Mating behaviors in ovoviviparous black rockfish (Sebastes schlegelii): molecular function of prostaglandin E2 as both a hormone and pheromone.

Prostaglandins (PGs) are profound hormones in teleost sexual behavior, especially in mating. PGs act as pheromones that affect the olfactory sensory neurons of males, inducing the initiation of a series of mating behaviors. However, the molecular mechanism by which PGs trigger mating behavior in ovoviviparous teleosts is still unclear. In the present study, we employed the ovoviviparous black rockfish (Sebastes schlegelii), an economically important marine species whose reproductive production is limited by incomplete fertilization, as a model species. The results showed that when the dose of PGE2 was higher than 10 nmol/L, a significant (P < 0.05) increase in mating behaviors was observed. Dual-fluorescence in situ hybridization indicated that PGE2 could fire specific neurons in different brain regions and receptor cells in the olfactory sac. After combining with specific neurons in the central nervous system (CNS), a series of genes related to reproduction are activated. The intracerebroventricular administration of PGE2 significantly increased lhb levels (P < 0.05) in both sexes. Moreover, steroidogenesis in gonads was also affected, inducing an increase (P < 0.05) in E2 levels in males and T levels in females. PGE2 levels were also increased significantly (P < 0.05) in both sexes. The present study revealed that PGE2 can activate mating behavior in black rockfish in both hormone and pheromone pathways, leading to variations in sex steroid levels and activation of reproductive behaviors. Our results provide not only novel insight into the onset of mating behaviors in ovoviviparous teleosts but also solutions for the incomplete fertilization caused by natural mating in cage aquaculture. Supplementary Information: The online version contains supplementary material available at 10.1007/s42995-023-00214-w.

Colonization pattern and thermal needs of immature phases of Sarcophaga argyrostoma (Diptera: Sarcophagidae): Significance for estimating postmortem interval.

Members of Sarcophagidae are necrophagous and are commonly found on decaying carcasses; and their developmental forms are important indicators for the approximation of lowest postmortem interval (PMImin). This work describes the biological characteristics of Sarcophaga argyrostoma from Tehran, Iran. Various temperature regimes were applied to estimate the thermal summation constant (k) and thermal requirements for development of S. argyrostoma. Five growth proceedings, containing 1st ecdysis, 2nd ecdysis, wandering, pupariation and eclosion, were investigated under eight fixed temperature regimes (6-30 °C). The effects of fly age, freshness, and availability of oviposition substrate on oviparity and viviparity was studied. At 6 °C, no development occurs, and at 8 °C only the first ecdysis occurs. At temperatures between 10 and 30 °C, all immature stages proceeded to the adult stage, and thus immature development was analyzed at these six remaining temperatures. The development phases needed minimum (Dz ± SE) 5.4(0.4), 8.5(0.26), 5.3(0.44), 3.8(0.1), and 6.6 (0.6)°C to attain one of the succeeding developmental occasion, correspondingly. The approximated K for those five occasions were 15.04 ± 1.12, 12.62 ± 0.65, 140.36 ± 4.35, 14.59 ± 0.6, and 222.8 ± 4.18°-day (DD) accordingly. When the food substrate is available and fresh, the female prefers to lay eggs, no matter how old she is. However, the chance of ovoviviparity increased when no oviposition substrate was available. The truth that S. argyrostoma able to either larviposit or to lay eggs encompasses serious consequences for the precise estimation of the PMImin, as the existence of larvae resulting from eggs laid on the carcass could add hours (based on ambient temperature) to the PMImin.

PGE2 functions in ovoviviparous teleost black rockfish (Sebastes schlegelii): evolutionary status between parturition and ovulation†.

