Sex and reproduction of the alfonsino Beryx splendens (Pisces, Berycidae) from the Macaronesian archipelagos

This paper provides comparative information on the reproductive biology of the alfonsino, Beryx splendens Lowe, 1834, species with commercial interest in the Azores, Madeira and the Canary Islands. A total of 846 individuals from Azores (14.0–42.0 cm fork length), 621 from Madeira (17.2–50.0 cm fork length) and 643 from the Canaries (18.2–38.9 cm fork length) were used for the study. The alfonsino is gonochoric with no evidence of sexual dimorphism. Females are more abundant than males; this dominance probably reflects certain differences in the spatial distribution and/or the catchability of males and females in the Macaronesian archipelagos. The spawning season was distinct for the three Macaronesian areas, with an observed North–South variation in the reproductive period: September–March in the Azores, March–June in Madeira and July–September in the Canary Islands. The size at sexual maturity estimated for Madeira and the Canary Islands is similar (32 and 30 cm fork length, respectively), while for the Azores it is reached at smaller length (23 cm fork length). The differences observed in the size at sexual maturity can be explained by the different exploitation levels in each archipelago. Life‐history parameters of the alfonsino suggest that this species has a specialistic life‐history strategy and fisheries based on this species are more susceptible to growth overfishing and population depletion.     

A review of the reproductive bionomics of aquatic gammaridean amphipods: variation of life history traits with latitude,depth, salinity and superfamily

Life history traits (mean and maximum body length of females, number of embryos per brood = brood size, embryo diameter, number of broods per female, lifespan of females) for 302 populations of aquatic gammaridean amphipods, representing 214 species in 16 superfamilies, were reviewed. The variation of these traits, of lifetime potential fecundity (i.e. the number of embryos produced per female lifespan) and of reproductive potential (i.e. the number of embryos produced per female per year), with temperature (latitude), depth, salinity and superfamily, was investigated by various univariate and multivariate methods. Gammaridean amphipods comprise semelparous and iteroparous populations and species, with semiannual, annual, biannual or perennial life cycles. However, most gammarideans studied so far are iteroparous annuals. Body length explains most of the variation in brood size and embryo diameter. The reproductive potential may be increased by increasing body size for a constant breeding frequency, by increasing brood size at the expense of smaller embryos, by increasing breeding frequency for a constant lifespan at the expense of smaller individual broods and/or embryos, and by increasing longevity for a constant breeding frequency and brood size. Combinations of these different options constitute the life history patterns of gammarideans, which vary across superfamilies, latitude and depth, and cannot simply be explained by variations in body length. High latitude species were generally characterized by biannual or perennial life histories, large body size, delayed maturity, and single or few broods with many, relatively large embryos; converse sets of traits characterized low latitude species. Deep-living species had relatively smaller broods and embryos than their shallow-living relatives, yet did not produce more broods. However, different superfamilies dominated in different habitats. The importance of natural selection relative to phylogenetic (historical) and physiological constraints in the forging of these patterns is discussed.     

Effects of maternal and embryo characteristics on post-fertilization provisioning in fishes of the genus <Emphasis Type="Italic">Gambusia</Emphasis>

Maternal provisioning of embryos in Gambusia (Poeciliidae) entails both production of large, yolky eggs and mother-to-embryo transfer of nutrients, the latter of which is readily quantified using injection of radiolabeled nutrients. We assayed patterns of nutrient transfer in broods of 26 Gambusia geiseri and 23 Gambusia affinis females, using injection of tritiated leucine. We examined maternal and embryo characteristics affecting the instantaneous rate of transfer and characterized the pattern of transfer to individual embryos within broods. Maternal (female size and condition) and brood characteristics (mean embryo size, developmental stage, brood size) did not predict the mean level of nutrient transfer to embryos in a brood for either species. Within broods, individual provisioning of embryos was not related to developmental stage, but was related to embryo mass in G. affinis with nutrient transfer higher to larger embryos. In addition, overall within-brood variation in nutrient transfer, measured as coefficient of variation in embryo radioactivity, was higher in G. affinis than in G. geiseri.     

