Reproductive biology of the eastern shovelnose stingaree Trygonoptera imitata from south-eastern Australia

Abstract. In applying a quantitative approach to the reproduction of Trygonoptera imitata, the present study contributes to understanding the wide diversity in the reproductive biology of the family Urolophidae and provides insights to help determine phylogenetic relationships. This localised species is taken as bycatch in several inshore fisheries and potentially impacted by a range of other anthropogenic pressures, including introduced species, particularly in shallow-water pupping areas.T. imitata can be characterised as a species of comparatively lowmatrotrophic histotrophy with an extended period of relatively large eggs in utero (5–8 months) followed by rapid growth of the embryos (4–6 months). The reproductive cycle is annual with parturition occurring during late-February–April, followed immediately by ovulation. Mean size-at-birth is ~225mm total length and there is a ~1000% gain in mean wet mass from egg (15 g) to full-term embryo in utero (150 g), the lowest reported for any viviparous batoid. Litter size increases with maternal length, reaching a maximum of seven, and sex ratio of embryos is 1 : 1. Maximum length and estimates of the maturity–ogive parameters l₅₀ and l₉₅ are similar for females and males.

On the growth and reproductive biology of asp, Aspius vorax, population from the middle reaches of Euphrates river

Endemic asp, Aspius vorax, from the middle section of the Euphrates River flowing through eastern Syria were studied to determine the main characteristics of their population structure, morphological parameters and reproductive biology. Samples ranged between 0+ and 4+ years of age and were dominated by 2+ years old group. Total length (TL) ranged between 19 and 70 cm corresponding with 46 to 2824.5 g weight, respectively. Fish growth has isometric pattern and the overall sex ratio was unbiased. Seasonal changes in the condition factor were related with the water temperature as well as the spawning season. Annual cycle of gonadosomatic index (GSI) readings indicated that spawning season occur around March when fish longer than 36 cm can mate. Average pre-spawning GSI was greater in individuals older than 2 years. Meanwhile, female fecundity was highly related to TL and weight. These findings did not always concur with previous observations from other asp populations, mainly in southern and northern Mesopotamia. Our results highlighted basic biological aspects of the local population and indicated differences between populations which can assist in fisheries management, conservation and commercial culture of the investigated species.

Studies of the biology of four species of Dicranoloma

Populations of Dicranoloma billardierei (Brid) Par., D. dicarpum (Nees.) Par., D. menziesii (Tayl.) Par. and D. platycaulon (C. Muell) Dix, from two pockets of cool temperate rainforest within the Yarra Ranges National Park (Cement Creek and Myrtle Loop), were sampled for a period of two years to establish their reproductive biology. The population dynamics within quadrats of D. billardierei, D. menziesii and D. platycaulon at Cement Creek also was investigated over a two year period, through the seasonal recording of shoot loss and/or gain, The four species of Dicranoloma were dioicous and sexually dimorphic, with dwarf males epiphytic on the female plants. Antheridia were initiated before archegonia and required ca, 6 months to reach maturity, compared with 1 to 2 months for archegonia. More archegonia than antheridia occurred per inflorescence and were more variable Fertilization occurred during winter in D. billardierei and summer/ autumn in D. menziesii and D. platycaulon. The duration of the sporophyte cycle of D. menziesii was 12 months, shorter than that of D. billardierei and D. platycaulon which lasted for a period of 18 months to 2 years. In the latter two species an overlap of sporophyte generations occurred. This was particularly pronounced in D. billardierei as sporophytes remained in the swollen venter maturation stage for a period of 6 months. The duration of the sporophyte cycle could not be ascertained as few fruiting stems of D. dicarpum were found. All four species of Dicranoloma regenerated from fragments cultured in the laboratory, and only two of the species showed evidence of production of asexual propagules in the field. Dicranoloma dicarpum was found to produce gemmae, an observation which had not been recorded before, and most of the leaves on stems of D. platycaulon had detached subulas. Shoot loss was minimal in all four species, and when it did occur, (eg D. billardierei) it was attributed to disturbance by animals. Within quadrats there was an increase in shoot density which resulted from the development of innovation(s) and/or side branches rather than from the recruitment of new plants from spores or the regeneration of asexual propagules. The four species of Dicranoloma investigated were robust, perennial mosses and formed an important component of the bryophytes found within the study area. Dicranoloma menziesii was the predominant species establishing on a variety of substrata, particularly as an epiphyte on Nothofagus cunninghamii The other species were more selective in their choice of substratum. Dicranoloma platycaulon was found exclusively on the trunks of myrtle beech and D. billardierei on fallen logs and exposed roots. Dicranoloma dicarpum which was not common, grew as an epiphyte on myrtle beech and on rocks.