Fish have evolved various reproductive strategies including oviparity, viviparity, and ovoviviparity, which undoubtedly affect the survival of the whole species continuity. As the final step in reproduction, parturition in viviparous vertebrate and ovulation in oviparous teleost seem to share a similar mechanism, when prostaglandins (PGs) act as the trigger to launch the whole process. In the present study, ovoviviparous teleost black rockfish (Sebastes schlegelii) is employed as the research object. Intraperitoneal injection showed that PGE2 (500 µg/kg) could activate the delivery reactions in perinatal black rockfish. RNA-seq data of ovary in perinatal period revealed transcriptional change in cell junction, inflammation, and apoptosis, which is related to mammal parturition and teleost ovulation. Further results proved the positive correlation between ptger EP2 and previous mentioned pathways. Subsequent experiment proved that PGE2 was able to induce the ovulation and spawning in unfertilized individuals, which had a bilayer follicular structure compared to monolayer follicular in perinatal period black rockfish. Both unfertilized and perinatal ovary matrix could response to PGE2 stimulation. In conclusion, the function of PGE2 in activating both parturition and ovulation in a relatively different pathways conserved with viviparity or oviparity provided novel evidence of the evolutionary status of ovoviviparous vertebrates.

Karyotype and reproductive traits of the unique symbiotic mealybug Orbuspedummachinator G.-Z. (Homoptera, Coccinea).

The karyotype and reproductive features of Orbuspedummachinator Gavrilov-Zimin, 2017 (Pseudococcidae) were studied for the first time. Diploid chromosome number is 18 in females. Reproduction is probably bisexual, as indicated by the presence of characteristic Lecanoid heterochromatinization of the paternal set of chromosomes in embryonic cells of about 50% of the embryos studied. The female reproductive system has a pair of lateral oviducts merged into enlarged common oviduct; the spermatheca and accessory glands are connected to the common oviduct in its proximal part. Complete ovoviviparity occurs in ontogenesis.

Combined effects of temperature, photoperiod, and salinity on reproduction of the brine shrimp Artemia sinica (Crustacea: Anostraca).

Background: Artemia sinica is a brine shrimp species distributed in hypersaline salt lakes in northern China and Siberia and a successful invasive species in some coastal salterns. Although it is a commercially harvested and cultured species, knowledge of its reproductive characteristics is limited, and existing studies are often contradictory. The combined effects of temperature, salinity, and photoperiod on reproduction characteristics are experimentally studied to better understand its reproductive features. Methods: There were 36 combinations of three environmental factors (3 × 3 × 4), each with three or four levels, namely temperature (16, 25, 30 °C), photoperiod (6 L:18 D, 12 L:12D, 18 L:6D), and salinity (50, 100, 150, 200 PSU). In each treatment, 48 to 80 pairs of A. sinica from Yuncheng Salt Lake (Shanxi, China) were cultured. Females were observed daily for reproductive mode and the number of offspring produced. Results: Temperature, photoperiod, salinity, and their interactions significantly affected the lifespan and reproduction of A. sinica. The reproductive period was the longest and accounted for the largest proportion of life span at moderate temperature (25 °C). Total offspring, offspring per brood, and offspring per day increased as salinity decreased, and the number of broods per female was highest at 25 °C. Temperature, photoperiod, and salinity significantly influenced reproductive modes, and interactions among these factors were identified. Artemia sinica primarily reproduces oviparously under low temperature and short daylight conditions, and ovoviviparously under high temperature and long daylight conditions, with the maximum oviparity ratio recorded in treatments of 16 °C, 6L:18D, and 50 or 100 PSU. The maximum ovoviviparity ratio was recorded under 30 °C, 12L:12D, and 100 PSU. Unlike that documented for other Artemia species or populations, the brood size of A. sinica kept increasing throughout the reproductive period. It did not decline even in the last two broods. For the same brood number, the sizes of oviparous and ovoviviparous broods were similar. The length of the oviparous interval was often greater than that of the ovoviviparous interval, suggesting that oviparous offspring might require additional energy and time to construct the multi-layered eggshell. Compared to other species and populations, the A. sinica from Yuncheng Salt Lake has a relatively shorter pre-reproductive development time, a preference for ovoviviparity, and relatively higher fecundity and population growth capacity, making it a suitable culture species for obtaining fresh biomass.

