Do Microbiota in the Soil Affect Embryonic Development and Immunocompetence in Hatchling Reptiles?

Reptile eggs develop in intimate association with microbiota in the soil, raising the possibility that embryogenesis may be affected by shifts in soil microbiota caused by anthropogenic disturbance, translocation of eggs for conservation purposes, or laboratory incubation in sterile media. To test this idea we incubated eggs of keelback snakes (Tropidonophis mairii, Colubridae) in untreated versus autoclaved soil, and injected lipopolysaccharide (LPS) into the egg to induce an immune response in the embryo. Neither treatment modified hatching success, water uptake, incubation period, or white-blood-cell profiles, but both treatments affected hatchling size. Eggs incubated on autoclaved soil produced smaller hatchlings than did eggs on untreated soil, suggesting that heat and/or pressure treatment decrease the soil’s suitability for incubation. Injection of LPS reduced hatchling size, suggesting that the presence of pathogen cues disrupts embryogenesis, possibly by initiating immune reactions unassociated with white-blood-cell profiles. Smaller neonates had higher ratios of heterophils to leucocytes, consistent with higher stress in smaller snakes, or body-size effects on investment into different types of immune cells. Microbiota in the incubation medium thus can affect viability-relevant phenotypic traits of hatchling reptiles. We need further studies to explore the complex mechanisms and impacts of environmental conditions on reptilian embryogenesis.

Offspring Size, Provisioning and Performance as a Function of Maternal Investment in Direct Developing Whelks

<p>Initial maternal provisioning has pervasive ecological and evolutionary implications for species with direct development, influencing offspring size and energetic content, with subsequent effects on performance, and consequences in fitness for both offspring and mother. Here, using three sympatric marine intertidal direct developing gastropods as model organisms (Cominella virgata, Cominella maculosa and Haustrum scobina) I examined how contrasting strategies of maternal investment influenced development, hatchling size, maternal provisioning and juvenile performance. In these sympatric whelks, duration of intra-capsular development was similar among species (i.e. 10 wk until hatching); nonetheless, differences in provisioning and allocation were observed. Cominella virgata (1 embryo per capsule; ~3 mm shell length [SL]) and C. maculosa (7.7 ± 0.3 embryos per capsule; ~1.5 mm SL) provided their embryos with a jelly-like albumen matrix and all embryos developed. Haustrum scobina encapsulated on average 235 ± 17 embryos per capsule but only ~10 reached the hatching stage (~1.2 mm SL), with the remaining siblings being consumed as nurse embryos, mainly during the first 4 wk of development. Similar chronology in the developmental stages was recognizable among species. Higher growth rates and evident juvenile structures became clear by the second half of development and larval characteristics were less frequently observed. Even after 10 weeks of encapsulation and despite emergent crawling juveniles, some hatchling H. scobina still retained “larval” traits, suggesting that this nurse embryo-based provisioning could result in intracapsular asynchrony of development, and that female of this species would be able to bet-hedge in a higher extent compared with female C. maculosa or C. virgata. Maternal investment in newly laid egg capsules differed among the three study species. The structural lipids phospholipid (PL) and cholesterol (ST) and the energetic lipids aliphatic hydrocarbon (AH), triglycerides (TG), diglycerides (DG) and free fatty acids (FFA) occurred in all three species. Only eggs (and also hatchlings) of the multiencapsulated embryos C. maculosa and H. scobina were provisioned with the energy lipids wax ester (WE) and methyl ester (ME), suggesting an interesting similarity with pelagic larvae of other invertebrates and fish where those lipid classes have also been recorded. Despite differences in hatchling size, the small H. scobina had significantly higher amounts of the energy storage lipid TG compared with C. maculosa and C. virgata, suggesting interesting trade-offs between offspring size and offspring energy resources. H. scobina was the only species that suffered a complete depletion of FFA during development (5th wk), suggesting an additional role of this energetic lipid during the early stages of development. Differences in the amount of lipids among newly laid capsules and siblings within capsules were also detected within species. In both species with multiple embryos per capsule, C. maculosa and H. scobina, these differences were largely explained by variation in TG and PL, enhancing the important role of the major structural (PL) and energy (TG) lipids during the early stages of these whelks, and also providing an integrative approach for evaluating maternally-derived lipids on a perindividual basis in direct developing species with contrasting provisioning and offspring size. Because in direct developers maternal provisioning to the embryos is the primary source of nutrition until offspring enter juvenile life, differences in performance should be closely related with initial provisioning, which in turn may reflect maternal nutritional conditions. Field-based surveys and manipulative experiments in the laboratory showed that different maternal environments (i.e. locations and sites) and contrasting offspring size influenced juvenile performance in different ways for C. virgata and C. maculosa. Despite the large differences in conditions and available resources between the Wellington Harbour and the nearby South Coast, the two locations did not influence the hatchling size of either species, and the most important source of variation was at the smallest scale (i.e. among sites), with substantial variation also occurring within and among females. Between and within species differences in hatching size reflected juvenile performance when fed, regardless of whether subjected to desiccation stress. When starved however, species-specific and size differences in performance were less significant. As has been described for many taxa, large offspring often perform better than small conspecifics; however, because this performance is likely to be context-dependent, understanding the importance of the different scales of variation is crucial for determining how variation in size reflects an organism’s performance. Despite the long recognized role of intra-specific variation in offspring size in mediating subsequent performance, the consequences of inter-specific variation in peroffspring maternal investment for co-occurring taxa have been rarely examined in a predator-prey context. Manipulative experiments in the laboratory with hatchling and juvenile C. virgata and C. maculosa revealed that vulnerability of their early life-stages to common crab predators (i.e. the shore crab Cyclograpsus lavauxi) is highly size-dependent. When predator size was evaluated, small crabs were unable to eat hatchlings of either whelk species. Medium and large shore crabs consumed both prey species; however, hatchlings of C. virgata were less vulnerable to predation by medium crabs than large ones, and C. maculosa were equally vulnerable to both sizes of crabs. In hatchlings of both prey species the shell length and shell thickness increased over time; however, only C. virgata reached a size refuge from predation after two months posthatch. Results showed that vulnerability to predators can be mitigated by larger sizes and thicker shells at hatch; nonetheless, other species-specific traits such as juvenile growth rates, may also play key roles in determining the vulnerability of hatchling and juvenile snails when exposed to shell-crushing predators. Overall, these findings suggest that when defining offspring size, provisioning and performance relationships, many context-dependent scenarios are likely to arise. Therefore examining the early life-history stages of direct developing whelks with contrasting maternal investment under an integrative morphological, physiological and experimental approach, allowed a better understanding of how these complex relationships arises and how mediated the species life-history in terms of offspring size, maternal provisioning and subsequent juvenile performance.</p>

