Studies on reproduction of the dragonfishes, Bathydraconidae, are scarce, and within this family, the reproductive biology of Parachaenichthys charcoti was poorly understood. Herein we present a histologic analysis of P. charcoti ovaries together with data on reproductive effort using fish collected with trammel nets in austral summer at Potter Cove, South Shetland Islands (SSI), and compare this information with that reported for the South Georgia congener Parachaenichthys georgianus. In gravid females of P. charcoti, GSI of 16–31%, mature oocytes of 1.8–3.9 mm and total fecundity (TF) of 9025–18,937 oocytes/individual (X ± SD = 12,617 ± 4019, n = 7) were recorded. The histology of the ovaries confirmed the common characteristics of the Notothenioidei observed macroscopically, i.e., two distinct batches of oocytes, one in the previtellogenic stage (primary growing or cortical alveoli stages) and the other in vitellogenesis and likely to be released in the current season. A longer incubation period of P. charcoti compared with P. georgianus is associated to the colder waters at the SSI. Based on our sampling and reproductive effort data, together with the reported nesting behavior for P. charcoti, it is assumed that this species spawns in nearshore, sheltered waters in summer, presumably from late December to February. Spawning periods of both congeners differ from those reported for other notothenioids in the same Seasonal Pack-ice Zone, suggesting divergence in some aspects of the life strategies in the genus Parachaenichthys. Likewise, although there are no substantial differences between P. charcoti and other notothenioids regarding gonadal development, the genus Parachaenichthys shows distinct features in its reproductive strategies (e.g., higher TF) compared with other bathydraconid species.
Mesophotic coral ecosystems (MCEs, between 30 and 150 m depth) are hypothesized to contribute to the recovery of degraded shallow reefs through sexually produced larvae (referred to as Deep Reef Refuge Hypothesis). In Okinawa, Japan, the brooder coral Seriatopora hystrix was reported to be locally extinct in a shallow reef while it was found abundant at a MCE nearby. In this context, S. hystrix represents a key model to test the Deep Reef Refuge Hypothesis and to understand the potential contribution of mesophotic corals to shallow coral reef recovery. However, the reproductive biology of mesophotic S. hystrix and its potential to recolonize shallow reefs is currently unknown. This study reports for the first time, different temporal scales of reproductive periodicity and larval settlement of S. hystrix from an upper mesophotic reef (40 m depth) in Okinawa. We examined reproductive seasonality, lunar, and circadian periodicity (based on polyp dissection, histology, and ex situ planula release observations) and larval settlement rates in the laboratory. Mesophotic S. hystrix reproduced mainly in July and early August, with a small number of planulae being released at the end of May, June and August. Compared to shallow colonies in the same region, mesophotic S. hystrix has a 4-month shorter reproductive season, similar circadian periodicity, and smaller planula size. In addition, most of the planulae settled rapidly, limiting larval dispersal potential. The shorter reproductive season and smaller planula size may result from limited energy available for reproduction at deeper depths, while the similar circadian periodicity suggests that this reproductive aspect is not affected by environmental conditions differing with depth. Overall, contribution of mesophotic S. hystrix to shallow reef rapid recovery appears limited, although they may recruit to shallow reefs through a multi-step process over a few generations or through random extreme mixing such as typhoons.
Ascidians are abundant and well-represented members of worldwide benthic communities, including Antarctica and the Arctic. These organisms exhibit different reproductive patterns usually related to a latitudinal gradient, as do many marine invertebrate species. Reproductive seasonality varies from one or two annual peaks in cold and temperate water species to continuous reproduction throughout the year in warm water species. Styela rustica (Linnaeus 1767) and Halocynthia pyriformis (Rathke 1806) are solitary species with external fertilization and a wide distribution range, from the North Atlantic to the Arctic. The reproductive patterns of these two species were assessed for Arctic populations by year-round sampling and structural analysis of the gonads. Both species are hermaphrodites and showed marked seasonality in oocyte maturity and spawning; S. rustica peaked during the boreal summer and H. pyriformis in late spring. The two species also showed marked differences in mature oocyte sizes: H. pyriformis almost doubled those of S. rustica and, while spermatocytes of H. pyriformis were mature year-round, the maturity of male and female gametes was synchronized in S. rustica. The species thus showed an annual reproductive cycle coupled with a higher production period in the ecosystem, but also exhibited different strategies developed under the same environmental pressures.
Indo-Pacific lionfishes, Pterois volitans (Linnaeus, 1758) and Pterois miles (Bennett, 1828), native to the Pacific and Indian Oceans, respectively, were first observed in the western Atlantic off Florida in 1985. They have since spread and are established throughout the broader Caribbean region. Despite potentially devastating ecological and economic effects, information on key life history characteristics for lionfish in the invaded range is sparse. Objectives of this study were to quantify 1) periodicity in gonad development and spawning, 2) spawning frequency, 3) batch fecundity and 4) female size at maturity for fish from Little Cayman. Calculation of gonadosomatic indices, histological and macroscopic staging of gonads, and counts of hydrated oocytes were applied to determine reproductive characteristics. Higher gonadosomatic indices were recorded for females during periods of stable warm or cool water temperatures indicating that extreme temperatures did not constrain reproduction. Histological and macroscopic staging suggested that male and female lionfish were capable of reproducing year-round. However, higher gonadosomatic indices in females, as expected before spawning, were most pronounced in March/April and August. Based on the proportion of females containing hydrated oocytes, mature lionfish had the potential to spawn every 2–3 d. Ovaries of mature females contained 1800–41945 oocytes that were hydrated in preparation for spawning, with greater numbers of oocytes in larger females. Female lionfish matured at 189–190 mm total length. Parameters estimated in this study can improve outputs from population dynamic models, which will help resource managers design removals and other efforts to control invasive lionfish.