Comparative transcriptomic analysis and genome-wide characterization of the Semaphorin family reveal the potential mechanism of angiogenesis around embryo in ovoviviparous black rockfish (Sebastes schlegelii).

To guarantee the quality and survival rate of their offspring, ovoviviparous teleost evolved special characteristics of in vivo fertilization and embryo development. Maternal black rockfish, having over 50 thousand embryos developing within the ovary simultaneously, provided around 40% nutrition throughout oocyte development, while the capillaries around each embryo contributed the rest 60% during pregnancy. Since fertilization, capillaries started to proliferate and developed into a placenta-like structure that covered over half of each embryo. Aimed to characterize the potential mechanism behind, comparative transcriptome analysis of samples collected according to the process of pregnancy. Three important time point in the process, including mature oocyte stage, fertilization and sarcomere period, were chosen for the transcriptome sequencing. Our study identified key pathways and genes involved in the cell cycle as well as DNA replication and repair, cell migration and adhesion, immune, and metabolic functions. Notably, several of the semaphoring gene family members were differently expressed. To confirm the accuracy of these genes, total of 32 sema genes were identified from the whole genome and distinct expression pattern of sema genes was observed in different pregnant stages. Our results revealed a novel insight for further investigating the functions of sema genes in reproduction physiology and embryo processes in ovoviviparous teleost.

Different Dynamics of Reproductive Cell Development in Oviparous Clausilia bidentata and Ovoviviparous Ruthenica filograna Snails.

Most terrestrial snails are oviparous and only some are ovoviviparous. The physiology of the reproductive system and its activity in these two groups have received little attention. We compared the month-to-month dynamics of reproductive cell formation between two species of Clausiliidae snails: Ruthenica filograna (an ovoviviparous species) and Clausilia bidentata (an oviparous species). Our aim was to test the hypothesis that the seasonal activity of gametogenesis is determined by reproductive strategy (oviparity /ovoviviparity). The results showed that the frequency and number of reproductive cells in different stages varied month-to-month, within each species, and between the two species. Ruthenica filograna maintained its reproductive activity throughout the entire observation period, whereas the gonadal activity of C. bidentata changed with the seasons (it was temperature dependent). Our results are in tune with the hypothesis of Baur, that ovovivipary has some advantage over oviparity under harsher environmental conditions.

Data on RNA-seq analysis of the oviducts of five closely related species genus Littorina (Mollusca, Caenogastropoda): L. saxatilis, L. arcana, L. compressa, L. obtusata, L. fabalis.

In the evolution of invertebrates, the transition from egg-layers to brooders occurred many times. However, the molecular mechanisms underlying this transition are still not well understood. Recently diverged species genus Littorina (Mollusca, Gastropoda, Caenogastropoda, Littorinimorpha): Littorina saxatilis, L. arcana, L. compressa, L. obtusata and L. fabalis might be a fruitful model for elucidation of these mechanisms. All five species sympatrically inhabit an intertidal zone. Only L. saxatilis is ovoviviparous while the other four species form clutches. Although in L. saxatilis jelly gland of the pallial oviduct function as a brood pouch, it is not deeply modified at the morphological level in comparison to egg-laying relatives. Comparative analysis of transcriptomic profiles of the pallial oviducts of these closely related species might help to uncover the molecular mechanisms of the egg-laying to brooding transition. Unraveling of the mechanisms underlying this transition in L. saxatilis is important not only in aspects of reproduction biology and strategy, but also in a broader view as an example of relatively fast evolutionary transformations. We generated an RNA-seq dataset (224 104 446 clean reads) for oviducts of five species genus Littorina. Libraries of all five species were sequenced using Illumina HiSeq 2500; additional reads for L. arcana were obtained using Illumina NovaSeq 6000. Transcriptomic profiles were analyzed in pooled samples (of three individuals) with two biological replicates for each species (each biological replicate was prepared and sequenced as a separate library). The transcriptome was assembled de novo and annotated with five assembles corresponding to each species. The raw data were uploaded to the SRA database, the BioProject IDs are PRJNA662103 ("obtusata" group) and PRJNA707549 ("saxatilis" group).

