Convergent evolution in toothed whale cochleae

BACKGROUND

Odontocetes (toothed whales) are the most species-rich marine mammal lineage. The catalyst for their evolutionary success is echolocation - a form of biological sonar that uses high-frequency sound, produced in the forehead and ultimately detected by the cochlea. The ubiquity of echolocation in odontocetes across a wide range of physical and acoustic environments suggests that convergent evolution of cochlear shape is likely to have occurred. To test this, we used SURFACE; a method that fits Ornstein-Uhlenbeck (OU) models with stepwise AIC (Akaike Information Criterion) to identify convergent regimes on the odontocete phylogeny, and then tested whether convergence in these regimes was significantly greater than expected by chance.

RESULTS

We identified three convergent regimes: (1) True's (Mesoplodon mirus) and Cuvier's (Ziphius cavirostris) beaked whales; (2) sperm whales (Physeter macrocephalus) and all other beaked whales sampled; and (3) pygmy (Kogia breviceps) and dwarf (Kogia sima) sperm whales and Dall's porpoise (Phocoenoides dalli). Interestingly the 'river dolphins', a group notorious for their convergent morphologies and riverine ecologies, do not have convergent cochlear shapes. The first two regimes were significantly convergent, with habitat type and dive type significantly correlated with membership of the sperm whale + beaked whale regime.

CONCLUSIONS

The extreme acoustic environment of the deep ocean likely constrains cochlear shape, causing the cochlear morphology of sperm and beaked whales to converge. This study adds support for cochlear morphology being used to predict the ecology of extinct cetaceans.

Supernumerary teeth observed in a live True's beaked whale in the Bay of Biscay

Mesoplodont beaked whales are one of the most enigmatic mammalian genera. We document a pod of four beaked whales in the Bay of Biscay breaching and tail slapping alongside a large passenger ferry. Photographs of the animals were independently reviewed by experts, and identified as True's beaked whales (Mesoplodon mirus). This is the first conclusive live sighting of these animals in the north-east Atlantic, and adds information to previous sightings that are likely to have been M. mirus. Photographs of an adult male appears to show two supernumerary teeth posterior to the apical mandibular tusks. Whilst analysed museum specimens (n = 8) did not show evidence of alveoli in this location, there is evidence of vestigial teeth and variable dentition in many beaked whale species. This is the first such record of supernumerary teeth in True's beaked whales.

P10.02 Differentiating microglia and tumour associated macrophages in high grade glioma

BACKGROUND

Glioblastoma multiforme (GBM) is the most common primary brain tumour that affects adults. This aggressive tumour is invariably fatal, carrying a rapid progression and a dismal median survival period of only 15 months despite multimodal treatment approaches. Central to GBM pathogenesis is the immunosuppressive profile of these tumours. The two cell types that are highly abundant in these tumours and play critical roles in the immunosuppressive niche are the brain’s resident microglia and their peripheral counterparts - tumour associated macrophages (TAMs). Despite microglia and TAMs being ontogenetically distinct, these cells have largely been grouped together in research owing to the previous lack of cell-specific markers. Recent evidence has suggested that although TAMs may hold a predominantly pro-tumoral role, microglia may adopt a more anti-tumoral phenotype. Therefore, the differentiation of these two cell types is critical in elucidating the potentially characteristic roles of these two cell types in GBM pathogenesis.

MATERIAL AND METHODS

Tissue sections from resected low- and high-grade glioma tumours, along with epilepsy tissue (control), were used for immunohistochemistry (IHC) staining of macrophage pan-makers (Iba1, CD45, PU.1) and microglial-specific markers (TMEM119, P2RY12). Marker co-localisation was then used to differentiate microglia from TAMs. We further investigated a wider subset of cell-specific markers using multicolour flow cytometry and immunocytochemical staining of isolated cells from patient tissue samples.

