Near-term Embryos Research Articles

Prenatal exposure to triclosan induced brain telomere shortening in a wild bird species

Exposure to the antimicrobial agent Triclosan (TCS) induces oxidative stress in diverse organisms, including birds. However, whether TCS-induced oxidative stress effectively translates into detrimental effects is still unclear. The present study examined whether prenatal TCS exposure induces oxidative stress and telomere shortening in the brain and the liver of near-term embryos of the yellow-legged gull (Larus michahellis). Prenatal TCS exposure caused a significant overproduction of reactive oxygen species (ROS) in the brain, but no oxidative damage occurred. Telomeres of TCS-exposed embryos had brain telomeres 30 % shorter compared to controls, probably because the relatively modest antioxidant defenses of this organ during prenatal development cannot counteract the impact of the TCS-induced ROS. No telomere shortening was observed in the liver. Our results demonstrated that prenatal exposure to TCS in wild bird species can modulate the oxidative status and induce telomere shortening in the brain of the yellow-legged gull embryos.

First complete description of the dark-mouth skate Raja arctowskii Dollo, 1904 from Antarctic waters, assigned to the genus Bathyraja (Elasmobranchii, Rajiformes, Arhynchobatidae)

The dark-mouth skate, Raja arctowskii Dollo, 1904 from Antarctic waters is an extraordinary case in skate taxonomy. For more than 100 years, this species has been known only from three empty egg capsules and the species as such has remained undescribed due to the lack of specimens that could be assigned to Dollo’s small capsules. Since trawled egg capsules and an egg capsule containing a near-term embryo became available, it finally was possible to connect specimens with the empty egg capsules and completely describe Dollo’s R. arctowskii with detailed external morphology, skeletal features, clasper morphology, and clasper skeleton and assign it to the genus Bathyraja Ishiyama, 1958a. Bathyraja arctowskii is one of the smallest known species of Bathyraja, attaining only a 61 cm total length (TL). It is characterized by an at least partly, usually completely medium to dark grayish pigmented mouth cavity, as well as the often dark underside of the nasal curtain from very small juvenile stages onwards. It further differs from most congeners in Antarctic and Subantarctic waters in the absence of thorns on the dorsal disc. It appears to be a wide-ranging, circumantarctic species found in the Atlantic, Pacific, and Indian Ocean sectors of the Southern Ocean. The species seems to be locally common at least in the Atlantic sector, with up to 94 juvenile to subadult specimens caught in one single haul.

Near-term embryos and gravid females of Lusitanian cownose ray (Rhinoptera marginata) in Mersin Bay, eastern Mediterranean Sea

Batoid chondrichthyans are vulnerable to commercial fisheries even though they are often not targeted. A greater understanding of their reproductive biology is important to facilitate their conservation. In February 2013, 89 female and 40 male Lusitanian cownose ray (Rhinoptera marginata) specimens were accidentally caught in Mersin Bay in the eastern Mediterranean Sea. Thirty-six fish were gravid, each bearing one embryo. Of the remaining females, 39 were sexually mature but not gravid and 14 were immature. There were 28 mature and 12 immature males. The average disc width (DW) of both mature females (80.2cm) and males (74.2cm) was significantly higher than that of immature females (60.7cm) and males (60.3cm). For all rays, DW and total weight (TW) were in the range 55.7–98.2cm and 1802–13600g. The DW and TW measured for all 16 female and 20 male embryos were in the range 15.6–29.2cm and 57–281g. Such a large single haul sample, including many gravid specimens and mature males, indicates a schooling formation at capture. The location in Mersin Bay near the estuaries of the Tarsus and Seyhan rivers, and its relative closeness to the sampling location of a previously reported neonate, suggests that this region may be a nursery area for Lusitanian cownose rays in the eastern Mediterranean.

