Mediterranean Fauna Research Articles

Species of the subgenera Aquilaspio and Prionospio (Polychaeta: Spionidae: Prionospio) from the southern coast of Turkey (Levantine Sea, eastern Mediterranean), with description of a new species and two new reports for the Mediterranean fauna

The present study deals with species of the subgenera Prionospio (Aquilaspio) and Prionospio (Prionospio) collected from various habitats and depths along the southern coast of Turkey in September and October 2005. The examination of a large collection of material revealed 10 species, of which one species, Prionospio (P.) ergeni n. sp., is new to science; two species, P. (P.) depauperata and P. (A.) krusadensis, are new to the Mediterranean fauna; and one species, P. (A.) sexoculata, is new to the Turkish marine fauna. Prionospio (P.) ergeni n. sp. differs from all other Prionospio species in having three pairs of pinnate branchiae between chaetigers 2 and 4 and one pair of apinnate branchiae on chaetiger 5. Four species―P. (P.) saccifera, P. (A.) sexoculata, P. (P.) depauperata, and P. (A.) krusadensis―are aliens. The former two species could have been introduced to the Mediterranean from the Red Sea through the Suez Canal (Lessepsian migrants) and the others from the Pacific or Indian Oceans via ballast water of ships. The morphological, ecological, and distributional features of these species are discussed.

Alien polychaete species (Annelida: Polychaeta) on the southern coast of Turkey (Levantine Sea, eastern Mediterranean), with 13 new records for the Mediterranean Sea

The examination of benthic material collected from different depths and habitats along the southern coast of Turkey (Levantine Sea, eastern Mediterranean) in September and October 2005 revealed 30 alien polychaete species belonging to 15 families. Thirteen species (Pisione guanche, Linopherus canariensis, Onuphis eremita oculata, Lumbrineris perkinsi, Dorvillea similis, Timarete caribous, Pherusa parmata, Pherusa saldanha, Streblosoma comatus, Polycirrus twisti, Laonome triangularis, Branchiomma bairdi and Janua steueri) are new to the Mediterranean fauna, 24 species are new to the Turkish fauna and 27 species are new to the Levantine coast of Turkey. The specimens collected from the Levantine coast of Turkey and northern Cyprus that were previously identified as Linopherus acarunculata and Branchiomma boholense are reidentified as L. canariensis and B. bairdi, respectively. In the light of present knowledge, the previous reports of Lumbrineris inflata and Streblosoma hesslei from the Mediterranean (Italian coast) could refer to the species L. perkinsi and S. comatus, respectively. The species new to the Mediterranean Sea are redescribed and discussed.

A gastropod from the tropical Atlantic becomes an established alien in the Mediterranean

We report the occurrence of an established population of the gastropod Mitrella psilla (Duclos, 1846), native on west African coasts of Mauritania, Senegal and Angola, on the shore of La Goulette, Bay of Tunis. The molluscan species of tropical West African affinity hitherto ascertained in the Mediterranean are not aliens, but have a native range which encompasses at least part of the Alboran Sea since historical times. Mitrella psilla appears therefore as the first instance of a mollusc with a tropical Atlantic origin being added to the Mediterranean fauna. The species was found near an important commercial harbour and is presumed to have been introduced by shipping.

New records of marine amphipod fauna (Crustacea: Peracarida) on the Algerian coast

Recent sampling surveys (1995–2001) of the shallow (3–136 m) soft-bottom communities along the Algerian coast in nine bays and gulfs and twelve harbours have allowed 206 species of marine amphipod to be recorded. Among the species recorded, 45 species appear to be new in terms of the inventory of the marine amphipod fauna of Algeria (Bakalem & Dauvin, 2005). This note reports on the number of specimens sampled for each of these 45 species and provides data on sediment type and depth at which they were sampled. Sixteen of these species are considered to be endemic to the Mediterranean Sea, twenty-six are north-eastern Atlantic species, and the last three have a wide geographical distribution in the Indo-Pacific and the Atlantic Oceans. The sampling also permitted the confirmation of the presence of five other Atlantic amphipod species not already reported in the inventory of the Mediterranean amphipod fauna (Bellan-Santini et al., 1998). The total number of marine amphipod fauna in Algeria is now 298.

