Functional morphology of the sperm-containing chambers of the sea slug Okenia polycerelloides in the context of sexual selection

Sea slugs are interesting models to study post-copulatory sexual selection in simultaneous hermaphrodites due to the enormous variation of their reproductive systems. However, the knowledge of the functional morphology of their reproductive system is limited to few species, and it is rarely discussed in the context of sexual selection theory. In this study, we investigated the functional morphology of the sperm-containing chambers (i.e., ampulla, seminal receptacle, and bursa copulatrix) of the reproductive system of Okenia polycerelloides (Ortea & Bouchet, 1983), based on light, confocal, and electron microscopy. Although the morphology of the ampulla is similar to other species, indicating that it is a site for autosperm storage, we found some sperm facing the ampullar epithelium, a feature commonly regarded as characteristic of the seminal receptacle of sea slugs. The seminal receptacle of O. polycerelloides showed secretory activity and contained sperm with distribution and orientation suggestive of stratification of allosperm from distinct mating events, a feature that would affect sperm competition. The bursa copulatrix had epithelial cells with secretory and absorptive characteristics, and contained degraded sperm and yolk granules within its lumen. Comparative analyses of the contents of each organ demonstrated that sperm digestion occurs in the bursa copulatrix and affects sperm heads first, changing their morphology from slender and curved to shorter and ellipsoid before complete lysis. Although digestion and absorption of surplus sperm are currently the main hypothesized functions for the bursa copulatrix, its role in cryptic female choice should not be ruled out. The close structural connection between the seminal receptacle and bursa copulatrix, as well as their muscular walls, would enable control over the fate of the sperm received in each mating event, that is, storage or digestion.     

Menopause in female rhesus monkeys

Fifteen female rhesus monkeys (Macaca mulatto), ranging in age from 8 to 34 years, were studied for one year to characterize the endocrine and menstrual changes associated with menopause in this species. Five monkeys were premenopausal; these younger monkeys, ages 8–11 years, menstruated and showed cyclic ovarian activity during the 12–month study period, as evidenced by menses and periodic elevations of serum estradiol (E₂) and luteinizing hormone (LH) concentrations. Four females, ages 24–26 years, were in transition to menopause. Two of these perimenopausal females menstruated and secreted E₂ and LH in a periodic fashion; the other two females showed elevated LH concentrations, consistently low E₂ levels, and no evidence of menstruation. Six females, ages 27–34 years, were clearly postmenopausal; LH concentrations were high, whereas E₂ concentrations were uniformly low. There was a significant inverse correlation between basal E₂ concentrations and age, and a significant positive correlation between age and LH concentrations across all 15 animals. Hormonal changes indicative of ovulation, when they occurred, were generally restricted to the winter and early spring months. Histological analysis of ovaries from four postmenopausal females revealed little or no evidence of active folliculogenesis. These data indicate that menopause in female rhesus monkeys does not occur until the second half of thethird decade of life. © 1995 Wiley-Liss, Inc.     

Role of cyclic nucleotides in pigment translocation within the freshwater shrimp, Macrobrachium potiuna, erythrophore

