World Congress of Malacology Antwerp ... - Unitas Malacologica

developmental constraint, pleiotropy of any maternal factor cannot be responsible for the differences
of RS in viability and morphology. Parents-offspring regression analyses showed that the narrowsense
heritability of hatching success is close to 0.9 in each of the dextral and sinistral that the
racemic mutant produces, while no genetic correlation exists between dextral and sinistral hatching
successes. Artificial selection of the best hatching sinistrals has improved the sinistral to be
equivalent to the dextral in one generation, confirming the extremely high heritability. These results
show that sinistral variants could overcome developmental constraint, where sinistrality is
advantageous as suggested in the examples of reproductive character displacement and specialized
predation of dextral snails by snakes. This study provides new insights into the genetic basis of
adaptive evolution of mirror-image species in snails.
What happens when it gets dark?
Biology of deep-sea nudibranch gastropod species and nocturnal behavior
Valdés, Ángel
Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California
90007, USA,
Email: avaldes@nhm.org
Several lineages of nudibranch gastropods have colonized the deep sea independently, including
hydrothermal vents and cold seeps. Many of these organisms have pale colorations or lack color
altogether, particularly those found at depths greater then 500 meters. This is a strong indication of
the significance of color for shallow water animals and its possible biological role in camouflage and
mimicry. However, many of these shallow water species with bright external colorations are
nocturnal, which seems to contradict the general agreement on the biological role of color. Recent
exploration of tropical eastern Pacific waters has revealed unusual properties of some species under
particular light conditions, which opens the door for further research and speculation.
In this talk, we discuss the different instances of colonization of the deep sea and the implications for
understanding the biology, evolutionary history and classification of nudibranch mollusks as well as
the properties of some species under specific light conditions.
Coral boring bivalve mollusks of Southeastern Thailand
Valentich-Scott, Paul
Santa Barbara Museum of Natural History, 2559 Puesta del Sol Road, Santa Barbara, CA 93105,
USA,
Email: pvscott@sbnature2.org
Anatomical and shell morphologies of twenty-one species of intertidal and subtidal coral boring
bivalves from southeast Thailand are compared. The coral boring fauna of the study region represents
the highest diversity yet recorded in the Indo-Pacific Ocean. Siphonal characters are presented for the
first time for many of the treated taxa, which has yielded many new useful characters to discriminate
cryptic species. The SE Thailand boring bivalves are represented in five families; Mytilidae,
Petricolidae, Trapezidae, Pholadidae, and Gastrochaenidae. A new species Botula (Mytilidae) will be
discussed.
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