Gonadal maturation,fecundity, spawning,and timing of reproduction in the mud snail,Cerithidea cingulata,a pest in milkfish ponds in the Philippines

Summary

Gonadal maturation, spawning, fecundity and timing of reproduction of the snail Cerithidea cingulata in a brackish water pond in Molo, Iloilo, Philippines, are described. Snails 4–41 mm in shell length were sampled monthly from May 1997 to May 1998; 25% were <25 mm, 67% were 20–30 mm, and 8% were >30 mm. The sexes are separate and could first be distinguished at 15 mm. Males are aphallic, have narrower shells than females of the same length, and have bright yellow-orange testes overlying the digestive gland deep inside the shell. Females have more robust shells, an ovipositor at the right side of the foot, and yellow-green ovaries overlying the digestive gland. The sex ratio was one male to two females in the pond population studied. Gonadal maturation was monitored by means of gonadosomatic index (GSI, gonad weight as a percent of visceral weight); maturation stages were based on the gonad appearance (immature, developing, mature) and histology (immature, developing, mature, redeveloping). GSI increased with snail size, and reached 16% in a 33-mm female. The smallest mature males and females were 18–19 mm, and most snails >20 mm were mature, spawning, or redeveloping. Histological sections showed all stages of gametogenesis in mature male snails. The oocyte size-frequency distributions in mature females showed mostly mature oocytes and secondary oocytes, but also oogonia and primary oocytes. GSI and the frequency of snails at different maturation stages varied over the year. Both GSI and the frequency of mature snails were highest during the summer months, April to August. Nevertheless, mature snails occurred throughout the whole year, as did mating and egg-laying. Fecundity (= number of oocytes >70 pμ) increased with size in mature females 2041 mm; an average 25-mm female produced about 1,500 oocytes and larger females produced a maximum of about 2,500 oocytes. Eggs strings laid on the pond bottom were 45–75 mm long; an average 64-mm string contained 2,000 eggs 210+20 pm in diameter. The density of eggs strings was highest (80–120/m²) during March-September. Eggs hatched after 6–7 d into planktonic veligers, which in turn settle on the pond bottom 11–12 d later as juveniles. Juveniles 2–6-mm long were most abundant in the pond during August-October.     

Preliminary Findings of Fecal Gonadal Hormone Concentrations in Six Captive Sea Otters (Enhydra lutris) after Deslorelin Implantation

The sea otter (Enhydra lutris) is a popular exhibit animal in many zoos and aquariums worldwide. Captive sea otters from these populations are owned by the United States Fish and Wildlife Service (USFWS). The USFWS has requested that these sea otters be prevented from breeding in order to save captive space for wild rescued animals. Sea otters are often housed in mixed sex groups, therefore a chemical contraceptive method or surgical removal of gonads must be used to prevent potential pregnancy. The contraceptive, Suprelorin® or deslorelin, has been used in many different species to effectively suppress reproduction but duration of effect may vary not only between species but also individuals. Here, we report the effects of one to several consecutive deslorelin implants on gonadal reproductive hormones found in fecal samples from six captive sea otters (two males and four females) compared to two control otters (one male and one female) housed at three zoological institutions. We documented the longitudinal hormone signatures of many stages of the contraceptive cycle including pretreatment (PT), stimulatory phase (S), effective contraception (EC), and hormone reversal (HR) that was characterized by a return to normal hormone levels. Deslorelin was found to be an effective contraceptive in sea otters and was found to be reversible documented by a live birth following treatment, however the duration of suppression in females was much longer than expected with a 6‐month and a 1‐year implant lasting between 3 and 4 years in females. Zoo Biol. 32:307–315, 2013. © 2012 Wiley Periodicals, Inc.     

Diurnal and seasonal changes in semen quality of men in subfertile partnerships

ABSTRACT

Circadian and circannual rhythms influence not only the environment, but also human physiology. In times of increasing numbers of couples struggling with infertility, and thus increasing demand for successful assisted reproduction, the aim of our study was to evaluate circadian and circannual rhythms and their association with semen quality. A total of 12 245 semen samples from 7068 men, collected at the andrology laboratory of the Department of Reproductive Endocrinology, University Hospital Zurich, between 1994 and 2015, were uniformly analysed in terms of sperm concentration, total sperm count, progressive motility and normal morphology. On the basis of these four parameters, we retrospectively examined the circadian and circannual changes of semen quality. The Mann–Whitney U test and multiple linear regression analysis were used for the statistical evaluation. The semen samples collected in the early morning before 7:30 a.m. showed the highest levels in sperm concentration, total sperm count and normal morphology, all with statistical significance. Progressive motility did not show any significant alterations based on circadian rhythm. Furthermore, a significant increase in sperm concentration and total sperm count was found in spring, with significant decreases in the summer. The highest percentage of normal morphology was found in summer. For progressive motility, no significant seasonal variation could be demonstrated. Male semen quality varies with both circadian and circannual rhythms. Collection of semen in the early morning, where semen quality was highest, can be used to improve natural fertility as well as fertility resulting from assisted reproduction.     

