An official website of the United States government
Abstract While adult stomatopod crustaceans are relatively well studied, understanding of larval stomatopod ecology is lacking, largely due to difficulties studying larvae in their natural habitat. This study investigated how light environment (i.e., spectral composition) and time of day affected prey consumption in two species of larval stomatopod, Gonodactylaceus falcatus (Forskål, 1775) and Gonodactylellus sp. Individual larvae were placed with 20 Artemia nauplii prey in feeding chambers treated to produce different light environments with respect to ultraviolet (UV) light: full spectrum light UV+, full spectrum UV–, and a dark control. Chambers were lowered to a depth of 3 m for 2 hours at three times of day (noon, twilight, and night) to test 1) if larval feeding rates changed at different times of day and 2) if UV vision was involved in prey capture. We found that light was important for successful feeding, with both species eating significantly more in lighted treatments than the dark controls during daytime experiments. Gonodactylellus sp. also had a significantly higher feeding rate at twilight in the UV+ treatment than in the dark control. Both species showed decreased consumption at night compared to daytime rates, and decreased consumption in all dark controls. This study is one of the first to examine how ecological conditions affect feeding behavior in larval stomatopods. Our results suggest that light is important for larval stomatopod feeding, with differences between species in daily feeding activity periods. There was also a difference in total consumption between the two species, with the slightly larger Gonodactylaceus falcatus consuming nearly double the prey items as Gonodactylellus sp. at peak feeding times. Follow up studies should incorporate a variety of prey types to test how feeding changes based on food source and density.
more »
« less
Ultraviolet vision in larval Neogonodactylus oerstedii
Stomatopod crustaceans have among the most complex eyes in the animal kingdom, with up to twelve different color detection channels. The capabilities of these unique eyes include photoreception of ultraviolet (UV) wavelengths (<400 nm). UV vision has been well characterized in adult stomatopods but has not been previously demonstrated in the comparatively simpler larval eye. Larval stomatopod eyes are developmentally distinct from their adult counterpart and have been described as lacking the visual pigment diversity and morphological specializations found in adult eyes. However, recent studies have provided evidence that larval stomatopod eyes are more complex than previously thought and warrant closer investigation. Using electroretinogram recordings in live animals we found physiological evidence of blue and UV sensitive photoreceptors in larvae of the Caribbean stomatopod species Neogonodactylus oerstedii. Transcriptomes of individual larvae were used to identify the expression of three distinct UV opsins transcripts, which may indicate the presence of multiple UV spectral channels. This is the first paper to document UV vision in any larval stomatopod, expanding our understanding of the importance of UV sensitivity in plankton. Similar to adults, larval stomatopod eyes are more complex than expected and contain previously uncharacterized molecular diversity and physiological functions.
more »
« less
- PAR ID:
- 10318364
- Date Published:
- Journal Name:
- Journal of Experimental Biology
- ISSN:
- 0022-0949
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Estimating stomatopod species diversity using morphology alone has long been difficult; though over 450 species have been described, new species are still being discovered regularly despite the cryptic behaviors of adults. However, the larvae of stomatopods are more easily obtained due to their pelagic habitat, and have been the focus of recent studies of diversity. Studies of morphological diversity describe both conserved and divergent traits in larval stomatopods, but generally cannot be linked to a particular species. Conversely, genetic studies of stomatopod larvae using DNA barcoding can be used to estimate species diversity, but are generally not linked to known species by analyses of morphological characters. Here we combine these two approaches, larval morphology and genetics, to estimate stomatopod species diversity in the Hawaiian Islands. Over 22 operational taxonomic units (OTUs) were identified genetically, corresponding to 20 characterized morphological types. Species from three major superfamilies of stomatopod were identified: Squilloidea (4 OTUs, 3 morphotypes), Gonodactyloidea (9, 8), and Lysiosquilloidea (6, 7). Among these, lysiosquilloids were more diverse based on larval morphotypes and OTUs as compared to previously documented Hawaiian species (3), while squilloids had a lower diversity of species represented by collected larvae as compared to the seven species previously documented. Two OTUs / morphotypes could not be identified to superfamily as their molecular and morphological features did not closely match any available information, suggesting they belong to poorly sampled superfamilies. The pseudosquillid, Pseudosquillana richeri, was discovered for the first time from Hawaiʻi. This study contributes an updated estimate for Hawaiian stomatopod diversity for a total of 24 documented species, provides references for identification of larval stomatopods across the three major superfamilies, and emphasizes the lack of knowledge of species diversity in more cryptic stomatopod superfamilies, such as Lysiosquilloidea.more » « less
-
