Conchological and molecular analysis of the “non-scaly” Bornean Georissa with descriptions of three new species (Gastropoda, Neritimorpha, Hydrocenidae)

Abstract

The Bornean representatives of the genus Georissa (Hydrocenidae) have small, dextral, conical, calcareous shells consisting of ca. three teleoconch whorls. Our recent study on the Georissa of Malaysian Borneo has revealed high intra- and inter-specific variation in the “scaly” group (a group of species with striking scale-like surface sculpture). The present study on the “non-scaly” Georissa is the continuation of the species revision for the genus. The “non-scaly” species are also diverse in shell sculptures. This informal group comprises Georissa with subtle spiral and/or radial sculpture. The combination of detailed conchological assessment and molecular analyses provides clear distinctions for each of the species. Conchological, molecular, and biogeographic details are presented for 16 species of “non-scaly” Georissa. Three of these are new to science, namely Georissacorrugatasp. n., Georissainsulaesp. n., and Georissatrusmadisp. n.

Morphological parallelism of sympatric cave‐dwelling microsnails of the genusGeorissaat Mount Silabur, Borneo (Gastropoda, Neritimorpha, Hydrocenidae)

“…Silabur is probably best explained by the rainwater flowing from the upper chambers of the cave to the deep cave habitat. While it is widely known that rock-dwelling microsnails of South-East Asia region possess great allopatric divergence in shell shape (e.g., in the genera Diplommatina, Georissa, Gyliotrachela, Hungerfordiana, Opisthostoma, and Plectostoma;Hoekstra & Schilthuizen, 2011;Khalik et al, 2018Khalik et al, , 2019Liew et al, 2014;Rundell, 2008;Schilthuizen et al, 2006;Schilthuizen et al, 2012;Tongkerd et al, 2004;Yamazaki, Yamazaki, & Ueshima, 2013), our findings provide evidence that morphological convergence may also occur.…”

“…Usually, these are considered as conspecific based on shared shell characters (Foon & Liew, 2017;Khalik, Hendriks, Vermeulen, & Schilthuizen, 2018, 2019Liew, Vermeulen, & Marzuki, & Schilthuizen, 2014;Thompson & Dance, 1983;Vermeulen, Liew, & Schilthuizen, 2015). Furthermore, phylogenetic analyses often reveal that the detailed conchology follows the patterns of phylogenetic relatedness (Khalik, Hendriks, Vermeulen, & Schilthuizen, 2018, 2019Schilthuizen, Cabanban, & Haase, 2005;Schilthuizen, Rutten, & Haase, 2012). Nonetheless, possible cases of morphological parallelism due to ecological similarity may be overlooked.…”

Microbiome and environment explain the absence of correlations between consumers and their diet in Bornean microsnails

“…‡Originally described (and collected by us) as Georissa similis E. A. Smith, 1894, but recently split into a radiation of highly similar and closely related taxa (Khalik et al 2019). With all phylogenetic relations within the radiation being much closer than those among all other taxa considered within this study, with the exception of G. nephrostoma Vermeulen, Liew and Schilthuizen, 2015, we treat G. similis s.l.…”

Annotated checklist of the land snail fauna from southern Cambodia (Mollusca, Gastropoda)

“…However, G. decora has an ovate conic shape with fine radial ribs on the last whorl, and G. chrysacme has an elongate conic shape with a deep and narrow suture. In addition, the shell shape of G. monterosatiana approaches the shape of G. insulae Khalik et al, 2019 from Borneo, but the former species has stronger and more undulated spiral ridges than the Bornean species (see Khalik et al 2019). Type material.…”

“…7). It is distinguished from Sesara polita Vermeulen et al, 2019 andS. sesarella Vermeulen et al, 2019, which were recently described from Kampot Province, Cambodia, in having strong and prominent radial ridges continuously covering the entire teleconch and last whorl, and without any apertural lamella.…”