Animals must regulate their sensory responsiveness appropriately with respect to their internal and external environments, which is accomplished in part via centrifugal modulatory pathways. In the olfactory sensory system, responsiveness is regulated by neuromodulators released from centrifugal fibers into the olfactory epithelium and bulb. Among the modulators known to modulate neural activity of the olfactory system, one of the best understood is gonadotropin-releasing hormone (GnRH). This is because GnRH derives mainly from the terminal nerve (TN), and the TN-GnRH system has been suggested to function as a neuromodulator in wide areas of the brain, including the olfactory bulb. In the present article we examine the modulatory roles of the TN and GnRH in the olfactory epithelium and bulb as a model for understanding the ways in which olfactory responses can be tuned to the internal and external environments.

In social insects, colony fission is a particular mode of dispersal by which an adult colony splits into two or more independent nests. In the monogynous ant Aphaenogaster senilis, field data suggest that new queens may be produced in queenless daughter nests after nest relocation. Because workers do not fly, colony fission limits dispersal distance, leading young sister colonies to compete together and with the mother queen. In the present study we analysed the effects of queen loss and diet change on nestmate recognition. Queenright colonies were separated into two queenless and one queenright fragments. One queenless group received the same food as the queenright group, while the other queenless group received a different diet for 150 days. Recognition bioassays revealed that aggression between queenright and queenless former nestmates increased progressively until day 20, when they could no longer be reunited. Different diets also induced aggression between orphaned groups. Chemical analyses indicated that cuticular hydrocarbon profiles were already different between groups after 5 days. Overall, our results are in accordance with the graded model of nestmate recognition and suggest that the loss of the mother queen progressively leads to the independence of the related nests after fission. This may also allow queenless ants to merge again with their mother colony during a short time window after fission.

In sea urchin embryos, Notch signaling is required to segregate non-skeletogenic mesoderm from early endomesoderm, and is involved in endoderm development. To further investigate the role of Notch signaling in the endoderm cell lineage, we cloned a cDNA for the Hemicentrotus pulcherrimus ortholog of Suppressor of Hairless (HpSu(H)), which is a major mediator of the Notch signaling pathway, examined the expression during development and performed a functional analysis. HpSu(H) mRNA was ubiquitously expressed up to the unhatched blastula stage, and expression was exclusively detected in the vegetal plate region from the hatched blastula stage and then in the archenteron at the gastrula stage. Perturbation of HpSu(H) by injection of the dominant negative form of HpSu(H) (dn-HpSu(H)) mRNA into fertilized eggs led to the disappearance of secondary mesenchyme cells at the tip of the archenteron in the gastrula and pigment cells in the pluteus larva, confirming that Notch signaling is required for non-skeletogenic mesoderm specification. In addition, injection of relatively high amounts of dn-HpSu(H) mRNA caused a defect or atrophy of the foregut in the archenteron at the pluteus stage. This result strongly suggests that Notch signaling is involved in foregut development during sea urchin development.

Sexual and seasonal variation in diet quality and the gastrointestine have important implications for forage acquisition and the feeding strategy. We assessed the botanical and chemical compositions of the diet and the gastrointestinal macrostructure of the sika deer (Cervus nippon) in western Japan. The sexual dimorphism-body size hypothesis predicts that smaller females will have a better diet than larger males to meet a higher nutritional demand due to a higher metabolic rate. According to the optimal digestion theory, the gut of larger males will retain a greater quantity of digesta of poor forage to compensate for the reduction in net energy obtained per unit of digesta. The relatively greater omasum content in winter than in summer was the only feature consistent with this prediction. This may suggest that the omasum is the organ that most sensitively reflects diet quality, because the summer diet quality is little better than that in winter. Contrary to predictions, the botanical composition of the diet did not show a sexual difference, but females had greater relative weights of stomach contents, tissues, and hindgut segments (small and large intestines, and cecum-colon), and a relatively greater small intestine length than males in summer. Further, females had greater relative weights of abomasum contents, ruminoreticulum tissue, and small intestine in summer than in winter, but no seasonal variation in gastrointestinal features was detected in males. The sexual variation in diet and in the gastrointestine in summer suggest that lactating females intake more forage and maintain more digesta in the gut, due to not body size but to higher energy requirements for lactation. The greater gut fill and tissue weight of females in summer than in winter likely resulted from a nutrient demand from lactation greater than that from gestation.

Despite extensive research, the function and adaptive significance of melanism remain controversial.In snakes, melanistic individuals enjoy a thermal advantage compared with normal-colored individuals due to superior thermoregulatory capabilities. The hypothetical consequences of this thermal advantage are that melanistic individuals have longer daily and seasonal active periods, and thus collect more food, resulting in a higher growth rate and larger body size. To test the generality of this hypothesis, I made intermorph comparisons of body size using a melanistic/striped color-dimorphic snake (Elaphe quadrivirgata) on Yakushima Island, Japan. Melanistic individuals were not significantly larger in body size than striped individuals in either males or females, and the largest individual was a striped morph in both sexes. Thus, the pattern predicted based on the hypothetical consequences of the thermal advantage of melanism was not observed in E. quadrivirgata on Yakushima Island. Based on this coupled with the results of a previous survey on the thermal ecology of the snake, I conclude that melanistic individuals of E. quadrivirgata on Yakushima Island may benefit from fast body warming, which shortens the time of basking, but this benefit is not sufficient to realize larger body size compared to that of striped individuals, and/or such a benefit is not realized in the hypothesized way. The thermal advantage of melanism in nature may be more limited in scope than has been assumed.

