Tijdschrift van de Nederlandse Malacologische Vereniging

Volume77 (4-6)

2013

BasteriaInhoudsopgaveBasteria volume 77(4-6): 41-96

Kronenberg, G.C. A specimen of Lobatus gigas (Caenogastropoda, Strombidae)with an abnormal eye .................................................................................................

Ter Poorten, J.J. Revision of the Recent species of the genus Nemocardium Meek,1876 (Bivalvia, Cardiidae), with the descriptions of three new species ..............

Gittenberger, A., Schrieken, N., Coolen, J.W.P. & Gittenberger, E. Shipwrecks,ascidians and Modiolarca subpicta (Bivalvia, Mytilidae, Musculinae) ..................

Páll-Gergely, B. & Coltro Junior, J. The southernmost localities of Xenophoraconchyliophora (Born, 1780) (Caenogastropoda, Xenophoridae) ...........................

Gittenberger, E. Spelaeodiscus dejongi (Gastropoda, Pulmonata, Spelaeodiscidae),its classification hesitantly confirmed......................................................................

Landau, B. & Vermeij, G.J. A new species of Pugilina (Gastropoda,Caenogastropoda, Melongeninae) from the Lower MioceneCantaure Formation of Venezuela............................................................................

Date of publication: 24-XII-2013

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RedactieProf. Dr E. Gittenberger (editor-in-chief),

Dr B. Kokshoorn (layout editor),G.C. Kronenberg (editor).

Overige redacteurenDr A.C. van Bruggen (niet-mariene mollusken),

Dr Th.C.M. Kemperman (terrestrische en mariene mollusken),Prof. Dr G. van der Velde (zoetwater mollusken),

Prof. Dr G. Vermeij (fossiele en recente mariene mollusken),Dr F. Wesselingh (fossiele mollusken).

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A specimen of the Caribbean species Lobatus gigas fromBonaire Island with an aberrant right eye is reported uponand illustrated. The cause of this aberration remains un-known.

Key words: Gastropoda, Lobatus, eyes, aberration, teratology.

Introduction

Animals of the gastropod family Strombidae are well knownfor their conspicuous eyes at the distal tip of long eyestalks.Already Rumphius (1705) noted “(…) close behind it, onewill see two short little Horns, with eyes on them, like Crabsdo.” (translation adopted from Beekman,1999: 158). Abbott(1960) noted that these eyes are “(…) usually adorned withcircular rings of yellow, orange or red colour.”. These pig-mented rings encircle the pupil of the eye of which the outeredge is defined by the innermost circle (Seyer, 1994), and is

here referred to as the iris (following Seyer, 1994, 1998). Itshould be noted however that this iris, nor the eye itself, ishomologous with the iris in vertebrates. Kronenberg & Berk-hout (1984: fig. 12) illustrated a number of eyes of strombids.Besides the colours mentioned by Abbott (1960), the figuresin Kronenberg & Berkhout (1984) also show black, whiteand violet circles. Based on a small number of then existingcolour images of living specimens Kronenberg & Berkhout(1984: 272, caption fig. 12) concluded that these colouredrings were different between, yet constant within everyspecies.

Apart from Strombidae, the living species of the strom-boidean families Rostellariidae (see e.g. figures in Man in ‘tVeld & Visser, 1998), Seraphsidae (see e.g. Jung &Abbott,1967: pl. 319, pl. 321 bottom figure) and Rimellidae (pers.obs.) also have their eyes at the tip of long peduncles. This isa synapomorphy of these families within the Stromboidea,setting these apart fromAporrhaidae and Struthiolariidae.Within this clade the families Strombidae and Rimellidaehave a sinus in the abapical part of the outer lip, the

A specimen of Lobatus gigas (Caenogastropoda, Strombidae)with an abnormal eye

Gijs C. KronenbergNaturalis Biodiversity Center, P.O. Box 9517, NL-2300 RA Leiden, The Netherlands;

gijs.kronenberg@naturalis.nl; adsl711249@telfort.nl

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so-called strombid notch that serves as a peeping hole forthe right eye.

An aberrant eye

On 19 August 2013, around noon, Ms Vanessa Costa wasscuba-diving with a group in the ‘White Hole’ (also knownas the Blue Hole), a dive site at the eastern coast of Bonaire,Dutch Caribbean at 12°05’39”N 68°13’40”W.