Offspring Size, Provisioning and Performance as a Function of Maternal Investment in Direct Developing Whelks

<p>Initial maternal provisioning has pervasive ecological and evolutionary implications for species with direct development, influencing offspring size and energetic content, with subsequent effects on performance, and consequences in fitness for both offspring and mother. Here, using three sympatric marine intertidal direct developing gastropods as model organisms (Cominella virgata, Cominella maculosa and Haustrum scobina) I examined how contrasting strategies of maternal investment influenced development, hatchling size, maternal provisioning and juvenile performance. In these sympatric whelks, duration of intra-capsular development was similar among species (i.e. 10 wk until hatching); nonetheless, differences in provisioning and allocation were observed. Cominella virgata (1 embryo per capsule; ~3 mm shell length [SL]) and C. maculosa (7.7 ± 0.3 embryos per capsule; ~1.5 mm SL) provided their embryos with a jelly-like albumen matrix and all embryos developed. Haustrum scobina encapsulated on average 235 ± 17 embryos per capsule but only ~10 reached the hatching stage (~1.2 mm SL), with the remaining siblings being consumed as nurse embryos, mainly during the first 4 wk of development. Similar chronology in the developmental stages was recognizable among species. Higher growth rates and evident juvenile structures became clear by the second half of development and larval characteristics were less frequently observed. Even after 10 weeks of encapsulation and despite emergent crawling juveniles, some hatchling H. scobina still retained “larval” traits, suggesting that this nurse embryo-based provisioning could result in intracapsular asynchrony of development, and that female of this species would be able to bet-hedge in a higher extent compared with female C. maculosa or C. virgata. Maternal investment in newly laid egg capsules differed among the three study species. The structural lipids phospholipid (PL) and cholesterol (ST) and the energetic lipids aliphatic hydrocarbon (AH), triglycerides (TG), diglycerides (DG) and free fatty acids (FFA) occurred in all three species. Only eggs (and also hatchlings) of the multiencapsulated embryos C. maculosa and H. scobina were provisioned with the energy lipids wax ester (WE) and methyl ester (ME), suggesting an interesting similarity with pelagic larvae of other invertebrates and fish where those lipid classes have also been recorded. Despite differences in hatchling size, the small H. scobina had significantly higher amounts of the energy storage lipid TG compared with C. maculosa and C. virgata, suggesting interesting trade-offs between offspring size and offspring energy resources. H. scobina was the only species that suffered a complete depletion of FFA during development (5th wk), suggesting an additional role of this energetic lipid during the early stages of development. Differences in the amount of lipids among newly laid capsules and siblings within capsules were also detected within species. In both species with multiple embryos per capsule, C. maculosa and H. scobina, these differences were largely explained by variation in TG and PL, enhancing the important role of the major structural (PL) and energy (TG) lipids during the early stages of these whelks, and also providing an integrative approach for evaluating maternally-derived lipids on a perindividual basis in direct developing species with contrasting provisioning and offspring size. Because in direct developers maternal provisioning to the embryos is the primary source of nutrition until offspring enter juvenile life, differences in performance should be closely related with initial provisioning, which in turn may reflect maternal nutritional conditions. Field-based surveys and manipulative experiments in the laboratory showed that different maternal environments (i.e. locations and sites) and contrasting offspring size influenced juvenile performance in different ways for C. virgata and C. maculosa. Despite the large differences in conditions and available resources between the Wellington Harbour and the nearby South Coast, the two locations did not influence the hatchling size of either species, and the most important source of variation was at the smallest scale (i.e. among sites), with substantial variation also occurring within and among females. Between and within species differences in hatching size reflected juvenile performance when