The Early Cretaceous of North-East Greenland: A crossroads of belemnite migration

Recent field work in Lower Cretaceous successions of Traill Ø and Wollaston Forland, North-East Greenland, have resulted in c. 2350 belemnite guards collected bed-by-bed from the upper Ryazanian – Hauterivian. The most common belemnite genera observed, Acroteuthis, Pachyteuthis, and Cylindroteuthis are of boreal-arctic affinities and closely related to NW European and Siberian faunas. Other taxa, including Hibolithes (common), Pseudobelus (relatively common) and Duvalia (rare), show faunal links to both NW European and Mediterranean faunas. This paper describes and discusses these findings in their taxonomic, biostratigraphic, palaeobiogeographic, palaeoecologic and palaeoceanographic context. In particular, the occurrence of Pseudobelus which is common in the circum Mediterranean area, is remarkable since it is the first observation of this Tethyan genus in the entire Boreal Realm. The palaeoecological interpretation of these observations result in the recognition of four different palaeobiogeographic belemnite assemblages for the Boreal Realm: 1) North-East Greenland, 2) Spitsbergen, 3) NW Europe and 4) Siberia. In contrast to the other assemblages, the belemnite faunas of North-East Greenland consist of a) Boreal-Arctic elements, b) Boreal-European taxa, c) endemic belemnites of Tethyan ancestry, and d) Tethyan species. These findings make North-East Greenland part of an immigration route from the Tethyan Realm via the north Atlantic to the high Boreal. This allowed Tethyan species, which are otherwise unknown from the Boreal Realm, to reach North-East Greenland. The occurrence of the Tethyan genus Pseudobelus in North-East Greenland also supports the interpretation of this taxon as a hemipelagic dweller, capable of crossing major distances. The belemnite patterns further suggest the existence of a proto Gulf-stream, documenting a south-to-north flow of warm surface waters as far north as Greenland already in the earliest Cretaceous (Valanginian). This has substantial implications for the interpretation of Early Cretaceous climate and oceanic current systems, as well as for the palaeobiology of belemnites.

The carnivoran community from the Miocene of Sandelzhausen (Germany)

From the Bavarian Early/Middle Miocene (MN5) site Sandelzhausen, nine species of carnivoran mammals are identified including the hemicyonine ursid Hemicyon stehlini, the amphicyonids Amphicyon cf. major and Pseudarctos bavaricus, the mustelids Ischyrictis zibethoides and Martes cf. munki, the mephitid Proputorius pusillus, the viverrid Leptoplesictis cf. aurelianensis, the felid Pseudaelurus romieviensis, and finally the recently described barbourofelid Prosansanosmilus eggeri. With these taxa present, Sandelzhausen shows a carnivoran community typical, though deprived, for the Lower to Middle Miocene of Europe, but different from roughly contemporary Mediterranean faunas such as those from Çandir or Paşalar in Turkey.

Mediterranean diversification of the grass‐feeding Anisopliina beetles (Scarabaeidae, Rutelinae, Anomalini) as inferred by bootstrap‐averaged dispersal–vicariance analysis

AbstractAim The circum‐Mediterranean region is one of the most complex regions of the Earth in terms of geography and natural history. The Old World species of the beetle subtribe Anisopliina (Scarabaeidae) feed almost exclusively on the pollen of grasses (Poaceae). Within this group, the ‘anisopliine clade’ forms a monophyletic group distributed mainly in the circum‐Mediterranean region. Here, we reconstruct the biogeographical history of the anisopliine beetles in relation to the diversification of grasses, and compare this reconstruction with previous hypotheses concerning the evolution of the Mediterranean fauna and with palaeogeographical accounts of the history of this region.Location The Mediterranean region, including North Africa, the Western Mediterranean, Balkans–Anatolia, Middle East and Caucasus.Methods Dispersal–vicariance analysis (diva) was used to reconstruct ancestral distributions based on the morphological phylogeny and to infer the biogeographical processes that have shaped the observed distribution patterns. To account for phylogenetic uncertainty in the biogeographical reconstruction, we ran alternative ancestral distributions derived by diva over a sample of trees obtained by bootstrapping the original data set, reflecting the relative confidence of the ancestral areas on the various clades in the phylogeny.Results The Eastern Mediterranean region and the Caucasus are inferred as the ancestral area of most of the anisopliine lineages. The Eastern Mediterranean region is also reconstructed as the source area of the majority of dispersal events, in particular towards North Africa and the Western Mediterranean. The Iberian Peninsula is inferred as part of the ancestral distribution of the anisopliine clade but also as the setting of several independent colonization events via both the North African platform (Anthoplia) and a European dispersal route (Anisoplia).Main conclusions Our results confirm the role played by the Eastern Mediterranean as an evolutionary cradle of diversity for Mediterranean lineages. This can be explained by a recent and intense orogenic activity that might have promoted isolation and allopatric speciation within lineages. Both the Anomalini fossil record and the close association of anisopliine beetles with grasses suggest that the anisopliine clade originated in the Late Tertiary and that its spatial and temporal evolution within the Mediterranean Basin coincided with that of its major food source, the Mediterranean Poaceae.

