Muscle Regression in Belostomatid Bugs (Heteroptera: Belostomatidae)

Differential flight muscle regression was registered in Belostoma elegans (Mayr, 1871) and B. oxyurum (Dufour, 1863). A two year survey in contrasting habitats showed the preference for the more stable ones by B. oxyurum, and the more unstable ones by B. elegans. Fibrillar muscles were regressed in most of the B. oxyurum specimens, and developed for flight in most B. elegans. No positive correlation between egg production and muscle regression was found in any species. IV^th and V^th instar larvae of both species were raised up in laboratory under unstable conditions. When moulting to adult stage none had their muscles developed, suggesting that the muscle development should be achieved later. B. oxyurum with its muscles regressed was found in quiescence during a dry-up of a sampled environment, thus this species would have to survive unexpected changes this way, and B. elegans would emigrate flying. The differential muscle development is associated with the ecological strategies of these two species.     

Use of field‐portable ultrasonography reveals differences in developmental phenology and maternal egg provisioning in two sympatric viviparous snakes

A thorough understanding of the life cycles underlying the demography of wild species is limited by the difficulty of observing hidden life‐history traits, such as embryonic development. Major aspects of embryonic development, such as the rate and timing of development, and maternal–fetal interactions can be critical features of early‐life fitness and may impact population trends via effects on individual survival. While information on development in wild snakes and lizards is particularly limited, the repeated evolution of viviparity and diversity of reproductive mode in this clade make it a valuable subject of study. We used field‐portable ultrasonography to investigate embryonic development in two sympatric garter snake species, Thamnophis sirtalis and Thamnophis elegans in the Sierra Nevada mountains of California. This approach allowed us to examine previously hidden reproductive traits including the timing and annual variation in development and differences in parental investment in young. Both species are viviparous, occupy similar ecological niches, and experience the same annual environmental conditions. We found that T. sirtalis embryos were more developmentally advanced than T. elegans embryos during June of three consecutive years. We also found that eggs increased in volume more substantially across developmental stages in T. elegans than in T. sirtalis, indicating differences in maternal provisioning of embryos via placental transfer of water. These findings shed light on interspecific differences in parental investment and timing of development within the same environmental context and demonstrate the value of field ultrasonography for pursuing questions relating to the evolution of reproductive modes, and the ecology of development.     

Vegetative and reproductive morphology of Herpochondria corallinae (Martens) Falkenberg and H. elegans (Okamura) Itono (Ceramiaceae,Rhodophyta) from Korea

The vegetative and reproductive morphology of two epiphytic Herpochondria species, H. corallinae (Martens) Falkenberg (the type species) and H. elegans (Okamura) Itono from Korea were investigated. They are bilaterally compressed and alternate-distichously branched, and lateral branches are produced by oblique divisions of the apical cell. Procarps are restricted to the first periaxial cell of the branches. Spermatangial mother cells produce one or two spermatangia. H. corallinae forms tetrasporangia on six periaxial cells, whereas H. elegans has them on only the two lateral periaxial cells. The prostrate habit, the production of six periaxial cells in opposite pairs, and tetrasporangial stichidia are confirmed as diagnostic characters of the genus Herpochondria.     

Reproductive development and timing of tropical sponges (Order Haplosclerida) from the Great Barrier Reef,Australia

Reproductive development of three species of the Haplosclerida, Haliclona amboinensis (Lévi 1961), Haliclona cymiformis (Esper 1794) and Niphates nitida Fromont (1993), was monitored for three years on a fringing reef in the central section of the Great Barrier Reef, Australia. All species are viviparous, and gonochoric. Haliclona amboinensis and N. nitida incubated eggs, embryos and larvae in brood chambers. The branching sponge. H. cymiformis, incubated eggs, embryos, and larvae along the central axis of branches. In all species, sperm cysts in high densities are evenly distributed throughout the mesohyl. Mature larvae of all species are creamy white, oval, parenchymella, with a dark coloured ring at the posterior pole. Eggs, embryos and larvae are present contemporaneously for periods of two consecutive months in individuals of H. cymiformis and seven months in H. amboinensis and N. nitida. The first observation of female reproductive products in H. amboinensis and N. nitida coincided with an increase in water temperature, while cessation of reproductive activity was associated with decreasing water temperature. Onset of reproduction in H. cymiformis coincided with peak sexual and vegetative reproductive activity of its algal symbiont, Ceratodictyon spongiosum.     

