Horatia ozimeci Grego & Falniowski, sp. nov.

Falniowski 1, Andrzej, Grego 2, Jozef, Rysiewska 1, Aleksandra, Osikowski 3, Artur & Hofman 4, Sebastian, 2021, Two new stygobiotic species of Horatia Bourguignat, 1887 (Hydrobiidae) from Croatia, Subterranean Biology 37, pp. 89-104 : 89

Horatia ozimeci Grego & Falniowski, sp. nov. Figs 4A-E , 5A

Type locality.

Spring Izvor Ruda - Beguša, Ruda, sand at the stream bottom below the spring lake, 13 km ESE of Sinj, Split district, Croatia; 43°40'06.6"N, 16°47'45.6"E.

Holotype.

Dry shell with operculum (Fig. 4B ), J. Grego, A. Falniowski, M. Olšavský and J. Olšavská leg., August 5-th 2020, OZRM 11600.

Paratypes.

The single live collected paratype (Fig. 4A ) has been destroyed for DNA extraction; GenBank number: MW448545.

From type locality: J. Grego, A. Falniowski, M. Olšavský and J. Olšavská leg August 5-th 2020, OZRM 11601/1 specimen; NHMW 113607/1 specimen, JG 1542/28 specimens (Fig. 4C-E ); Type locality, J. Grego, G. Jakab and B. Šmída leg. March 17-th 2017, JG F0724/24 specimens.

Diagnosis.

Shell minute, valvatoid, distinguished from the other species of Horatia by its body whorl separated at its terminal sector from the penultimate one (scalarity at this part), the circular and complete peristome and extremely wide umbilicus showing earlier whorls inside.

Description.

Shell (Fig. 4B ) 2.14 mm high and 1.62 mm broad, valvatoid, whitish, translucent, rather thin-walled, consisted of about 3 ½ whorls, growing rapidly and separated by moderately deep suture, more prominent closer to the aperture: the terminal part of the body whorl completely separated from the penultimate one. Spire low and narrow, body whorl large. Aperture prosocline, circular in shape, peristome complete and separated from the columella, swollen, umbilicus extremely wide, with the earlier whorls visible inside. Shell surface smooth, with growth lines delicate but visible. Operculum reddish-brown, translucent, paucispiral.

Shell variability restricted (Fig. 4A, C-E ), and shell less variable than in H. klecakiana (Figs 1 , 4J-P ).

Protoconch (Fig. 5A ) smooth, similar as in H. klecakiana .

Measurements of holotype, illustrated paratypes, and shells of H. klecakiana : Table 2 .

Soft parts morphology and anatomy. The body white, pigmentless, with no eyes. The anatomy unknown.

Derivatio nominis

. The specific epithet Horatia ozimeci refers to our friend Mr.sc. Roman Ozimec, a biospeleologist from Bast, Croatia, deeply devoted to the study and protection of the subterranean habitats in the Dinarides and Balkans.

Distribution and habitat.

Known from the type locality. The type locality is a karst spring lake surrounded by three outflow caves intermittently draining the karst conduit at high water saturation. The spring draining water from sinkholes at Buško Jezero (Bosna and Hercegovina) and supports the river Ruda, a left tributary of Cetina River. The following Hydrobiidae species were detected in the habitat: Horatia klecakiana , Orientalina curta germari (Frauenfeld, 1863), Montenegrospeum sketi Grego & Glöer, 2018, Kerkia jadertina sinjana ( Kuščer, 1933).

Molecular distinctness and relationships of Horatia ozimeci .

We obtained eight new sequences of COI (409 bp, GenBank Accession Numbers MW448545-MW448552). The tests by Xia et al. (2003) revealed no saturation. The topologies of the resulting phylograms were identical in both the ML and BI. All the seven sequences of H. klecakiana , collected at five localities, were identical. H. ozimeci formed a sister clade with H. klecakiana (bootstrap support 100%, Bayesian probability 1.0), confirming the congenerity of the two taxa (Fig. 6 ). Within genus Horatia the p-distance between the taxa was 0.074. This well supported clade belongs to the Horatiinae , subfamily of Hydrobiidae . Deeper relationships within the Horatiinae remain unresolved, because of the lack of acceptable support for deeper nodes, which is typical of the phylograms based on COI.

Figures

Figure 1. Type material of taxa described by Bourguignat, 1887 A syntype of H. klecakiana MHNG - 110592. Croatie, ex Yougoslavie, Ribaric, Vallee de La Cettina (= Cetina) (= Vrijovac spring in the source area of the Cetina River), Vriovac spring in Pasko polje, near to village Cetina. The following species are junior synonyms of H. klecakiana: B syntype of H. verlikana MHNG 110600 Marais entre Verlika (= Vrlika = Verlicca) et Ribaric C syntype of H. palustris MHNG 110597 Fontaine a Ervac (= Hrvace) D syntype of H. obtusa MHNG 110596 Sorgente de La Cetina E syntype of H. letourneuxi MHNG 110593 Fontaine du moulin a Ervac (= Hrvace) F syntype of H. fontinalis MHNG 110589, Sorgente de La Cettina G syntype of H. albanica MHNG 110587, Source du moulin Cetina, a Durazzo (= Durres), not Durres in Albania, likely the misspelling of the watermill name in village Cetina H syntype of H. obliquq MHNG 110594 Fontaine du moulin a Ervac (= Hrvace). (Photo MHNG by Estee Bochud and Eike Neubert, kindly provided by Emmanuel Tardy).

Figure 4. Shell variability of two Horatia species A-E H. ozimeci A sequenced specimen (2 H 76) B holotype OZRM 11603 C-E paratypes E NHMW 113607, (Photo NHMW by Ivo Gallmetzer) F-H H. stygorumina F holotype OZRM 11600 G-H paratypes NHMW 113608, (Photo NHMW by Gallmetzer) I Cf. Horatia knorri Schuett, 1961, spring of Ombla in Komolac, holotype SMF 164247 (Photo SMF by Sigrid Hof) J-P sequenced specimens of H. klecakiana J Vrelo Kosinac 2 K H. klecakiana, Gala spring L H. klecakiana, Ruda Begusa M, N, P H. klecakiana, Vrelo Kosinac 1 O H. klecakiana, Grabske Mlinice. The shell measurements are also shown: a shell height, b body whorl breadth, c aperture height, d spire height, e aperture breadth, α apex angle, β angle between body whorl suture and horizontal surface. Scale bars: 1 mm.

Figure 5. SEM images of H. ozimeci (A) juvenile specimen from the type locality (SBMNH 635080) and H. stygorumina (B) juvenile shell from cave Mali Rumin (SBMNH 635079). SEM SBMNH by Vanessa Delnavaz.

Figure 6. Maximum Likelihood tree inferred from mitochondrial COI. Bootstrap support above 60 % and corresponding Bayesian probabilities are given. Bold indicates newly obtained sequences.