Sawfish (Pristidae) records along the Eastern Amazon coast

Sawfishes are the most endangered cartilaginous fishes on the planet. Their external morphology facilitates entanglement in fishing nets and their K-selected life history hinders the recovery of exploited populations. The Eastern Amazon coast (EAC) is known to be an area where sawfishes occur in Brazil, but few studies have been conducted in the area to better understand their biology and ecology. The present study reports sawfish captures along the coast of Brazil's second largest state. Data were collected from interviews with fishermen, a literature review, and media reports. In total, 23 captures were recorded between 1984 and 2016. Records include adults, a pregnant female with near-term embryos, juveniles, and young-of-the-year specimens. Most catches were reported in the Canal do Navio, an area under strong human pressure. Sawfish saws are valuable items and, for many anglers in precarious economic and social situations, high market prices eclipse the fishing prohibitions laid down under federal laws. Urgent research is required to understand sawfishes' life history, identify their critical habitats, and effectively manage and conserve these species along the EAC.

Gill dimensions in near-term embryos of Amazonian freshwater stingrays (Elasmobranchii: Potamotrygonidae) and their relationship to the lifestyle and habitat of neonatal pups

This comparative study of gill morphometrics in near-term embryos of freshwater stingray potamotrygonids examines gill dimensions in relation to neonatal lifestyle and habitat. In embryos of the potamotrygonids Paratrygon aiereba, Plesiotrygon iwamae, Potamotrygon motoro, Potamotrygon orbignyi, and cururu ray Potamotrygon sp. the number and length of filaments, total gill surface area, mass-specific surface area, water-blood diffusion distance, and anatomical diffusion factor were analysed. In all potamotrygonids, the 3rd branchial arch possessed a larger respiratory surface than the other gill arches. Larger embryos had more gill surface area and large spiracles, which are necessary to maintain the high oxygen uptake needed due to their larger body size. However, the higher mass-specific gill surface area observed in near-term embryos may be advantageous because neonates can use hypoxic environments as refuges against predators, as well as catch small prey that inhabit the same environment. As expected from their benthic mode of life, freshwater stingrays are sluggish animals compared to pelagic fishes. However, based on gill respiratory morphometry (such as gill area, mass-specific gill area, the water-blood diffusion barrier, anatomical diffusion factor, and relative opening of the spiracle), subtypes of lifestyles can be observed corresponding to: active, intermediate, and sluggish species according to Gray's scale.

Maturity, reproductive cycle and fecundity of common torpedo, Torpedo torpedo (Chondrichthyes, Torpedinidae) from the Lagoon of Bizerte (Northeastern Tunisia, central Mediterranean)

Common torpedo Torpedo torpedo (Linnaeus, 1758) is widely distributed in the Mediterranean Sea, especially in southern and northern regions. The species is known throughout the Tunisian coast and entered brackish areas, such as the northeastern Lagoon of Bizerte, where it is commonly captured. Investigations conducted in this latter area showed that males and females sexually matured between 234–285 mm and 245–280 mm total length (TL), respectively. The largest male and female were 403 mm and 435 mm TL, respectively and weighed 721.5 and 1273.5 g, respectively. There was a not significant relationship total mass versus TL between males and females. Conversely, the relationship of liver mass versus TL significantly differed between sexes. The diameter of the largest yolky oocytes ranged between 43 and 47 mm (mean 45.08 ± 0.98)}, while the mass ranged between 29.5 and 37.4 g (mean 31.79 ± 2.20). Near term embryos ranged from 19.34 to 31.28 mm TL (mean: 24.60 ± 4.12) and weighed from 3.9 to 9.0 g (mean 5.97 ± 1.41). Ovarian fecundity ranged from 4 to 36 (mean = 11.60 ± 5.96). Uterine fecundity or litter size ranged from 3 to 13 (mean = 6.36 ± 2.67). Both fecundities showed a positive relationship with TL of females. A chemical balance of development based on mean dry masses of yolky oocytes and near-term embryos was 0.75 and suggested that T. torpedo could be considered as a pure lecithotrophic species. Hepatosomatic index (HSI) and gonadosomatic index (GSI) calculated for females presented significant higher values than those of males. HSI values of males significantly differed differences between juveniles, sub-adults and adults, and in females, HSI values were not significantly different between juveniles and sub-adults and significantly different between sub-adults and adults. The values of male GSI increased with TL of specimens; additionally, they showed significant differences between juveniles and subadults, but not between sub-adults and adults. Monthly mean values of adult male and female HSI significantly varied throughout the year. Monthly mean of females GSI showed significant changes especially from January to April, due to a high vitellogenic activity, GSI decreased from May to August, during this period all yolky oocytes were ovulated, then GSI increased progressively from September. The reproductive cycle lasted one year approximately and gestation period 4 months, while near-term females were captured in August. Vitellogenesis did not proceed in parallel with embryonic development: during ovarian vitellogenic activity, the uteri were empty and in an appearent resting phase, conversely during gestation, the ovaries did not exhibit an appearent activity, by contrast other specimens exhibited a vitellogenic activity during gestation. With special regard to the latter case, it remains difficult to state if these small yolky oocytes were not ovulated, or if they were new oocytes produced immediately after ovulation, both hypothesis remaining suitable.

