ABSTRACT

Introduction: Once again, simultaneously with the malacological studies carried about the country of Venezuela (Agudo-Padrón2023 a-b) and the immediate neighboring islands of Trinidad & Tobago (Agudo-Padrón2023 c), since 2014 the “Projeto AM” (Brazil) has carried parallel out taxonomic, bioecological and conservation research of the non-marine (land/ terrestrial) molluscs present in the neighbor insular set territory artificially denomined “ABC”(Aruba, Bonaire and Curaçao islands). To date, the aspects of the natural history of this geographic region, equally located in the Northern sector of South America, although in the West sector of the Dutch Southeast Caribbean facing to Venezuela mainland, have been regularly studied. Objective: Substantial updating of this knowledge through an exhaustive review of the regional malacological literature of historical and recent nature available. Methodology: Between 2014 and the present, a sequential review of the species occasionally referred to in the regional literature was carried out, examined from the perspective of the current taxonomy in force. Results and conclusions: Verification and determination of fifty-three (53) valid referred nominal taxons, including 15 subspecies & 38 species of land/ terrestrial gastropods, taxonomically grouped into seventeen (17) families and thirty (30) genera

Abstract
Background: In general shell-less slugs are considered to be slimy animals with a rather dull appearance and a pest to garden plants. But marine slugs usually are beautifully coloured animals belonging to the less-known Opisthobranchia. They are characterized by a large array of interesting biological phenomena, usually related to foraging and/or defence. In this paper our knowledge of shell reduction, correlated with the evolution of different defensive and foraging strategies is reviewed, and new results on histology of different glandular systems are included. Results: Based on a phylogeny obtained by morphological and histological data, the parallel reduction of the shell within the different groups is outlined. Major food sources are given and glandular structures are described as possible defensive structures in the external epithelia, and as internal glands.

Conclusion: According to phylogenetic analyses, the reduction of the shell correlates with the evolution of defensive strategies. Many different kinds of defence structures, like cleptocnides,
mantle dermal formations (MDFs), and acid glands, are only present in shell-less slugs. In several cases, it is not clear whether the defensive devices were a prerequisite for the reduction of the shell, or reduction occurred before. Reduction of the shell and acquisition of different defensive structures had an implication on exploration of new food sources and therefore likely enhanced adaptive radiation of several groups.