Reproductive biology of the prawn Melicertus kerathurus (Decapoda: Penaeidae) in Thermaikos Gulf (N. Aegean Sea)

The reproductive biology including insemination frequency, ovarian maturation, gonadosomatic index (GSI), size at first maturity, and fecundity of Melicertus kerathurus were investigated using monthly samples from Thermaikos Gulf. Insemination was recorded by the presence of a spermatophore in the thelycum, and ovarian development was based on macroscopic ovarian staging (ST1–ST5). Inseminated females were found throughout the year with high percentages recorded from April to July. Although all ovarian stages were represented in mated females, insemination increased with size and ovarian maturation. High percentages of vitellogenic or mature ovarian stages were observed from May to July, while immature and developing ovaries were predominant mainly in winter. Spawned ovaries occurred from May to October. Carapace length at first maturity based on the presence of a spermatophore (CL_50sp) was estimated at 39.20 mm, while that based on the presence of vitellogenic and mature ovaries (CL_50ov) at 40.70 mm. The seasonal peak in the proportion of mature females (ST4) varied with size. Inseminated females at ST4 and GSI peaked in June–July. GSI varied in relation to insemination status and ovarian stage. In large females (>50 mm CL), the decline in mature ovaries and GSI increment with size indicates a relative reduction in the reproductive output. The number of oocytes ranged from 62,742 to 602,947 (mean ± SD: 268,000 ± 113,000). As the prawns are targeted during the spawning season, mainly by the artisanal fishery, and female size at first maturity is selected by artisanal net size, managerial measures toward artisanal fishery should be implemented.     

Fecundity and reproductive output of the caridean shrimp Periclimenes paivai associated with scyphozoan jellyfish

Periclimenes paivai is notable for its symbiotic lifestyle with jellyfish. The objective of this study was to investigate the fecundity and reproductive output of females, and specifically to determine whether females protected in their host have a greater reproductive success than other shrimp species. All anatomical parts of the medusae were analyzed and the P. paivai individuals were separated. Among 83 females analyzed, 65 presented embryos in the first developmental stage, and 18 were in the final stage of development. The mean fecundity was 229.08 ± 120.04 in initial-stage embryos and 191 ± 114.76 in final-stage embryos. We observed a positive relationship between the embryo number and the female size; however, the embryo number was not related to the embryonic stage, which indicates that females did not lose their embryos during the incubation period. The weight of brood mass during production is closely related to the female weight according to the results of linear regression, as fecundity increased with female size. In its symbiosis, P. paivai can increase the amount of energy used to produce embryos (mean reproductive output = 10.38%) and can elevate the reproductive success.     

Ovarian development of albacore (Thunnus alalunga Bonnaterre, 1788) in the Eastern Mediterranean Sea: a histological characterisation

In order to investigate the stages of oogenesis in the albacore Thunnus alalunga, 129 females (64.0?83.5 cm fork length‐FL) were captured by gill nets from April to August 2002–2008, in the eastern Mediterranean Sea. Based on histological examination of the ovaries, a total of seven ovarian developmental stages were identified: perinucleolar, lipid, early vitellogenesis, late vitellogenesis, migratory nucleus, pre‐hydrated and hydrated. The monthly gonadosomatic index values and the results of the histological analysis indicated that the females mature in May. The spawning stage becomes predominant in June and reaches a maximum in July. The evidence reported here indicates that the size of females at first sexual maturity was lower for the Mediterranean albacore stock than for the Pacific and Atlantic stocks.     

Re-evaluation of reproductive cycle and fecundity of finetooth sharks Carcharhinus isodon (Valenciennes 1839) from the Northwest Atlantic Ocean,with new observations on ovarian cycle and reproductive endocrinology of biennially reproducing sharks

