Figure 4: Adult Berghia verrucicornis. The dark brown pigmentation in the cerrata is due to hundreds of thousands of symbiotic algae called zooxanthellae. Berghia gets these algae from its prey, the sea anemone Aiptasia pallida.
Literature Cited:
Candelario-Martinez, A., Reed, D.M., Prichard, S.J., Doble, K.E., Lee, T.D., Lesser, W., Price, D.A. Greenburg, M.J. 1993. SCP-related peptides from bivalve mollusks: identification, tissue distribution and actions. Biol. Bull. 185: 428-439.
Carroll, D.J., and Kempf, S.C. 1994. Changes occur in the central nervous system of the nudibranch Berghia verrucicornis (Mollusca, Ophisthobranchia) during metamorphosis. Biol. Bull. 186: 202-212.
Croll, R.P., Jackson, D.L., Voronezhskaya, E.E. 1997. Catecholamine-containing cells in larval and post larval bivalve mollusks. Biol. Bull. 193 (3): 116-124.
Erdman, W. 1935. Uber die Entwicklung und die Anatomie der ‘ansatzreifen’ Larve von Ostrea edulis, mit Bemerkungen uber die Lebensgeschichte der Auster. Wiss Meeresunters., Abt. Helgoland, N.F. 19: 1-25.
Kempf, S.C., Page, L.R., Pires, A. 1997. Development of serotonin-like immunoreactivity in the embryos and larvae of nudibranch mollusks with emphasis on the structure and possible function of the apical sensory organ. J. Comp. Neuro.. 386: 507-528.
Kempf, S.C., Masinovsky, B., Willows, A.O.D. 1987. A simple neuronal system characterized by a monoclonal antibody to SCP neuropeptides in embryos and larvae of Tritonia diomedea (Gastropoda: Nudibranchia). J. Neurobiol. 18: 217-236.
Kriegstein, A.R., 1997. Development of the nervous system of Aplysia californica. Proc. Natl. Acad. Sci. USA. 74 (1): 375-378.
Kreiling, J.A., Jessen-Eller, K., Miller, J., Seegal, R.F., Reinisch, C.L. 2001. Early development of the serotonergic and dopaminergic nervous system in Spisula solidissima (surf clam) larvae. Comparative Biochemistry and Physiology Part A.130: 341-351.
National Research Council, 2004. Non-native oysters in the Chesapeake Bay. Committee on Non-native Oyster in the Chesapeake Bay, Ocean Studies Board, Division on Earth and Life Studies, National Research Council of the National Academies. The National Academies Press, Washington, DC.
Nestlerode, J.A. Luckenbach, M. W., O’Beirn, F.X. 2007. Settlement and survival of the oyster Crassostrea virginica on created oyster reef habitats in the Chesapeake Bay. Rest. Ecol. 15 (2): 273-283.
Page, L. 1992. A new interpretation of the nudibranch central nervous system based on ultrastructural analysis of neurodevelopment in Melibe leonina. I. Cerebral and visceral loop ganglia. Biol. Bull. 182: 348-365.
Perry, S.J., Dobbins, A.C., Schofield, M.G., Piper, M.R. Benjamin, P.R. 1999. Small cardioactive peptide gene: structure, expression and mass spectrometric analysis reveals a complex pattern on co-transmitters in a snail feeding neuron. Euro. J. Neuorscience. 2: 655-662.
Voronezhskaya, E.E., Nezlin, L.P., Odintsove, N.A., Plummer, J.T., Croll, R.P. 2007. Neruonal development in larval mussel Mytilus trossulus (Mollusca; Bivalvia). Zoomorphology. Online. January 11, 2008.
B. verrucicornis is a species that provides a helpful comparative foundation, due to the considerable amount of information available on opisthobranch larval nervous systems (Kriegstein, 1997; Kempf et al., 1987; Page, 1992; Carroll and Kempf, 1994; Kempf et al., 1997;).