Repeated acute activation of the hypothalamo-pituitary adrenal axis prior to and during estrus did not affect reproductive performance in gilts

We investigated the effects of repeated acute activation of the hypothalamo-pituitary adrenal axis, prior to and during estrus, on reproduction in gilts. Individual gilts (n = 24 per treatment) either served as controls or were subjected to daily acute stress ("negative handling," brief electric shock with a battery-operated prodder during confinement with the experimenter) commencing, on average, 8 days prior to estrus. Gilts subjected to negative handling had a significant elevation in plasma concentrations of cortisol that lasted at least 3-4 h, and these gilts were slower than control gilts to approach and interact with the experimenter in a standard test. Nevertheless, reproductive performance--as measured by sexual receptivity and proceptivity, ovulation, the percentage of gilts that became pregnant, the number of embryos 20-21 days after insemination, and the weight of embryos--was not affected by repeated acute activation of the hypothalamo-pituitary adrenal axis. Our results suggest that repeated acute activation of the hypothalamo-pituitary adrenal axis prior to and during estrus does not affect the factors that control estrus and ovulation in gilts.

Spawning season, fecundity and proximate composition of the gonads of wild-caught blacklip abalone (Haliotis rubra) from Port Fairy waters, south eastern Australia

This study was based on wild-caught blacklip abalone Haliotis rubra L., from Port Fairy waters, south eastern Australia (142°15′E; 38°21′S), from July  1998 to November 1999, and was initiated to evaluate the spawning season and other aspects of its reproductive biology. The shell length and body weight of female and male abalone sampled ranged from 12.0 to 18.6 and 12 to 15 cm, and 137 to 529 and 148 to 585 g, respectively. The sex ratio did not vary significantly from 1:1 through the year. The gonadosomatic index (GSI) ranged from 3.0% to 8.4% in males, and 2.5% to 14.1% for females, and the highest GSI as well as the highest proportion of mature animals were recorded from September to October. During these months the hepatosomatic index (HSI) was low, and an inverse correlation between GSI and HSI (P < 0.05) was evident. Fecundity of blacklip abalone ranged from 1.09 to 7.5 million eggs for females of 12–14.5 cm in length, and 115–487 g in total body weight, respectively. The lipid content of the female gonad increased significantly from about July to November, and an opposite trend was observed for lipid content of the digestive gland. Seasonal changes in the protein and ash contents of the gonad and/or the digestive gland were not always significant.

Control of ovarian development in the yabby (Cherax destructor)