fed, regardless of whether subjected to desiccation stress. When starved however, species-specific and size differences in performance were less significant. As has been described for many taxa, large offspring often perform better than small conspecifics; however, because this performance is likely to be context-dependent, understanding the importance of the different scales of variation is crucial for determining how variation in size reflects an organism’s performance. Despite the long recognized role of intra-specific variation in offspring size in mediating subsequent performance, the consequences of inter-specific variation in peroffspring maternal investment for co-occurring taxa have been rarely examined in a predator-prey context. Manipulative experiments in the laboratory with hatchling and juvenile C. virgata and C. maculosa revealed that vulnerability of their early life-stages to common crab predators (i.e. the shore crab Cyclograpsus lavauxi) is highly size-dependent. When predator size was evaluated, small crabs were unable to eat hatchlings of either whelk species. Medium and large shore crabs consumed both prey species; however, hatchlings of C. virgata were less vulnerable to predation by medium crabs than large ones, and C. maculosa were equally vulnerable to both sizes of crabs. In hatchlings of both prey species the shell length and shell thickness increased over time; however, only C. virgata reached a size refuge from predation after two months posthatch. Results showed that vulnerability to predators can be mitigated by larger sizes and thicker shells at hatch; nonetheless, other species-specific traits such as juvenile growth rates, may also play key roles in determining the vulnerability of hatchling and juvenile snails when exposed to shell-crushing predators. Overall, these findings suggest that when defining offspring size, provisioning and performance relationships, many context-dependent scenarios are likely to arise. Therefore examining the early life-history stages of direct developing whelks with contrasting maternal investment under an integrative morphological, physiological and experimental approach, allowed a better understanding of how these complex relationships arises and how mediated the species life-history in terms of offspring size, maternal provisioning and subsequent juvenile performance.</p>

Born With Bristles: New Insights on the Kölliker’s Organs of Octopus Skin

The entire skin surface of octopus embryos, hatchlings and juveniles bears scattered tufts of tiny chitinous setae within small pockets, from which they can be everted and retracted. Known as Kölliker’s organs (KO), they disappear before the subadult stage. The function of these structures during the early life of the octopus is unknown, despite having been first described nearly two centuries ago. To investigate these organs further, general trends in size of KO distribution and density were analyzed in hatchlings and juveniles of 17 octopod species from all oceans, representing holobenthic, holopelagic and meropelagic modes of life. The size of the KO is fairly constant across species, unrelated to mode of life or hatchling size. The density of KO is similar on ventral and dorsal body surfaces, but hatchlings of smaller size tend to have a higher density of KO on the aboral surface of the arms. Analysis of a series of post-hatching Octopus vulgaris shows KO size to be constant throughout ontogeny; it is therefore a consistent structure during the octopus early life from planktonic hatchling to benthic juvenile. New KO are generated on the skin of the arm tips during the planktonic period and initial benthic lives of juveniles. Their density, on both the mantle and arms, gradually decreases as the octopus grows. In older benthic juveniles, the KO degrades, losing its setae and the base of its follicle becomes exposed as a nearly circular stump of muscle. It is estimated that fully everted KO increase the body surface area by around two-thirds compared to when the KO are retracted. This modular mechanism of body surface extension and roughness probably influences flow-related forces such as drag and propulsion of the moving surface of the young octopus while it is of small size with a relatively large surface area. In addition, the distribution of these organs on the aboral surface of the arms of the octopus and their birefringent properties suggest a role in camouflage. Further research is needed to test these hypotheses of KO function in live animals.

