Sirenians Research Articles

Spatial and Temporal Variation in the Effects of Climatic Variables on Dugong Calf Production.

Knowledge of the relationships between environmental forcing and demographic parameters is important for predicting responses from climatic changes and to manage populations effectively. We explore the relationships between the proportion of sea cows (Dugong dugon) classified as calves and four climatic drivers (rainfall anomaly, Southern Oscillation El Niño Index [SOI], NINO 3.4 sea surface temperature index, and number of tropical cyclones) at a range of spatially distinct locations in Queensland, Australia, a region with relatively high dugong density. Dugong and calf data were obtained from standardized aerial surveys conducted along the study region. A range of lagged versions of each of the focal climatic drivers (1 to 4 years) were included in a global model containing the proportion of calves in each population crossed with each of the lagged versions of the climatic drivers to explore relationships. The relative influence of each predictor was estimated via Gibbs variable selection. The relationships between the proportion of dependent calves and the climatic drivers varied spatially and temporally, with climatic drivers influencing calf counts at sub-regional scales. Thus we recommend that the assessment of and management response to indirect climatic threats on dugongs should also occur at sub-regional scales.

Correction to: Rewriting the history of an extinction-was a population of Steller's sea cows (Hydrodamalis gigas) at St Lawrence Island also driven to extinction?

The Kommandorskiye Islands population of Steller's sea cow (Hydrodamalis gigas) was extirpated ca 1768 CE. Until now, Steller's sea cow was thought to be restricted in historic times to Bering and ...

The dilemma of trade samples and the importance of museum vouchers—caveats from a study on the extinction of Steller's sea cow: a comment on Crerar et al. (2014)

Crerar et al. [[1][1]] recently argued that a population of Steller's sea cows ( Hydrodamalis gigas ) persisted on St Lawrence Island (SLI), Alaska, well into historical time. If true, then Steller's sea cows were hunted to extinction in multiple places at different times in the past millennium [[2

Serendipity in research--investigation into illegal wildlife trade discovers a new population of Steller's sea cows: a reply to Pyenson et al. (2016).

According to Stejneger [[1][1]], it is most likely that the last of the great northern sea cows went extinct around 1768. Many Steller's sea cow ( Hydrodamalis gigas ) bones have been located on the Commander and Aleutian Islands to date [[2][2],[3][3]]. However, no verified H. gigas bones have ever

FIRST RECORD OF DUGONGIDAE (MAMMALIA: SIRENIA) FROM THE FLORESTA CALCARENITES FORMATION (LATE BURDIGALIAN – EARLY LANGHIAN, REGGIO CALABRIA, SOUTHERN ITALY)

A sirenian rib has been recovered at Motta San Giovanni (Reggio Calabria) in the “Floresta Calcarenites”, a Formation cropping out in Sicily and Calabria and dated late Burdigalian-Langhian. Although the rib is not a diagnostic bone for taxonomy, its presence in southern Calabria extends the knowledge about the paleobiogeography of the Family Dugongidae in the Mediterranean basin. The find is hitherto the only record of sirenians in the Floresta calcarenites. Moreover, the specimen extends back to the Early-Middle Miocene (late Burdigalian-Langhian) the occurrence of sirenians in Calabria, previously determined thanks to substantial material from the Late Miocene (Tortonian) of the Monte Poro area (Vibo Valentia). The paleoenvironment of the Floresta calcarenites was a warm and shallow sea, consistent with the paleoecology of Dugongidae.

SIRENIA FOSSILS FROM QOM FORMATION (BURDIGALIAN) OF THE KABUDAR AHANG AREA, NORTHWEST IRAN

Fossil remains of sirenians (Mammalia; Dugongidae) are reported from the late early Miocene (Burdigalian) Qom Formation near the town of Shirin Su, northwest Kabudar Ahang region, west of Tehran, Iran. The fossils consist of partial postcranial skeletons preserved mostly as natural molds in limestone. In the absence of skulls or other diagnostic elements, it is not evident which dugongid subfamily these specimens represent: Halitheriinae or Dugonginae. Both subfamilies were present in contemporaneous Western Tethys (Mediterranean) deposits, but so far only dugongines have been found in Neogene rocks of Eastern Tethys. Since the Iranian deposits are located between these two parts of the former Tethys Seaway, it will be interesting to see which group(s) the Iranian sirenians prove to represent, once their taxonomic identity has been determined through future discoveries.

