Endocrine control of reproduction in two rhynchocoelan worms

This brief review of the reproductive endocrinology in two distant species of Rhynchocoela examines selected results of earlier studies on the heteronemertean, Lineus ruber, and reports current and unpublished research on the hoplonemertean, Amphiporus lactifloreus.

Experimental evidence is presented for existence in the brain of a gonad-inhibiting hormone (GIH) that controls reproduction in male and female worms of both species. In adults deprived of GIH during the quiescent phase of the reproductive cycle, sexual characteristics grow rapidly and precociously; GIH replacement therapy prevents the anticipated sexual development. In L. ruber, the removal of GIH stimulates macromolecular syntheses in sexual target cells of both sexes: RNA synthesis is promoted in young oocytes; DNA synthesis is increased in spermatogonia, and induced in primary spermatocytes; and protein synthesis is significantly increased in gametocytes and sex-specific skin glands. GIH might be a regulating hormone which would inhibit the secretion of sex-specific stimulating substances produced by cells in proximity to the gonads.     

Dispersal differences of a pest and a protected Cerambyx species (Coleoptera: Cerambycidae) in oak open woodlands: a mark–recapture comparative study

1. Cerambyx welensii (Cw) and Cerambyx cerdo (Cc) are two large saproxylic beetles living on Quercus trees in the Western Palearctic whose current pest and legal status differs markedly. Cw is an emerging pest involved in oak decline while Cc is an internationally protected species. 2. Acquiring knowledge of the ecology, demography and behaviour of Cw and Cc in forests harbouring mixed populations is a demanding task to optimise their management or protection. Here, we report the results of a mark–recapture study on the flight behaviour and dispersal potential of both species in holm oak open woodlands. 3. Average flights, dispersal rates and diffusion models were remarkably similar in Cw and Cc, reflecting a low‐dispersal tendency and sedentary behaviour. However, a subset of adults in both species exhibited a huge propensity to disperse and flew more than 1 km. An aggregated distribution of dispersal distances suggested that a behavioural polymorphism might underlie the flight pattern. 4. Adults moved preferentially in those spatial directions with neighbouring trees, while prevailing winds did not significantly affect dispersal patterns. The main interspecific differences were as follows: (i) Cc performed longer crosswind flights than Cw on windy days; (ii) Cc tended to fly farther than Cw at low temperatures; and (iii) adult feeding improved dispersal but only in small Cw females. Moon phase did not affect flight activity. 5. The results are discussed in an effort to interpret how these ecological and behavioural differences might shape the life history of both congeneric species when they live in sympatry in dehesa woodlands.     

Breeding system and pollination by mimicry of the orchid Tolumnia guibertiana in Western Cuba

The mimicry of malpighiaceous oil‐flowers appears to be a recurrent pollination strategy among many orchids of the subtribe Oncidiinae. These two plant groups are mainly pollinated by oil‐gathering bees, which also specialize in pollen collection by buzzing. In the present study, the floral ecology of the rewardless orchid Tolumnia guibertiana (Oncidiinae) was studied for the first time. The orchid was self‐incompatible and completely dependent on oil‐gathering female bees (Centris poecila) for fruit production. This bee species was also the pollinator of two other yellow‐flowered plants in the area: the pollen and oil producing Stigmaphyllon diversifolium (Malpighiaceae) and the polliniferous and buzzing‐pollinated Ouratea agrophylla (Ochnaceae). To evaluate whether this system is a case of mimetism, we observed pollinator visits to flowers of the three plant species and compared the floral morphometrics of these flowers. The behavior, preferences and movement patterns of Centris bees among these plants, as well as the morphological data, suggest that, as previously thought, flowers of T. guibertiana mimic the Malpighiaceae S. diversifolium. However, orchid pollination in one of the studied populations appears to depend also on the presence of O. agrophylla. Moreover, at the two studied populations, male and female pollination successes of T. guibertiana were not affected by its own floral display, and did not differ between populations. The results are discussed in relation to the behavior and preferences of Centris bees, as well as the differential presence and influence of each of the two floral models.     

