Reproductive biology of deep-sea catsharks (Chondrichthyes: Scyliorhinidae) in the eastern North Pacific

Apristurus brunneus, A. kampae, and Parmaturus xaniurus were caught by trawl and longline between Washington and southern California (48°N to 32°N latitude) from June 2001 through October 2004. In females, oviducal gland width increased with TL in all three species but remained within 4 to 6% of TL. Oocyte diameter increased with TL during reproductive development in all species, and continued to increase with size after reproductive maturity was reached. The weight-length relationships differed significantly among species but not between sexes of any species from the eastern North Pacific combined. Using logistic regression, it was determined that total length at 50% maturity (TL₅₀) of A. brunneus males was 514 mm TL and all A. brunneus males were mature at 547 mm TL. Female A. brunneus reached TL₅₀ at 501 mm TL and all female A. brunneus were mature at 581 mm TL. Apristurus kampae males and females reached TL₅₀ at approximately 485 mm TL and 490 mm TL, respectively. Parmaturus xaniurus males reached TL₅₀ at 444 mm TL and females at 501 mm TL. Gravid female A. brunneus were found in all months of the year, but gravid P. xaniurus were found primarily June through September. Adult A. kampae females were found only in July through November and there were gravid females in all these months. Based upon gonadosomatic indices, I _G, these species may mate within a defined period of time (April through June); however, A. brunneus appear to reproduce throughout the year and P. xaniurus reproduce within a defined season (approximately July through September).     

Size at maturity of Atlantoraja platana (Günther, 1880) (Chondrichthyes: Rajidae: Arhynchobatinae) in the south-west Atlantic Ocean

The sexual development of Atlantoraja platana from the south-west Atlantic Ocean was analysed. According to the reproductive variables considered for both sexes, males were found to mature at 620 mm and females at 715 mm total length.     

Composition of uterine milk and its changes with gestational period in red stingrays (Hemitrygon akajei)

Uterine milk is secreted in the uterus for embryo nutrition in several elasmobranch species and may contribute to rapid embryonic growth, but the details of its composition and its functions are poorly understood. In this study, to explore the roles of uterine milk for embryos, its components throughout the gestational period were analysed in detail. Uterine milk was collected from pregnant red stingrays (Hemitrygon akajei) in the early, middle and late gestational periods, respectively (n= 3 for each period). The crude composition, constituent proteins and fatty acids in the milk were analysed. The uterine milk was rich in proteins throughout the gestational period, whereas lipids dramatically increased in the middle period and reduced slightly towards the late period. Some proteins potentially associated with nutrition, cartilage growth and embryonic immunity were found. Several enzymes related to central metabolism were also detected. The constituent fatty acids in the middle and late periods were similar to those in the egg yolks of elasmobranchs, except for C18:2, which was rich only in the uterine milk. The most abundant fatty acid in the milk was C16:1, which could function as a lipokine to promote lipid metabolism in the embryo. This study's data suggest that uterine milk may be secreted in addition to the egg yolk in elasmobranchs to support rapid and healthy embryonic growth.     

Reproductive biology of the swell shark Cephaloscyllium ventriosum (Carcharhiniformes: Scyliorhinidae)

The Cephaloscyllium ventriosum shark is present in the artisanal fisheries of elasmobranchs on the western coast of Baja California Sur, Mexico. The main characteristics of the sexual maturation of this species based on individuals captured from off north-west Mexico in 2013–2016 are described. The size at maturity of this species was determined for the first time (total length 82 cm for females and 76 cm for males). Most females had one egg case per one uterus, and two per one uterus was an isolated event of low incidence. From the histological analysis of females, it was possible to show sperm storage in the oviducal gland. Fully developed sperm in immature organisms were identified in the testes. The main indicator of the maturity stage of males and their mating activity is the clasper. The present study provides evidence for a reliable estimation of the sexual maturity of these organisms, demonstrating the need for the combination of macroscopic and microscopic methods.     

Reproductive aspects of the Atlantic angel shark Squatina dumeril

Atlantic angel sharks Squatina dumeril were collected by fishery‐dependent and independent trawls from 2002 to 2008 for reproductive analysis. Female S. dumeril have only one functional ovary (left), with an average litter size of seven pups. The reproductive cycle is at least biennial, though the seasonality of vitellogenesis could not be determined. Gestation is c. 12 months, and embryo data support a seasonal trend in reproduction, with parturition occurring in the spring months (February to June). Mature male S. dumeril have spines on the outer margins of their pectoral fins, and there is an apparent peak in gonad size in the spring. The total length at which 50% of the population is mature is 85·8 and 92·9 cm for females and males, respectively.     