The participation of cyclic nucleotide-dependent intracellular signalling pathways in the pigment translocation induced by pigment-dispersing hormone (α -PDH) or pigment-concentrating hormone (PCH) was investigated in the erythrophores of the freshwater shrimp, Macrobrachium potiuna. Cholera toxin, forskolin and dibutyryl cyclic adenosine 3′5′ monophosphate (dbcAMP) were able to induce pigment dispersion with effective agonist concentrations for half maximal response (EC₅₀s) of 2.8 · 10⁻¹¹ mol · l⁻¹, 7.0 · 10⁻⁷ mol · l⁻¹ and 3.3 · 10⁻⁷ mol · l⁻¹, respectively. KT5720 (10⁻⁷ mol · l⁻¹ and 10⁻⁶ mol · l⁻¹) significantly shifted the dose response curve to α -PDH to the right. Dibutyryl cyclic guanosine 3′5′ monophosphate (dbcGMP) was ineffective in inducing either pigment aggregation or dispersion. 2′5′ dideoxyadenosine (DDA) and SQ22,536 essentially elicit a pigment-aggregating response in a dose-dependent manner. These effects were not due to the activation of purinergic receptors, since concentrations up to 10⁻⁴ mol · l⁻¹ of adenosine and adenosine triphosphate (ATP), and up to 10⁻³ mol · l⁻¹ of uracil triphosphate (UTP) did not elicit pigment aggregation. In order to verify if PCH decreased cyclic adenosine 3′5′ monophosphate (cAMP) levels, cumulative dose-response curves to PCH in the absence and presence of pertussis toxin and 8-MOM-IBMX were determined. However, neither drug significantly affected PCH activity. The levels of cAMP in the integument cells of M. potiuna were significantly increased (P < 0.05) by α -PDH (10⁻⁷ mol · l⁻¹) and forskolin (10⁻⁶ mol · l⁻¹), but were not affected by PCH (10⁻⁷ or 10⁻¹⁰ mol · l⁻¹). In conclusion, α -PDH seems to elicit pigment dispersion through the activation of a Gs-protein coupled receptor resulting in cAMP increase and cAMP-dependent protein kinase (PKA) activation. Furthermore, although a decrease in cAMP was assumed to be responsible in turn for the action of PCH, such a decrease could not be directly demonstrated. Accepted: 11 August 1998     

Oxygen uptake of growth hormone transgenic coho salmon during starvation and feeding

Oxygen uptake of growth hormone transgenic coho salmon Oncorhynchus kisutch was measured in individual fish with a closed-system respirometer and was compared with that of similar-sized non-transgenic control coho salmon during starvation and when fed a fixed ration or to satiation. Transgenic and control fish did not differ in their standard oxygen uptake after 4 days of starvation, although control fish had a higher routine oxygen uptake, scope for spontaneous activity and initial acclimation oxygen uptake. During feeding, transgenic fish ate significantly more than control fish, and had an overall oxygen uptake that was 1·7 times greater than control fish. When fish that had eaten the same per cent body mass were compared, transgenic fish had an oxygen uptake that was 1·4 times greater than control fish. Differences in oxygen uptake in growth hormone transgenic coho salmon and non-transgenic fish appear to be due to the effects of feeding, acclimation and activity level, and not to a difference in basal metabolism.     

Allatotropic and nervous control of corpora allata in the adult male loreyi leafworm, Mythimna loreyi (Lepidoptera: Noctuidae)

Allatotropic activity is found in methanolic extracts of the brain–suboesophageal ganglion (SOG)–corpora cardiaca (CC) complex from virgin males of Mythimna loreyi Duponchel (Lepidoptera, Noctuidae). Corpora allata (CA) from 6‐day‐old virgin males exhibit low rates of release of Juvenile Hormone (JH) acid (JHA) in vitro. Release of JHA can be activated by the addition of an extract of brain–SOG–CC complex in a dose‐dependent manner, and this allatotropic activation can be sustained consistently in the continuous presence of such extracts. Based on its trypsin sensitivity and heat stability, the allatotropic factor is most likely a peptide. The allatotropic activity is dependent on the concentration of calcium ions in the medium, with the highest activation achieved beyond 2 m m . The results of nerve transection experiments suggest that both nervi corporis allati I (NCA I) and NCA II are involved in mediating the allatotropic control of CA in vitro. Isolated CA alone show significantly higher rates of release of JHA than the intact brain–SOG–CC–CA complex during the first 3 h of incubation, but the release of JHA reaches almost the same range in both groups by the end of the fourth hour of incubation.     

Differences in prolyl-leucyl-glycinamide metabolism by hypothalamus,pituitary and cerebral cortex of male and female rats

l-Prolyl-l-leucyl-glycinamide is rapidly hydrolyzed by hypothalamic, hypophyseal and cortical homogenates from male or female rats. The peptidase activity is higher in the pituitary followed in decreasing order by the hypothalamus and the cerebral cortex. It is mostly localized in the supernatant fraction of a 100,000 g centrifugation and is inhibited by bacitracin.Tissues from female rats are half as active as those from male rats and show variations during the estrous cycle, with very low PLG metabolism at diestrus 1 in pituitary and hypothalamus. In contrast, the cerebral cortex at proestrus and estrus has significant lower hydrolyzing activity than at diestrus. No change of the peptidase activity is observed in tissues from ovariectomized animals after treatment with estrogen or progesterone.The results obtained suggest the existence of a correlation between peptidasic activity and melanotropin secretion.     

