Runcina caletensis, Araujo, Ana Karla, Pola, Marta, Malaquias, Manuel Antonio E, Ballesteros, Manuel, Vitale, Fabio & Cervera, Juan Lucas, 2022

Araujo, Ana Karla, Pola, Marta, Malaquias, Manuel Antonio E, Ballesteros, Manuel, Vitale, Fabio & Cervera, Juan Lucas, 2022, Molecular phylogeny of European Runcinida (Gastropoda, Heterobranchia): the discover of an unexpected pool of complex species, with special reference to the case of Runcina coronata, Zoological Journal of the Linnean Society 194 (3), pp. 761-788 : 779

RUNCINA CALETENSIS ARAUJO, POLA, MALAQUIAS & CERVERA, SP. NOV.

( FIGS 4G–I , 5C , 6C , 7A, B )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: EC216698-6700-4607-9E35-515AB69BD17C

Examined material: Holotype: MNCN 15.05 /200113, La Caleta (Cádiz) (36º31’59”N; 6º18’31”W), Andalusia, south-western Spain, coll. Josep Romà, 17 May 2015, 3 mm living animal, depth 0.5–1 m (dissected and sequenced) . Paratype: MNCN: ADN 118949 , La Caleta (Cádiz) (36º31’59”N; 6º18’31”W), Andalusia, southwestern Spain, coll. Josep Romà, 16 June 2015, 1.5 mm in length preserved, depth 0.5–1.0 m. (dissected and sequenced) .

Etymology: Named after the type locality: the beach of La Caleta in Cádiz, Spain.

External morphology ( Fig. 7A, B ): Living and preserved specimens 3.0 mm and 1.5 mm in length, respectively. Body elongated and broad. Lateral grooves on both sides between notum and foot. Anterior part of notum (‘head’) slightly bilobed. Posterior part of notum rounded. Foot as wide as notum. Foot extends posteriorly beyond notum. Ground colour translucent pale fawn or yellowish. Digestive system visible as broad brownish blotch in juvenile specimens. Tiny white, black and yellow spots all over the body. White spots on the lobes of the head and on the anterior ventral surface of the foot. Triangular white patches behind the eyes. White semicircle anterior to the notum end. Very few white spots in juvenile. Small black dots forming two longitudinal lines on head region. Black spots concentrated on the notum end posteriorly to white semicircle. In juveniles, only a few larger black spots are present along the margin of the notum. Eyes inconspicuous. Dark band on middle of posterior region of foot. Three rounded gill laminae located on right side of anus. Gills yellowish with slightly brown margins. Anus located in the midline of the body beneath the notal edge.

Internal anatomy ( Figs 4G–I , 5C , 6C ): Radular formula 13 × 1.1.1 (15.05/200113). Rachidian tooth slightly bilobed with long and smooth lateral wings on each side. Central part of rachidian tooth contains a pair of pads, each possessing seven to eight developed denticles. Central depression between pads absent. Denticles long and pointed, decreasing in size towards middle of the tooth ( Fig. 4G ). Lateral teeth denticulate, elongate, hooked shaped with 33–36 long and pointed denticles ( Fig. 4H ). Triangular jaws present. Four gizzard plates with seven to ten crests ( Fig. 4I ). Shell absent. Reproductive system monaulic. Female gland mass placed on right side and behind digestive gland. Female gland opens to exterior through common genital duct ( Fig. 5C ). Male pore opens next to mouth, on right side. Elongated and cylindrical male copulatory organ. Short, conical and unarmed penial papilla projects into large atrium. Cylindrical prostate gland strongly curved. Long and slender seminal vesicle with black pigmentation ( Fig. 6C ).

Distribution: Cádiz, southern Spain (present study).

Remarks: The species R. caletensis shares with R. coronata the presence of white bands and spots on the notum, and is overall externally similar to R. aurata . However, in R. caletensis the yellow ground colour is opaque, while in R. aurata the colour is translucent ( Figs 3E, F , 7B ). In addition, R. caletensis lacks black spots on the ventral surface of the foot, a feature present in R. aurata . Based on available data, R. caletensis is the only one among these species with rachidian teeth lacking the depression between the pads and with well-developed denticles of similar length along the masticatory edge of pads ( Fig. 4G ). The female gland mass of R. caletensis has a rounded shape and the common genital duct is larger than in the other two species ( Fig. 5A–C ). The seminal vesicle in R. caletensis is thinner than in R. coronata and more elongated than in R. aurata . Unlike for R. coronata and R. aurata , a penial papilla was observed in R. caletensis .