Sipunculans along the Aegean coast of Turkey

Faunistical analysis of benthic samples collected from different depths and biotopes (0–195 m) at 108 stations along the Turkish Aegean coast yielded 11 species and 5 subspecies of Sipuncula. Two species (Phascolion (Isomya) tuberculosum and Aspidosiphon (Aspidosiphon) misakiensis) are new to the eastern Mediterranean fauna and 8 species are new to the Turkish fauna. Onchnesoma steenstrupii steenstrupii has the highest dominance and frequency index values in the study area. Aspidosiphon (Aspidosiphon) elegans and Apionsoma (Apionsoma) misakianum are alien species. Of the biotopes examined, muddy sand was characterized by the highest number of species and specimens, whereas sponges and coralligenous substrata were characterized by the lowest number of species and specimens. The biometrical and reproductive features of the species are presented and discussed.

Effects of persistent organic pollutants on the thyroid function of the European sea bass ( Dicentrarchus labrax) from the Aegean sea, is it an endocrine disruption?

We evaluated the alterations of organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) on the thyroid in wild and cultured sea bass ( Dicentrarchus labrax) at environmental concentrations. These compounds influence the endocrine system of many fish species and are qualified as endocrine disruptors. The thyroid seems to be a target organ. Two alteration endpoints: the thyroid histology and the muscular thyroid hormone concentrations, were used simultaneously. High concentrations in PCBs and DDT were detected in muscles, supporting the idea that the Mediterranean fauna could be more polluted than the Atlantic fauna. The high abundance of DDE indicates a progressive degradation of remnant DDT load and the absence of new inputs in this area. Aquaculture sea bass shows a significant higher amount of pollutants on fresh weight basis (especially PCBs) in their muscles compared to the wild sea bass. Those differences may be related mainly to the contaminations of diet. Thyroid parameters vary between wild and aquaculture sea bass, wild sea bass were characterized by higher follicle diameters, epithelial cell heights and muscular T 4 concentrations. A significant relationship between persistent organic pollutants (muscular PCBs and DDT concentration) and the different thyroid parameters (diameters of follicles, epithelial cell heights and muscular T 4 levels) could be observed, which support the hypothesis that these compounds have an adverse impact on thyroid morphometry and function.

Early Oligocene fish otoliths from the Castellane area (SE France) and an overview of Mediterranean teleost faunas at the Eocene-Oligocene boundary

Early Oligocene fish otoliths from the Castellane area (SE France) and an overview of Mediterranean teleost faunas at the Eocene-Oligocene boundary

Recent brachiopods from the Persian Gulf and their biogeographical significance

Two brachiopod species Discradisca indica (Dall, 1920) and Argyrotheca jacksoni Cooper, 1973, together with Lingula sp., have been identified from the Persian Gulf. These species, added to the two species Terebratulina retusa (Linnaeus, 1758) and Megerlia truncata (Linnaeus, 1767) previously identified by Jackson (1921), and Lingula anatina Lamarck, 1819 by Emig (1988) bring the total to 5 species for the region. The genera Discradisca and Argyrotheca are recorded for the first time from the Persian Gulf. This fauna shows biogeographical affinities to the Indian Ocean and the Mediterranean faunas. The disjunct geographical distribution of Discradisca suggests this genus is a relict of an ancient Tethyan fauna.

Historical colonization of the Mediterranean Sea by Atlantic fishes: do biological traits matter?