RESULTS

Immunofluorescent staining of glioma and epilepsy tissue revealed two clear populations of cells; one population displayed long processes and co-labelling for both pan- and microglial-specific markers, whilst the other population displayed an amoeboid phenotype with only pan-maker staining. Preliminary analysis comparing microglia/TAM populations in low-grade, high-grade and epilepsy tissue suggests a clear difference in the proportions of these cells.

CONCLUSION

Our work complements RNA-Seq studies, showing that TMEM119 and P2RY12, alongside other markers, can indeed identify two distinct myeloid cell populations within glioma tissue. This provides a strong basis for further study where we aim to elucidate the respective roles of microglia and TAMs within tumours. Ultimately, this may hold the potential for differential targeting of these cells using immunotherapies.

Validation of a nomogram to predict the risk of cancer in patients with intraductal papillary mucinous neoplasm and main duct dilatation of 10 mm or less

BACKGROUND

Intraductal papillary mucinous neoplasm (IPMN) is premalignant pancreatic lesion. International guidelines offer limited predictors of individual risk. A nomogram to predict individual IPMN malignancy risk was released, with good diagnostic performance based on a large cohort of Asian patients with IPMN. The present study validated a nomogram to predict malignancy risk and invasiveness of IPMN using both Eastern and Western cohorts.

METHODS

Clinicopathological and radiological data from patients who underwent pancreatic resection for IPMN at four centres each in Eastern and Western countries were collected. After excluding patients with missing data for at least one malignancy predictor in the nomogram (main pancreatic duct diameter, cyst size, presence of mural nodule, serum carcinoembryonic antigen and carbohydrate antigen (CA) 19-9 levels, and age).

RESULTS

In total, data from 393 patients who fit the criteria were analysed, of whom 265 were from Eastern and 128 from Western institutions. Although mean age, sex, log value of serum CA19-9 level, tumour location, main duct diameter, cyst size and presence of mural nodule differed between the Korean/Japanese, Eastern and Western cohorts, rates of malignancy and invasive cancer did not differ significantly. Areas under the receiver operating characteristic (ROC) curve values for the nomogram predicting malignancy were 0·745 for Eastern, 0·856 for Western and 0·776 for combined cohorts; respective values for the nomogram predicting invasiveness were 0·736, 0·891 and 0·788.

CONCLUSIONS

External validation of the nomogram showed good performance in predicting cancer in both Eastern and Western patients with IPMN lesions.

Is Antibiotic Prophylaxis Cost-effective for Dental Patients Following Total Knee Arthroplasty?

Introduction:

Routine antibiotic prophylaxis (AP) to prevent prosthetic joint infection remains controversial. The lack of prophylaxis guideline consensus from the American Academy of Orthopaedic Surgeons (AAOS) and the American Dental Association (ADA) contributes to clinician confusion.

Objectives:

This cost-effectiveness decision model informs the AP debate and guideline development by comparing the benefits, harms, and costs of alternative prophylaxis strategies.

Methods:

A Markov state-transition model was developed comparing lifetime health outcomes and costs of alternative AP strategies for dental patients aged 65 y with a history of total knee arthroplasty (TKA). Based on our interpretation of AP recommendations from the AAOS and ADA, incremental cost-effectiveness ratios were calculated to compare the following strategies: no AP, AP for the first 2 y after a TKA, and lifetime AP.

Results:

The no-AP strategy had the lowest average lifetime costs ($17,119) and quality-adjusted life years (11.2151). Compared with a no-prophylaxis strategy, the 2-y AP strategy had incremental costs of $56 and 0.0006 QALYs gained and was cost-effective (incremental cost-effectiveness ratio = $95,100) when a willingness-to-pay threshold of $100,000 per quality-adjusted life year was used. Based on the results of 1-way sensitivity analysis, the no-AP strategy was cost-effective when we modestly increased base case amoxicillin adverse event estimates that were substantially lower than estimates reported in previous models. When plausible combinations of important model parameters were varied, model results suggested that there may be clinical scenarios when AP may be appropriate for some medically at-risk patient populations.