Bone histology of the Middle Jurassic turtle shell remains from Kirtlington, Oxfordshire, England

The Middle Jurassic (Bathonian) turtle material from the Mammal Bed at Kirtlington, Oxfordshire, England, has recently been tentatively referred to the Pleurosternidae, although the known synapomorphies of this clade were absent from the specimens. Here we present new evidence from shell bone histology that corroborates reports of pleurosternids at Kirtlington and further reveal that two different histomorphs (= two different taxa) are present in this locality. The first histomorph presents the distinctive histological structure of pleurosternids, which is described herein for the first time: the external cortical bone layers are differentiated into an inner zone of coarse, irregularly interwoven structural fibre bundles and an outer fine-fibred zone. The second histomorph has a more plesiomorphic structure and can only be assigned to Cryptodira indet. A morphological reassessment of the Kirtlington material fails to recognize two different taxa and shows that only sparse evidence supports the presence of pleurosternids in this locality. Shell bone histology thus appears as a powerful tool to study poorly preserved specimens and may in some case (like with pleurosternids) help resolve phylogenetic relationships. According to our results, the stratigraphic appearance of the Pleurosternidae is adjusted from the Kimmeridgian (Late Jurassic) to the Bathonian (Middle Jurassic), which significantly reduces the ghost lineage of Paracryptodira.     Bone histology, turtles, Paracryptodira, Pleurosternidae, Middle Jurassic, Kirtlington.     

New Technology for Estimating Seed Production of Moist-Soil Plants

ABSTRACT Waterfowl biologists estimate seed production in moist-soil wetlands to calculate duck-energy days (DEDs) and evaluate management techniques. Previously developed models that predict plant seed yield using morphological measurements are tedious and time consuming. We developed simple linear regression models that indirectly and directly related seed-head area to seed production for 7 common moist-soil plants using portable and desktop scanners and a dot grid, and compared time spent processing samples and predictive ability among models. To construct models, we randomly collected approximately 60 plants/species at the Tennessee National Wildlife Refuge, USA, during September 2005 and 2006, threshed and dried seed from seed heads, and related dry mass to seed-head area. All models explained substantial variation in seed mass (R²< 0.87) and had high predictive ability (R²_predicted < 0.84). Processing time of seed heads averaged 22 and 3 times longer for the dot grid and portable scanner, respectively, than for the desktop scanner. We recommend use of desktop scanners for accurate and rapid estimation of moist-soil plant seed production. Seed predictions per plant from our models can be used to estimate total seed production and DEDs in moist-soil wetlands.     

Stability of floral specialization in Trollius europaeus in contrasting ecological environments

Specialization of some plants on seed‐eating pollinators is intriguing, especially when co‐pollinators exclusively feeding on nectar are also present. We examined the stability of the morphological specialization of Trollius europaeus (L.) globeflowers with respect to Chiastocheta (Pokorny) flies by artificially opening the flowers. In the montane and subalpine environments studied, other visitors contributed 2% and 28% of all the visits, respectively, and visited open flowers nearly eight times more often than closed flowers, but in both environments their contribution to pollination did not compensate for Chiastocheta aversion against open phenotypes. Net seed set (female success) was slightly higher (+4%) and pollen export (male success) was much higher (+85%) for closed than open flowers. Selection in favour of the closed phenotype was even more intense in patches where open phenotypes were most common, precluding the evolution of open flowers in the study populations.     

Effects of pyriproxyfen and buprofezin on immature development and reproduction in the stable fly*

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is one of the most significant biting flies that affect cattle. The use of traditional insecticides for stable fly control has only a limited success owing to the insect's unique feeding behaviours and immature development sites. A laboratory study was conducted to evaluate the effects of two insect growth regulator (IGR) products, pyriproxyfen and buprofezin, on the development of the immature stages of the stable fly and the effects of pyriproxyfen on oviposition and egg hatch. Both pyriproxyfen and buprofezin had significant inhibitory effects on immature development. The LC₅₀s of pyriproxyfen and buprofezin were 0.002 and 18.92 p.p.m., respectively. Topical treatment of adult females with different doses of pyriproxyfen had significant negative effects on both female oviposition and egg hatching when 1‐ and 3‐day‐old females were treated, and the effects were dose dependent. A significant reduction in the mean number of eggs laid was observed only at the highest pyriproxyfen dose (8 µg/fly) and egg hatch was unaffected by pyriproxyfen treatment when 5‐day‐old females were treated. Results from the present study indicate that pyriproxyfen has the potential to be used as part of an integrated stable fly management programme.