Edentellina rotnesti (Jensen, 1993)

EdenTellina cf. roTnesti (Jensen, 1993)

( Figs 4O, P, 28–30)

Berthelinia rotnesti Jensen 1993: 209–14 , figs 1–4, 5A, 6A. Type locality: Natural Jety, Rotnest Island, Western Australia.

Type material

Berthelinia rotnesti , holotype, complete specimen, 3.5 mm long

( WAM S14570 View Materials ), paratypes, six specimens ( ZMUC) .

Additional material examined

Sloping Main, Tasmania, Australia, 3 January 2014, one specimen 2.6 mm long (shell), isolate JC40, Morrison Australia Expedition (stn. TA21 ), leg. Bouchet and Strong ( MNHN IM-2013-53068 ) ; one specimen, 2.5 mm long (shell), isolate JC41, Morrison Australia Expedition (stn. TA21 ), leg. Bouchet and Strong ( MNHN IM-2013-53069 ) ; one specimen, 2 mm long (shell), isolate JC42, Morrison Australia Expedition (stn. TA21 ), leg. Bouchet and Strong ( MNHN IM-2013-53070 ) ; one specimen, 1.8 mm long (shell), isolate JC39, Morrison Australia Expedition (stn. TA21 ), leg. Bouchet and Strong ( MNHN IM-2013-53071 ) ; one specimen, 3 mm long (shell), isolate JC37, Morrison Australia Expedition (stn. TA21 ), leg. Bouchet and Strong ( MNHN IM-2013-53072 ) ; four specimens 3–3.2 mm long, isolates JC38A–D, Morrison Australia Expedition (stn. TA21 ), leg. Bouchet and Strong ( MNHN IM-2013-53073 ) .

Description

No live specimens were examined for this study. Body completely retractable inside of shell.

Shell up to 3 mm × 1.8 mm in size, tallest point near anterior margin, widest point near ventral margin; shell shape ovoid, dorsal margin regularly curved, ventral margin more flatened; anterior margin convex, regularly curved, slightly more flatened dorsally, posterior margin shorter, narrowing gradually ( Fig. 28G, H). Protoconch on lef valve of teleoconch, ~190 µm long, with 1.5 whorls ( Fig. 28K). Hinge on dorsal margin of shell, formed by flatened, corrugated, nearly straight area, margin on both valves; large, elongate condyloid tooth at posterior end of hinge on right valve, fossete-like depression on lef valve, at posterior end of hinge ( Fig. 28I, J). Shell translucent, with no visible markings or spots on shell surface, sof parts of body typically visible through it ( Fig. 28A–D) but not always ( Fig. 28E, F).

Adductor muscle anterior to highest point of shell, in line with widest point ( Fig. 29A). Adductor scar visible on shell ( Fig. 28H). Gill large, occupying almost height of body, posterior to adductor muscle, covering anterior portion of digestive gland. Anterior half of body in preserved specimens with a visible elongate head retractor muscle ( Fig. 29B). Pharyngeal bulb with a small pharyngeal appendage ( Fig. 29C). Penis elongate; distal end pointed, lacking a stylet ( Fig. 29D).

Radula with 19 teeth in descending limb and 4 fully formed teeth + 1 ghost tooth in ascending limb, in 2-mm-long specimen from Tasmania, Australia ( MNHN IM- 2013-53073) ( Fig. 30A). Active tooth ~140 μm long ( Fig. 30B), with sharp, bifid tip; blade elongate, with short row of elongate, delicate denticles near tip; base short, curved. Ascus containing a few very small pre-radular teeth ( Fig. 30C).

Remarks

Jensen (1993) introduced the name Berthelinia rotnesti Jensen, 1993 based on several specimens collected around Rotnest Island, Western Australia. Te body was described as pale, transparent green, with some white spots forming an indistinct band about halfway up the rhinophores, in addition to a marginal band; the mantle was described as green with white spots and brownish, with mostly radiating lines, including a row of alternating white and brown spots along the mantle edge, not quite reaching the umbo (Jensen 1993). Jensen (1993) noted that the shell and the position of the protoconch were variable, and described the radula as formed of blade-shaped teeth with fine lateral denticles on both sides of the blade, including four to six teeth (plus one incompletely formed ghost tooth) in the ascending limb, and 22–23 teeth in the descending limb. Based on the observation of a newly metamorphosed specimen, Jensen (1993) suggested that B. rotnesti appeared to have direct development.

