Biology subjects

Laakkonen, J.

Publications and source records attributed to Laakkonen, J..

3 recordsLinked to original sources

bioRxiv2026

Rat hepatitis E virus and novel paramyxoviruses in synanthropic rodents and shrews in Kenya

The majority of emerging infectious diseases are zoonotic, having their origin in wildlife before spilling over into the human population. While small mammals are recognized as critical reservoirs for these viruses, their viral diversity remains largely uncharacterized across many African countries. We conducted molecular surveillance of synanthropic rodents and shrews in the Kibera informal settlement in Nairobi and the rural Taita Hills region of Kenya to detect and characterize potential zoonotic viruses. Tissue samples from 228 rodents and shrews were screened for six viral families using PCR assays. Rat hepatitis E virus (HEV) (Rocahepevirus ratti), a rodent-associated virus with potential for human spillover, was identified in Mus musculus and Rattus norvegicus from Kibera. NGS was conducted for the HEV positive samples, and we obtained two near-complete HEV genomes from Rattus norvegicus, which clustered within rodent-associated HEV genotypes in the phylogenetic analysis. The two sequences from the Rattus norvegicus cluster together, indicating a close genetic relationship. Paramyxoviruses belonging to the genera Jeilongvirus and Parahenipavirus were detected both from Taita and Kibera in nine different samples from Rattus norvegicus, Mus minutoides, Crocidura sp and Acomys ignitus. One paramyxovirus positive sample (Acomys ignitus) from Taita was selected for further sequencing with NGS, and a complete genome of a new jeilongvirus was assembled. Phylogenetic analysis of the detected viruses confirmed the close relation to previously known rodent-borne jeilongviruses but also revealed potentially novel jeilong- and parahenipavirus species. Our findings highlight the circulation of potentially zoonotic viruses in both urban and rural small mammals in Kenya. It emphasizes the necessity of continued genomic surveillance of zoonotic viruses to mitigate risks of their spillover into human populations. HighlightsO_LISurveillance reveals diverse rodent-borne viruses circulating in Kenya. C_LIO_LIRat-HEV was detected in Rattus norvegicus and Mus musculus from an urban low-income area. C_LIO_LIParamyxoviruses were detected across multiple rodent and shrew species, including novel Acomys ignitus jeilongvirus. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/719784v1_ufig1.gif" ALT="Figure 1"> View larger version (66K): org.highwire.dtl.DTLVardef@86c94aorg.highwire.dtl.DTLVardef@10946adorg.highwire.dtl.DTLVardef@1ff45eforg.highwire.dtl.DTLVardef@4876f1_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2025

Deep origins and distinct adaptations indicated for a glacial relict seal

Isolated populations of postglacial relicts are known from many regions and are typically found on mountains for terrestrial species and in lakes for aquatic species. Among the few aquatic mammalian relicts, the Saimaa ringed seal (Pusa hispida saimensis) has been landlocked in Lake Saimaa, Finland, for the last 10,000 years. Saimaa ringed seals show genetic, behavioral, and morphological differences to the other ringed seal subspecies, but the extent these differences stem from the end of the last glacial period remains unclear. Here, we demonstrate with comprehensive sampling and state-of-the-art genomic methods that the Saimaa ringed seals are much older than the lake they inhabit, having formed a separate evolutionary branch for at least 60,000 years. This deep evolutionary origin of the Saimaa ringed seals is further underscored by our ecomorphological analyses revealing adaptively distinct features in their dentition and tongue. Overall, glacial relicts, many threatened by extinction, may harbor a richer selection of evolutionary history than might be expected from their recent isolation history alone.

zoology↗

bioRxiv2024

Realisation threshold revisited: does the minimum tooth size scale with body size?

Based on his analyses of lynx and brown bear teeth, Bjorn Kurten coined the concept of realisation threshold, the smallest size at which a tooth can form and erupt properly. Kurten found the smallest sizes of the studied lynx and bear teeth to be 2.5 mm and 3.5 mm, respectively, much larger than for example the smallest rodent teeth known to readily erupt. A recent study comparing developing teeth from shrews to elephants suggested a relatively unchanged theoretical minimum tooth size for mammalian teeth. Together, these studies have left open the question of whether realisation thresholds of teeth are larger in larger mammals than in small ones. In this study, we follow Kurtens line of thought and compare the sizes of teeth that are variably present in dentitions, and therefore likely cross the realisation threshold only occasionally. First, we show using published reports that variably present teeth are relatively small in large mammals, but larger than the previously suggested theoretical minimum tooth size. Next, we examine the canines of mares that are known to be variably present. We report one canine that, compared with information found in the literature, is by far the smallest compared to the body size. In conclusion, whereas the variably present teeth tend to be larger in large mammals, there may be overlooked potential for large mammals to develop very small teeth. This information can be helpful in extrapolating findings from common small model organisms, such as mice, to larger mammals, including humans.

developmental biology↗