To provide updated information on life history for improved fishery management, the reproductive cycle of the finetooth shark Carcharhinus isodon from Northwest Atlantic (NWA) populations was investigated by examining temporal changes in morphology and histology of reproductive organs. Changes in plasma concentrations of gonadal sex hormones in relation to reproductive stage were also examined. Increases in testis width, epididymis head width, plasma testosterone concentrations and occurrence of mature spermatozoa were observed in male sharks between December and April, suggesting a seasonal pattern in reproduction that culminates with copulatory activity in May. Increases in maximum follicular diameter, oviducal gland width, plasma 17β-estradiol concentrations and occurrence of vitellogenic follicles were observed in non-pregnant female sharks during the same time period along with the occurrence of newly pregnant females in May, demonstrating strong synchronicity between male and female reproductive cycles. Pregnant females bearing full-term embryos were also observed in May, indicating that parturition occurs between mid-May and early June and gestation requires 12 months. Only transient temporal changes in follicle size and oviducal gland width were observed in pregnant females, indicating that reproductive periodicity is biennial; nonetheless, a single female exhibiting signs of concurrent vitellogenesis and pregnancy was observed. Mean brood size ± S.D. was 3.9 ± 0.9 offspring/female. Fecundity was not significantly correlated with female size, in part due to an unexpectedly high rate of early embryo mortality, which occurred in 11% of pregnant females, and was more common in larger individuals. Changes in ovarian activity during mid-pregnancy were observed, suggesting possible roles for the ovary in regulating some aspects of early to mid-gestation. This study confirms that earlier characterizations of the reproductive cycle and fecundity in NWA finetooth sharks remain valid for use in fishery management. This study also highlights unusual features of finetooth shark pregnancy (e.g., early embryo death, mid-pregnancy changes in ovarian function) that may have broader relevance to understanding elasmobranch reproduction.     

Ovarian development, spawning frequency and batch fecundity in Encrasicholina heteroloba (Ruppell, 1858)

A histological and gravimetric analysis of oocyte development in Encrasicholina heteroloba (Ruppell, 1858) indicated that this species spawns serially and has a group-synchronous mode of ovarian development. A six stage maturity scale, based on both external morphology and oocyte composition, was proposed to classify ovarian development in E. heteroloba . The incidence of females with hydrated oocytes and post-ovulatory follicles in samples from two regions; the south Java Sea and Roviana lagoon, in the Solomon Islands were used to estimate spawning frequency. Estimates of mean inter-spawning intervals ranged from around 2 days in fish from Roviana lagoon to up to 16.7 days in fish from the south Java Sea. Batch fecundity was determined from the number of oocytes in the largest oocyte size class in ripe stage ovaries. Batch fecundity was related to size and was significantly greater for a given size in the Roviana lagoon population ( F = 0.081 × L ^4.89, Roviana population; F = 1.682 × L ^2.83, Jepara population).     

Clanculus bertheloti D'Orbigny, 1839: Eine brutpflegende prosobranchiate schnecke aus der brandungszone von teneriffa

Zusammenfassung Clanculus bertheloti (Prosobranchia, Trochidae) lebt auf Steinen und Lavablöcken in Tümpeln in der Brandungszone der Kanarischen Inseln und Madeira. Die Eier sowie die Embryonen entwickeln sich in den Spiralfurchen der Schalen der Elterntiere. Diese Schalen sind von einer zähen Mucusschicht eng überzogen. Die Tiere sind getrenntgeschlechtlich. Obwohl kein männlicher Begattungsapparat vorhanden ist, findet die Brutpflege sowohl auf weiblichen als auch männlichen Schalen statt, doch meistens mit der größten Brut auf den weiblichen Schalen. Eine Pseudokopulation kommt also vor, wobei das Weibchen wahrscheinlich zuerst seine eigene Schale prall mit Eiern füllt, um dann den Rest auf die Schale des assistierenden Männchens zu übertragen. In der Natur werden die Schnecken meistens paarweise angetroffen. Die Männchen sind etwas kleiner als die Weibchen. Nur reife Individuen der beiden Geschlechter scheinen Brut auf der Schale zu tragen. — Die Entwicklung ist direct, ohne pelagisches Larvenleben. Etwa 80% der Eier und Embryonen überleben his zum Schlüpfen. Innerhalb der Monate Januar bis April scheinen 3 Gelege abgelegt zu werden. Ein Weibchen kann sofort nach dem Schlüpfen einer Brut eine neue anlegen. Eine Brut von einem großen Weibchen beträgt, verteilt auf das Weibchen und das assistierende Männchen, im ganzen etwa 330–530 Eier oder Embryonen.

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Summary Clanculus bertheloti (Prosobranchia, Trochidae), living under stones or lavablocks in surf-beaten intertidal rock-pools of the Canary Islands and Madeira, broods its eggs and developing embryos in the spiral furrows of its own shell, which is covered by a tough sheat of mucus. The sexes are separate. Although male copulatory organs are missing, brood will be deposited on shells of females as well as males, the females usually carrying the larger broods. A pseudoeopulation must occur, during which the female probably, after having packed her own shell with eggs, will transfer the spare portion of its brood to the shell of the assisting male. In nature the animals often occur in pairs. The development is direct, without any pelagic larval life. About 80 % of the eggs and embryos seem to survive to the stage when the creeping young leave the shells of their parents. Within the months January to April 3 broods are probably produced. A single female may produce a new brood as soon as the former brood has hatched. A single brood of a large female, distributed on the shells of the female and the assisting male, may comprise about 330 to 530 embryos.