Since its opening 5.33 million years ago, the Gibraltar Strait has always contributed to the Mediterranean fauna and flora. Despite the increasing importance of the phenomenon, ecological determinants underlying colonization success of Atlantic fishes in the Mediterranean Sea have been poorly investigated. Here we reconstruct the recent historical colonization of the whole Mediterranean Sea by Atlantic fishes and we aim to determine where Atlantic fishes preferentially establish and whether some biological traits and ecological factors can be correlated to the colonization success (climate match, position in the water column, maximum body length, propagules, confamilial resistance, depth). A database on Atlantic fish species records from 1810 to 2006 was built and the colonization rate of each introduced species was estimated. Analysis of Variance, Chi squared test and logistic regression were used to investigate the relationships between ecological variables and colonization success. In addition, an index of asymmetry was used to analyse the relative colonization on the two sides of the Mediterranean Sea. Overall 48.33% of Atlantic species introduced in the Mediterranean Sea succeeded in colonizing eastwards. We found that habitat depth of Atlantic species is significantly related to their colonization success due to the obstacle of the shallow depth of the Gibraltar Strait (300 m). It also appears that despite the cyclonic general water circulation on the North Western basin, the northern side is more colonized than the southern one: 70.40% of the studied species colonize the northern side, while only 29.62% colonize the southern one. Two hypotheses may explain this trend: the bottom-up process that enhances the colonization success of Atlantic fishes along the Spanish coast of Alboran Sea owning to its high productivity and the intensiveness of the scientific explorations along the northern Mediterranean side. We conclude that crossing the Gibraltar Strait does not guarantee the colonization success and that species life-history and functional traits are poor predictors. Instead we suggest that environmental factors may determine favourable locations for invasive species installation.

Assessing relationships between Mediterranean and Afrotropical taxa of Cleonini (Coleoptera: Curculionidae: Lixinae): a survey based on Bayesian analysis and lineage geohistory reconstruction

Blogeographia vol. XX/X - 2008 (Pubblicato il 30 dicembre 2008) The Mediterranean-southern African disjunct distribution pattern Assessing relationships between Mediterranean and Afrotropical taxa of Cleonini (Coleoptera: Curculionidae: Lixinae): a survey based on Bayesian analysis and lineage geohistory reconstruction MASSIMO MEREGALLI, DANIELE SILVESTRO Dzjnzrtiiizmto 512' Bio/ogizz Animzzle .9 ale//’U0m0, Um'1/erszriz di Torino 2/in Amza'e772ia A/bertzizzz 13, 10123 T072320 (Italy) e—mzzz'[: 77znr5in2o. meregzz[li@zim't0. it Key words: Curculionidae, Cleonini, African Fauna, Mediterranean Fauna, phylogenetic relationships, Bayesian analysis, historical biogeography. SUMMARY Relationships between the Mediterranean and southern African genera oFCleonini (Curculionidae) were assessed using preliminary phylogenetic analysis and palaeohistorical reconstruction by maximum likelihood inference of ancestral distributions. Intergeneric relationships were found to be present only between sister taxa belonging to basal branches of the trees, suggesting that the faunas of the two regions were connected only during the early stages of radiation ofthe tribe. A critical revision ofthe species composition ofsome Afro—Mediterranean genera revealed that only Pram/oremizoriiyinzir has a disjunct Mediterranean—southern African distribution. This is regarded as having been determined by a recent expansion of the range of the genus from the Mediterranean region towards southern Africa via the eastern Africa grasslands. INTRODUCTION The Curculionidae subfamily Lixinae Schoenherr, 1823 is composed of about 100 genera, presently included in three tribes: Lixini Schoenherr, 1823; Rhinocyllini Lacordaire, 1863; and Cleonini Schoenherr, 1826. This last tribe accounts for most of the genera, more than 80. Its taxonomy is still based on Faust (1904), who also provided the only available key to all the genera. Lacking any comprehensive and comparative evaluation of characters, genera are not always clear and unequivocal; in some cases they seem to be para- phyletic taxa, with uncertain boundaries. A phylogenetic analysis of the tribe

Heteromurus (Verhoeffiella) Anagastumensis n. Sp. (Collembola, entomobryidae), a new cave springtail from Montenegro

A thorough analysis of a specimen of the collembolan family Entomobryidae from a cave in Montenegro has yielded a species new to science: Heteromurus (Verhoeffiella) anagastumensis n. sp. This is the first known cave-dwelling member of the subgenus Verhoeffiella Absolon in Montenegro. Heteromurus (V.) anagastumensis n. sp. is described, illustrated, and diagnosed; it is a phenetically close congener of H. (V.) longicornis (Absolon) from Herzegovina. Some biogeographical and evolutionary characteristics of this new Verhoeffiella species are discussed in the light of the origin of the North Mediterranean fauna.