[Patterns of maternal transfer of trace elements in the pelagic thresher shark (Alopias pelagicus) of the Eastern Pacific Ocean]. / ä¸œå¤ªå¹³æ´‹æµ æµ·é•¿å°¾é²¨æ¯ä½“å’ŒèƒšèƒŽé—´ç—•é‡å ƒç´ çš„è¿ç§»è§„å¾‹.

Pelagic sharks are vulnerable to overfishing due to slow growth rates, late-at-maturity and low fecundity, 90% of which are Near Threatened with an elevated risk of extinction according to IUCN Red List Criteria. Trace elements can be accumulated by marine predators and may have detrimental effects on population dynamics. In this study, we analyzed the concentrations of 11 trace elements (Zn, Cu, Cr, Ni, Mn, Se, Co, Hg, Cd, Pb, and As) in muscle and liver tissues of 10 pregnant pelagic thresher sharks (Alopias pelagicus) and their 18 embryos. The results showed that four essential elements (Cu, Cr, Mn, and Se) were accumulated in both tissue types of embryos. Ni and Zn concentrations were higher in embryonic muscle than that in the liver. For nonessential elements, concentrations of As, Cd and Hg in both embryonic tissues were lower than those of their mothers. Though maternal and embryonic tissues had high levels of Hg, the Se/Hg molar ratios in both tissues of the embryo were above 1 with larger values in the embryos, indicating that Se played a protective role against Hg toxicity in embryonic tissues. Liver is the primary energy resource of embryo development. There was no correlation for element concentrations between embryonic and maternal liver tissues, indicating there is a regulatory mechanism to maintain the stability of element contents during maternal transfer in pelagic thresher shark.

Definition of the Gonioctena subgeminata species group (Coleoptera, Chrysomelidae, Chrysomelinae), with descriptions of two new species from China and Vietnam.

This paper defines and reviews the Gonioctena subgeminata species group of the subgenus Asiphytodecta Chen, 1935. The group contains the following five species, including two new to science: G. subgeminata (Chen, 1934), G. tonkinensis (Chen, 1934), G. oudai Cho & Borowiec, 2016, G. allardi sp. nov., and G. mantillerii sp. nov. The species group restricted to China and Vietnam is characterized by a labrum without a tooth-like projection, elytral punctures arranged in discernible rows, and a setose aedeagus with a broad apical process. Gonioctena tonkinensis is newly reported as an ovoviviparous species. Habitus photographs, illustrations of diagnostic characters of each species, and a key to the species are provided.

Morphology, development stages, and phylogeny of the Rhabditolaimus ulmi (Nematoda: Diplogastridae), a phoront of the bark beetle Scolytus multistriatus from the elm Ulmus glabra Huds. in Northwest Russia.