SCPs in other invertebrate species have been suggested to function in gut motility and feeding (Candelario-Martinez et al., 1993, Perry et al., 1999). I will investigate what tissues the SCP-like neuropeptides innervate to reveal possible function of this neurotransmitter in bivalve and gastropod larvae. My analysis of the central and peripheral patterns of SCPergic innervations will be the first supported by a detailed histological description of the central and peripheral nervous system in C. virginica. This will allow the formulation of hypotheses and design of future experiments that will provide information concerning the relationship between neural morphology, neurochemistry and larval behaviors, in particular the behaviors dealing with settlement of competent larvae.
3) perform a comparative analysis of the central nervous system of these two species.
Figure 5: Larval enbryos of Berghia verrucicornis enclosed within their egg capsules. These larvae are competent and ready to hatch (approximately 11 days old). Note the two eyespots, larval foot and ciliated velum.
Figure 3: Immunohistochemical labeling of small cardioactive peptides (SCPs) in the pediveliger stage of Crassostrea virginica. A cental loop of axons can be seen in the connectives and commissures that connect the various ganglia of the central nervous system. Axons are also present in peripheral tissues.
Scale bar = 50 microns
2) conduct a similar examination of larvae of the opisthobranch gastropod Berghia verrucicornis (Figures 4 & 5)
Figure 2: Histological transverse section of Crassostrea virginica depicting the pedal ganglia (center) innervating the larval foot.
Scale bar = 50 microns
Figure 1: Micrograph taken by Ivey Ellis of the pediveliger stage of Crassostrea virginica. Note ciliated velum on right and larval foot at bottom of picture.
1) examine the anatomy and development of the larval nervous system in the eastern oyster, Crassostrea virginica through histological analyses (Figure 1, 2) and immunolabeling of SCP-like neuropeptides (Figures 3)
Ivey and her best friend. (-;{
Research:
Oysters are delicious. In addition to being considered a delicacy, oysters are recognized as a keystone species, one that functions as an indicator of the status and condition of the entire estuarine habitat (National Research Council, 2004). Many species populations have recently suffered due to overharvesting for commercial purposes, increased sedimentation, and habitat degradation (Nestlerode et al., 2007). It has been reported that oyster larvae prefer to settle and metamorphose on existing oyster shells (Nestlerode et al., 2007), therefore, overharvesting would also decrease the proper substratum for larval settlement. At the same time, oyster aquaculture practices are steadily rising (National Research Council, 2004). In fact, one hatchery facility produces 37.5 billion eyed larvae a year (National Research Council, 2004). Expanding our knowledge of both adult and larval oysters can facilitate restoration efforts and also assist in commercial rearing of oysters. Furthermore, understanding the larval nervous systems of these species will help bridge the link between neural morphology and larval behavior, such as settling.
The class Bivalvia is the second largest class within the phylum Mollusca; however, surprisingly little attention has been paid to the structure and function of the nervous system in larval bivalves. An early histological analysis by Erdmann (1935) provides an overview of the larval nervous system in Ostrea edulis; however, there are no detailed descriptions. More recently, a number of studies have followed the development of the larva while also using immunohisotchemical methods to track the expression of certain neurotransmitters or neurohormones. Some of the compounds previously examined include, but are not limited to, serotonin or 5-hydroxy-tryptamine (5-HT) (Croll et al., 1997; Voronezhskaya et al., 2007; Kreiling et al, 2001), FMRF-amide (Voronezhskaya et al., 2007), and the catecholamines norepinephrine, epinephrine, and dopamine (Kreiling et al., 2001; Voronezhskaya et al., 2007).
While these immunohistochemical studies provide interesting and useful data, it is difficult to formulate hypotheses and design experiments without a detailed histological analysis of development of the bivalve larval nervous system. Also, there has been no documentation to date of the location of small cardioactive peptides (SCPs), a common neuropeptide in molluscan larvae. My thesis research has three goals, to
Ivey R. Ellis
M.S. Graduate Student
E-mail: elliir@auburn.edu
Kempf Lab