Baby tyrannosaurid bones and teeth from the Late Cretaceous of western North America

Tyrannosaurids were the apex predators of Late Cretaceous Laurasia and their status as dominant carnivores has garnered considerable interest since their discovery, both in the popular and scientific realms. As a result, they are well studied and much is known of their anatomy, diversity, growth, and evolution. In contrast, little is known of the earliest stages of tyrannosaurid development. Tyrannosaurid eggs and embryos remain elusive, and juvenile specimens — although known — are rare. Perinatal tyrannosaurid bones and teeth from the Campanian–Maastrichtian of western North America provide the first window into this critical period of the life of a tyrannosaurid. An embryonic dentary (cf. Daspletosaurus) from the Two Medicine Formation of Montana, measuring just 3 cm long, already exhibits distinctive tyrannosaurine characters like a “chin” and a deep Meckelian groove, and reveals the earliest stages of tooth development. When considered together with a remarkably large embryonic ungual from the Horseshoe Canyon Formation of Alberta, minimum hatchling size of tyrannosaurids can be roughly estimated. A perinatal premaxillary tooth from the Horseshoe Canyon Formation likely pertains to Albertosaurus sarcophagus and it shows small denticles on the carinae. This tooth shows that the hallmark characters that distinguish tyrannosaurids from other theropods were present early in life and raises questions about the ontogenetic variability of serrations in premaxillary teeth. Sedimentary and taphonomic similarities in the sites that produced the embryonic bones provide clues to the nesting habits of tyrannosaurids and may help to refine the prospecting search image in the continued quest to discover baby tyrannosaurids.

Contributions of source population and incubation temperature to phenotypic variation of hatchling Chinese skinks

Phenotypic plasticity and local adaptation are viewed as the main factors that result in between-population variation in phenotypic traits, but contributions of these factors to phenotypic variation vary between traits and between species and have only been explored in a few species of reptiles. Here, we incubated eggs of the Chinese skink (Plestiodon chinensis) from 7 geographically separated populations in Southeast China at 3 constant temperatures (24, 28, and 32 °C) to evaluate the combined effects of clutch origin, source population, and incubation temperature on hatchling traits. The relative importance of these factors varied between traits. Nearly all examined hatchling traits, including body mass, snout–vent length (SVL), tail length, head size, limb length, tympanum diameter, and locomotor speed, varied among populations and were affected by incubation temperature. Measures for hatchling size (body mass and SVL) varied considerably among clutches. Source population explained much of the variation in hatchling body mass, whereas incubation temperature explained much of the variation in other examined traits. Our results indicate that between-population variation in hatchling traits of P. chinensis likely reflects the difference in natural incubation conditions and genetic divergence.

On the effects of climate change on Galápagos green turtle Chelonia mydas agassizii neonate mortality in A1B

Climate change affects every crevice and corner of the ecological world. Already we see seasonal effects on important ecosystems such as the marine habitats of the Galápagos Archipelago. This paper looks at the year 2100 in the IPCC scenario A1B, looking specifically at Chelonia mydas agassizii and seeing whether it will be a “winner” or a “loser” under climate change. We discover that while neonate hatchlings may benefit from a compressed laying period that offers them protection by way of numbers, and speed from the increased ocean temperatures (SST), they lose out many other places. Frigatebird and reef fish predation will increase, hatchling size and fitness may decrease, and a surplus of female hatchlings will be produced, or none at all as nest temperatures rise above the thermal mortality limit. Chelonia mydas agassizii will need serious conservation help if we wish to keep it on this earth by the year 2100 even if we opt for the A1B strategy.