Conclusion:

The results of cost-effectiveness decision modeling generally support questioning routine AP for dental patients with TKA. Sensitivity analyses suggest that prophylaxis may be cost-effective for patient populations with a higher medical risk of infection. This finding is consistent with the recommendations of the 2015 ADA practice guideline and the appropriate use criteria jointly developed by the AAOS and the ADA.

Knowledge Transfer Statement:

The results of this decision modeling research support the contention that routine AP before invasive dental procedures to prevent prosthetic joint infection may not be cost-effective for patients without medical conditions, potentially conferring a higher infection risk. Model sensitivity analyses suggest that there may be clinical situations when medically at-risk patients benefit from AP.

A Miocene pygmy right whale fossil from Australia

Neobalaenines are an enigmatic group of baleen whales represented today by a single living species: the pygmy right whale, Caperea marginata, found only in the Southern Hemisphere. Molecular divergence estimates date the origin of pygmy right whales to 22–26 Ma, yet so far there are only three confirmed fossil occurrences. Here, we describe an isolated periotic from the latest Miocene of Victoria (Australia). The new fossil shows all the hallmarks of Caperea, making it the second-oldest described neobalaenine, and the oldest record of the genus. Overall, the new specimen resembles C. marginata in its external morphology and details of the cochlea, but is more archaic in it having a hypertrophied suprameatal area and a greater number of cochlear turns. The presence of Caperea in Australian waters during the Late Miocene matches the distribution of the living species, and supports a southern origin for pygmy right whales.

Low-frequency hearing preceded the evolution of giant body size and filter feeding in baleen whales

Living baleen whales (mysticetes) produce and hear the lowest-frequency (infrasonic) sounds among mammals. There is currently debate over whether the ancestor of crown cetaceans (Neoceti) was able to detect low frequencies. However, the lack of information on the most archaic fossil mysticetes has prevented us from determining the earliest evolution of their extreme acoustic biology. Here, we report the first anatomical analyses and frequency range estimation of the inner ear in Oligocene (34-23 Ma) fossils of archaic toothed mysticetes from Australia and the USA. The cochlear anatomy of these small fossil mysticetes resembles basilosaurid archaeocetes, but is also similar to that of today's baleen whales, indicating that even the earliest mysticetes detected low-frequency sounds, and lacked ultrasonic hearing and echolocation. This suggests that, in contrast to recent research, the plesiomorphic hearing condition for Neoceti was low frequency, which was retained by toothed mysticetes, and the high-frequency hearing of odontocetes is derived. Therefore, the low-frequency hearing of baleen whales has remained relatively unchanged over the last approximately 34 Myr, being present before the evolution of other signature mysticete traits, including filter feeding, baleen and giant body size.

A behavioural framework for the evolution of feeding in predatory aquatic mammals

Extant aquatic mammals are a key component of aquatic ecosystems. Their morphology, ecological role and behaviour are, to a large extent, shaped by their feeding ecology. Nevertheless, the nature of this crucial aspect of their biology is often oversimplified and, consequently, misinterpreted. Here, we introduce a new framework that categorizes the feeding cycle of predatory aquatic mammals into four distinct functional stages (prey capture, manipulation and processing, water removal and swallowing), and details the feeding behaviours that can be employed at each stage. Based on this comprehensive scheme, we propose that the feeding strategies of living aquatic mammals form an evolutionary sequence that recalls the land-to-water transition of their ancestors. Our new conception helps to explain and predict the origin of particular feeding styles, such as baleen-assisted filter feeding in whales and raptorial 'pierce' feeding in pinnipeds, and informs the structure of present and past ecosystems.

Ultrasonic hearing and echolocation in the earliest toothed whales

The evolution of biosonar (production of high-frequency sound and reception of its echo) was a key innovation of toothed whales and dolphins (Odontoceti) that facilitated phylogenetic diversification and rise to ecological predominance. Yet exactly when high-frequency hearing first evolved in odontocete history remains a fundamental question in cetacean biology. Here, we show that archaic odontocetes had a cochlea specialized for sensing high-frequency sound, as exemplified by an Oligocene xenorophid, one of the earliest diverging stem groups. This specialization is not as extreme as that seen in the crown clade. Paired with anatomical correlates for high-frequency signal production in Xenorophidae, this is strong evidence that the most archaic toothed whales possessed a functional biosonar system, and that this signature adaptation of odontocetes was acquired at or soon after their origin.