The nematode Rhabditolaimus ulmi was found in galleries, adults, and larvae of Scolytus multistriatus, the vector of the Dutch elm disease, in St. Petersburg parks. This nematode co-occurred with Bursaphelenchus ulmophilus, which is another phoretic partner of S. multistriatus. Nematodes were cultured on the fungus Botryotinia fuckeliana in potato sugar agar (PA) and used for morphological analyses of adults, juveniles, eggs, and dauers. Nematode females showed a didelphic female genital tract rather than a monoprodelphic gonad as reported in the original description. Male bursa peloderan, caudal papillae include three preanal pairs and one precloacal unpaired papillae; seven postanal papilla pairs, among which one is pore-like and possibly the phasmid homolog, one subdorsal, and a pair of three closely situated posteriorly at bursa alae. The juvenile stages differ in size and structure of their sexual primordia. Sex of juveniles may be identified from the third stage. The dauer juvenile is a phoretic third juvenile stage (DJ3), which enters and remains localized in the buccal cavity of beetle adults and last-instar larvae and also under the elytra and in the ovipositor's cavity of pupae and imagoes. The first molt J1-J2 occurred inside the eggshell. Adult females laid eggs in early stages of embryonic development or containing molted J2. The propagative non-phoretic J2 inside the egg and J3 have a long and well-developed median bulb. The phoretic dauer DJ3 has a small spherical bulb like the J1 juvenile within the egg. In a sterile fungal culture, the nematodes feed on both mycelium and their unidentified ecto-symbiotic bacteria, located on nematode surface coat and multiplying in PA. Diagnosis and tabular key to the Rhabditolaimus species are given. Phylogenetic analysis of the D2-D3 of 28S rRNA gene sequences resulted in the Bayesian consensus tree with the highly supported clade of the Rhabditolaimus species.

Possibility of Undeveloped Egg Absorption during Embryogenesis: A Unique Phenomenon Observed in the Ovoviviparous Mayfly Cloeon dipterum.

Oviparous, ovoviviparous and viviparous reproduction are interesting subjects for understanding animals' evolutionary pathways and adaptation to their life history and habitat conditions. In this study, we examined the reproductive mode of the ovoviviparous mayfly Cloeon dipterum, particularly comparing embryogenesis between hand-pairing and unmated females' common oviduct. Our study suggested that the high developmental rate of C. dipterum observed in a recent study could be ascribed to their absorption of unfertilized eggs. The developmental rates of hand-paired females were almost 100%, while their egg-bearing numbers were lower than those of virgin females. Thus, such reduced egg numbers suggest the maternal absorption of unfertilized eggs. This trait is thought to have evolved with the ovoviviparous characteristics of C. dipterum. We identified the basis of the irregularity of this species exhibiting such a high (i.e., 100%) developmental rate in our previous recent study.

Reproductive pattern in the solanum mealybug, Phenacoccus solani: A new perspective.

BACKGROUND: The reproductive pattern of most scale insects is ovoviviparity. The solanum mealybug, Phenacoccus solani (Hemiptera: Pseudococcidae), is known as a thelytokous parthenogenetic species, but there is still debate about the reproductive strategies of this species. METHODS: Here, we investigated the oviposition characteristics of P. solani and used scanning/transmission electron microscopy and RNA-seq to identify the differences between two types of eggs. RESULTS: We found that P. solani laid two types of eggs in one batch, with no significant difference in apparent size: one with eyespots that hatched and another without eyespots that failed to hatch. Furthermore, the physiological and molecular differences between the two types of eggs were highly significant. KEGG enrichment analysis revealed significant enrichment for the JAK-STAT, Notch, Hippo, and Wnt signaling pathways and dorsoventral axis formation, wax biosynthesis, cell cycle, insulin secretion, and nitrogen metabolism pathways. The results suggest that the embryo of the egg undergoes development inside the mother and only a short molting period outside the mother. DISCUSSION: Ovoviviparous species produce eggs and keep them inside the mother's body until they are ready to hatch, and the offspring exits the egg shell during or immediately following oviposition. Therefore, we suggest that the reproductive pattern of P. solani can be described as ovoviviparity.

Redescription of mature larva and biological notes on the nominotypical subgenus Gonioctena Chevrolat (Coleoptera: Chrysomelidae: Chrysomelinae) from South Korea.

