World Congress of Malacology Antwerp ... - Unitas Malacologica

Protothaca thaca (Molina, 1782) is an important species for small-scale benthic fisheries, inhabiting
shallow (5-15 m) sandy bottoms of the upwelling ecosystem of Chile and Peru. Temperatures in these
ecosystem change dramatically during El Niño events. P. thaca exhibits good tolerance to high
temperatures. To understand the metabolic processes behind this adaptation we studied the effects of
temperature on: standard metabolism, growth and body condition index of P. thaca from Northern
Chile Antofagasta (23º 42`17``S; 70º 25`33``W; mean annual sea surface temperature 17.4 °C),
Chile. Oxygen consumption of animals acclimated to 12º, 16º and 20º C was measured using an
intermittent flow-through system. Animals were stained by immersion in the flourochrome Calcein
(100 mg·l -1 , 3h) to estimate daily growth rates. Our results show that standard metabolism, growth
and body condition index are significantly lower at 12° C compared to 16° and 20°C. No differences
are observed between the higher temperatures. Our results are well in line with previous studies
showing a wide temperature tolerance window of P. thaca. The relative thermal independence of
routine metabolism is suggested to conserve energy, which allows the species to be more tolerant to
high temperatures.
This study was financed and conducted in the frame of the EU-project CENSOR (Climate variability
and El Niño Southern Oscillation: Implications for Natural Coastal Resources and Management,
contract 511071) and is CENSOR contribution 0109.
The genus Buccinanops (d’ Orbigny, 1841): No eyes or blind eyes?
Averbuj, Andres; Penchaszadeh, Pablo E.
Av. Angel Gallardo 470 3° p. lab 57, C1405DJR Buenos Aires, Argentina,
Email: andresbuj95@hotmail.com; penchas@bg.fcen.uba.ar
The genus Buccinanops groups seven species, all endemic to the South Western Atlantic.
Buccinanops cochlidium ranges from Rio de Janeiro, Brazil (23º S) to Comodoro Rivadavia in
Patagonia, Argentina (45º S). They occur constantly during the whole year and are easily collected by
SCUBA diving around Península Valdés. In San José Gulf (42º25' S; 64º31' W) they commonly live
in shallow waters between 4 y 15 meters depth, buried in sandy bottoms. Animals are medium in size
reaching up to 120 mm length, and are typically blind. The genus name means no eyes, due to the
lack of visible eyes.
In this work we recognize for the first time the presence of eyes in this genus. Observations
evidenced the presence of eye spots in the embryos of Buccinanops cochlidium, during intracapsular
development as well as in the young hatchlings. The tentacles were histologicaly studied in late
“veliger” stage embryos, juveniles and adults. Eyes were found only in embryonary tentacles which
presented censory cells, corneal cells and a lens. No evidence of an eye was found in continuouse
seried cuts of an adult tentacle. The possible location and functionality, if any, of the eyes in the
adults remain unknown.
Tentative hypothesis on embryonary eye evolution, at he beginning of this work, were:
1) The embryonic eye is reabsorbed and disappears.
2) The eye is conserved but is covered by the overgrowth of tentacle tissue (inner migration)
3) The eye is modified so that it is no longer functional and then migrates into the tentacle.
Ontogenic development evolution of the eye’s ultrastructure, functionality and location is currently
being studied.
14