Taxonomy of some sponges (Porifera: Demospongiae) collected from the Aegean Sea and description of a new species

A systematic survey of the sponge fauna of the Aegean Sea has been carried out. Twenty-eight stations located in the Aegean Sea were explored and 59 species of Demospongiae were collected from this particular area, which covers a broader geographical area of the Aegean and Cretan Seas. Some of the species found are poorly known for the Mediterranean fauna, like Cerbaris curvispiculifera and Spongosorites flavens, which are reported for the first time in the Aegean Sea and generally in the eastern Mediterranean. The species Axinyssa michaelis sp. nov. (Halichondriidae: Halichondrida) is new to science. In this paper, a description of the new species is presented along with the description of the first recorded species in the Aegean Sea. In addition to the taxonomic description of the species, some ecological data and a distribution pattern are also presented.

Species richness and complementarity of beetle faunas in a mediterranean-type biodiversity hotspot

Regions of mediterranean-type climate represent most extra-tropical biodi- versity hotspots, being both highly diverse and highly endangered. Though renowned for their plant richness, these regions' insects constitute the bulk of their alpha diversities. Data on insect distribution and rarity are generally lacking for such regions, and are often considered unattainable. Intensive field inventories combined with statistical extrapolation methods can provide a sufficient understanding of alpha, beta, and gamma diversity components for application to conservation planning. These are essential to assessing the adequacy of a regional reserve network for the conservation of insect diversity. Here the beetle faunas of three protected areas spanning three major ecoregions in the California Floristic Province were inventoried and analyzed for species richness, complementarity, and uniqueness. These surveys produced collectively nearly 1,200 species from all three sites, estimated to be about 80% of their total faunas. Diversity was highly partitioned among sites, no one site containing more than 60% of the species. Dissimilarity was moderate to high for all comparisons, and all sites contained >40% unique species. Comparison of these results with those based on species of co-occurring plants reveal incongruent species richness but congruent similarities among sites. These results provide quantitative support to the perception that mediterranean insect faunas show high spatial variability. Along with online specimen level data on distribution, rarity, and seasonality, these results will help speed the incorporation of insect data into serious conservation planning.

Environmental and geographical determinants of beta diversity of leaf beetles (Coleoptera: Chrysomelidae) in the Iberian Peninsula

Abstract 1. The effect and relative importance of both environmental and geographic factors on species turnover of Chrysomelidae assemblages in the Iberian Peninsula was explored.2. Ordination and classification analysis of species lists from well‐sampled local areas identified two main biogegraphic groups of inventories, discriminating between Eurosiberian and Mediterranean faunas.3. After describing this pattern, the underlying determinants were explored, separating pure from combined effects of environment and geography by means of partial canonical correspondence analysis.4. Results indicate that pure effects of environment and geographic position are of similar magnitude (about 20% of the variation from each), and quite important in comparison with combined effects.5. The power of the pure effect of geographical variables, together with beta‐diversity independence of species richness gradients, point to the inadequacy of environmental measurement explanation of beta‐diversity patterns, and to the existence of a major component of geographical variation independent of environment.

A diverse crinoid fauna from the Middle Jurassic (Upper Bajocian–Callovian) of the Polish Jura Chain and Holy Cross Mountains (south-central Poland)

A systematic account of a diverse crinoid fauna from the Middle Jurassic (Upper Bajocian–Callovian) of the Polish Jura Chain and Holy Cross Mountains (south-central Poland) is presented. The description is supplemented with a list of all crinoid species found hitherto in the Tatra Mountains and the Pieniny Klippen Belt (Poland), which were a part of the northern margin of the Tethys during Middle Jurassic time. Balanocrinus hessi seems to be endemic and established its own population in the epicontinental sea. Other stalked crinoids entered from the Tethys through the East-Carpathian Gate or from a westerly way, and constitute a typical Mediterranean fauna. Stemless forms are regarded to be unsuccessful immigrants. The crinoid remains are preserved mostly as columnals and pluricolumnals, the majority of which are encrusted and bored by various epi- and endobionts. No encrustation or boring, however, occurred during the lifetime of these crinoids. The association of well-preserved columnals/pluricolumnals with the broken and abraded isolated columnals, may be the evidence of a within-habitat time-averaging of the crinoid assemblages.