The cochlea of the enigmatic pygmy right whale Caperea marginata informs mysticete phylogeny

The pygmy right whale, Caperea marginata, is the least understood extant baleen whale (Cetacea, Mysticeti). Knowledge on its basic anatomy, ecology, and fossil record is limited, even though its singular position outside both balaenids (right whales) and balaenopteroids (rorquals + grey whales) gives Caperea a pivotal role in mysticete evolution. Recent investigations of the cetacean cochlea have provided new insights into sensory capabilities and phylogeny. Here, we extend this advance to Caperea by describing, for the first time, the inner ear of this enigmatic species. The cochlea is large and appears to be sensitive to low-frequency sounds, but its hearing limit is relatively high. The presence of a well-developed tympanal recess links Caperea with cetotheriids and balaenopteroids, rather than balaenids, contrary to the traditional morphological view of a close Caperea-balaenid relationship. Nevertheless, a broader sample of the cetotheriid Herpetocetus demonstrates that the presence of a tympanal recess can be variable at the specific and possibly even the intraspecific level.

Tuning the ferromagnetic phase in the CDW compound SmNiC2 via chemical alloying

We report a study on tuning the charge density wave (CDW) ferromagnet SmNiC2 to a weakly coupled superconductor by substituting La for Sm. X-ray diffraction measurements show that the doped compounds obey Vegard's law, where La (Lu) alloying expands (shrinks) the lattice due to its larger (smaller) atomic size than Sm. In the series Sm1-xLaxNiC2, CDW transition (TCDW = 148 K) for SmNiC2 is gradually suppressed, while the ferromagnetic (FM) ordering temperature (TC) at 17 K slightly increases up to x = 0.3. For x > 0.3, TC starts to decrease and there is no signature that could be related with the CDW phase. Electrical resistivity, magnetic susceptibility and specific heat measurements point toward the possible presence of a FM quantum critical point (QCP) near x = 0.92, where the TC is extrapolated to zero temperature. Superconductivity in LaNiC2 (Tsc = 2.9 K) is completely suppressed with small amount of Sm inclusion near the proposed FM critical point, indicating a competition between the two ordered phases. The tunable lattice parameters via chemical substitution (La,Lu) and the ensuing change among the ordered phases of ferromagnetism, CDW and superconductivity underscores that SmNiC2 provides a rich avenue to study the rare example of a FM QCP, where the broken symmetries are intricately correlated.

New Miocene Fossils and the History of Penguins in Australia

Australia has a fossil record of penguins reaching back to the Eocene, yet today is inhabited by just one breeding species, the little penguin Eudyptula minor. The description of recently collected penguin fossils from the re-dated upper Miocene Port Campbell Limestone of Portland (Victoria), in addition to reanalysis of previously described material, has allowed the Cenozoic history of penguins in Australia to be placed into a global context for the first time. Australian pre-Quaternary fossil penguins represent stem taxa phylogenetically disparate from each other and E. minor, implying multiple dispersals and extinctions. Late Eocene penguins from Australia are closest to contemporaneous taxa in Antarctica, New Zealand and South America. Given current material, the Miocene Australian fossil penguin fauna is apparently unique in harbouring 'giant penguins' after they went extinct elsewhere; and including stem taxa until at least 6 Ma, by which time crown penguins dominated elsewhere in the southern hemisphere. Separation of Australia from Antarctica during the Palaeogene, and its subsequent drift north, appears to have been a major event in Australian penguin biogeography. Increasing isolation through the Cenozoic may have limited penguin dispersal to Australia from outside the Australasian region, until intensification of the eastwards-flowing Antarctic Circumpolar Current in the mid-Miocene established a potential new dispersal vector to Australia.