A study under controlled conditions of ovarian development and rematuration in the yabby (Cherax destructot) was undertaken. The purpose of the study was to improve fundamental understanding of the reproductive biology of the species and provide a basis for application to hatchery management in culture. A review was made of the current status of yabby culture in Australia and the present understanding of reproductive biology of decapod Crustacea. The review emphasised factors controlling several aspects of ovarian development, in particular the processes of vitellogenesis. The subsequent study was designed within the context of current hatchery practice and was based on existing knowledge of decapod reproduction, The sexual differentiation of the yabby after hatching was investigated by serial histological sections, and experiments were carried out to investigate the possibility of sex reversal of males. Most of this Investigation was concerned with removing the influence of the androgenic gland in directing male development, with the intent of observing the development of the elementary gonadal tissue into ovary. It was found that in contrast to other crustacean species, the sex of the yabby becomes fixed before the development of external secondary sexual characteristics, and before the androgenic gland can be discerned. Ovarian tissue developed in females at less than 8 weeks after hatching. A preliminary examination was undertaken for feminising parasites in gonadal tissue of a hermaphrodite yabby. Investigation of the ovary after spawning demonstrated that whilst the female was held under constant conditions of temperature and photoperiod, little rematuration occurred. Except for generation of previtellogenic oocytes during the first two days, the gonaciosomatic index remained low for up to 5 months after spawning. If the temperature of the female was reduced to 10°C and maintained constant, the previtellogenic oocytes were partially resorbed over a three week period. Rematuration then commenced, albeit at a low rate because of the reduced temperature, A method for standardising gonadosomatic indices was developed which took into account differences in hepatopancreatic nutrient reserves of individuals and loss of one or more appendages. This part of the study also considered constraints to rematuration and developed a method of accounting for differences in the ability of females to remature after spawning. Experiments were carried out to investigate the effect of crowding and temperature manipulation on initiating ovarian rematuration and to determine the rate of rematuration at 22°C once initiated. The duration of low temperature had no effect on rematuration; an overnight cooling was sufficient to initiate the process, Rematuration to the end of stage 2 vltellogenesis was substantially complete within 10 days. Crowding of females suppressed rematuration, but less than ideal water quality was not found to have any effect. The presence of a male initiated rematuration at a similar rate, but also led to stage 3 vitetlogenesis and spawning. A study was made of the pheromonal influence of the male through water borne factors without success. Rematuration could not be induced in ovigerous females. The literature review indicated that ovarian rematuration was under the control of an ovary stimulating hormone produced by the thoracic nerve ganglia. Attempts were therefore made to stimulate ovarian rematuration by incorporating the thoracic nerve into the diet of females. Attempts were also made to induce the release of ovary stimulating hormone from the thoracic nerve with 5-hydroxytryptamine, and also with octopamine. No effects were found, but a significant difference between the neurophysiology of the yabby and northern hemisphere crayfish was observed, and the implications of this finding are discussed. The study did not produce any conclusive evidence of an ovary stimulating hormone for the yabby. A model of ovarian rematuration which collects the findings of the experimental investigations was developed, and was used to suggest a hatchery broodstock management protocol. This model differs from existing models in that rematuration triggers and nutritional status are considered.

Age, growth and reproduction of deepwater dogfishes from southeastern Australia

The productivity of six deepwater dogfishes was investigated by examining their age, growth and reproductive biology. A new method of ageing was developed, and compared with existing techniques. Some species live greater than 50 years, and populations may not sustain commercial fisheries.

Structural and functional characterization of the oxidoreductase a-DsbA1 from wolbachia pipientis

The α-proteobacterium Wolbachia pipientis is a highly successful intracellular endosymbiont of invertebrates that manipulates its host's reproductive biology to facilitate its own maternal transmission. The fastidious nature of Wolbachia and the lack of genetic transformation have hampered analysis of the molecular basis of these manipulations. Structure determination of key Wolbachia proteins will enable the development of inhibitors for chemical genetics studies. Wolbachia encodes a homologue (α-DsbA1) of the Escherichia coli dithiol oxidase enzyme EcDsbA, essential for the oxidative folding of many exported proteins. We found that the active-site cysteine pair of Wolbachia α-DsbA1 has the most reducing redox potential of any characterized DsbA. In addition, Wolbachia α-DsbA1 possesses a second disulfide that is highly conserved in α-proteobacterial DsbAs but not in other DsbAs. The α-DsbA1 structure lacks the characteristic hydrophobic features of EcDsbA, and the protein neither complements EcDsbA deletion mutants in E. coli nor interacts with EcDsbB, the redox partner of EcDsbA. The surface characteristics and redox profile of α-DsbA1 indicate that it probably plays a specialized oxidative folding role with a narrow substrate specificity. This first report of a Wolbachia protein structure provides the basis for future chemical genetics studies.

Global research priorities for sea turtles : informing management and conservation in the 21st century

Over the past 3 decades, the status of sea turtles and the need for their protection to aid population recovery have increasingly captured the interest of government agencies, non-governmental organisations (NGOs) and the general public worldwide. This interest has been matched by increased research attention, focusing on a wide variety of topics relating to sea turtle biology and ecology, together with the interrelations of sea turtles with the physical and natural environments. Although sea turtles have been better studied than most other marine fauna, management actions and their evaluation are often hindered by the lack of data on turtle biology, human–turtle interactions, turtle population status and threats. In an effort to inform effective sea turtle conservation a list of priority research questions was assembled based on the opinions of 35 sea turtle researchers from 13 nations working in fields related to turtle biology and/or conservation. The combined experience of the contributing researchers spanned the globe as well as many relevant disciplines involved in conservation research. An initial list of more than 200 questions gathered from respondents was condensed into 20 metaquestions and classified under 5 categories: reproductive biology, biogeography, population ecology, threats and conservation strategies.