Holocene sea-level oscillations and environmental changes on the Eastern Black Sea shelf

A multi-proxy study of four sediment cores from the Eastern (Caucasian) Black Sea shelf revealed five transgressive–regressive cycles overprinted on the general trend of glacioeustatic sea-level rise during the last 11,000 14C yr. These cycles are well represented in micro-and macrofossil assemblages, sedimentation rates, and grain size variations. The oldest recovered sediments were deposited in the Neoeuxinian semi-freshwater basin (∼ 10,500–9000 14C yr BP) and contain a Caspian-type mollusk fauna dominated by Dreissena rostriformis. Low δ 18O and δ 13C values are measured on this species. The first appearance of marine mollusks and ostracodes from the Mediterranean is established in this part of the Black Sea at ∼ 8200 14C yr BP, i.e., about 1000–2000 yr later than the appearance of marine microfossils in the deeper part of the sea. The Early Holocene (Bugazian to Vityazevian) condensed section of shell and shelly mud sediments with at least two hiatuses represent a high-energy shelf-edge facies. It contains a transitional assemblage representing a mixture of Caspian and Mediterranean fauna. This pattern suggests a dual-flow regime via the Bosphorus after 8200 14C yr BP. Caspian species disappear and oligohaline species decrease in abundance during the Vityazevian–Prekalamitian cycle. Later, during the Middle to Late Holocene, low sea-level stands are characterized by shell layers, whereas silty mud with various mollusk and ostracode assemblages rapidly accumulated during transgressions. Restricted mud accumulation, as well as benthic faunal composition and abundance, suggest high-energy and well-ventilated bottom water during low sea-level stands. A trend of 18O enrichment in mollusk shells points to an increase in bottom-water salinity during the Vityazevian to Kalamitian transgressions (∼ 7000 to 5700 14C yr BP) due to a more open connection with the Mediterranean, while a pronounced increase in polyhaline species abundance is established during the Kalamitian to Djemetean transgressions (∼ 6400 to 2700 14C yr BP). However, the composition of the faunal assemblage indicates that bottom-water salinity never exceeded modern values of 18–20 psu.

Ecological implications of molluscan ontogenetic strategies ‐ examples from aquatic ecosystems of the Cenozoic Iberian Peninsula

Molluscs from marginal marine and intra-continental basins of the Iberian Peninsula are described with special emphasis on the early ontogenetic shell formation, which reflects the embryogenesis and larval ecology. The fossils, covering a time span from the Early Oligocene to the Early Pleistocene, are compared to contemporaneous fossil faunas of the Mediterranean and Paratethys, and to extant Mediterranean faunas. Larval shells occur in bivalves and gastropods of Upper Tortonian coastal lagoons near Crevillente (Alicante), indicating marine larval stages and a connection of the adult habitat with the open sea. The euryhaline marginal marine gastropods display planktotrophic larval shells, which enable a marine distribution, but prevented generally euryhaline genera, such as Granulolabium and Terebralia (Cerithioidea, Potamididae), from colonizing continental saline ecosystems. The establishment of athalassic saline populations implies the preadaptational loss of planktotrophy. For the first time lecithotrophic larval development in an athalassic saline system is documented for Potamides gaudryi (Cerithioidea, Potamididae) from the late Middle to early Upper Miocene of the Duero Basin. With regard to the early ontogenetic development, P. gaudryi is distinguished from its possible descendant, the extant Potamides conicus (Blainville, 1829), which represents a direct developer that lacks any larval stage. In comparison to direct development, lecithotrophic larval development was advantageous in the colonization of temporary habitats, such as flood areas. Two different modes of direct development with hatching of crawling young are documented: Feeding on embryonic yolk until the hatching stage and adelphophagy. Adelphophagous embryonic development appears to be advantageous in neritids, thiarids and pulmonates that live in habitats with strong predation of juvenile fishes based on the advanced developmental stage and larger shell size of the hatchlings.