During human ontogeny, GM-CSF is produced by TEC of Hassal’s corpuscles and might play a key role in the differentiation of TDC having Langerhans-cell-like phenotypes.