The mature larvae of the nominotypical subgenus Gonioctena Chevrolat, 1836 are redescribed and illustrated: G. coreana (Bechyne, 1948), G. gracilicornis (Kraatz, 1879), G. jacobsoni (Ogloblin Medvedev, 1956), and G. viminalis (Linnaeus, 1758). The tubercular pattern, chaetotaxy, and shape of tarsugulus were used as diagnostic characters for the species determination of Gonioctena s. str. larvae. The literature on larval morphology of each species has been summarized. Furthermore, the biology, behavior, and host plant are presented. Ovoviviparity is newly reported in G. coreana.

A revision of the Afrotropical species of Pachylophus Loew (Diptera: Chloropidae) and some related Ovoviviparous genera.

In Pachylophus all described Afrotropical species are treated and P. aristalis, ismayi, nigeriensis, tschirnhausi, mirabilis, lacteibasis and stuckenbergi are described as new species. Pachylophus tellinii Bezzi is placed in synonymy. In Phyladelphus the type species thalhammeri and the single described Afrotropical species, P. geminus, are treated and P. woodi and P. maraisi are described as new species. The genus Sabeurina is erected to accommodate Eurina minuta Loew and a new Afrotropical species S. occidentalis. Some taxonomic notes are given on the Afrotropical species currently included in Platycephala. The immature stages and biological notes concerning the treated genera are described and discussed in the contexts of ovoviviparity and classification. Keys are provided for the identification of all the Afrotropical species known in each of the genera treated.

Halogenated organic pollutants in aquatic, amphibious, and terrestrial organisms from an e-waste site: Habitat-dependent accumulation and maternal transfer in watersnake.

Dichlorodiphenyltrichloroethanes (DDTs), Polychlorinated biphenyls (PCBs), and halogenated flame retardants (HFRs) were measured in aquatic, amphibious, and terrestrial wildlife collected from an e-waste contaminated pond and its surrounding region. The species-specific bioaccumulation and maternal transfer of chemicals in the watersnake were investigated. Total concentrations of target chemicals ranged from 1.3 × 103 to 4.8 × 105 ng g-1 lipid weight. PCBs were the predominant (72-95%) contaminants, followed by polybrominated biphenyl ethers (PBDEs, 4-27%). The concentrations of PCBs and HFRs except decabromodiphenyl ethane (DBDPE) were higher in aquatic organisms and terrestrial birds than in amphibians and lizards. Relatively high DDT levels were observed in the terrestrial birds and toads, but high DBDPE was found in the aquatic species except for waterbird eggs. Species-specific congeners profiles for PCB and PBDE and isomeric composition for dechlorane plus were observed. These results indicated a habitat-dependent accumulation among different species. Maternal transfer examined by the ratio of egg to carcass for watersnakes indicated multi-linear correlations between maternal transfer potential and octanol-water partition coefficient (log KOW) of chemicals. The same maternal transfer efficiencies were found for chemicals with log KOW between 6 and 8, then the maternal transfer potential rapidly decreased with increasing of log KOW.

A cryptic diapause strategy in Halotydeus destructor (Tucker) (Trombidiformes: Penthaleidae) induced by multiple cues.

BACKGROUND: The polyphagous mite pest, Halotydeus destructor, typically has three generations during the cool moist season in Australia and produces over-summering diapause eggs in spring. Diapause eggs have a distinct thick and dark chorion and can survive heat, desiccation and the application of pesticides. Farmers suppress mites producing diapause eggs by a carefully timed spring pesticide application using Timerite® , which predicts the onset of diapause egg production based largely on day length. We investigated the association between diapause induction and other environmental factors that may complicate diapause predictions. RESULTS: Diapause in H. destructor induction was influenced by three interacting environmental factors, namely day length, temperature and soil moisture. A cryptic type of diapause egg that lacked a thick chorion and was instead morphologically similar to non-diapause eggs was also discovered. Like diapause eggs, this newly discovered egg type could also survive hot and dry summer conditions. CONCLUSIONS: There is an opportunity to refine the Timerite® spring spray by incorporating knowledge of other environmental factors inducing diapause in H. destructor. Compared with typical diapause eggs, the production of cryptic diapause eggs could reflect a strategy to deal with diversifying environmental stresses and/or represent a bet-hedging strategy to adapt to unpredictable environments. © 2018 Society of Chemical Industry.

