Spawn and development of Falsilunatia eltanini (Mollusca: Gastropoda), a deep-sea naticid from a Southwestern Atlantic Canyon

AVERBUJ, A.; PENCHASZADEH, P. E.; PASTORINO, G.

MARINE BIOLOGY

SPRINGER

Año: 2018 vol. 165

0025-3162

A series of cruises to the Mar del Plata Submarine Canyon (38ºS/54ºW)off Argentina in 2012−2013 has provided biological material that enablesinsights into the various modes of development of deep-sea invertebrates atdepths up to 2,420 m. This study describes the unusually large encapsulatedembryos of the globose moon snail, Falsilunatiaeltanini Dell, 1990 (Naticidae), and compares them with another directly-developing naticid from thesame collections, Bulbus carcellesi.Embryos of F. eltanini developin sand collar egg masses that contain up to 6 conspicuous egg capsules of 5.0−8.5 mm in diameter. Each F. eltanini egg capsule contains a single, ~170-µm diameter egg andan abundant extraembryonic white anddense nutritive substance (supplementary food). This allows F. eltanini crawlingpre-hatching juveniles to grow to a size up to 4.7 mm in shell diameter. Falsilunatiaeltanini egg collars showed several different stages of development at the samedate, which suggests a long reproductive season which could be continuous or periodic(lasting more than a year). Thenumber of whorls in the hatchling juvenile shells and the significant size theyattain support the occurrence of a long period of embryonic development in F.eltanini. A successful reproductive modality in suchextreme environments requires a large maternal investment that is expressed in Falsilunatia eltanini withextremely large egg capsules and abundant nutritive supplementary content. This extraordinary modality is only observed among thefamily Naticidae in several otherspecies inhabiting deep-sea and boreal cold waters