Jumping from turtles to whales: a Pliocene fossil record depicts an ancient dispersal of Chelonibia on mysticetes

The barnacles included in the superfamily Coronuloidea are epizoic symbionts of various marine vertebrates (including cetaceans, sirenians, and sea turtles) and other crustaceans (crabs and horseshoe crabs). Among Coronuloidea, the so-called turtle barnacles (Chelonibiidae) are known from Paleogene times, whereas the whale barnacles (Coronulidae) likely appeared in the late Pliocene (Piacenzian). Although a derivation from the turtle barnacles (and especially from the genus Chelonibia ) has been proposed, the evolutionary origin of Coronulidae remains to date obscure. In this work we reappraise a fossil record from upper Pliocene (Piacenzian) marine deposits at Casenuove (Empoli municipality, Tuscany, Italy) comprising various shells of Chelonibia testudinaria associated to a partial skeleton of a balaenid mysticete. Based on taphonomic and morpho-functional considerations, we discuss the hypothesis that the barnacles were hosted on the baleen whale, possibly on its callosities, which could have represented an analogous of the horny carapace of marine turtles. This record strongly suggests that the baleen whales can be added to the list of the possible hosts of the barnacles of the genus Chelonibia , thus hinting that the whale barnacles may have evolved from an ancient phase of dispersal of Chelonibia (or a similar ancestor) on mysticete cetaceans.

Fossils and living taxa agree on patterns of body mass evolution: a case study with Afrotheria.

Most of life is extinct, so incorporating some fossil evidence into analyses of macroevolution is typically seen as necessary to understand the diversification of life and patterns of morphological evolution. Here we test the effects of inclusion of fossils in a study of the body size evolution of afrotherian mammals, a clade that includes the elephants, sea cows and elephant shrews. We find that the inclusion of fossil tips has little impact on analyses of body mass evolution; from a small ancestral size (approx. 100 g), there is a shift in rate and an increase in mass leading to the larger-bodied Paenungulata and Tubulidentata, regardless of whether fossils are included or excluded from analyses. For Afrotheria, the inclusion of fossils and morphological character data affect phylogenetic topology, but these differences have little impact upon patterns of body mass evolution and these body mass evolutionary patterns are consistent with the fossil record. The largest differences between our analyses result from the evolutionary model, not the addition of fossils. For some clades, extant-only analyses may be reliable to reconstruct body mass evolution, but the addition of fossils and careful model selection is likely to increase confidence and accuracy of reconstructed macroevolutionary patterns.

Sea otters, kelp forests, and the extinction of Steller’s sea cow

The late Pleistocene extinction of so many large-bodied vertebrates has been variously attributed to two general causes: rapid climate change and the effects of humans as they spread from the Old World to previously uninhabited continents and islands. Many large-bodied vertebrates, especially large apex predators, maintain their associated ecosystems through top-down forcing processes, especially trophic cascades, and megaherbivores also exert an array of strong indirect effects on their communities. Thus, a third possibility for at least some of the Pleistocene extinctions is that they occurred through habitat changes resulting from the loss of these other keystone species. Here we explore the plausibility of this mechanism, using information on sea otters, kelp forests, and the recent extinction of Steller's sea cows from the Commander Islands. Large numbers of sea cows occurred in the Commander Islands at the time of their discovery by Europeans in 1741. Although extinction of these last remaining sea cows during early years of the Pacific maritime fur trade is widely thought to be a consequence of direct human overkill, we show that it is also a probable consequence of the loss of sea otters and the co-occurring loss of kelp, even if not a single sea cow had been killed directly by humans. This example supports the hypothesis that the directly caused extinctions of a few large vertebrates in the late Pleistocene may have resulted in the coextinction of numerous other species.

Resurrecting phenotypes from ancient DNA sequences: promises and perspectives

Anatomical changes in extinct mammalian lineages over evolutionary time, such as the loss of fingers and teeth and the rapid increase in body size that accompanied the late Miocene dispersal of the progenitors of Steller’s sea cows (Hydrodamalis gigas (Zimmermann, 1780)) into North Pacific waters and the convergent development of a thick pelage and accompanying reductions in ear and tail surface area of woolly mammoths (Mammuthus primigenius (Blumenbach, 1799)) and woolly rhinoceros (Coelodonta antiquitatis (Blumenbach, 1799)), are prime examples of adaptive evolution underlying the exploitation of new habitats. It is likely, however, that biochemical specializations adopted during these evolutionary transitions were of similar or even greater biological importance. As these “living” processes do not fossilize, direct information regarding the physiological attributes of extinct species has largely remained beyond the range of scientific inquiry. However, the ability to retrieve genomic sequences from ancient DNA samples, combined with ectopic expression systems, now permit the evolutionary origins and structural and functional properties of authentic prehistoric proteins to be examined in great detail. Exponential technical advances in ancient DNA retrieval, enrichment, and sequencing will soon permit targeted generation of complete genomes from hundreds of extinct species across the last one million years that, in combination with emerging in vitro expression, genome engineering, and cell differentiation techniques, promises to herald an exciting new trajectory of evolutionary research at the interface of biochemistry, genomics, palaeontology, and cell biology.