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Herrn Prof. Dr. Ankel zum 70. Geburtstag in langjähriger Freundschaft gewidmet.     

Litter Overlap in Gambusia hubbsi: Superfetation Revisited

The frequency of litter overlap, the simultaneous presence of two litters at different stages of development within a single female, varies among populations of Gambusia hubbsi in different habitats on Andros, Bahamas. In freshwater bluehole and shallow water populations, less than 2% of the females carried two litters, independent of the difference in developmental stage between the litters. In well field populations, 2% of the females carried two litters composed of immature and mature oocytes, whereas 10% carried developing oocytes and late stage embryos, and 16% carried mature oocytes (or older) and late stage embryos. Among females from populations that we introduced into unoccupied well fields 2% carried two litters composed of immature and mature oocytes, about 14% carried developing oocytes and late stage embryos, and less than 6% carried mature oocytes (or older) and late stage embryos. When two litters composed developing oocytes and late stage embryos were present, the two litters were of equal size, and the total number of offspring was 1.5 times larger than expected on the basis of female body length. When two litters composed mature oocytes (or older stages) and late stage embryos were present, the two litters were also of equal size, and the total number of offspring was as expected on the basis of female body length. Litter overlap was independent of female size. A comparison of the consequences of litter overlap for strictly lecithotrophic and strictly matrotrophic modes of reproduction with the patterns of litter overlap observed in G. hubbsi, suggests that litter overlap in G. hubbsi reduces the cost of reproduction, but does not increase the rate of offspring production.     

Adaptations for matrotrophy in the female reproductive system in the pseudoscorpion Chelifer cancroides (Chelicerata: Pseudoscorpiones,Cheliferidae)

Pseudoscorpiones (pseudoscorpions, false scorpions) is an order of small terrestrial chelicerates. While most chelicerates are lecithotrophic, that is, embryos develop due to nutrients (mostly yolk) deposited in the oocyte cytoplasm, pseudoscorpions are matrotrophic, that is, embryos are nourished by the female. Pseudoscorpion oocytes contain only a small amount of yolk. The embryos develop within a brood sac carried on the abdominal site of the female and absorb nutrients by a pumping organ. It is believed that in pseudoscorpions nutrients for developing embryos are produced in the ovary during a postovulatory (secretory) phase of the ovarian cycle. The goal of our study was to analyze the structure of the female reproductive system during the secretory phase in the pseudoscorpion Chelifer cancroides, a representative of the family Cheliferidae, considered to be one of the most advanced pseudoscorpion taxa. We use diverse microscopic techniques to document that the nutritive fluid is produced not only in the ovaries but also by the epithelial cells in the oviducts. The secretory active epithelial cells are hypertrophic and polyploid and release their content by fragmentation of apical parts. Our observations also indicate that fertilization occurs in the oviducts. Moreover, in contrast to previous findings, we show that secretion of the nutritive material starts when the fertilized oocytes reach the brood sac and thus precedes formation of the pumping organ. Summing up, we show that C. cancroides exhibits traits of advanced adaptations for matrotrophy due to coordinated secretion of the nutritive fluid by the ovarian and oviductal epithelial cells, which substantially increases the efficiency of nutritive fluid formation. Since the secretion of nutrients starts before formation of the pumping organ, we suggest that the embryos are able to absorb the nutritive fluid also in the early embryonic stages.     