The minimum uncorrected p- distances for the COI gene is 7.8% between R. caletensis and R. coronata ,

Figures

Figure 3. Living animals of Runcina coronata (A, B) and Runcina aurata (C–F). A, MNCN 15.05/88105, 3 mm in length, Swanage (southern England). B, MNCN 15.05/90423, 4 mm in length, Swanage (southern England) (photos Ian F. Smith). C, MNCN/ADN 118948, 1.5mm in length, La Caleta, Cádiz (south-western Spain; Atlantic Ocean). D, MNCN/ADN 118950, 1mm in length, La Caleta, Cádiz (south-western Spain; Atlantic Ocean). E, MNCN 15.05/88106, 2 mm in length, La Caleta, Cádiz (south-western Spain; Atlantic Ocean). F, MNCN 15.05/88107, 2mm in length, La Caleta, Cádiz (south-western Spain; Atlantic Ocean). Photos A and B, courtesy of Ian F. Smith; photos C–F by Ana Karla Araujo.

Figure 4. Scanning electron micrographs of radula and gizzard plates. A–C, Runcina coronata. A, rachidian teeth (MNCN 15.05/88105). B, lateral teeth (MNCN 15.05/88105). C, gizzard plate (MNCN 15.05/90423). D–F, Runcina aurata. D, rachidian teeth (MNCN 15.05/91500). E, lateral teeth (MNCN 15.05/88106). F, gizzard plate (MNCN 15.05/88106). G–I, Runcina caletensis (MNCN 15.05/200113) G, rachidian teeth. H, lateral teeth. I, gizzard plate. J–M, Runcina tingensis. J, rachidian teeth (MNCN 15.05/200114). L, lateral teeth (MNCN 15.05/200114). M, gizzard plate (MNCN 15.05/91514). Scale bars: A, B, E, J, L = 10 μm; C, F, I, M = 50 μm; D, G = 20 μm; H = 5 μm.

Figure 5. Female reproductive system. A. R. coronata, southern England (MNCN 15.05/90423). B. R. aurata, La Caleta, Cádiz, south-western Spain, Atlantic Ocean (MNCN 15.05/88106). C. R. caletensis, La Caleta, Cádiz, south-western Spain, Atlantic Ocean (MNCN 15.05/200113). D.R. tingensis, Tangier, north-western Morocco,Atlantic Ocean (MNCN 15.05/91514). Abbreviations: FM, female mass; CGD, common genital duct; GO, gonopore.

Figure 6. Male reproductive system. A, Runcina coronata, southern England (MNCN 15.05/90423). B, Runcina aurata, La Caleta, Cádiz, south-western Spain, Atlantic Ocean (MNCN 15.05/88106). C, Runcina caletensis, La Caleta, Cádiz, southwestern Spain, Atlantic Ocean (MNCN 15.05/200113). D, Runcina tingensis, Tangier, north-western Morocco, Atlantic Ocean (MNCN 15.05/91514). Shaded area indicates the presence of sperm. Abbreviations: MO, male opening; PP, penial papilla; PG, prostate gland; SV, seminal vesicle.

Figure 7. Living animals of Runcina caletensis (A, B) and Runcina tingensis (C, D). A, MNCN/AND 118949, 1.5 mm in length, La Caleta, Cádiz (south-western Spain; Atlantic Ocean). B, MNCN 15.05/200113, 3 mm in length, La Caleta, Cádiz (south-western Spain; Atlantic Ocean). C, MNCN 15.05/91514, 1.5mm in length, Tangier (north-western Morocco; Atlantic Ocean). D, MNCN 15.05/200114, 2mm in length, Tangier (north-western Morocco; Atlantic Ocean). A, B images by Ana Karla Araujo; C, D images courtesy of Naoufal Tamsouri.