Egg morphology, early juvenile development, and confirmed occurrence of Drusia ibera (Gastropoda: Parmacellidae) in İstanbul, Türkiye

The reproductive biology and early developmental morphology of Drusia ibera (Eichwald, 1841) remain insufficiently documented. This study provides anatomically confirmed evidence of D. ibera from İstanbul, Türkiye, together with quantitative and photographic observations of egg morphology and early post-hatching juveniles under semi-natural conditions. Five egg clusters containing 247 eggs were recorded, with a mean clutch size of 49 eggs. The eggs were ellipsoidal, measuring approximately 3.9 × 2.7 mm and weighing 0.024 g, with a whitish-cream, semitranslucent, rigid and brittle outer covering. Early juveniles, observed outside their egg envelopes 24–32 days after the recorded oviposition interval, measured approximately 2.9 × 2.2 mm and exhibited conspicuous translucent amber-coloured shell-like structures and distinctive dark brown, approximately D-shaped apertural coverings. The rigidity of egg coverings observed within the reproductive tract of a deceased specimen further suggests that this characteristic may develop before oviposition. These findings provide new quantitative and photographic evidence of reproductive and early juvenile morphology, establishing a comparative reference for developmental studies within Parmacellidae.