Natural and synthetic estrogens, Including diethylstilbestrol (DES), given during the critical period of newborn life Induce abnormalities in ovaries of mice. Induction of polyovular follicles (PFs) containing two or more oocytes in a follicle is one example. In this study, the involvement of estrogen receptor subtypes ERα and ERβ in induction of PFs by neonatal treatment with DES was analyzed by using ERα knockout (αERKO) and ERβ knockout (βERKO) mice. Ovaries of mice injected with 3 µg DES for 5 days from the day of birth were examined histologically from 10 to 60 days of age, and the expression of genes involved in folliculogenesis was analyzed by real-time quantitative PCR. The PF incidence (percent of PFs per 100 follicles greater than 50 µm in diameter) in the ovary of αERKO mice treated with DES was not different from that in the DES-treated wild-type mice. However, neonatal DES treatment did not increase the PF incidence in βERKO mice, suggesting that PFs were induced by DES through ERβ but not ERα. The expression of bone morphogenetic protein 15, growth differentiation factor 9, inhibin-α, Müllerian inhibiting substance, and other genes in the ovaries of DES-treated βERKO mice was not different from that in the ovaries of DES-treated wild-type mice. These results indicate that ERβ but not ERα is essential for DES to induce PFs in mice.

The brown-eared bulbul (Hysipetes amaurotis) is commonly found in Japan where it is regarded as a harmful bird that causes damage to agricultural products. Few studies have investigated the sensory apparatus of this bird, and consequently little is known of the sensory modalities it uses. Here we analyzed the anatomical and histological properties of the nasal cavity and olfactory bulb (OB) of the bulbul in order to investigate the functional level of olfaction in this species. Although both anterior and maxillary conchae were observed in the bulbul nasal cavity, there was no structure equivalent to the posterior concha. The OB located on the ventral side of the anterior extremity of the cerebrum and the ratio of olfactory bulb size to that of the cerebral hemisphere were very small. Interestingly, the left and right OBs were completely fused at the midline of the cerebrum. Furthermore, certain types of lectins that bind to the olfactory nerve of vertebrates with a well-developed sense of smell also bound positively to the olfactory nerve and glomerular layers of the bulbul OB. These findings suggest that the brown-eared bulbul has an anatomically and functionally less well developed sense of smell compared to other avian species. Although the molecular and developmental mechanisms underlying the fusion of the OB remain unknown, we suggest that the fused OB may offer a unique model for studying the evolution and development of the central olfactory nervous system in vertebrates.

We evaluated the presence of G protein subtypes Gα_o, Gα_i2, and Gα_olf in the main olfactory system (MOS) and accessory or vomeronasal system (VNS) of Rhinella (Bufo) arenarum tadpoles, and here describe the fine structure of the sensory cells in the olfactory epithelium (OE) and vomeronasal organ (VNO). The OE shows olfactory receptor neurons (ORNs) with cilia in the apical surface, and the vomeronasal receptor neurons (VRNs) of the VNO are covered with microvilli. Immunohistochemistry detected the presence of at least two segregated populations of ORNs throughout the OE, coupled to Gα_olf and Gα_o. An antiserum against Gα_i2 was ineffective in staining the ORNs. In the VNO, Gα_o neurons stained strongly but lacked immunoreactivity to any other Gα subunit in all larval stages analyzed. Western blot analyses and preabsorption experiments confirmed the specificity of the commercial antisera used. The functional significance of the heterogeneous G-protein distribution in R. arenarum tadpoles is not clear, but the study of G- protein distributions in various amphibian species is important, since this vertebrate group played a key role in the evolution of tetrapods. A more complete knowledge of the amphibian MOS and VNS would help to understand the functional organization and evolution of vertebrate chemosensory systems. This work demonstrates, for the first time, the existence of a segregated distribution of G-proteins in the OE of R. arenarum tadpoles.

The nature of the structural regression of the corpus luteum of pregnancy (PCL) was investigated in rats from day 19 of pregnancy (PRG19) through day 6 postpartum (PP6). A pre-partum decrease in tissue weight of the PCL during the last 4 days of pregnancy was apparent (nearly a 40% decrease) and seemed to parallel the fall in plasma progesterone. The PCL in normally lactating rats further experienced a gradual decrease in the postpartum period, but the reduction was significantly slowed by PP6 in non-lactating rats that were forced to wean from the parturient day (PP0). TUNEL analysis revealed that apoptotic cell death in the regressing PCL showed a 3–4 fold increase in signals after parturition (on PP3) but was fairly limited. Instead, luteal steroidogenic cells came to have cytoplasmic vacuoles by PRG21, and vacuoles increased through PP3. A decelerated decrease in PCL weight following forced weaning was potentially reversed by repeated administration of exogenous prolactin (10 IU) twice daily. This study adds evidence that structural regression of the rat PCL 1) starts to occur before the completion of functional regression, 2) involves a modest incidence of TUNEL-reactive apoptosis, and 3) is promoted by the suckling stimulus, presumably through the effects of prolactin.

A new polychaete species of the longosomatid genus Heterospio is described from the coastal shelf off Angola in the Southeast Atlantic. This species was found from two sampling points at depths of 105 and 146 m, and differs from other members of the family in having eight short thoracic setigers, in the lack of neuropodial acicular hooks in the first setiger, and in having only three pairs of branchiae. The material consists of 21 adults with gametes in the body cavity of posterior segments and one Juvenile. Size-dependent variation in morphological features such as the length of midbody setigers, number of spines per rami, and occurrence of cinctures, is discussed. A key to the currently recognized species and possible undescribed forms of Heterospio is given.