Third Grade Manatee Curriculum—Lesson 2: Reading Rainbow, “Sam the Sea Cow”

This 4-page fact sheet is the second lesson of the Third Grade Manatee Workbook series. This curriculum provides a series of individual lessons covering manatee biology and ecology, as well as highlighting some of the ways that humans impact and can protect manatees. The curriculum has been written at a third-grade level but can be adapted for older or younger students. Written by Ruth Francis-Floyd and Maia McGuire, and published by the Veterinary Medicine—Large Animal Clinical Sciences Department, UF/IFAS Extension, July 2015. (Photo credit: Keith Ramos, USFWS)
 VM205/VM205: Third Grade Manatee Curriculum—Lesson 2: Reading Rainbow, "Sam the Sea Cow" (ufl.edu)

Interordinal gene capture, the phylogenetic position of Steller’s sea cow based on molecular and morphological data, and the macroevolutionary history of Sirenia

The recently extinct (ca. 1768) Steller’s sea cow (Hydrodamalis gigas) was a large, edentulous North Pacific sirenian. The phylogenetic affinities of this taxon to other members of this clade, living and extinct, are uncertain based on previous morphological and molecular studies. We employed hybridization capture methods and second generation sequencing technology to obtain >30kb of exon sequences from 26 nuclear genes for both H. gigas and Dugong dugon. We also obtained complete coding sequences for the tooth-related enamelin (ENAM) gene. Hybridization probes designed using dugong and manatee sequences were both highly effective in retrieving sequences from H. gigas (mean=98.8% coverage), as were more divergent probes for regions of ENAM (99.0% coverage) that were designed exclusively from a proboscidean (African elephant) and a hyracoid (Cape hyrax). New sequences were combined with available sequences for representatives of all other afrotherian orders. We also expanded a previously published morphological matrix for living and fossil Sirenia by adding both new taxa and nine new postcranial characters. Maximum likelihood and parsimony analyses of the molecular data provide robust support for an association of H. gigas and D. dugon to the exclusion of living trichechids (manatees). Parsimony analyses of the morphological data also support the inclusion of H. gigas in Dugongidae with D. dugon and fossil dugongids. Timetree analyses based on calibration density approaches with hard- and soft-bounded constraints suggest that H. gigas and D. dugon diverged in the Oligocene and that crown sirenians last shared a common ancestor in the Eocene. The coding sequence for the ENAM gene in H. gigas does not contain frameshift mutations or stop codons, but there is a transversion mutation (AG to CG) in the acceptor splice site of intron 2. This disruption in the edentulous Steller’s sea cow is consistent with previous studies that have documented inactivating mutations in tooth-specific loci of a variety of edentulous and enamelless vertebrates including birds, turtles, aardvarks, pangolins, xenarthrans, and baleen whales. Further, branch-site dN/dS analyses provide evidence for positive selection in ENAM on the stem dugongid branch where extensive tooth reduction occurred, followed by neutral evolution on the Hydrodamalis branch. Finally, we present a synthetic evolutionary tree for living and fossil sirenians showing several key innovations in the history of this clade including character state changes that parallel those that occurred in the evolutionary history of cetaceans.

