World Congress of Malacology Antwerp ... - Unitas Malacologica

Vanatta, 1896) in north-central California. A. stramineus forms a separate clade and should be a
distinct species, and there is fourth distinct clade that is an undescribed species on Mount Palomar,
San Diego County, California. The fifth clade (Meadarion) is comprised of 4 subclades, three already
named as species or subspecies. We propose that each be considered a species distinguished by
morphology and sexual behavior. A. californicus and A. dolichophallus are found mainly in San
Mateo and Santa Cruz counties, respectively, while A. brachyphallus has a disjunct distribution and
is found on the northern tip of the San Francisco Peninsula, the Monterey Peninsula, and Cambria in
San Luis Obispo County. A fourth clade represents an undescribed species found on Fremont Peak,
San Benito County. More in-depth analyses will be needed to resolve the relationship among these
clades, and whether the subgenus Ariolimax is paraphyletic with respect to Meadarion.
Reproductive studies on volutes of the South West Atlantic (Neogastropoda: Volutidae)
Penchaszadeh, Pablo E. 1 ; Arrighetti, Florencia 1 ; Bigatti, Gregorio 2 ; Cledón, Maximiliano 3 ;
Giménez, Juliana 1 ; Carlos Sanchez, Antelo 1
1- Laboratorio de Invertebrados, Facultad de Ciencias Exactas y Naturales (UBA) & MACN-
CONICET, Av. A. Gallardo 470, 1405 Buenos Aires, Argentina,
Email: penchas@bg.fcen.uba.ar, flora@bg.fcen.uba.ar, jgimenez@bg.fcen.uba.ar,
cjmsanchez@bg.fcen.uba.ar
2- Centro Nacional Patagónico CENPAT – CONICET. Bvd. Brown 3500 U9120ACV. Puerto
Madryn, Chubut, Argentina,
Email: gbigatti@cenpat.edu.ar
3-Dpto. Cs. Marinas, Facultad de Cs Exactas (UNDMP) & CONICET, Funes 3350, Mar del Plata.,
Argentina,
Email: mcledon@mdp.edu.ar
Reproductive patterns and season of five volutid neogastropods have been studied: Adelomelon
brasiliana (Lamarck, 1811), Zidona dufresnei (Donovan, 1823) and Adelomelon beckii (Broderip,
1836) from the subfamily Zidoninae in Mar del Plata; Odontocymbiola magellanica (Gmelin, 1791)
and Adelomelon ancilla (Lightfoot, 1786) from north Patagonia (subfamilies Odontocymbiolinae and
Zidoninae respectively).
Volutids spawn large egg capsules containing few eggs. The embryos develop and grow for a period
of up to three months; eggs ranged between 90 to 300 µm in diameter, feed extravitelline food
contained in the intracapsular fluid; no nurse eggs occur and they hatch as crawling juveniles
exceeding 1 cm in shell length.
The reproductive season of Adelomelon brasiliana extended from September to April. This is the
only volutid known to lay free egg capsules.
Gonad development in Zidona dufresnei reveals a reproductive season from October to March. Size
at which 50% of the population was mature was 15.7 cm in females and 15.0 cm in males.
Preliminary studies of Adelomelon beckii showed the spawning season from August to January. Egg
capsules are attached to hard substrate, is semi-spherical, with a diameter of 50 mm and 35 mm high
and the number of embryos varies from 7 to 9.
Odontocymbiola magellanica spawn white, spherical, calcareous egg capsules attached to hard flat
surfaces. Major oviposition events occurred from July to December, characterized by females’
aggregation. Male individuals reach maturity at 80 mm and females mature at 90 mm (7 and 8 years
of age respectively).
Oviposition in Adelomelon ancilla occur mainly from June to December. Minimum shell length of a
females laying egg capsules was 114 mm.
In the patagonic species oviposition was coincident with increasing of photoperiod from winter to
summer solstices and not apparently by increasing of water temperature as observed in the species
from Mar del Plata.
166