Reproductive fitness and dietary choice behavior of the genetic model organism Caenorhabditis elegans under semi-natural conditions

Laboratory breeding conditions of the model organism C. elegans do not correspond with the conditions in its natural soil habitat. To assess the consequences of the differences in environmental conditions, the effects of air composition, medium and bacterial food on reproductive fitness and/or dietary-choice behavior of C. elegans were investigated. The reproductive fitness of C. elegans was maximal under oxygen deficiency and not influenced by a high fractional share of carbon dioxide. In media approximating natural soil structure, reproductive fitness was much lower than in s tandard laboratory media. I n seminatural media, the reproductive fitness of C. elegans was low with the standard laboratory food bacterium E. coli (γ-Proteobacteria), but significantly higher with C. arvensicola (Bacteroidetes) and B. tropica (β-Proteobacteria) as food. Dietary-choice experiments in semi-natural media revealed a low preference of C. elegans for E. coli but significantly higher preferences for C. arvensicola and B. tropica (among other bacteria). Dietary-choice experiments under quasi-natural conditions, which were feasible by fluorescence in situ hybridization (FISH) of bacteria, showed a high preference of C. elegans for Cytophaga-Flexibacter-Bacteroides, Firmicutes, and β-Proteobacteria, but a low preference for γ-Proteobacteria. The results show that data on C. elegans under standard laboratory conditions have to be carefully interpreted with respect to their biological significance.     

Population and reproductive dynamics of the polychaete Pygospio elegans in a boreal estuary complex

Pygospio elegans is an opportunistic, wide‐spread spionid polychaete that reproduces asexually via fragmentation and can produce benthic and pelagic larvae, hence combining different developmental modes in one species. We documented the density, size distribution, and reproductive activity of P. elegans at four sites in the Danish Isefjord‐Roskilde Fjord estuary complex, where all modes of reproduction were reported. We compared population dynamics of this species to environmental parameters such as salinity, temperature, and sediment characteristics (grain size, sorting, porosity, water content, organic content, C/N). We observed that new cohorts—resulting either from sexual or asexual reproduction—appeared in spring and fall, and old ones disappeared in late summer and winter. Sexual reproduction occurred from September until May, and although their timing was variable, there were two reproductive peaks at three sites. At those sites, we also observed a switch in larval developmental mode. Asexual reproduction peaked in April. While the seasonal dynamics can be related to temperature to a large extent, the differences in population dynamics among sites also correlated with sediment structure and salinity. Populations from sites with coarse and heterogeneous sediment had high levels of sexual reproduction. At the site with lower salinity, intermediate and benthic larvae were present during winter in contrast to pelagic larvae found at the other sites. However, we could not identify one clear environmental factor determining the mode of development. At present, it remains unclear to what degree genetic background contributes to mode of development. Hence, whether the differences in developmental mode are the result of genetically different cohorts will be further investigated.     

Maternal effects on offspring size in a natural population of the viviparous tsetse fly

1. Theory predicts that mothers should adaptively adjust reproductive investment depending on current reserves and future reproductive opportunities. Females in better intrinsic state, or with more resources, should invest more in current reproduction than those with fewer resources. Across the lifespan, investment may increase as future reproductive opportunities decline, yet may also decline with reductions in intrinsic state. 2. Across many species, larger mothers produce larger offspring, but there is no theoretical consensus on why this is so. This pattern may be driven by variation in maternal state such as nutrition, yet few studies measure both size and nutritional state or attempt to tease apart confounding effects of size and age. 3. Viviparous tsetse flies (Glossina species) offer an excellent system to explore patterns of reproductive investment: females produce large, single offspring sequentially over the course of their relatively long life. Thus, per‐brood reproductive effort can be quantified by offspring size. 4. While most tsetse reproduction research has been conducted on laboratory colonies, maternal investment was investigated in this study using a unique field method where mothers were collected as they deposited larvae, allowing simultaneous mother‐offspring measurements under natural conditions. 5. It was found that larger mothers and those with a higher fat content produced larger offspring, and there was a trend for older mothers to produce slightly larger offspring. 6. The present results highlight the importance of measuring maternal nutritional state, rather than size alone, when considering maternal investment in offspring. Implications for understanding vector population dynamics are also discussed.     