Sharks of North America

Castro's 20 cm × 17 cm 2.5 kg book treats sharks that occur inside an area from the Artic Ocean, the Eastern Pacific from Alaska to Southern Mexico and the Western Atlantic from Greenland to the Gulf of Mexico and Northern Caribbean. (This information is in the preface not in the text or on a map). Sharks of North America is a labor of love spanning two decades since Castro's 1983 Sharks of North American Waters. He scoured the world to see a specific shark and/or to study and photograph its reproductive stages.Sharks of North America encompasses 135 species (5 as undescribed species) in 22 families. The introduction tells us how to use the book. Keys occupy pp. 11–18. Species accounts (pp. 22–531) contain information on : spanish name, common name, specific name, synonyms, identification ranges, size and maturity, biology , sexual maturity, reproduction, size and growth and relation to humans. Diana Rome Peoples illustrated the 135 species which also include ventral snout and teeth drawings and scanning electron images of dermal denticles. A glossary fills pages 601–604, indices to scientific names pp. 601–604, common names pp. 611–615. Appendix 1 is a primer on shark reproduction and contains vivid pictures of early embryonic stages pp. 553–545; Appendix 2 is an essay on the conservation of sharks pp. 547–550. References to 2008 encompass pp. 551–593.Highlights of the volume are the family names that stand out in red, making them easy to find in the text; the vivid reproductive photographs; and the mass of information in the text gathered during Castro's world travels. Although the keys to families pp. 11–18 and all species keys work except the Carcharhinus keys pp. 390–392 as you can't get past couplet 5. Likewise too many sharks are depicted tan rather they should be gray, black, or some other color i.e.: bramble shark p. 49 should be chocolate colored see reference 3, rough skinned spiny dogfish p. 52 should be gray, angelshark p. 167 should be tan 8, nurse shark p. 184 is chocolate colored as an adult, light tan with 1/8 inch blue spots as young, basking shark p. 249 is black not gray with lateral bands 5, marbled catshark p. 323 is grey not light tan on the sides, Meades shark p. 342 grey between the spots, chain shark p. 342 should be darker tan, blacknose shark p. 393 is greenish yellow in summer, dark brown in winter 1, spinner shark p. 407 is gray not tan, silky shark p. 413 is grey not tan, bull shark p. 426 is gray year around, black tipped shark is gray not tan, Caribbean reef shark p. 449 is gray 1, and Atlantic sharpnose shark p. 496 is gray in summer dark brown in winter.Ranges of several sharks should have included North Carolina i.e., sharpnosed seven gill shark 6, rough skinned shark, bramble shark 3, marbled shark 5, Galapagos 5, and Caribbean reef shark 2. Large adult tiger sharks become grayer and lose most of their bars and stripes with age.An adult female tiger shark 3,943 mm TL 4 caught 5 August 1993 off Shallote, NC contained 55 near-term embryos 4 and weighed 454 kg. Basking shark 7 vertebrae deposit two annuli per year rather than one.Castro's volume is a remarkable effort bringing much information on Sharks of North America to all. Hopefully we will heed his call for action to conserve sharks. Yet despite all that has been presented, much remains to be learned about sharks. Meanwhile, you don't want to be without a copy of the Sharks of North America.