Low level of extrapair parentage in wild zebra finches

The captive zebra finch, Taeniopygia guttata, has become one of the key vertebrate model systems for studying a range of behavioural, physiological and neurological phenomena. In particular, this species has played a key role in developing our understanding of sexual selection and sperm competition. In contrast with the large number of studies using domesticated zebra finches, relatively few studies have focused on free-living populations of wild zebra finches. Investigating the incidence of extrapair paternity in zebra finches in the Australian desert, we found a very low level; 1.7% of 316 offspring from four of 80 broods fathered outside the pair bond. These numbers contrast with the high levels of extrapair paternity observed in domesticated aviary populations, and suggest a low level of sperm competition and sexual selection in natural populations. Our finding of such a low rate of extrapair paternity in the wild zebra finch suggests that it is one of the most genetically monogamous of all passerine species and that has important implications for future studies of this model organism in studies of sexual selection and reproductive biology. In addition, we found that 5.4% of 316 offspring were not related to either putative parent and hatched from eggs that had been dumped by intraspecific brood parasites.

Reproduction in five sympatric batoid species (family urolophidae) from south-eastern Australia

This PhD determines the reproductive biology of five stingaree species caught as bycatch from south-eastern Australian commercial fisheries for fisheries stock assessments, ecological risk assessments, and species extinction risk evaluations.

The effect of repeated boar exposure on cortisol secretion and reproduction in gilts

It has been proposed that short-term activation of the hypothalamo-pituitary adrenal axis, with a consequent increase in the secretion of cortisol, amy disrupt the endocrine events prior to ovulation and thereby impair reproduction in females. We investigated this concept in gilts in which oestrus was detected by introduction to boars, where intense physical contact is possible, or by applying pressure to the back of gilts (back-pressure test) during fence-line exposure to boars, where intense physical contact is prohibited. We expected that there would be a greater release of cortisol and that reproduction would be inhibited in gilts introduced to boars compared to gilts in which the back-pressure test was used. As expected, introduction of gilts to boars resulted in a significant transient increase in plasma concentrations of cortisol while there was no significant effect of using the back-pressure test on plasma cortisol. Nevertheless, introduction of gilts to boars did not impair reproduction and there was no effect of method of detecting oestrus on duration of oestrus, sexual receptivity, fertility or fecundity. The length of the oestrous cycle was decreased and ovulation rate increased in gilts that were introduced to boars compared to gilts that underwent the back-pressure test, indicating that introduction of gilts to boars may have stimulated these aspects of reproduction. These stimulatory effects may have been due to an increased exposure of gilts to sexual behaviour and stimuli from boars when introduced to boars and/or to stimulatory effects of the hypothalamo-pituitary adrenal axis on some aspects of reproduction.

Sustained but not repeated acute elevation of cortisol impaired the luteinizing hormone surge, estrus, and ovulation in gilts

We tested the hypothesis that sustained and repeated acute elevation of cortisol would impair the LH surge, estrus, and ovulation in gilts. Cortisol was injected intramuscularly, to achieve a sustained elevation of plasma concentrations of cortisol, or intravenously, to achieve an acute elevation of plasma concentrations of cortisol. Control gilts received i.m. injections of oil and i.v. injections of saline. These treatments were administered to gilts (n = 6 per treatment) at 12-h intervals from Days 7 to 11 of the estrous cycle until after estrus ceased or until Day 27 or 28 of the estrous cycle, whichever came first. The repeated acute elevation of cortisol had no effect on the LH surge, estrus, or ovulation. In contrast, when the elevation of cortisol was sustained, the LH surge, estrus, and ovulation were inhibited. We conclude that cortisol is capable of direct actions to impair reproductive processes in female pigs but that plasma concentrations of cortisol need to be elevated for a substantial period for this to occur.