Drosophilalarvae are an established model system for studying the mechanisms of innate and simple forms of learned behavior. They have about 10 times fewer neurons than adult flies, and it was the low total number of their neurons that allowed for an electron microscopic reconstruction of their brain at synaptic resolution. Regarding the mushroom body, a central brain structure for many forms of associative learning in insects, it turned out that more than half of the classes of synaptic connection had previously escaped attention. Understanding the function of these circuit motifs, subsequently confirmed in adult flies, is an important current research topic. In this context, we test larvalDrosophilafor their cognitive abilities in three tasks that are characteristically more complex than those previously studied. Our data provide evidence for (i) conditioned inhibition, as has previously been reported for adult flies and honeybees. Unlike what is described for adult flies and honeybees, however, our data do not provide evidence for (ii) sensory preconditioning or (iii) second-order conditioning inDrosophilalarvae. We discuss the methodological features of our experiments as well as four specific aspects of the organization of the larval brain that may explain why these two forms of learning are observed in adult flies and honeybees, but not in larvalDrosophila.more » « less
-
Many marine organisms have a biphasic life cycle that transitions between a swimming larva with a more sedentary adult form. At the end of the first phase, larvae must identify suitable sites to settle and undergo a dramatic morphological change. Environmental factors, including photic and chemical cues, appear to influence settlement, but the sensory receptors involved are largely unknown. We targeted the protein receptor, opsin, which belongs to large superfamily of transmembrane receptors that detects environmental stimuli, hormones, and neurotransmitters. While opsins are well-known for light-sensing, including vision, a growing number of studies have demonstrated light-independent functions. We therefore examined opsin expression in the Pteriomorphia, a large, diverse clade of marine bivalves, that includes commercially important species, such as oysters, mussels, and scallops. Methods Genomic annotations combined with phylogenetic analysis show great variation of opsin abundance among pteriomorphian bivalves, including surprisingly high genomic abundance in many species that are eyeless as adults, such as mussels. Therefore, we investigated the diversity of opsin expression from the perspective of larval development. We collected opsin gene expression in four families of Pteriomorphia, across three distinct larval stages, i.e., trochophore, veliger, and pediveliger, and compared those to adult tissues.Results We found larvae express all opsin types in these bivalves, but opsin expression patterns are largely species-specific across development. Few opsins are expressed in the adult mantle, but many are highly expressed in adult eyes. Intriguingly, opsin genes such as retinochrome, xenopsins, and Go-opsins have higher levels of expression in the later larval stages when substrates for settlement are being tested, such as the pediveliger. Conclusion Investigating opsin gene expression during larval development provides crucial insights into their intricate interactions with the surroundings, which may shed light on how opsin receptors of these organisms respond to various environmental cues that play a pivotal role in their settlement process.more » « less
-
Abstract BackgroundThere are a wide range of developmental strategies in animal phyla, but most insights into adult body plan formation come from direct-developing species. For indirect-developing species, there are distinct larval and adult body plans that are linked together by metamorphosis. Some outstanding questions in the development of indirect-developing organisms include the extent to which larval tissue undergoes cell death during the process of metamorphosis and when and where the tissue that will give rise to the adult originates. How do the processes of cell division and cell death redesign the body plans of indirect developers? In this study, we present patterns of cell proliferation and cell death during larval body plan development, metamorphosis, and adult body plan formation, in the hemichordateSchizocardium californium(Cameron and Perez in Zootaxa 3569:79–88, 2012) to answer these questions. ResultsWe identified distinct patterns of cell proliferation between larval and adult body plan formation ofS. californicum. We found that some adult tissues proliferate during the late larval phase prior to the start of overt metamorphosis. In addition, using an irradiation and transcriptomic approach, we describe a genetic signature of proliferative cells that is shared across the life history states, as well as markers that are unique to larval or juvenile states. Finally, we observed that cell death is minimal in larval stages but begins with the onset of metamorphosis. ConclusionsCell proliferation during the development ofS. californicumhas distinct patterns in the formation of larval and adult body plans. However, cell death is very limited in larvae and begins during the onset of metamorphosis and into early juvenile development in specific domains. The populations of cells that proliferated and gave rise to the larvae and juveniles have a genetic signature that suggested a heterogeneous pool of proliferative progenitors, rather than a set-aside population of pluripotent cells. Taken together, we propose that the gradual morphological transformation ofS. californicumis mirrored at the cellular level and may be more representative of the development strategies that characterize metamorphosis in many metazoan animals.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1242/jeb.243256