Aspects of reproduction and their implications for the conservation of the endangered limpet,Patella ferruginea

Summary

The protandric limpet, Patella ferruginea G., is the most endangered marine species in the Western Mediterranean and is at serious risk of extinction. Nevertheless, its biology and ecology are little known. In the present work, several reproductive aspects are studied. Recruitment take place in June and the largest individuals are the most scarce. The sex ratio is slanted towards the largest sizes, and the species seems to show sex change at sizes from 60 mm upwards, although males can be observed up to 80 mm. There is no correlation between size of oocytes and shell length; however, the larger females contribute greatly to the reproductive event, with high fecundity and GSI values. The mean diameter of oocytes was observed to be 149.78 μm, whereas the heads of spermatozoa were 3.78 μm long. The results of the present study increase the maximum length for males by double that cited in previous literature and highlight the importance of strictly protecting females (i.e., most of the largest individuals, >60 mm), since their population percentage is very low, in order to develop adequate strategies to preserve the species.     

When similar beginnings lead to different ends: Constraints and diversity in cirripede larval development

Summary

Cirripedes are fascinating models for studying both functional constraints and diversity in larval development. Adult cirripedes display an amazing variation in morphology from sessile suspension feeders that still retain many crustacean characters to parasites that have lost virtually all arthropod traits. In contrast, cirripede larval development follows a common scheme with pelagic larvae comprising a series of nauplii followed by a cyprid. Variations are mostly concerned with whether or not the nauplii are feeding and the degree of abbreviation of development, culminating in species where the larvae hatch as cyprids. The cypris larvae are very similar among the ingroups of the Cirripedia, but interesting variations occur in structures used for substrate location and attachment. The cyprid is specialized to both swim through the water and actively explore the substratum by walking on the antennules and using an array of sensory organs in search for a suitable site to attach. This unique morphology and behavior of the cyprid have enabled the Cirripedia to colonize widely different habitats ranging from hard rock to soft animal tissue. Yet, the cyprid can metamorphose into juveniles as different as a setose feeding barnacle and the vermiform stages of the parasitic forms. This emphasizes the importance of the cyprid as one of the key features for the evolutionary success of the Cirripedia.     

The ovarian maturation cycle of the Norway lobster Nephrops norvegicus (Linnaeus, 1758) (Crustacea,Decapoda) from the western Mediterranean Sea

Summary

The Norway lobster Nephrops norvegicus lives in the continental margins of the western Mediterranean Sea at depths between 100 and 600 m. It constitutes an important fisheries resource and presents a seasonal reproductive pattern. Female Norway lobsters were obtained each month from a vessel fishing off Barcelona. One hundred females caught in June 2002 were kept in the laboratory. After spawning, ovarian samples were taken every 30 days with the objective of monitoring the first steps in ovarian maturation. The gonado-somatic index (GSI) remained low over the 6 months during which the females carried their eggs, plus for a further 2–3 months. However, this study suggests that ovarian maturation is a continuous process with two different phases, taking at least 6–8 months during which the female carries its eggs. There is an increase in oocyte numbers; the germinal zone produces oogonia; and the oocytes that develop migrate to the periphery, pushing the post-ovulatory follicles to the wall of the ovary and reinforcing it for subsequent spawning. Besides this increase in the number of oocytes, vitellogenesis begins 2–3 months after the eggs hatch. Oocytes then grow and the ovaries gain weight and change from a cream color to a blackish-green. When the GSI reached 10, spawning occurred and, from then on, the ovary is mainly composed of post-ovulatory follicles.     