Contrasting reproductive traits in two species of mangrove‐dwelling littorinid snails in a seasonal tropical habitat

Previous studies on the reproductive biology of littorinid snails have focused on rocky shore species, investigating how these gastropods can achieve maximal reproductive success, as well as on processes of sexual selection. This study documented differences in the reproductive traits of two mangrove‐dwelling littorinids, Littoraria ardouiniana and L. melanostoma, in Hong Kong. Reproductive activity of both species was most intense during the summer months. Mating pairs of the two species generally occurred in the tree canopies. Few false mating pairs (same sex or heterospecific pairs: <10%) were recorded, and members of both species showed size‐assortative mating. Littoraria ardouiniana had a shorter reproductive season but a higher intensity of mating and higher seasonal fecundity, than did L. melanostoma. Members of both species showed bi‐lunar periodicities of egg or larval release, synchronized with spring tides. Fecundity showed a strong positive relationship with body size in L. ardouiniana, but not in L. melanostoma. Females of L. ardouiniana released entire broods of larvae in a single brief event, whereas females of L. melanostoma released fewer eggs over 1–8 d. Release of larvae in L. ardouiniana involved a series of short bursts and was much faster than the trickle release of eggs in L. melanostoma. The contrasting reproductive traits in these two species represent different strategies to optimize reproductive success in mangrove habitats.     

Adrenoceptor Compounds Prevent the Settlement of Marine Invertebrate Larvae: Balanus amphitrite (Cirripedia), Bugula neritina (Bryozoa) and Hydroides elegans (Polychaeta)

The effects of the neurotransmitter blockers idazoxan and phentolamine on the larval settlement of three marine invertebrate species belonging to three different phyla were investigated by using in vitro concentration-response bioassays. Since neurotransmitters are known to influence metamorphic transitions in invertebrate larvae, neurotransmitter blockers were tested to evaluate their sublethal effects on larvae. The α-adrenergic antagonists idazoxan and phentolamine inhibited settlement of Balanus amphitrite (Cirripedia), Bugula neritina (Bryozoa) larvae, and larvae of the polychaete Hydroides elegans (Polychaeta) in a concentration- and taxon-dependent manner. At concentrations of 10^?3 M of both agents, larvae of all three species became immobile and subsequently died within 24 h. While cumulative settlement rates were observed after 48 h for B. amphitrite and H. elegans, and after 5 h for B. neritina, > 90% of the larvae that settled did so within 24 h for the first two species and within 1 h for B. neritina. The tendency of the hydrophobic idazoxan and phentolamine to accumulate at solid surfaces most probably contributes to their successful inhibition of larval settlement. This ability makes them particularly attractive as candidates for the development of slow-release carriers in antifouling paints.     

Reproductive biology of viviparous and oviparous species of the leaf beetle genus Oreina

In five species of the genus Oreina Chevrolat (Coleoptera, Chrysomelidae) we compared the size of offspring, the fecundity of the females, the timing of offspring production and female investment over the season. Two of the species, O. elongata and O. luctuosa, laid eggs, while O. cacaliae, O. gloriosa and O. variabilis gave birth to larvae. Offspring size corrected for female size was similar in the two oviparous species and in the viviparous O. cacaliae. In the two other viviparous species the larvae were two to three times bigger in relation to the female. The greater size of the offspring was not traded off for lower fecundity in these latter two species, yet the production of bigger larvae was associated with a longer laying period and thereby a spreading of reproductive investment over the season. The prediction of life history theory that higher investment in individual offspring should be traded off for lower fecundity could not be confirmed. The investigation of egg and larval development showed that in one of the oviparous species, O. luctuosa, the length of the egg stage was more variable. This corroborates the view that in this species the eggs can be retained for varying times before being laid. Greater size at birth does not necessarily lead to shortened developmental times: the larval periods of O. cacaliae, O. elongata, O. gloriosa and O. variabilis were all comparable although the larvae of the first two species were relatively smaller when laid; only the small larvae of O. luctuosa needed significantly longer for their development. For all growth parameters examined the differences between species were larger than the differences between populations. A comparison of larval growth of the oligophagous species O. cacaliae on three plant genera showed that larval growth rate is influenced by the food plant. However, the plant on which the larvae grew worst is apparently not chosen for oviposition in the field. A comparison with a phylogeny of the species based on allozymes suggests that species with similar reproductive parameters are closely related, yet that viviparity evolved independently in O. cacaliae on one hand and O. variabilis and O. gloriosa on the other.     