The Roles of the Kisspeptin System in the Reproductive Physiology of the Lined Seahorse (Hippocampus erectus), an Ovoviviparous Fish With Male Pregnancy.

The kisspeptin/GPR54 system plays a crucial role in the regulation of the reproductive axis in vertebrates. Male pregnancy and ovoviviparity are special reproductive phenomena among vertebrates. To better understand the neuroendocrine mechanisms of male pregnancy, cDNAs encoding kiss2 and GPR54 were cloned and functionally characterized from the lined seahorse, Hippocampus erectus, an ovoviviparous teleost with male pregnancy. The core mature peptide of seahorse Kiss2 is high conserved among seahorses, but unique among vertebrate Kiss orthologs. In the phylogenic analysis, the seahorse Kiss clustered with the teleost Kiss2 clade. The kiss2 transcripts were shown to be widely expressed in various tissues, notably in the brain and gonad of the seahorse, while GPR54-2 mRNA was expressed exclusively in the brain. In addition, kiss2 mRNA found in male seahorse brain tissue increased significantly at the early pubertal stage, and decreased significantly during pregnancy. Intraperitoneal administration of seahorse Kiss2-10 to sexual mature male seahorses demonstrated to stimulate lutropin ß (LHß) and follitropin ß (FSHß) release and increased serum testosterone levels. In summary, we first identified the kisspeptin/GPR54 system in an ovoviviparous fish with male pregnancy, which might be involved in the regulation of the reproductive functions of pubertal onset, gonadal development, and male pregnancy via regulating the synthesis of both gonadotropic hormone (GTH) and testosterone.

Parasphaerolaimus magdolnae sp. n. (Nematoda, Sphaerolaimidae) with intra-uterine development of its offspring from a Brazilian estuarine system.

One new species of Parasphaerolaimus is described from a Brazilian estuarine system with intra-uterine development of its offspring. Parasphaerolaimus magdolnae sp. n. is distinguished from other species of the genus by the presence of only one anterior testis, spicules morphology and size and a gubernaculum without dorsal apophysis. The cuticle of the new species is striated and the position of the vulva is far posterior on the body, almost reaching the anus. The taxonomy of Parasphaerolaimus was also re-examined and two other species were transferred from Sphaerolaimus to Parasphaerolaimus after the last revision: P. pentasetus (Pastor de Ward, 1984) comb. n. and P. striatus (Allgén, 1935) comb. n. An updated identification key for all valid species of Parasphaerolaimus is included.

Potential targets for selection during the evolution of viviparity in cold-climate reptiles.

Viviparity (live-bearing) has evolved from oviparity (egg-laying) in more than 100 lineages of squamate reptiles (lizards and snakes). This transition generally has occurred in cool climates, where thermal differentials between eggs in the (cool) nest versus the (warm) maternal oviduct influence embryonic development, in ways that may enhance offspring fitness. To identify specific traits potentially under selection, we incubated eggs of a montane scincid lizard at conditions simulating natural nests, maternal body temperatures, and an intermediate stage (2-week uterine retention of eggs prior to laying). Incubation at maternal temperatures throughout incubation affected the hatchling lizard's activity level and boldness, as well as its developmental rate, morphology, and locomotor ability. A treatment that mimicked the initial stages of the transition toward viviparity had a major effect on some hatchling traits (locomotor speeds), a minor effect on others (tail length, total incubation period) and no effect on yet others (offspring behaviors). More generally, different aspects of the phenotype are sensitive to incubation conditions at different stages of development; thus, the evolution of reptilian viviparity may have been driven by a succession of advantages that accrued at different stages of embryogenesis.