Reproductive biology and embryonic development of <i>Squalus blainvillei</i> in the eastern Mediterranean Sea

A total number of 526 Squalus blainvillei was sampled from the bottom trawl and bottom longline catches in the eastern Mediterranean Sea from December 2004 to December 2009. Females outnumbered males and the overall sex ratio was 1.26:1. Females ranged from 182 to 779 mm in total length and males from 180 to 799 mm. Both females and males showed allometric growth (b > 3) and we found statistically significant differences in the relationship between length and weight. Out of the specimens examined, 36% of females and 63% of males were sexually mature. Males reached sexual maturity at smaller sizes than females. The smallest sexually mature female was 523 mm in total length, while the smallest sexually mature male was 425 mm in total length. Mean length at 50% maturity was estimated at 564.4 mm for females and 457.7 mm for males. Sexually mature specimens of both sexes with mature gonads and high GSI were present in high proportions in every season of the year, which indicates a continuous reproductive cycle. Ovarian oocytes continued to develop throughout gestation. Females carrying near-term embryos had large, equally developed ovarian oocytes, which suggests that they ovulate soon after parturition. Ovarian fecundity ranged from 1 to 7 and uterine fecundity ranged from 1 to 6. Embryo length and yolk sac weight were negatively correlated.

Maturity, reproductive cycle and fecundity of the spiny dogfish Squalus acanthias (Chondrichthyes: Squalidae) off the Languedocian coast (southern France, northern Mediterranean)

The spiny dogfish Squalus acanthias is widely distributed in Atlanto-Mediterranean regions, being captured off the Languedocian coast (southern France, northern Mediterranean), despite a decline of landings. The male and female sexually matured between 635–700 mm and 860–880 mm total length (TL), respectively. The largest male and female were 800 mm and 1110 mm TL, respectively and weighed 2220 g and 8900 g, respectively. There was a significant relationship for total mass versus TL, and liver mass versus TL between males and females. The diameter of the largest yolky oocytes ranged between 43 and 47 mm (mean 45.08 ± 0.98), while the mass ranged between 29.5 and 37.4 g (mean 31.79 ± 2.20). Near- term embryos ranged from 245 to 271 mm TL (mean: 258.85 ± 7.28) and weighed from 47.5 to 55.9 g (mean 53.35 ± 2.26). Ovarian fecundity ranged from 6 to 15 (mean = 10.38 ± 2.66). Uterine fecundity or litter size ranged from 4 to 12 (mean = 8.15 ± 2.07). Both fecundities showed a positive relationship with TL of females. A chemical balance of development based on mean dry masses of yolky oocytes and near-term embryos was 0.87 and suggested that S. acanthias is a pure lecithotrophic species. Hepatosomatic index (HSI) and gonadosomatic index (GSI) significantly increased with size in both males and females. HSI reached the highest values in both sub-adult and adult specimens, reflecting the role of the liver in the gonadal production as well as in buoyancy, while in the GSI the highest values were observed in pregnant females. Vitellogenesis proceeds in parallel with embryonic development. Near-term females were captured in different months of the year while a short period of resting could not be excluded between parturition and the beginning of a new pregnancy, so it appears difficult to delineate the length of gestation. However, a reproductive cycle with a wide range from 18 to 24 months remains a suitable hypothesis.

