Many authors have studied the biogeography of the Southern Ocean (SO), defined its limits and proposed their division into biogeographical zones and provinces. In this work we analyse the biogeography of sea slugs in a broad sense (Mollusca, Gastropoda, Heterobranchia) in the different areas and zones of the SO below 41°S. Most of the published scientific publications, databases and technical reports where records of benthic sea slugs appear in the SO have been analysed in addition to our own records, cataloguing a total of 355 different benthic species. The following areas and zones of the SO have been considered: Antarctica (Weddell Sea, West Antarctica, Ross Sea, East Antarctica), the sub-Antarctic zone (Falkland Islands, South Georgia Island, South Orkney Islands, South Sandwich Islands, Bouvet Island, Crozet and Prince Edward islands, Kerguelen Islands, Macquarie Island), southern South America (Patagonia/Magellan), Tasmania and New Zealand (South Island). A presence/absence table for all recorded species in the different zones has been compiled, and the differences and similarities between them have been calculated using the Sorensen index. The best representation has been obtained by classifying the zones into five groups: G1 (the four Antarctic zones, South Georgia Island, South Sandwich Islands, South Orkney Islands), G2 (Kerguelen Islands, Crozet and Prince Edward islands and Macquarie Island), G3 (Falkland Islands and Patagonia/Magellan), G4 (Tasmania and New Zealand’s South Island) and G5 (Bouvet Island). In addition, the concordance between the non-hierarchical classification (K-mean) and the hierarchical classification obtained using the WARD and UPGMA cluster analysis methods has been verified. The representative and distinctive species of each of these groups are indicated. In this work, as regards benthic sea slugs, the biogeographical affinities between the Antarctic zones and some of the sub-Antarctic zones are confirmed, as well as between the fauna of these molluscs in the Patagonian/Magallan zone and the Falkland Islands, while the affinities between the other zones need further confirmation when more species records become available.

The Cambrian Explosion saw the widespread development of mineralized skeletons. At this time, nearly every major animal phylum independently evolved strategies to build skeletons through either agglutination or biomineralization. Although most organisms settled on a single strategy, Salterella Billings, 1865 employed both strategies by secreting a biocalcitic exterior shell that is lined with layers of agglutinated sediments surrounding a central hollow tube. The slightly older fossil, Volborthella Schmidt, 1888, shares a similar construction with agglutinated grains encompassing a central tube but lacks a biomineralized exterior shell. Together these fossils have been grouped in the phylum Agmata Yochelson, 1977, although no phylogenetic relationship has been suggested to link them with the broader metazoan tree, which limits their contribution to our understanding of the evolution of shells in early animals.

To understand their ecology and place them in a phylogenetic context, we investigated Salterella and Volborthella fossils from the Wood Canyon and Harkless formations of Nevada, USA, the Illtyd Formation of Yukon, Canada, and the Shady Formation of Virginia, USA. Thin-section petrography, acid maceration, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray tomographic microscopy were used to provide new insights into these enigmatic faunas. First, morphological similarities in the aperture divergence angle and ratio of central tube diameter to agglutinated layer thickness suggest Salterella and Volborthella are related. Second, both fossils exhibit agglutinated grain compositions that are distinctive from their surrounding environments and demonstrate selectivity on the part of their producers. Finally, the calcitic shell composition and simple layers of blocky prismatic shell microstructure in Salterella suggest a possible cnidarian affinity. Together these data point to these organisms being sessile, semi-infaunal filter or deposit feeders and an early experimentation in cnidarian biomineralization chronicling a hypothesized transition from an organic sheath in Volborthella to a biomineralized shell in Salterella.

Morphological characters are central to phylogenetic inference, especially for fossil taxa for which genomic data are unavailable. While Bayesian methods have gained popularity in recent years, they typically assume characters evolve independently, despite known correlations among characters. Here, we assess the impact of character correlation and evolutionary rate heterogeneity on Bayesian phylogenetic inference using extensive simulations of binary characters evolving under independent and correlated models. We find that Bayesian inference assuming character independence accurately recovers tree topologies even when characters are strongly correlated or evolve under heterogeneous rates. However, branch lengths or clock rates tend to be underestimated, particularly under extreme rate heterogeneity. These biases are partially corrected using models that integrate over character-state heterogeneity. Our results demonstrate that Bayesian methods are robust to violations of character independence in topological inference, supporting their continued use in morphological phylogenetics.

This study investigates the prevalence of coliform contamination in fresh milk and the occurrence of multidrug-resistant (MDR) bacteria within poultry environments on an integrated farm in Minna, Niger State. Bacterial isolates obtained from raw milk, poultry cloacal swabs, and intestinal swabs from commensal rats included Salmonella, Escherichia coli, and Klebsiella species. These isolates were screened for extended-spectrum beta-lactamase (ESBL) production and antimicrobial resistance (AMR) profiles. The results revealed a high level of bacterial contamination in milk samples, with significant associations between contamination levels and poor hygiene practices during milking and handling. Moreover, ESBL-producing bacteria displaying resistance to critically important antibiotics such as third-generation cephalosporins and fluoroquinolones were identified across both dairy and poultry sources. These findings highlight a pressing public health concern and emphasize the need for improved biosecurity, hygiene interventions and integrated AMR surveillance to safeguard food safety and reduce the spread of MDR pathogens in animal-source foods.

Antimicrobials are widely used to maintain animal health and productivity; however, their misuse contributes to antimicrobial resistance (AMR), a critical One Health and global health concern. This study assessed the knowledge, awareness, and practices of animal health practitioners regarding antimicrobial use and AMR in Niger State, Nigeria. A questionnaire-based cross-sectional survey was conducted using purposive sampling, and data were analyzed at a 95% confidence level. A total of 62.8% of targeted practitioners participated. About 42.3% used antimicrobials for treating infections, while 12.2% used them for growth promotion. Only 19.5% correctly identified misuse as under-dosing, and 13.0% were unaware of what misuse entailed. Although 69.1% adhered to daily dosages as prescribed, only 1.6% performed confirmatory diagnoses before administration. Tetracycline (99.2%) and penicillin-streptomycin (82.1%) were the most frequently used antimicrobials. Satisfactory knowledge of antimicrobial use was significantly associated with practitioners aged 50–59 years (p = 0.002) and veterinarians (p = 0.001). Factors influencing misuse included improper usage (p < 0.001), weak regulation (p = 0.005), poor client finances (p = 0.001), low expertise (p = 0.001), and counterfeit drugs (p = 0.001). The findings underscore the urgent need for antimicrobial stewardship, stricter regulation, and continuous education of animal health practitioners.