Structure and innervation of the pineal gland of the rabbit,Oryctolagus cuniculus (L.)

Summary A light microscopic investigation of the rabbit pineal gland with the aid of silver-stained sections gave the following results. In the gland a medulla and a cortex can be distinguished, the medulla containing so-called light and dark pinealocytes, the cortex only light ones. Autonomic nerve fibres reach the pineal organ by two routes: (1) via the perivascular spaces of pineal blood vessels and (2) via two distinct nerve bundles, the nervi conarii. Bilateral superior cervical ganglionectomy revealed that these pinealo-petal nerve fibres are mainly orthosympathetic postganglionic. Intramural pineal neurones with synaptic-like structures on their cell bodies and dendrites point to the presence of a parasympathetic innervation next to the orthosympathetic one. Direct afferent or efferent neural connections with the brain appeared to be absent. Acknowledgements. The author wishes to thank Professor Dr. J. Ariëns Kappers for encouragement and help, Mr. H. K. Koerten for his technical assistance and Miss A. M. Feddema for typing the manuscipt.     

The induction of normal and teratoid viviparae by a juvenile hormone and kinoprene in two species of aphids

ABSTRACT. Topical application of a juvenile hormone (JH1) and the JH mimic, kinoprene, to short-day, ovipara-producers of Megoura viciae usually leads to the production of oviparous/viviparous intermediate forms in the progeny sequence, in place of the expected sexual females (oviparae). The ovaries of these abnormal forms may contain embryos rather than the haploid yolky eggs of oviparae; 'mixed' ovaries containing both haploid eggs and embryos are also observed. The intermediates range in form from winged (alate) to wingless (apterous). The fully alate individuals usually contain only parthenogenetic ovaries but differ from the naturally occurring alate viviparae in that they are invariably infertile, have fewer antennal sense organs and often bear pheromone releasing glands on the metathoracic tibiae. The hormonally induced production of normal viviparae is difficult in this species but has been achieved by rearing short-day aphids on kinoprene-treated bean plants.
In Aphis fabae similar oviparous/viviparous teratomorphs have been reported and, in addition, single JH1 treatments were shown to induce normal viviparae at the end of the progeny sequence. Multiple applications, beginning prenatally and continuing through the postnatal development of the gynopara (winged ovipara-producer), showed that the numbers of viviparae born were related to the earliness of the treatment and to the dosage. The results are compared with the effect of a switch in photoperiod and discussed in relation to the endocrine control of aphid polymorphism.     

Cyclic Nucleotides and the Release of Vasopressin from the Rat Posterior Pituitary Gland

Abstract: The effect of ATP, Mg²⁺, or MgATP on the release of luteinizing hormone-releasing hormone (LH-RH) from hypothalamic granules was examined under in vitro conditions. Granules, isolated from adult male hypothalami, were incubated at 37°C in a buffered (pH 7.8) medium containing 0.15 m -KCl. The addition of ATP to the incubation mixture did not stimulate the release of LH-RH. In contrast, the addition of MgATP stimulated the release of LH-RH, the release being 62% greater than control. The addition of Mg²⁺ to the incubated granules also stimulated the release of LH-RH. However, the magnitude of this Mg²⁺-stimulated release of LH–RH was significantly ( P < 0.01) lower than that of the MgATP-stimulated release, indicating that ATP stimulates LH-RH release in a Mg²⁺-dependent manner. As both MgATP and Mg²⁺ alone stimulated LH-RH release, we characterized further these two release processes by incubating the granules under one of the following conditions: incubation at 4°C in a buffered medium containing 0.15 m -KCl or incubation at 37°C in a medium that does not contain KCl. Under these two incubation conditions, the MgATP-stimulated release of LH-RH was not manifested, whereas the Mg²⁺-stimulated release of LH-RH was manifested. On the basis of these differences, we propose that two different processes can lead to the release of LH-RH from isolated hypothalamic granules: one process involves ATP and Mg²⁺ (MgATP) and another process involves Mg²⁺ alone.