Oocytes development,maturity classification,maturity size and spawning season of the red mullet (Mullus barbatus barbatus Linnaeus, 1758)

The present study was designed to identify maturity of female red mullet, Mullus barbatus barbatus, using microscopic criteria, offering an accurate determination of the ovarian cycle and estimation of maturity size. Histological analysis of 499 females from 13 monthly samplings was applied (Thermaikos Gulf, N. Aegean Sea, Greece). Oocyte development was divided into five stages, with a mean oocyte size range from 56 to 363 μm in diameter. Ovarian maturity was defined by the maturation stage of the most advanced oocytes and divided into four phases. By using the monthly changes in the percentage frequency of ovarian phases, the ovarian cycle of M. barbatus was divided into three periods: a long period of early oogenesis (November to February), a short period of vitellogenesis (February to April) and a spawning period from April through June with peak activity in May. Both gonadosomatic (up to 7.5%) and hepatosomatic indices (up to 2%) can be used together to predict the spawning period. Red mullet should be classified as a multiple spawning species. Females reached 50% maturity (Lm₅₀) at 11.4 cm and 95% maturity (Lm₉₅) at 15.5 cm TL. The Lm₅₀ values for female red mullet populations across the Mediterranean Sea tended to show differences ranging from 11 to 14.4 cm FL or 11.4–14 cm TL. The current European Union fisheries management plan stipulates a minimum landing size (MLS) of 11 cm TL for Mullidae spp. fisheries in the Mediterranean. This MLS is at the lower part of the Lm₅₀ range, thus allowing an extensive removal of immature juveniles. A revision of this MLS value is recommended to help ensure that red mullet stocks remain within safe biological limits.     

Hermaphroditism in the lantern sharkEtmopterus unicolor (Squalidae,chondrichthyes)

Of the 70 specimens of the lantern shark,Etmopterus unicolor, collected in Suruga Bay and adjacent waters 22.9% were abnormal hermaphrodites, 30.0% normal males, and 47.1% normal females. Fifteen hermaphrodites had female reproductive organs composed of normal ovaries, oviducts, nidamentai glands and uteri as well as claspers. The clasper lengths of these hermaphrodites increased rapidly after the sharks reached 510 mm TL, the length about equal to the size at maturity for normal females. The ovary and uterus of abnormal females became mature at a total length greater than 500 mm, whereas the size at maturity was about 500 mm TL for normal females compared to 460 mm TL for normal males. In one specimen, the left gonad contained both ovarian and testicular tissues, the bulk of which was testicular.     

Sexual dimorphism and female reproductive cycle in the scincid lizard Trachylepis vittata (Olivier, 1804) in Lebanon (Reptilia: Scincidae)

Sexual dimorphism and the female reproductive cycle were studied in a population of the viviparous lizard Trachylepis vittata at 2000 m a.s.l. on Mount Sannine, Lebanon. Females have larger body sizes than males and males have relatively larger heads than females. Females reach maturity at 56 mm snout-vent length. They spend at least six months in hibernation, from October to March. Adult females emerge from hibernation in April. Fertilization occurs mid-May and gestation lasts for 8-10 weeks. All females collected on the same date had embryos at the same embryonic developmental stage. Females produced 1-4 embryos. There is a significant positive relationship between female body size and number of embryos. Parturition lasts for two weeks and new-borns achieve adult size within about ten months.     

Preliminary observations on fecundity of the processid shrimp Nikoides schmitti (Decapoda,Caridea) from Mexican Caribbean

Nikoides schmitti is widely distributed along the Atlantic coast of the Americas, from North Carolina to Bahia, Brazil and Cuba and Guadeloupe; however, the knowledge about their reproductive biology is poorly known. In this study, data such as sex ratio, fecundity, size and volume of the embryos, and brood loss of material collected in July 1997 from Mahahual, Quintana Roo, Mexico is provided. The sample of 728 specimens had a sex ratio of 0.40 males per female. Fecundity (N = 31) of ovigerous females (Stage I) varied from 219 to 817, with an average of 432 ± 177 embryos. The newly extruded embryos of N. schmitti were small (0.41 ± 0.030 mm) and similar in size to those reported for other species of the genus. The mean volume of the embryos changed significantly during development, increasing 60.9% from stages I to III. Embryo loss during incubation was estimated in 32.9%. This study provides baseline information about the reproduction of N. schmitti and contributes to a better knowledge of this species little studied.     