Sexual Dimorphism in Juvenile Hormone Synthesis by Corpora Allata and in Juvenile Hormone Acid Methyltransferase Activity in Corpora Allata and Accessory Sex Glands of Some Lepidoptera

Summary

The kinetic profiles of vitellin accumulation in the oyster ovary during oocyte growth and the effects in vivo and in vitro of estradiol-17β (E₂) on vitellin formation were examined in this study. The relative vitellin content measured by an enzyme-linked immunosorbent assay (ELISA) shows an apparent increase as the oocyte develops. Immunoblotting of the vitellin using anti-vitellin indicated that two main bands (179 and 110 kD), which begin to accumulate at an early stage of maturation, become pronounced during oocyte growth. Meanwhile, the major peak of the intact form of vitellin (530 kD) in gel filtration also enlarges with oocyte growth, supporting the results of immunoblot analysis and vitellin determination. E₂ treatment in vivo causes significant increases in oocyte diameter and vitellin content in the female oyster. A similar trend was observed in ovarian tissues cultured in the presence of E₂. It is concluded that E₂ is one of the major factors which control the vitellogenesis in the oyster and that the ovary is undoubtedly the site of synthesis of vitellin.     

Interaction of photoperiod and nutritive state in female reproduction of Lymnaea stagnalis

Summary

A study was made of the interaction of the photoperiod and the availability of food in influencing egg laying of the freshwater snail Lymnaea stagnalis. At a long day photoperiod (LD = 16 h light/8 h dark) egg laying of fed snails had increased compared with that of fed animals kept at a medium day photoperiod (MD = 12 h light/12 h dark). In MD snails oviposition ceased within a week of the beginning of a starvation period. This is most probably due to a reduction in the activities of the neuroendocrine caudodorsal cells which secrete an ovulation hormone. In contrast, in starved LD snails a low rate of ovipository activity continued, indicating that a lowered frequency of caudodorsal cell release cycles occurred under these conditions. The decreased mean size (number of eggs) of the egg masses in starved LD snails indicates that the activities of the endocrine dorsal bodies, which control vitellogenesis and synthetic activities in the female accessory sex organs, had decreased.

All MD snails survived, but nearly all LD snails died during the course of the experiment. Determinations of the mantle glycogen stores of LD snails suggest that the high mortality of LD snails is due to exhaustion of the animal's energy reserves.     

Identifying reproductive events using archival tags: egg‐laying behaviour of the small spotted catshark Scyliorhinus canicula

The use of archival depth telemetry as a means of remotely assessing the reproductive rates of free‐ranging fishes is explored. This is achieved by electronically tracking the vertical movements of individual female small spotted catsharks Scyliorhinus canicula in the natural environment, whilst simultaneously evaluating the temporal and vertical distributions of egg‐laying in this species. Distinctive patterns of short‐term (0·3–3·7 h), shallow‐water activity are documented in the time–depth profiles of female S. canicula that occur at an appropriate depth (1·0–2·3 m) and periodicity (every 10–12 days) to represent egg‐laying behaviour. Putative egg‐laying behaviour was exhibited simultaneously by two individually tracked female S. canicula during late‐spring and early‐summer. The results highlight that, provided species behaviour is suitable and complementary methods such as previous data, laboratory experiments and field surveys can be used to validate the patterns observed, archival depth telemetry offers an unobtrusive means by which egg production and egg‐laying behaviour of free‐living fishes can be estimated. As precise information regarding life‐history parameters is difficult to obtain for free‐ranging fish species, this technique could be used to improve the parameterization of species demographic models that are relevant to the management of wild fish populations.     

Identity and phylogenetic placement of Spirogyra species (Zygnematophyceae,Charophyta) from California streams and elsewhere1

Diversity of the filamentous green algae in the genus Spirogyra (Zygnematophyceae) was investigated from more than 1,200 stream samples from California. We identified 12 species of Spirogyra not previously known for California (CA), including two species new to science, Spirogyra californica sp. nov. and Spirogyra juliana sp. nov. Environmental preferences of the Californian species are discussed in the light of their restricted distribution to stream habitats with contrasting nutrient levels. We also investigated the systematic relationships of Spirogyra species from several continents using the chloroplast‐encoded genes ribulose‐1,5‐bisphosphate carboxylase/hydrogenase large subunit (rbcL) and the beta subunit of the ATP synthase (atpB). Californian species were positioned in most major clades of Spirogyra. The phylogeny of Spirogyra and its taxonomic implications are discussed, such as the benefits of combining structural and molecular data for more accurate and consistent species identification. Considerable infraspecific genetic variation of globally distributed Spirogyra species was observed across continental scales. This finding suggests that structurally similar species from distant regions may be genetically dissimilar and that Spirogyra may contain a large number of cryptic species. Correlating the morphological and genetic variation within the genus will be a major challenge for future researchers.