Evaluating commercially available rodenticide baits for invasive Gambian giant pouched rats (Cricetomys gambianus)

Gambian giant pouched rats (Cricetomys gambianus) are native to Africa, but they are popular in the pet industry in the United States. They were reservoir hosts during a monkeypox outbreak in the Midwestern United States in 2003. A free-ranging population became established on Grassy Key in the Florida Keys, apparently because of a release by a pet breeder. These rodents could cause significant damage to agricultural crops should they reach the mainland. Research under controlled conditions was needed to identify effective rodenticides for Grassy Key or other cases where an invasion of Gambian rats might occur. We tested 2 formulations of diphacinone baits and 1 formulation each of brodifacoum, zinc phosphide, bromethalin, and chlorophacinone baits with captive Gambian rats in multiple-choice food trials. Both the brodifacoum and zinc phosphide rodenticide baits were highly effective (100% mortality). Also, brodifacoum and zinc phosphide treatments performed similar to the Environmental Protection Agency’s standard for toxicants of (i.e., 90% mortality in laboratory trials). The chlorophacinone, diphacinone, and bromethalin baits did not appear to be very effective at killing Gambian rats (≤50% mortality) in our study. Effective tools to combat Gambian giant pouched rats have been identified in a laboratory trial. Further field testing of commercially available brodifacoum and zinc phosphide baits may prove useful for controlling the potentially invading Gambian rats.     

Is ASEAN ready to move to multilateral cross-border electricity trade?

This paper reviews progress towards the establishment of an Association of Southeast Asian Nations (ASEAN) Power Grid (APG) and the key barriers to multilateral cross-border electricity trade in ASEAN. An analysis across political, technical, institutional, economic, environmental, social and time dimensions is employed. Using a policy sequencing framework, the paper concludes it remains premature for ASEAN to pursue a strong form of power sector market integration on account of the sizeable barriers that currently remain, especially economic and institutional barriers. Focusing on bilateral power purchase agreements and large-scale investments in solar and wind power over 2022–2030 would help to develop stronger foundations for ASEAN to make steps towards deeper regional integration in the electricity sector in subsequent years, while also being consistent with renewables adoption goals.     

Relationship between soil enzyme activities, nutrient cycling and soil fungal communities in a northern hardwood forest

Soil fungi are highly diverse and act as the primary agents of nutrient cycling in forests. These fungal communities are often dominated by mycorrhizal fungi that form mutually beneficial relationships with plant roots and some mycorrhizal fungi produce extracellular and cell-bound enzymes that catalyze the hydrolysis of nitrogen (N)- and phosphorus (P)- containing compounds in soil organic matter. Here we investigated whether the community structure of different types of mycorrhizal fungi (arbuscular and ectomycorrhizal fungi) is correlated with soil chemistry and enzyme activity in a northern hardwood forest and whether these correlations change over the growing season. We quantified these relationships in an experimental paired plot study where white-tailed deer (access or excluded 4.5 yrs) treatment was crossed with garlic mustard (presence or removal 1 yr). We collected soil samples early and late in the growing season and analyzed them for soil chemistry, extracellular enzyme activity and molecular analysis of both arbuscular mycorrhizal (AM) and ectomycorrhizal/saprotrophic fungal communities using terminal restriction fragment length polymorphism (TRFLP). AM fungal communities did not change seasonally but were positively correlated with the activities of urease and leucine aminopeptidase (LAP), enzymes involved in N cycling. The density of garlic mustard was correlated with the presence of specific AM fungal species, while deer exclusion or access had no effect on either fungal community after 4.5 yrs. Ectomycorrhizal/saprotrophic fungal communities changed seasonally and were positively correlated with most soil enzymes, including enzymes involved in carbon (C), N and P cycling, but only during late summer sampling. Our results suggest that fine scale temporal and spatial changes in soil fungal communities may affect soil nutrient and carbon cycling. Although AM fungi are not generally considered capable of producing extracellular enzymes, the correlation between some AM taxa and the activity of N acquisition enzymes suggests that these fungi may play a role in forest understory N cycling.     

Uterine motility during the estrous cycle: studies in healthy bitches

Natural and drug-induced uterine motilities (UM) were recorded via uterine-implanted catheter-tip pressure transducers in 5 bitches during proestrus and estrus and in 6 bitches during early (30 days) and late (60 days) diestrus. The UM was monitored in unanesthetized bitches for 2 days after the estrous-cycle stage had been determined by vaginal cytologic findings. Natural UM, expressed as Alexandria units (pressure X frequency X duration of contractions), was greatest during estrus, moderate during proestrus, and appreciably decreased or lacking during early and late diestrus. During proestrus and estrus, prostaglandin F2 alpha (5 micrograms/kg of body weight, IV) induced intrauterine pressures of 107 and 115 mm of Hg, respectively, and oxytocin (0.05 USP units/kg, IV) induced pressures of 106 and 116 mm of Hg, respectively. In contrast, the intrauterine pressure values induced by prostaglandin F2 alpha given IV during early and late diestrus were 61 and 58 mm of Hg, respectively, and for oxytocin, were 61 and 51 mm of Hg, respectively. Prostaglandin F2 alpha given IM (50 micrograms/kg) also induced a greater intrauterine pressure during proestrus and estrus than during diestrus. We concluded that in the bitch, natural and drug-induced UM are decreased during early and late diestrus.     

Precocious puberty in tamoxifen‐treated cockerels: Hypothalamic gonadotrophin‐releasing hormone‐I and plasma luteinising hormone,prolactin, growth hormone and testosterone

1. The administration of the anti‐oestrogen, tamoxifen (TAM) to juvenile chicks results in precocious puberty. In the present study the effects of TAM administration (1 mg/kg body weight on alternate days from 12 d of age) on testicular function, hypothalamic chicken gonadotropin‐re‐leasing hormone (cGn‐RH‐I), plasma luteinising hormone (LH), growth hormone (GH), prolactin (PRL) and testosterone were studied in juvenile White Leghorn cockerels.

2. The increase in hypothalamic GnRH‐I content which occurs during sexual development was advanced in TAM‐treated birds, in association with precocious testicular development, an early rise of plasma testosterone content and enhanced comb growth.

3. Plasma LH concentrations behaved similarly and were higher in the TAM‐treated than in control birds, during most of the experimental period. Plasma PRL concentration, which is high at hatching, decreased more quickly in TAM‐treated than in control birds; plasma GH values were not consistently affected by TAM treatment.

4. Both the growth and the involution of the bursa of Fabricius in the TAM‐treated cockerels preceded that in the control chicks.

5. It is concluded that TAM treatment induces precocious puberty in the cockerel by blocking the negative feedback action of aromatised testicular androgens on the hypothalamus.