Thermoregulation during gravidity in the children's python (Antaresia childreni): a test of the preadaptation hypothesis for maternal thermophily in snakes

Pregnant squamate reptiles (i.e. lizards and snakes) often maintain higher and more stable body temperatures than their nonpregnant conspecifics, and this maternal thermophily enhances developmental rate and can lead to increased offspring quality. However, it is unclear when this behaviour evolved relative to the evolution of viviparity. A preadaptation hypothesis suggests that maternal thermophily was a preadaptation to viviparity. Oviparous squamates are unique among oviparous reptiles for generally retaining their eggs until the embryos achieve one fourth of their development. As a result, maternal thermophily by gravid squamates may provide the same thermoregulatory benefits, at least during early development, that have been associated with viviparity. Thus, the evolution of viviparity in squamates may reflect an expanded duration of a pre-existing maternal thermoregulatory behaviour. Despite its evolutionary relevance, thermoregulation during gravidity in oviparous squamates has not yet been explored in depth. In the present study, we examined whether gravidity was associated with thermoregulatory changes in the oviparous children's python, Antaresia childreni . First, we discovered that, compared to most snakes, A. childreni is at an advanced stage of embryonic development at oviposition. Second, using surgically implanted temperature loggers, we detected a significant influence of reproductive status on thermoregulation. Reproductive females maintained higher and less variable body temperatures than nonreproductive females and this difference was most pronounced during the last 3 weeks of gravidity. Overall, these results highlight the continuum between oviparity and viviparity in squamate reptiles and emphasize the importance of thermal control of early embryonic development independent of reproductive mode.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 499–508.     

Egg cases of the genus Apristurus (Chondrichthyes: Scyliorhinidae): phylogenetic and ecological implications

The genus Apristurus has been divided formerly into three species subgroups based on morphological and molecular phylogenies. Previous studies have agreed on the separation into distinct species groups, the largest two of which have been described as the brunneus and spongiceps groups. An examination of the egg cases produced by these oviparous catsharks corroborates the distinction in species groups: egg cases of the brunneus group have long fibrous and curly tendrils at either end, whereas egg cases of the spongiceps group lack tendrils. The egg cases of A. kampae, A. manis, A. spongiceps and Apristurus sp. D are described for the first time, and the egg cases of A. brunneus and A. riveri are re-described to include comparable morphological characteristics. The ecological implications of egg case morphology on oviposition and ventilation are also discussed.     

Reproductive biology of the southern thorny skate Amblyraja doellojuradoi (Chondrichthyes,Rajidae)

The total lengths (L_T) of 193 males (209–556 mm) and 130 females (275–515 mm) of Amblyraja doellojuradoi, a commercial by‐catch species on the Argentinean continental shelf, which are increasingly retained, were analysed. No sexual dimorphism was observed in the L_T at which 50% of individuals were sexually mature; males matured at 448 mm and females at 411 mm, c. 80 and 82% of maximum L_T. The hepato‐somatic index was similar among sexes, but significantly different between maturity stages, being lower in mature than immature specimens. Males had no seasonal difference in the hepato‐somatic index and females had the lowest index in autumn. The gonado‐somatic index was lower in males than in females and significantly higher in mature than immature specimens of both sexes. Males had the highest index in autumn and females had no seasonal difference. Collectively, these results would indicate that A. doellojuradoi breeds in autumn.     

Scanning electron microscopy of the fetal membranes of an oviparous squamate,the corn snake Pituophis guttatus (Colubridae)

Although the fetal membranes of viviparous squamates have received much study, morphology of their homologues among oviparous reptiles is poorly understood. The scarcity of information about these membranes in egg‐laying reptiles hampers attempts to distinguish specializations for viviparity from ancestral oviparous features. We used scanning electron microscopy to examine fetal membranes of an oviparous snake (Pituophis guttatus) throughout the developmental period from oviposition to hatching. The external surface of the chorion contains broad, flattened cells that lack surface features; these cells form a continuous layer over the allantoic capillaries and offer a minimal barrier to respiratory exchange. In contrast, the surface epithelium of the omphalopleure bears elaborate surface ridges suggestive of absorptive capabilities. These ridges are prominent in the first few weeks after oviposition, but diminish thereafter. During development, the isolated yolk mass (IYM) of the omphalopleure becomes depleted, and the tissue becomes heavily vascularized by allantoic vessels. Surface features of the omphalopleure progressively take on the appearance of the chorioallantois, but the changes are not synchronous with loss of the IYM or membrane vascularization. Previous studies on viviparous snakes suggest that the chorioallantois and omphalopleure are respectively specialized for gas exchange and absorption in the intrauterine environment. Our studies of fetal membranes in P. guttatus offer evidence that cytological specializations for these functions originated under oviparous conditions, reflecting functional capacities that predate viviparity. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

Reproductive cycle of the blacknose shark Carcharhinus acronotus in the Gulf of Mexico

The reproductive periodicity of blacknose sharks Carcharhinus acronotus in the northern Gulf of Mexico was determined by examining reproductive tissues from specimens collected monthly from 2002 to 2005. Monthly changes in shell gland mass, right ovary mass and ovarian follicle diameter were assessed for 74 mature females. Temporal changes in testes mass, testes width and proportion of mature spermatocysts were examined for 64 mature males. Trends in female reproductive tissues suggested an annual peak in reproductive activity during June and July, while trends in male variables suggested an annual reproductive peak during May and June. Although male and female reproductive activity peaked in different months, a strong synchronicity existed between the proportion of mature spermatocysts and the diameter of the largest ovarian follicle. Based on these results, the mating season of blacknose sharks lasts from mid-May to July in the Gulf of Mexico. Maximum embryo sizes were observed in May, which suggested that partition occurs during late May or early June. Results indicate that blacknose sharks have a clearly defined annual cycle in the Gulf of Mexico. This conclusion is further supported by the complete absence of gravid females without vitellogenic ovarian follicles among all mature females examined.     