Differences in the life histories of twoCochlearia species

Cochlearia bavarica Vogt andC. pyrenaica Dc. are closely related and highly endangered species in Bavaria (SE Germany).Cochlearia bavarica (2n=36) is a hybrid ofC. pyrenaica (2n=12) andC. officianalis (2n=24) stabilized by polyploidy.Cochlearia officinalis does not occur in Bavaria. The question being addressed is whether the present non-overlapping distribution of the two Bavarian species, both of which are restricted to calcareous springs with a continuous water supply or drainage ditches, is due to competitive exclusion or to subtle differences of ecological requirements. I did not find any evidence for the second case, i.e. niche differentiation, because both species occurred in all the habitat types that I could define by floristic and ecological criteria. The population structures of bothC. bavarica andC. pyrenaica vary in parallel with different habitat types. Both species have the greatest reproductive output (viable seeds) and the highest population densities in habitats with high light availability and/or low interspecific competition. Thus, I expected that one of the two species might be competitively superior over the other, but that it would fail to reach all its potential sites of occurrence. Cochlearia bavarica individuals (dry mass =5.75 g) grow significantly larger thanC. pyrenaica individuals (3.62 g;P<0.05) and produce more, larger and heavier seeds, possibly due to hybrid vigour. Flowering individuals ofC. bavarica also allocate more biomass to vegetative structures thanC. pyrenaica. The analysis of population dynamics reveals a higher life expectancy and reproductive output inC. bavarica. The calculated population growth rates although negative over the observation period in both species, suggest a significantly higher fitness ofC. bavarica (λ=0.66) compared withC. pyrenaica (λ=0.44). Thus, our data are in line with the competitive exclusion hypothesis andCochlearia bavarica appears as an example of a species with hybridogenous origin possessing higher fitness than its progenitor. However, considering the rarity of both species it seems at present unlikely that the former will displace the latter over a large distributional region.     

Oocyte production and sperm utilization patterns in semi-fertile strains of <Emphasis Type="Italic">Caenorhabditis elegans</Emphasis>

Background  

Caenorhabditis elegans hermaphrodites are capable of producing hundreds of progeny. However, genetic and environmental factors can keep many animals from attaining their full reproductive potential. In these situations, efficient use of any functional gametes becomes more important for reproductive success. To learn about this aspect of C. elegans reproductive biology, we examined oocyte production and sperm utilization patterns in a unique collection of semi-fertile sperm function mutants.     

A Wild C. Elegans Strain Has Enhanced Epithelial Immunity to a Natural Microsporidian Parasite

Microbial pathogens impose selective pressures on their hosts, and combatting these pathogens is fundamental to the propagation of a species. Innate immunity is an ancient system that provides the foundation for pathogen resistance, with epithelial cells in humans increasingly appreciated to play key roles in innate defense. Here, we show that the nematode C. elegans displays genetic variation in epithelial immunity against intestinal infection by its natural pathogen, Nematocida parisii. This pathogen belongs to the microsporidia phylum, which comprises a large phylum of over 1400 species of fungal-related parasites that can infect all animals, including humans, but are poorly understood. Strikingly, we find that a wild C. elegans strain from Hawaii is able to clear intracellular infection by N. parisii, with this ability restricted to young larval animals. Notably, infection of older larvae does not impair progeny production, while infection of younger larvae does. The early-life immunity of Hawaiian larvae enables them to produce more progeny later in life, providing a selective advantage in a laboratory setting—in the presence of parasite it is able to out-compete a susceptible strain in just a few generations. We show that enhanced immunity is dominant to susceptibility, and we use quantitative trait locus mapping to identify four genomic loci associated with resistance. Furthermore, we generate near-isogenic strains to directly demonstrate that two of these loci influence resistance. Thus, our findings show that early-life immunity of C. elegans against microsporidia is a complex trait that enables the host to produce more progeny later in life, likely improving its evolutionary success.     

Detection of ecological hybrid inviability in a pair of sympatric phytophagous ladybird beetles (Henosepilachna spp.)