Effects of sevoflurane on electroencephalography in immature rat brain

Objective To investigate the effects of sevoflurane on neonatal rats electrocephalography(EEG)and the mechanism. Methods Thirty neonatal rats, aged 14 days, weighing 35- 45 g, were randomly divided into 3 groups: without sevoflurane group(group C,n= 10), low sevoflurane concentration group(group S1,n= 10), high sevoflurane concentration group(group S2). Electroencephalogram recording started immediately after completion of the implant surgery. Anesthesia was induced with 6.0% sevoflurane over 3 min and maintained with 2.1% over 60 min in group S1. In group S2 anesthesia was induced with 8.0% sevoflurane and maintained with 3.5%. Acquisition of the EEG was performed using the Sirenia software. Sirenia Score programs were used for the EEG data analysis. Results As compared with group D and group S1, spike's frequency and amplitude were significantly increased in group S2 during anesthesia induction. Spike's frequency was higher in group S2 than group D during anesthesia maintenaed. The concentration of corticosterone among three groups were:26.8±3.8, 106.5±15.1 and 155.9±13.6, respectively. Compared with group D, the level of corticosterone were significantly increased in group S1 and group S2. Conclusion Sevoflurane anesthesia can induce spike EEG in 14- days rats, which may be induced by high level of corticosterone. Key words: Sevoflurane; Immature rat; Electrocephgraphy; Spike

Rewriting the history of an extinction-was a population of Steller's sea cows (Hydrodamalis gigas) at St Lawrence Island also driven to extinction?

The Kommandorskiye Islands population of Steller's sea cow (Hydrodamalis gigas) was extirpated ca 1768 CE. Until now, Steller's sea cow was thought to be restricted in historic times to Bering and Copper Islands, Russia, with other records in the last millennium from the western Aleutian Islands. However, Steller's sea cow bone has been obtained by the authors from St Lawrence Island, Alaska, which is significantly further north. Bone identity was verified using analysis of mitochondrial DNA. The nitrogen-15 (δ(15)N)/carbon-13 (δ(13)C) values for bone samples from St Lawrence Island were significantly (p ≤ 0.05) different from Bering Island samples, indicating a second population. Bone samples were dated to between 1030 and 1150 BP (approx. 800-920 CE). The samples date from close to the beginning of the mediaeval warm period, which could indicate that the population at St Lawrence Island was driven to extinction by climate change. A warming of the climate in the area may have changed the availability of kelp; alternatively or in addition, the animals may have been driven to extinction by the expansion of the Inuit from the Bering Strait region, possibly due to opening waterways, maybe following bowhead whales (Balaena mysticetus), or searching for iron and copper. This study provides evidence for a previously unknown population of sea cows in the North Pacific within the past 1000 years and a second Steller's sea cow extirpation event in recent history.

Anthracobunids from the middle eocene of India and pakistan are stem perissodactyls.

Anthracobunidae is an Eocene family of large mammals from south Asia that is commonly considered to be part of the radiation that gave rise to elephants (proboscideans) and sea cows (sirenians). We describe a new collection of anthracobunid fossils from Middle Eocene rocks of Indo-Pakistan that more than doubles the number of known anthracobunid fossils and challenges their putative relationships, instead implying that they are stem perissodactyls. Cranial, dental, and postcranial elements allow a revision of species and the recognition of a new anthracobunid genus. Analyses of stable isotopes and long bone geometry together suggest that most anthracobunids fed on land, but spent a considerable amount of time near water. This new evidence expands our understanding of stem perissodactyl diversity and sheds new light on perissodactyl origins.

Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils

Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction.

A new archaeocete and other marine mammals (Cetacea and Sirenia) from lower middle Eocene phosphate deposits of Togo

Lutetian lower middle Eocene phosphate deposits of Kpogamé-Hahotoé in Togo yield new information about whales and sea cows in West Africa. Most specimens are individual teeth and bones, collected as isolated elements, but some appear to have been associated. Most are conservatively interpreted to represent a new 300–400 kg protocetid archaeocete, Togocetus traversei. This genus and species is distinctly primitive for a protocetid in retaining a relatively small mandibular canal in the dentary and retaining a salient metaconid on the lower first molar (M1), but it is derived relative to earlier archaeocetes in having large, dense, osteosclerotic tympanic bullae. Mandibular canal size and large dense bullae are not as tightly linked in terms of function in hearing as previously thought. Postcranially Togocetus traversei had many characteristics found in other semiaquatic protocetids: a relatively long neck, mobile shoulder, digitigrade manus, large pelvis, well-developed hind limbs, and feet specialized for swimming. Loss of a fovea on the head of the femur indicates loss of the teres ligament stabilizing the hip, which is a derived specialization consistent with life in water. Protocetid specimens distinctly smaller and larger than those of Togocetus traversei indicate the presence of at least three protocetids at Kpogamé. Sirenian vertebral and rib pieces indicate the presence of a protosirenid and a dugongid. Finally, a vertebral centrum and piece of humerus appear to represent a large land mammal. A diverse fauna of archaic whales and early sirenians inhabited the western margin of Africa and the eastern Atlantic Ocean as early as 46–44 million years before present, showing that both cetaceans and sirenians were widely distributed geographically by this time.