Sexually dimorphic body proportions in the catshark genus Scyliorhinus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae)

Intersexual differences in morphometrics were investigated in five species of the catshark genus Scyliorhinus. ANCOVA was used to test 59 measurements, considering capture location and total length as covariates. In all examined species, pelvic–anal distances and pelvic-fin inner margin lengths were greater in males than in females, representing a clear pattern for the genus.     

Pregnancy in Squaliolus laticaudus (Elasmobranch: Dalatiidae) from Brazil

Synopsis A pregnant female of the Dwarf deep-sea shark, Squaliolus laticaudus with four embryos was caught by the nocturnal longline vessel “Progress?o” from southern Brazil, on September 1999. It was donated by the fishermen. Embryos ranged in size 105 – 100 mm of total length. The aim of this article is to contribute to the knowledge of the Dwarf deep-sea shark reproduction and distribution on the Brazilian coast. It is been considered the first record to know about pregnant Dwarf deep-sea shark in the world.     

The Reproductive Biology and Reproductive Success of Pterocarpus macrocarpus Kurz1

The reproductive biology of Pterocarpus macrocarpus Kurz (pradu) was studied in 37‐year‐old plantation trees in Thailand to determine the causes of seed and fruit loss. Trees flowered at the end of March or early in April at the end of the hot dry season and start of the rainy season. Flowering occurred over about a one‐month period. Fruits developed over the next six months during the rainy season and matured at the start of the cool dry season in October and November. Phenology was similar in the four trees that were studied in detail. Racemes averaged 30 flowers each and each raceme was receptive for several days, although each flower was only receptive for one day. After pollination, floral parts were shed over several days and fruits began to develop. Pradu is entomopholous but its insect pollinators were not identified. The stigma is covered by hairs and a secretion is produced. A high proportion of flowers were pollinated. Then, there was a rapid loss of flowers and young fruits. These observations and earlier genetic studies indicate the probability of a high level of self‐incompatibility in this predominantly outbreeding species. Pradu may have a very late‐acting self‐incompatibility mechanism found in many other hardwoods. The zygote remains quiescent for six weeks as the endosperm develops. During this time most of the ovules and fruits abort, suggesting resource allocation preferentially to cross‐pollinated ovules. Pradu has a high reproductive potential but a low preemergence reproductive success (0.8), which is common for many hardwood species. The major cause of the low reproductive success was fruit loss during early development. Fruit production may be enhanced by increased cross‐pollination among unrelated parent trees. This may be accomplished in seed orchards and seed production areas by the introduction of additional insect pollinators that travel greater distances between trees and by the relatively close spacing of unrelated parent trees.     

Variation in eggshell characteristics and in intrauterine egg retention between two oviparous clades of the lizard Lacerta vivipara: insight into the oviparity-viviparity continuum in squamates

The concept of the oviparity-viviparity continuum refers to the wide range in the length of intrauterine egg retention and, hence, in the stage of embryonic development at oviposition existing in squamates. The evolutionary process underlying this continuum may involve not only a lengthening of egg retention in utero, but also a marked reduction in the thickness of the eggshell. The idea that there may exist a negative correlation between the developmental stage reached by the embryo at oviposition and the eggshell thickness within squamates, although supported by the comparison of oviparous vs. viviparous species, has seldom been evaluated by comparing eggshell thickness of oviparous forms with different lengths of intrauterine egg retention. Eggs of two distinct oviparous clades of the lizard Lacerta vivipara were compared. The eggs laid by females from Slovenian and Italian populations have thicker eggshells, contain embryos on average less developed at the time of oviposition, and require a longer incubation period before hatching than the eggs laid by females from French oviparous populations. Our data and several other examples available from the literature support the idea that the lengthening of intrauterine retention of eggs and the shortening of the subsequent external incubation of eggs are associated with reduction in the thickness of the eggshell, at least in some lineages of oviparous squamates. The current hypotheses that may account for this correlation are presented and a few restrictions and refinements to those hypotheses are discussed. In particular, other changes, such as increased vascularization of the oviduct and of the extraembryonic membranes, may play the same role as the decrease of eggshell thickness in facilitating prolonged intrauterine egg retention in squamates. Future studies should also consider the hypothesis that the length of intrauterine retention might directly depend on the extent of maternal-fetal chemical communication through the eggshell barrier.