Population biology of the shark, Squalus megalops, harvested in the central-east Atlantic Ocean

This is the first study to analyse the structure and biological characteristics of Squalus megalops and the impact of fishing on its population in the Northern Hemisphere (central-east Atlantic). The sex ratio (1:2.59) diverged significantly from 1:1 in favour of females. The length at maturity for males and females was 490 and between 634 and 659 mm total length, respectively. The lengths at pregnancy and maternity were 661 and 681 mm, respectively. S. megalops is an asynchronous breeder in which ovulation, parturition and pregnancy do not take place at a specific time of year. The maximum litter size was six, and the ovulation–gestation period was two years, which is equal to a maximum productivity of 36 offspring per lifetime. The sex ratio of near-term embryos (1:1.15) did not show any significant differences. The mean growth rate of the embryos was 179 mm/year in the first year and 47 mm/year in the second, indicating a period of gestation of two years. Age estimates ranged between 4 and 26 years for males and 4 and 32 years for females. Males and females of all total lengths were found in the same area and bathymetric strata in different seasons of the year. The estimate of total mortality for females was 0.22 year −1 and 0.19 year −1 for males. Natural mortality was 0.107 years −1 and 0.12 years −1 for females and males, respectively. The values for fishing mortality and the exploitation ratio were 0.113 years −1 and 0.51 for females and 0.07 years −1 and 0.38 for males, respectively. The estimated biological parameters indicate that S. megalops is highly susceptible to overfishing, given the high fishing pressure this species experiences in the central-east Atlantic.

Uterine and Placental Angiogenesis in the Australian Skinks, Ctenotus taeniolatus, and Saiphos equalis

The evolution of viviparity requires modifications to multiple integrated physiological features to support embryonic development during pregnancy. Embryonic growth during pregnancy is dependent upon the capacity of the uterine vascular system to satisfy increasing embryonic oxygen demand throughout gestation. We tested the hypothesis that total surface area of uterine blood vessels increases in concert with embryonic growth, and hence its oxygen demand, during gestation. We used immunofluorescence and laser-scanning confocal microscopy to quantify uterine microvascular density and morphology during gestation in the oviparous skink Ctenotus taeniolatus and in Saiphos equalis, a skink species with prolonged egg retention. For C. taeniolatus, vessel density (Nv) and vessel length-density (Lv) in the embryonic hemisphere of the uterus is 23% and 17% less, respectively, than that of S. equalis and vascular surface-area does not differ as a function of embryo stage. For S. equalis, overall Nv, Lv, and vessel diameter (Dv), does not change during the first half of gestation but increases by 36% (Nv), 44% (Lv), and 60% (Dv) by near-term embryo stages late in gestation. The chorioallantoic membrane of S. equalis increases in absolute size but vascular density does not differ as a function of embryo stage. The marked increase in uterine vascular density during late gestation coincides with the phase of rapid growth in embryo mass and concomitant increase in metabolic rate. Expansion of the uterine vascular bed in concert with embryo size and metabolism is likely to be an important transitional step in the evolution of viviparity.

Reproductive biology of the guitarfish Rhinobatos hynnicephalus (Batoidea: Rhinobatidae) in Ariake Bay, Japan

Size at sexual maturity, reproductive cycle, and fecundity of the guitarfish, Rhinobatos hynnicephalus, were examined in Ariake Bay, Japan. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: males, 431 mm; females, 476 mm]. Monthly gonadosomatic indices of males decreased abruptly from July to August. Histological examinations confirmed the presence of mature spermatozoa in the testes in July, with semen in seminal vesicles in July and August. Preovulatory ova were observed in females with near-term embryos in August. Parturition occurred in August, immediately followed by mating, ovulation, and fertilization. Gestation period is approximately 1 year. Fertilized uterine eggs without embryonic development were present throughout the annual reproductive cycle. Embryonic development began in June and ended in August, indicating that R. hynnicephalus undergoes embryonic diapause (9 months). Fecundity increased with TL and ranged from 1 to 9 (mean, 4.4) embryos per litter.