Ecological speciation is a process by which reproductive isolation evolves as the result of divergent natural selection between populations inhabiting distinct environments or exploiting alternative resources. Ecological hybrid inviability provides direct evidence for ecological speciation. To detect ecological hybrid inviability, we examined survival rates to the second instar of F1 hybrids and backcross hybrids in a pair of sympatric phytophagous ladybird beetles, Henosepilachna niponica Lewis and Henosepilachna yasutomii Katakura (Coleoptera: Coccinellidae: Epilachninae), reared on their respective host plants, thistle [Cirsium alpicola Nakai (Asteraceae)] and blue cohosh [Caulophyllum robustum Maxim. (Berberidaceae)], and on a common food plant, Japanese nightshade [Solanum japonense Nakai (Solanaceae)]. Hybrid larvae reared on leaves of the Japanese nightshade always had high rates of survival, irrespective of the crossing type of their parents, suggesting a lack of intrinsic hybrid inviability between the two species. In contrast, survival rates on thistle and blue cohosh varied greatly. On blue cohosh, the survival rate of F1 hybrids was nearly as high as that of H. yasutomii, but on thistle, survival was significantly lower than of H. niponica. Survival rates of backcross hybrids on the two host plants were intermediate between those of the parents, showing a reversed rank order of different types of backcross hybrids on the two food plant species. These results suggest that ecological hybrid inviability exists between H. niponica and H. yasutomii, although the two species do not show intrinsic hybrid inviability. Thus, our study supports the hypothesis that H. niponica and H. yasutomii underwent ecological speciation by divergent selection.     

Proteomic profiling during the pre-competent to competent transition of the biofouling polychaete Hydroides elegans

The polychaete, Hydroides elegans, is a tube-building worm that is widely distributed in tropical and subtropical seas. It is a dominant fouling species and thus a major target organism in antifouling research. Here, the first high-throughput proteomic profiling of pre-competent and competent larvae of H. elegans is reported with the identification of 1,519 and 1,322 proteins, respectively. These proteins were associated with a variety of biological processes. However, a large proportion was involved in energy metabolism, redox homeostasis, and microtubule-based processes. A comparative analysis revealed 21 proteins that were differentially regulated in larvae approaching competency.     

Cost of reproduction as reduced growth in genotypes of two congeneric species with contrasting life histories

Summary We examined the effect of reproduction on growth in 33 genotypes of Plantago major and 14 genotypes of P. rugelii. These two herbaceous perennials have contrasting life histories; P. major reproduces at a smaller size, and allocates a larger proportion of its biomass to reproduction, than P. rugelii. The effect of reproduction on frowth was determined experimentally using photoperiod manipulations to control level of reproduction. The difference in growth between reproductive treatments was divided by the difference in capsule weight to produce a measure of reproductive cost per g of capsule for genotypes of the two species. In both species there was substantial variation among genotypes in the effect of reproduction on growth. Much of this variation could be correlated with differences among genotypes in the extent of reproductive investment and plant size. Cost in terms of reduction in growth per g of capsule increased with reproductive investment in P. rugelii, and with plant size in P. major. We suggest the differences between species in timing and extent of reproduction are related to the differences between species in effect of reproduction on growth. Plantago rugelii may reproduce to a lesser extent than P. major because cost per g of capsule in terms of reduced vegetative biomass, increases with reproductive output in the former species, but not in the latter. Similarly, P. major may reproduce earlier than P. rugelii because cost per g of capsule increases with plant size in P. major, but not in P. rugelii.     

The density and spatial arrangement of the invasive oyster Crassostrea gigas determines its impact on settlement of native oyster larvae

Understanding how the density and spatial arrangement of invaders is critical to developing management strategies of pest species. The Pacific oyster, Crassostrea gigas, has been translocated around the world for aquaculture and in many instances has established wild populations. Relative to other species of bivalve, it displays rapid suspension feeding, which may cause mortality of pelagic invertebrate larvae. We compared the effect on settlement of Sydney rock oyster, Saccostrea glomerata, larvae of manipulating the spatial arrangement and density of native S. glomerata, and non‐native C. gigas. We hypothesized that while manipulations of dead oysters would reveal the same positive relationship between attachment surface area and S. glomerata settlement between the two species, manipulations of live oysters would reveal differing density‐dependent effects between the native and non‐native oyster. In the field, whether oysters were live or dead, more larvae settled on C. gigas than S. glomerata when substrate was arranged in monospecific clumps. When, however, the two species were interspersed, there were no differences in larval settlement between them. By contrast, in aquaria simulating a higher effective oyster density, more larvae settled on live S. glomerata than C. gigas. When C. gigas was prevented from suspension feeding, settlement of larvae on C. gigas was enhanced. By contrast, settlement was similar between the two species when dead. While the presently low densities of the invasive oyster C. gigas may enhance S. glomerata larval settlement in east Australian estuaries, future increases in densities could produce negative impacts on native oyster settlement. Synthesis and applications: Our study has shown that both the spatial arrangement and density of invaders can influence their impact. Hence, management strategies aimed at preventing invasive populations reaching damaging sizes should not only consider the threshold density at which impacts exceed some acceptable limit, but also how patch formation modifies this.     