The petrosal of the earliest elephant-shrew Chambius (Macroscelidea: Afrotheria) from the Eocene of Djebel Chambi (Tunisia) and the evolution of middle and inner ear of elephant-shrews

Macroscelidea (elephant-shrews or sengis) are small insectivorous mammals restricted to Africa; they belong to the super-cohort Afrotheria along with other insectivorans (aardvarks, tenrecs and golden moles) and ungulates (elephants, sea cows and hyraxes). Though their fossil record extends back to the Eocene, cranial remains of Palaeogene elephant-shrews, including the middle and inner ear structure, remain unknown. Two macroscelid isolated petrosal bones are described from the late Early–early Middle Eocene Djebel Chambi locality in Tunisia. Chambius kasserinensis is the only macroscelid represented in this locality. A cladistic analysis based on petrosal and inner ear characters highlights the crucial interest of the petrosal and inner ear morphology for understanding the evolution of Macroscelididae. It confirms the attribution of these isolated petrosals to C. kasserinensis. This hypothesis is supported by a common pattern of circulatory system, the morphology of the rostral and caudal tympanic processes, and the shape of the cochlea. In addition, Chambius appears to be the basal-most taxon among the macroscelid sample; this position is supported by the lack of some specializations of the middle ear such as inflated ossicular bones and pneumatized bulla. The presence of a secondary common crus in Chambius suggests a convergent loss of this structure, at least in Macroscelidea and Tenrecoidea. The petrosal and inner ear characters support the clade Afroinsectivora, which gathers macroscelids with other endemic African insectivorans (tenrecs and golden moles), reinforcing the hypothesis of an African origin of macroscelids. The petrosal bone and inner ear characters provide further morphological support for the debated clade (Petrodromus, Elephantulus rozeti, Macroscelides). New data underlines the fact that the cranial arterial pattern of the Eocene macroscelid Chambius was already similar to that of modern macroscelid species. It also suggests that early elephant-shrews were probably not as capable of hearing low frequencies as their extant representatives.

A New Genus and Species of Late Miocene Paleoparadoxiid (Mammalia, Desmostylia) from Calieornia

The Desmostylia are an extinct order of quadrupedal, marine, herbivorous, placental mammals whose closest living relatives are Proboscidea (elephants and their relatives) and Sirenia (sea cows and manatees). Desmostylians lived around the margins of the North Pacific Ocean from the Oligocene until the end of the Miocene. A 10- to 11-million-year-old fossil skeleton, here named Neoparadoxia cecilialina, new genus and new species, was found in the early late Miocene part of the Monterey Formation in Orange County, coastal southern California, USA. This is the geochronologically youngest named species of desmostylian. The holotype of this species is the most complete known paleoparadoxiid desmostylian skeleton and only the second desmostylian skeleton yet reported from North America that includes a cranium. The skeleton is exhibited in the Age of Mammals hall of the Natural History Museum of Los Angeles County. Among previously named desmostylians, N. cecilialina is most closely related to middle Miocene (approximately 14-million-year-old) Paleoparadoxia repenningi Domning and Barnes, 2007. The two species share sufficient numbers of characters to warrant transferring P. repenningi to the new genus Neoparadoxia. These species demonstrate that geochronologically late paleoparadoxiids evolved enhanced adaptations for life in water (larger body size, larger manus and pes, enlarged external nares, elevated orbits) and other adaptations related to bulk aquatic feeding (enlarged oral cavity, ventrally turned snout and anterior end of the mandible, larger molars). Neoparadoxia cecilialina has incisors that are flatter and wider than those of any other known desmostylian. Other derived features of N. cecilialina, such as delayed eruption of canines and posterior-most molars, possibly extended its life span, with a result being larger adult body size. Such adaptations in the last known desmostylians may have been responses to competition with dugongid sirenians, also herbivores, that appeared in the North Pacific Ocean after the earlier endemic desmostylians and ultimately supplanted them in that realm. The comparatively small and primitive species, Paleoparadoxia weltoni Clark, 1991, from the latest Oligocene Skooner Gulch Formation in Mendocino County, California, USA, is assigned to the new genus Archaeoparadoxia.

"Ecology and Conservation of the Sirenia. Dugongs and Manatees" by Helene Marsh et al. 2011. [book review

"Ecology and Conservation of the Sirenia. Dugongs and Manatees" by Helene Marsh et al. 2011. [book review