Silhouettella loricatula (Arachnida, Araneae, Oonopidae): a Haplogyne spider with complex female genitalia

The female genital system of the oonopid Silhouettella loricatula is astonishingly complex. The genital opening is situated medially and leads into an oval receptaculum that is heavily sclerotized except for the ventral half of the posterior wall that appears chitinized only. A large striking sclerite lying in the posterior wall of the uterus externus is attached anteriorly to the receptaculum and continues dorsally into a globular appendix that bears a furrow. The uterus externus shows a peculiar modification in its anterior wall: a paddle-like sclerite with a nail-like posterior process. This sclerite lies opposite to the furrow proceeding in the globular appendix and may serve females to lock the uterus externus by muscle contractions. Massive muscles connect the sclerite with the anterior scutum of the opisthosoma and with two other sclerites that are attached to the receptaculum and serve as attachments for further muscles. Gland cells extend around a pore field of the receptaculum. They produce secretion that encloses spermatozoa in a discrete package (secretory sac) inside the receptaculum. In this way, the mixing of sperm from different males and thus sperm competition may be severely limited or completely prevented. During a copulation in the laboratory the ejection of a secretory sac that most probably contained spermatozoa was observed, indicating sperm dumping in S. loricatula. The ejection of the secretory sac may be caused by female muscle contractions or by male pedipalp movements. The majority of the investigated females have microorganisms in the receptacula that could represent symbionts or infectious agents. The microorganisms can be identified partly as bacteria. They are enclosed in secretion and are always found in the same position inside the receptaculum.

Complex genital system of a haplogyne spider (Arachnida, Araneae, Tetrablemmidae) indicates internal fertilization and full female control over transferred sperm

The female genital organs of the tetrablemmid Indicoblemma lannaianum are astonishingly complex. The copulatory orifice lies anterior to the opening of the uterus externus and leads into a narrow insertion duct that ends in a genital cavity. The genital cavity continues laterally in paired tube-like copulatory ducts, which lead into paired, large, sac-like receptacula. Each receptaculum has a sclerotized pore plate with associated gland cells. Paired small fertilization ducts originate in the receptacula and take their curved course inside the copulatory ducts. The fertilization ducts end in slit-like openings in the sclerotized posterior walls of the copulatory ducts. Huge masses of secretions forming large balls are detectable in the female receptacula. An important function of these secretory balls seems to be the encapsulation of spermatozoa in discrete packages in order to avoid the mixing of sperm from different males. In this way, sperm competition may be completely prevented or at least severely limited. Females seem to have full control over transferred sperm and be able to express preference for spermatozoa of certain males. The lumen of the sperm containing secretory balls is connected with the fertilization duct. Activated spermatozoa are only found in the uterus internus of females, which is an indication of internal fertilization. The sperm cells in the uterus internus are characterized by an extensive cytoplasm and an elongated, cone-shaped nucleus. The male genital system of I. lannaianum consists of thick testes and thin convoluted vasa deferentia that open into the wide ductus ejaculatorius. The voluminous globular palpal bulb is filled with seminal fluid consisting of a globular secretion in which only a few spermatozoa are embedded. The spermatozoa are encapsulated by a sheath produced in the genital system. The secretions in females may at least partly consist of male secretions that could be involved in the building of the secretory balls or play a role in sperm activation. The male secretions could also afford nutriments to the spermatozoa.

Fossil bubble in porphyritic basaltic pyroclasts produced by small and large strombolian eruption at Pacaya, Guatemala

We investigate compositionally monotonous, but energetically diverse, tephra samples from Pacaya to see if fossil bubbles in pyroclasts could reflect eruptive style. Bubble size distributions (BSD) were determined for four ash to lapilli size tephra samples using an adapted version of stereology conversion by Sahagian and Proussevitch (1998). Eruptions range from very weak to very energetic. Hundreds of ESEM BSEs images were processed throughout ImageJ software for a robust and statistically correct data set of vesicles (minimum 700 bubbles per sample). Qualitative textural analysis and major element chemical compositions were also executed. There is higher vesicularity for explosive pyroclasts and an inverse correlation between bubble number density (NV) and explosivity.

FOSSIL PLANTS AND PALYNOMORPHS FROM THE LATE PALEOZOIC CUTLER FORMATION, EASTERN PARADOX BASIN

The late Paleozoic Cutler Formation, where exposed near the modern-day town of Gateway, Colorado, has traditionally been interpreted as the product of alluvial fan deposition within the easternmost portion of the Paradox Basin. The Paradox Basin formed between the western margin of the Uncompahgre Uplift segment of the Ancestral Rocky Mountains and the western paleoshoreline of the North American portion of Pangea. The Paradox Basin region is commonly thought to have experienced semi-arid to arid conditions and warm temperatures during the Pennsylvanian and Permian. Evidence described in this paper support prior interpretations regarding paleoclimate conditions and the inferred depositional environment for the Cutler Formation near Gateway, Colorado. Plant fossils collected from the late Paleozoic Cutler Formation in The Palisade Wilderness Study Area (managed by the U.S. Department of the Interior, Bureau of Land Management) of western Colorado include Calamites, Walchia, Pecopteris, and many calamitean fragments. The flora collected is interpreted to have lived in an arid or semi-arid environment that included wet areas of limited areal extent located near the apex of an alluvial fan system. Palynological analysis of samples collected revealed the presence of the common Pennsylvanian palynomorphs Thymospora pseudothiessenii and Lophotriletes microsaetosus. These fossils suggest that warm and at least seasonally and locally wet conditions existed in the area during the time that the plants were growing. All evidence of late Paleozoic plant life collected during this study was found along the western margin of the Uncompahgre Uplift segment of the Ancestral Rocky Mountains. During the late Paleozoic, sediment was eroded from the Uncompahgre Uplift and deposited in the adjacent Paradox Basin. The preservation of plant fossils in the most proximal parts of the Paradox Basin is remarkable due to the fact that much of the proximal Cutler Formation consists of conglomerates and sandstones deposited as debris flow and by fluvial systems. The plants must have grown in a protected setting, possibly an abandoned channel on the alluvial fan, and been rapidly buried in the subsiding Paradox Basin. It is likely that there was abundant vegetation in and adjacent to low-lying wet areas at the time the Cutler Formation was deposited.