The humpback smooth-hound shark (Mustelus whitneyi) is one of the most captured shark species in the south-east Pacific and is classified as vulnerable, yet its reproductive biology has been poorly studied. The aim of this study was to increase our knowledge of the reproductive biology of the humpback smooth-hound shark. In all, 41 pregnant females, 386 macroscopically visible embryos in utero and 16 neonates were sampled off northern Peru. Pregnant females measured between 73- and 118-cm total length (TL) and the number of embryos per litter ranged from 6 to 18, with a mean of 10. Size at birth ranged between 21 and 22cm TL. Litter size increased with the TL of the mother, yet this relationship was not strong (r(2)=0.36). The gestation period had a minimum duration of 7 months and a synchronous cycle in which birth occurred in September. The humpback smooth-hound shark is a placental viviparous elasmobranch. This study represents the most comprehensive research of the reproductive biology of the humpback smooth-hound shark, and is the first time the embryonic development is described for this species. These findings could contribute to the design and implementation of local management plans for this species.
is an antipatharian species common to Macaronesia, occurring in depths between 20 and 1425 m. Despite its importance as a habitat-forming species, there is no information about its basic biology. The aim of the current study is to describe its reproductive strategy, gametogenic cycle and reproductive timing. Sampling was performed monthly on six tagged colonies during one year and specimens were histologically processed. was found to be a gonochoric broadcast spawner. Gametogenesis took place within the primary transversal mesenteries, and followed an annual cycle. The reproductive season coincided with an increase in seawater temperature but spawning, inferred from the disappearance of gametes, likely happened after the sea surface temperature peak of the year (September 2009). Polyp fecundity ranged from 1 to 309 oocytes/polyp. A decrease in polyp fecundity was detected in samples at the higher pre-spawning maturity stage, indicating possible repetitive spawning or oocyte absorption. Intra-colonial comparisons revealed a longer duration of the reproductive cycle in the medial colony section, and a gradient of increased oocyte size towards the apical section, possibly due to intra-colonial differences in energy allocation between reproduction and other biological processes, or as a strategy against predation on gametes/larvae. Colony height was positively correlated with polyp fecundity indicating that the reproductive output increases with colony size.
Sunken whale carcasses, known as “whale falls”, deliver large, but relatively ephemeral pulses of organic material to the seafloor and serve as habitat for unique assemblages of deep-sea fauna that include generalist-scavenging species, chemosynthetic fauna and bone-specialist species. Despite the great deal of interest that fauna associated with whale falls have attracted, very little is known about this fauna in the deep Atlantic Ocean. Here we describe a new species of Ampharetidae that was found in an experiment using cow carcasses in the Setúbal Canyon (NE Atlantic), as a surrogate of a whale fall. Further, we analyse the size and structure of the population at two different times and use histological analyses to investigate the reproductive biology of this new species. We propose that sp. nov. is a bone-specialist adapted for life in ephemeral habitats. Reproductive traits include rapid maturation, continuous and non-synchronous gametogenesis. Recruitment seems to be controlled by habitat availability and biological interactions that result in post-settlement mortality.
In the Indo-Pacific region, rivers are inhabited by amphidromous gobies. They are often subjected to a heavy fishing pressure, highlighting the urgent need to acquire knowledge on their biology for management purposes. This study investigated the reproductive strategy of Sicyopterus lagocephalus, a widespread amphidromous goby, in two rivers of La Réunion Island. Histological observations of ovarian samples and oocyte-size frequency distributions revealed that females had a group-synchronous ovarian follicle development (i.e., two cohorts of oocytes were distinguished simultaneously in ovaries). Females laid an entire clutch in a unique event (from 14,304 to 232,475 eggs) and then another batch of oocytes was recruited, showing that the annual fecundity is indeterminate. Ovarian growth was isometric at all oocyte development stages showing that the gonadosomatic index (GSI) is a good proxy of reproductive condition. The main reproductive season of S. lagocephalus spanned from early February to May with a narrower range upstream and a wider one downstream. Reproduction activity is mainly restricted by water temperatures in upstream areas, whereas it is likely influenced by female body condition and competition in downstream areas. The variability of reproductive traits leads to size structure variation in stocks of spawning females throughout the year.
The reproductive biology of the blue shark (Prionace glauca) in the western North Pacific Ocean was investigated to contribute to future stock assessments because of limitations of recent studies and the lack of information about the reproductive cycle. Reproductive data were obtained from 490 males (precaudal length (PCL), 33.4-252.0 cm) and 432 females (PCL, 33.4-243.3 cm). Size at 50% maturity was estimated to be 160.9 cm for males and 156.6 cm PCL for females. Litter size varied from 15 to 112 (mean 35.5) and was positively correlated with maternal PCL. Parturition, ovulation and mating occurred sequentially from spring to summer. The gestation period was estimated to be 11 months. The ovarian follicles of pregnant females developed synchronously throughout the gestation period along with embryonic growth, indicating that females reproduce annually. Our results showed that the productivity of North Pacific blue sharks is higher than previously thought, based on larger fecundity and a shorter reproductive cycle. These new findings will improve future stock assessments and provide management advice.