This dive site is located in front of Lac Bay, a very shal-low lagoon that merges into a mangrove forest. The WhiteHole is an oblong pit approximately 50 x 100 metres, with amaximum depth of about 13 metres. On that day the watertemperature was 28°C. At a depth of 12 metres, she encoun-tered a specimen of Lobatus gigas (Linnaeus, 1758) (Fig. 1).Upon closer examination this specimen had an aberrantright eye in that there were two miniature eyes on the tip ofthe right eye stalk, distinctly smaller than the normal lefteye, with the two irises touching one another, not overlap-ping (Fig. 2).

Discussion

Gréton et al. (1993) examined the influence of retinoic acidduring the early development of some fresh water gas-tropods. As a result, defects on the eyes were observed thatranged from a slight reduction in size to complete absence ofthe eyes. They also observed that one eye of the embryocould be affected more severely than the other (Gréton et al.,1993: 358). From these observations it is clear that at thepresence of a substance, that in normal conditions does notoccur in water, can affect the development of eyes in gas-tropods. Although the duplication of one of the eyes as inthe case reported here was not observed by Gréton et al.(1993), I do not exclude the possibility that some substance(or a combination of substances) might cause an aberration

as reported here. There are also other explanations, such asdamage to the soft tissues (i.e. the eyestalk) at some point inthe development of the animal or a genetic defect (whetheror not exacerbated by inbreeding).

The specimen was not collected and has not been exam-ined any further.

Despite this aberration, the animal grew to full maturityas one can judge from the complete and already slightlythickened outer lip. Therefore it cannot be excluded that theanimal will reproduce or has already reproduced. A surveyof the population of Lobatus gigas around the Island ofBonaire might provide an answer to the causes of thisstrange aberration.

Acknowledgements

Many thanks are due to ms Vanessa Costa, Leiden, TheNetherlands, for sending images of the specimen discussedherein and providing detailed information about the local-ity; Dr. Bas Kokshoorn, for first bringing this specimen tomy attention and drawing my attention to the Gréton et al.paper.

Dr. Menno Schilthuizen and Dr. A.C. van Bruggen, bothNaturalis Biodiversity Center, read the manuscript and pro-vided useful remarks for improvement.

References

Abbott, R.T., 1960. The genus Strombus in the Indo-Pacific. — Indo-Pa-cific Mollusca 1 (2): 33-146.

Beekman, E.M., 1999. The Amboinese curiosity cabinet Gerogius Ever-hardus Rumphius: i-cxii, 1-567. New Haven and London.

Créton, R., Zwaan, G. & Dohmen, R., 1993. Specific developmental de-fects in molluscs after treatment with retinoic acid during gastrula-tion. — Development, Growth & Differentiation 35 (3): 357-364.

Jung, P. & Abbott, R.T., 1967. The genus Terebellum (Gastropoda: Strom-bidae). — Indo Pacific Mollusca 1 (7): 445-454.

Kronenberg, G.C. & Berkhout, J., 1984. Strombidae. — Vita Marina 31(1-6): sect. buikpotigen 263-362.

Man in ‘t Veld, L.A. & Visser, G.J., 1998. On the status of Tibiamelanocheilus (Adams, 1854) and some notes on the appearance ofits shell. — La Conchiglia 288: 51-56, 60.

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Kronenberg, G.C. – A specimen of Lobatus gigas with an abnormal eye

Figs 1, 2. Lobatus gigas White Hole, Bonaire Island, 19.VIII.013.1, Adult specimen encountered at 12 m depth; 2, Detail of Fig. 1, noteaberrant right eye. Photo’s: Vanessa Costa.

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Rumphius, G.E., 1705. D’Amboinsche Rariteitkamer, Behelzende eeneBeschryvinge van allerhande zoo weeke als harde Schaalvisschen,te weeten raare Krabben, Kreeften, en diergelyke Zeedieren, alsmede allerhande Hoorntjes en Schulpen, die men in d’AmboinscheZee vindt: Daar beneven zommige Mineraalen, Gesteenten, en soor-ten van Aarde, die in d’Amboinsche, en zommige omleggende Ei-landen gevonden worden. Verdeelt in drie Boeken, (…). 1-340, pls.I-XL, index, Amsterdam.

Seyer, J.-O., 1994. Structure and optics of the eye of the Hawk-WingConch, Strombus raninus (L.). — Journal of Experimental Zoology268: 200-207.

Seyer, J.-O., 1998. Comparative optics of prosobranch eyes: 1-86. — PhDThesis, Lund University, Sweden.

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