Reproductive biology of the fanray, Platyrhina sinensis (Batoidea: Platyrhinidae) in Ariake Bay, Japan

The reproductive biology of the fanray, Platyrhina sinensis, was examined in Ariake Bay, Japan, from May 2002 until December 2006. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: male, 393 mm; female, 421 mm]. The present data support a distinct annual reproductive cycle for P. sinensis. The gonadosomatic index (GSI) for mature males showed a clear seasonal trend, declining from August to November. Histological observations showed that mature sperm in the testes occurred from August to November when monthly GSI declined. Concomitantly, pre-ovulatory ova were observed in females collected from August to November. These data indicate that mating, ovulation and fertilization occurred from August to November. Near-term embryos, neonates and recent post-partum females also occurred from August to November. Additionally, all post-partum females possessed large pre-ovulatory ova. Parturition occurred from August to November followed immediately by mating, ovulation and fertilization. Mature females become pregnant every year, and the gestation period is almost 1 year. Fertilized uterine eggs without macroscopic embryonic development were present throughout the annual reproductive cycle, indicating that P. sinensis utilizes embryonic diapause as its reproductive strategy. Both reproductive tracts of females were functional, and fecundity ranged from 1 to 12 with a mean of 6.0, increasing with TL.

Corticosterone stimulates hatching of late-term tree lizard embryos

The regulation of hatching in oviparous animals is important for successful reproduction and survival, but is poorly understood. We unexpectedly found that RU-486, a progesterone and glucocorticoid antagonist, interferes with hatching of viable tree lizard (Urosaurus ornatus) embryos in a dose-dependent manner and hypothesized that embryonic glucocorticoids regulate hatching. To test this hypothesis, we treated eggs with corticosterone (CORT) or vehicle on Day 30 (85%) of incubation, left other eggs untreated, and observed relative hatch order and hatch time. In one study, the CORT egg hatched first in 9 of 11 clutches. In a second study, the CORT egg hatched first in 9 of 12 clutches, before vehicle-treated eggs in 10 of 12 clutches, and before untreated eggs in 7 of 9 clutches. On average, CORT eggs hatched 18.2 h before vehicle-treated eggs and 11.6 h before untreated eggs. Thus, CORT accelerates hatching of near-term embryos and RU-486 appears to block this effect. CORT may mobilize energy substrates that fuel hatching and/or accelerate lung development, and may provide a mechanism by which stressed embryos escape environmental stressors.

Determining reproductive parameters for population assessments of chondrichthyan species with asynchronous ovulation and parturition: piked spurdog (Squalus megalops) as a case study

Population assessments of chondrichthyan species require several key parameters of their reproductive biology, which were estimated for Squalus megalops (Macleay, 1881). Length-at-maturity differed depending on the criterion adopted for defining maturity. In the case of males, length-at-maturity was smallest when condition of seminal vesicles was adopted as a maturity criterion. For females, length-at-maturity was smallest when the largest follicle diameter >3 mm was adopted as the criterion for maturity; this was appropriate only as an indicator of the onset of maturity. Mature males are capable of mating throughout the year. Females have a continuous asynchronous reproductive cycle. The sex ratio of embryos is 1 : 1 and litter size and near-term embryo length increase with maternal length. Females have an ovarian cycle and gestation period of two years. This was reflected in the differences found between the maturity and maternity ogives. Although all females are mature at 600 mm, only 50% of them contribute to annual recruitment each year. Hence, for chondrichthyan species with reproductive cycles of two, three or more years, if maturity ogives are used in population assessments instead of maternity ogives, the models will overestimate recruitment rates.

A developmental mechanism of intestinal villus malformation

Abstract Introduction: The intestinal villi are a unique morphological component critical to intestinal function, and their malformation can lead to malabsorption, chronic wasting syndromes, and failure to thrive. The Fibroblast growth factor 10 (Fgf10) plays a critical role in gastrointestinal development and maturation. Fibronectin is an extracellular protein that forms an important part of the extracellular matrix and the basement membrane. The goal of the current study is to evaluate the role of the Fgf10 signaling pathway in epithelial growth and development by evaluating structural proteins. Methods: Transgenic Fgf10−/− and wild type (Wt) mice were bred, and near-term embryos were harvested from timed pregnancy mothers. The duodenum and proximal jejunum were harvested, fixed, and sectioned. They were then analyzed histologically and by immunofluorescent markers for epithelial structural proteins. Photomicrographs were taken. Results: The villi in the Fgf10−/− mutant mice are markedly abnormal. They are fewer in number, the crypt-villus height is shortened, and they have a broader base. On staining, fibronectin can be seen to form the basement membrane of the intestinal wall and penetrates each villus. In the mutant the fibronectin appears to pool at the bases of the villi, and there is a decreased amount of fibronectin inside each villus. Conclusions: The significance of these data is the normal development of epithelial architecture is dependent on the Fgf10 signaling pathway. Malformed villi, as seen with Fgf10 loss of function, result from improper distribution of fibronectin.