Effects of mating order and male size on embryo survival in a pipefish

In species that provide parental care, individuals should invest adaptively in their offspring in relation to the pre‐ and post‐zygotic care provided by their partners. In the broad‐nosed pipefish, Syngnathus typhle L., females transfer large, nutrient‐rich eggs into the male brood pouch during mating. The male broods and nourishes the embryos for several weeks before independent juveniles emerge at parturition. Given a choice, females clearly prefer large partners. Yet, females provide protein‐richer eggs when the same individual mates with a smaller than a larger male. In the present study, we allowed each female to mate with one small and one large male, in alternated order. We found a strong effect of female mating order, with larger clutches and higher embryo mortality in first‐ than second‐laid broods, which may suggest that eggs over‐ripen in the ovaries or reflect the negative effects of high embryo density in the brood pouch. In either case, this effect should put constraints on the possibility of a female being selective in mate choice. We also found that small and large males produced embryos of similar size and survival, consistent with the reproductive compensation hypothesis, suggesting that, in this species, larger males provide better nourishment to the embryos than smaller males. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 639–645.     

Relative growth and size at onset of sexual maturity of the brown crab,Cancer pagurus in the Isle of Man,Irish Sea

In this study, the relative growth, size–weight relationships and size at onset of maturity of the brown crab Cancer pagurus were investigated in the Isle of Man. For the analyses of relative growth and size at onset of maturity, the samples were collected seasonally between autumn 2012 and spring 2013 using several methods: pot surveys, dredge and trawl surveys, market surveys and shore surveys. Results showed that allometric growth occurred in the chelipeds of males (n?=?87) and in the abdomen of females (n?=?222). Four different measures of maturity (behavioural, functional, morphometric and physiological) were examined. With respect to the behavioural maturity, the smallest female crab found with a sperm plug measured 110?mm CW, whereas in terms of functional maturity the smallest ovigerous female had a CW of 134?mm. Based on direct observations of gonad maturity, 50% of females were mature at 108?mm CW, whereas 50% of males were mature at 89?mm CW. The size at the onset of maturity measurements of female and male C. pagurus based on gonad development is smaller than the current minimum landing size (130?mm), and therefore this suggests that the current minimum landing size is an adequate management measure.     

Reproductive biology of the East African lungfish (Protopterus aethiopicus) in Mwanza Gulf, Lake Victoria

The population of lungfish (Protopterus aethiopicus (Heckel)) was sampled by bottom trawling for 12 months from June 1984 to May 1985. A total of 576 lungfish were investigated. The sex ratio in the population was 1 male : 1 -98 females. Average size at maturity was found to be 960cm total length (TL) but the smallest matured male measured 72-9 cm and the female 840 cm TL. It was not possible to establish spawning times and reproductive activity trends either from the variation in relative condition factor ‘kn’ or from gonadosomatic index (GSI). Whereas male lungfish seem to show no further increase in GSI after gonadal maturity stage III, females exhibit GSI values that vary directly with oocyte maturation and ovarian weights. Fat deposited along the gonads was found to be a better basis for assessing maturation and spawning in lungfish. The potential spawning period was found to be from September to May. Absence of lungfish with spent gonads over the 12-month period and the presence of different egg sizes in ovaries, suggest that the fish is a multiple spawner. Fecundity was found to range from 705 eggs (in 84-cm TL fish) to 14,922 eggs (in 130-cm TL Fish).     

Interpopulation variation in life-history traits of Poeciliopsis prolifica: implications for the study of placental evolution

Placental reproduction is widespread across vertebrate taxa, but little is known about its life-history correlates and putative adaptive value. We studied variation in life-history traits in two populations of the placental poeciliid fish Poeciliopsis prolifica to determine whether differences in post-fertilization maternal provisioning to embryos have a genetic basis and how food availability affects reproduction. Life histories were characterized for wild-caught females and for second-generation lab-born females raised under two levels of food availability. We found that the two populations did not differ significantly in the wild for any life-history traits except for the lipid dry weight in females and in embryos at an advanced stage of development. When environmental effects were experimentally controlled, however, populations exhibited significant differences in several traits, including the degree of maternal provisioning to embryos. Food availability significantly affected female size at first parturition, brood size and offspring dry weight at birth. Altogether, these results demonstrate that population differences in maternal provisioning and other life-history traits have a genetic basis and show a plastic response to food availability. We infer that phenotypic plasticity may mask population differences in the field. In addition, when comparing life-history patterns in these two populations with known patterns in placental and non-placental poeciliids, our results support the hypotheses that placentation is an adaptive reproductive strategy under high-resource conditions but that it may represent a cost under low-food conditions. Finally, our results highlight that age at maturity and reproductive allotment may be key life-history traits accompanying placental evolution.