Seasonal growth differences of larval Hyporhamphus picarti (Hemiramphidae) in the Sine Saloum estuary,Senegal

The African halfbeak Hyporhamphus picarti (Hemiramphidae) is one of the most abundant species within the ichthyoplankton community of the Sine Saloum estuary (Senegal). A year‐round occurrence of larvae suggests that the Sine Saloum is an important spawning habitat for this species. Annual fluctuations in water temperature, however, can have severe impacts on the survival probabilities of marine fish larvae. To determine whether temperature has an effect on the growth of H. picarti during its larval development, larval age at length and somatic growth rates were investigated for two contrasting spawning seasons in 2014: February (cold season, 20.8°C) and June (warm season, 26.4°C). In both months H. picarti larvae were sampled at the mouth of the Saloum River using neuston nets. Sagittal otoliths’ increments were counted to estimate the larva age at a given standard length (SL). The age of larvae ranged between 2 and 22 days, with SL of 3.86–21.68 mm, respectively. In order to describe larval age at length during the contrasting spawning seasons, two distinctive Gompertz functions were applied. Accordingly, specimens sampled in June (0.94 ± 0.17 mm per day) exhibited significantly higher somatic growth rates than those sampled in February (0.60 ± 0.06 mm per day). These findings suggest that water temperature is an important factor influencing larval growth in H. picarti. Information concerning the early life stages of H. picarti are scarce and the results of the present study may contribute to a better understanding of the species’ biology and ecology.     

Can chaoborid larvae control their zooplanktonic prey populations in a neotropical lake?

Although it is well known that predatory Chaoborus Lichtenstein 1800 larvae have a strong negative impact on zooplankton populations in many Holarctic lakes, this top‐down control is still not entirely clear in the Neotropics. In Lake Carioca, a Brazilian monomictic lake, chaoborids became one of the main zooplankton predators after the depletion of planktivorous fish by non‐native piscivorous fish. The aim of this research was to test the hypothesis that Chaoborus spp. larvae control the density of their prey populations. Enclosures simulated conditions with higher (Pr+) and lower (Pr?) predatory Chaoborus spp. larva densities over 30 days in two periods (stratification and mixing). Our results indicated that the dominant copepod species was affected only in the stratification period when its population was smaller. In this circumstance, predated individuals were probably not replaced in the same proportion by reproductive output of the smaller population. Rotifers were not sensitive to changes in chaoborids densities in both periods. The lack of a strong top‐down effect recorded by our mesocosm experiments emphasises the importance of continuing to investigate the ecological roles played by this invertebrate predator in aquatic food webs and if its ability to regulate the zooplankton in most Holarctic lakes can (or cannot) be widely generalised to Neotropical communities. Such a result also suggests that alternative research approaches, besides in‐situ experiments, may be necessary to better clarify this topic. Specifically for cladocerans, parallel paleolimnological analyses in Lake Carioca have supported the idea of a possible negative impact of Chaoborus larvae on bosminids after the introduction of non‐native piscivorous fishes. Abstract in Portuguese is available with online material.     

A comparative study of sperm morphology, cytology and activation in Caenorhabditis elegans, Caenorhabditis remanei and Caenorhabditis briggsae

Studies of sterile mutants in Caenorhabditis elegans have uncovered new insights into fundamental aspects of gamete cell biology, development, and function at fertilization. The genome sequences of C. elegans, Caenorhabditis briggsae and Caenorhabditis remanei allow for informative comparative studies among these three species. Towards that end, we have examined wild-type sperm morphology and activation (spermiogenesis) in each. Light and electron microscopy studies reveal that general sperm morphology, organization, and ultrastructure are similar in all three species, and activation techniques developed for C. elegans were found to work well in both C. briggsae and C. remanei. Despite important differences in the reproductive mode between C. remanei and the other two species, most genes required for spermiogenesis are conserved in all three. Finally, we have also examined the subcellular distribution of sperm epitopes in C. briggsae and C. remanei that cross-react with anti-sera directed against C. elegans sperm proteins. The baseline data in this study will prove useful for the future analysis and interpretation of sperm gene function across nematode species.