Jensen (1993) indicated that B. rotnesti is anatomically similar to B. babai ; both species have bifid denticulate teeth and a similar penis; but according to Jensen (1993), the denticles of B. rotnesti are shorter than those of B. babai ; additionally, the morphology of the pharynx is different between these two species. Jensen (1993) also compared B. rotnesti with B. limax and suggested that they could represent ecotypes of one species. According to Jensen (1993), the small differences between B. rotnesti and B. limax could be explained by reduced gene flow owing to the direct development mode in the two species.

According to Burn (2006), B. rotnesti is the western cognate of, if not identical to, Midorigai australis , because both species have an obligate association with the green alga Caulerpa simpliciuscula . However, the external shell coloration of these two species is very different. Midorigai australis is completely covered with pale round spots, whereas B. rotnesti is nearly uniformly green. Wells and Bryce (1993) illustrated a live animal, possibly belonging to B. rotnesti from Western Australia, that was green with white spots on the head and neck, more densely covering the rhinophores, and the mantle edged by a line of white dots.

Based on the description by Jensen (1993), B. rotnesti appears to be different from other species here examined. Unfortunately, we had no access to specimens from Western Australia and therefore could not confirm the validity of this species with molecular data. Terefore, we maintain B. rotnesti as a valid species until more material becomes available. Although we did not have molecular data for B. rotnesti , this species is morphologically similar to other species within Edentellina here examined. Terefore, B. rotnesti is provisionally transferred to this genus.

In this study, we examined specimens from Tasmania with an external morphology and anatomy very similar to those in the original description of B. rotnesti . For example, the radular teeth and the penis here examined are very similar to the description of those organs by Jensen (1993). Jensen (1993: fig. 5A) described and illustrated the radular teeth of B. rotnesti as having bifid radular teeth with a short row of denticles near the apical end, very similar to the teeth here illustrated ( Fig. 30B); no other species of Edentellina here examined has similar characteristics. Jensen (1993; fig. 6A) described the penis of B. rotnesti as elongate and lacking a stylet, which is also similar to the material here examined; all other species from southern Australia studied to date have a penial stylet. Additionally, the pharyngeal bulb of the material here examined, with a dorsal pharyngeal appendage, is very similar to the descriptions and illustrations by Jensen (1993: fig. 4). Because of the morphological similarities between the specimens from Tasmania and the original description of B. rotnesti , we tentatively assign our specimens to this species. However, owing to the geographical distance between Tasmania and Rotnest Island (the type locality of B. rotnesti ) and the lack of genetic data for B./ E. rotnesti , we cannot dismiss the possibility that the specimens from Tasmania could represent an undescribed species.

EdenTellina darwini (Jensen, 1997)

Berthelinia daroini Jensen 1997a: 170–5 , figs 6–9. Type locality: Lee Point , Darwin, Australia.

Type material

Berthelinia daroini , holotype, complete specimen, 2.5 mm long ( NTM P6969 View Materials ), not examined; paratype, East Point , Darwin, Australia, one specimen 3.5 mm long ( ZMUC), not examined .

Remarks

Jensen (1997a) introduced the new species Berthelinia daroini Jensen, 1997 based on several specimens collected in Darwin, Australia. Jensen (1997a) described the shell as nearly elliptical, rounded at both ends, and not particularly narrow posteriorly; protoconch ~200 µm long, located just anterior to the posterior third of the shell length, with a variable angle of insertion. Live animals were described as different shades of green, with white rhinophoral tips, white motling scatered over the head and mantle, and brown pigment along the mantle margin, alternating with white patches ( Jensen 1997a). Te radula had six or seven fully formed teeth (and one ghost tooth) in the ascending limb, 20–30 in the descending limb, and ≤10 teeth, plus the rod-shaped pre-radular tooth in the coiled ascus; the teeth were blade-shaped, with fine lateral denticles and pointed tips. Jensen (1997a) compared the anatomy of B. daroini with that of B. typica and B. australis (the other two species whose anatomy was known) and concluded that the penial morphology and the radular teeth were all different. According to Jensen (1997a), the relatively large protoconch of B. daroini indicates that this species has direct development. Additionally, this species deposited an egg mass with 15 eggs with ‘large’ capsules ( Jensen 1997a), potentially indicating low dispersal ability. Terefore, it is likely that B. daroini might constitute a species endemic to northern Australia. Unfortunately, we had no access to specimens from this region. Although we did not have molecular data for B. daroini , this species is morphologically similar to other species in Edentellina here examined. Terefore, B. daroini is provisionally transferred to this genus.