Latitudinal variation in life-history traits of bonnethead sharks, Sphyrna tiburo, (Carcharhiniformes : Sphyrnidae) from the eastern Gulf of Mexico

Life-history traits (size at age, growth rates, size and age at maturity, size of near-term embryos and litter sizes) of bonnetheads, Sphyrna tiburo, were analysed to test for latitudinal differences by comparing data collected from three areas along Florida's Gulf of Mexico coastline between March 1998 and September 2000. A total of 539 sharks were collected during the study: 207 in north-west Florida (latitude ~30�N), 176 in Tampa Bay (~28�N) and 156 in Florida Bay (~25�N). Male and female bonnetheads in north-west Florida had the largest predicted asymptotic sizes (1007�mm and 1398�mm TL, respectively) and attained the largest estimated median size at maturity (830�mm and 944�mm, respectively) and the oldest estimated median age at maturity (3.0+�years and 4.0+�years, respectively). The largest near-term embryos (297�mm TL) were also collected at the highest latitude, but no latitudinal difference in litter size was found. These differences in life-history traits provide supporting evidence that a pattern of latitudinal variation exists. Male and female bonnetheads in north-west Florida also had the fastest growth rate compared with the other locations, supporting the hypothesis that growth rate is inversely related to the length of the growing season (i.e. a pattern of countergradient variation exists).

Wetness of the nest environment influences cardiac development in pre- and post-natal snapping turtles ( Chelydraserpentina)

We dissected hearts from near-term embryos and hatchlings of common snapping turtles (Chelydridae: Chelydra serpentina) whose eggs had incubated on wet or dry substrates, and then dried and individually weighed the heart and yolk-free carcass from each animal. Hearts and carcasses of prenatal and neonatal animals grew at different rates, and the patterns of growth by both heart and carcass differed between wet and dry environments. Hearts grew faster, both in actual mass and in mass adjusted for variation in body size, in embryos and hatchlings whose eggs were incubated on dry substrates than in animals whose eggs were held on wet media. This finding is consistent with a hypothesis that embryos incubating in dry settings experience hypovolemia secondary to dehydration and that enlargement of the heart compensates, in part, for the associated increase in viscosity of the blood. Embryonic turtles seemingly exhibit the same plasticity and response that would be expected from other vertebrate ectotherms subjected to the physiological challenges associated with desiccation and an associated reduction in blood volume.

Closing the Knowledge Gap Between Scientist and Nonscientist

Closing the Knowledge Gap Between Scientist and Nonscientist

Biology of the ornate angel shark (Squatina tergocellata) from the Great Australian Bight

Ornate angel sharks were sampled from commercial catches from the Great Australian Bight trawl fishery during the period from February 1992 to February 1993. Size structure, reproduction and diet were studied. Both sexes exhibited similar length–weight relationships. Morphological data indicate that the most accurate conversion to total length (TL) would be obtained from the distance between the granular ocelli on the trunk near the pectoral fins. Males reached sexual maturity at a TL of 810–910 mm, females at 1150–1250 mm. The male:female ratio was 1:3 for the post partum population and 1:1 for embryos. Both ovaries were functional throughout the year, but the left ovary contained more ovarian follicles than the right. Follicle diameters ranged from 1 to 68 mm; the largest follicle was found during autumn, before ovulation, the smallest during spring, after ovulation. Eighteen near-term embryos from four females were observed during January and February 1993. The number of young per female ranged from 2 to 9. It appears that S. tergocellata has a minimum gestation period of 6–12 months and parturition may occur biennially. The most common stomach contents were squid (Notodarus gouldi) and fish (mainly Monacanthidae).