Sessiline ciliophorans associated with Haliotis species (Mollusca: Archaeogastropoda) from the South Coast of South Afica

Abstract

English: Abalone, locally known as perlemoen, are herbivorous marine gastropods with all species in one genus, Haliotis Linneaus, 1758. Abalone have been commercially exploited since ancient times. Along the southern African coast, the genus Haliotis comprises six endemic species. Surveys carried out from 1995 to 1999 at the De Hoop Nature Reserve along the south coast of South Africa, revealed the presence of scyphidiid peritrichs, of the genus Mantoscyphidia Jankowski, 1980, occurring in abundance on the gills of Haliotis spadicea Donovan, 1808 and H. midae Linnaeus, 1758. These were described as two new species, i.e. M spadiceae sp. nov. and M midae sp. nov. The mantoscyphidians in turn hosted ellobiophryids of the genus Caliperia Laird, 1953, which was also described as a new species, Caliperia perlemoenae sp. nov., occurring on both mantoscyphidian species. During the study a perlemoen aquaculture facility, Danger Point Abalone Farm, was also visited, specimens of H. midae were examined and found to harbour the same species of scyphidiid peritrich and caliperid than H. midae collected from the De Hoop Nature Reserve. In the present study, severe infections of redial, cercarial and metacercarial stages and a few adult specimens of a digenean trematode were also found in the digestive gland of Haliotis spadicea as well as on the gill filaments. In order to elucidate the symbiont/host associations field experiments and histopathological examinations were carried out. These led to the conclusions that the host/scyphidiid peritrich associations are most likely not parasitic. In the case of the mantoscyphidianlcaliperid association, no clear evidence was found that the caliperids are pathogenic to their mantoscyphidian hosts. On the other hand, the trematodes could be potential pathogens since they can cause tissue destruction and affect the reproductive organs in the host.

Afrikaans: Verteenwoordigers van die genus Haliotis Linnaeus, 1758 is mariene herbivore met ses endemiese spesies versprei rondom die Suid-Afiikaanse kus. Die kommersiële verbruik van spesies in die genus Haliotis is al vir baie eeue bekend. Opnames wat tydens 1995- 1999 by De Hoop Natuur Reservaat langs die suidkus van Suid-Afiika uitgevoer is, het die voorkoms van groot getalle sessiele siliofore wat aan die genus Mantoscyphidia Jankowski, 1980, behoort, op die kieue van Haliotis spadicea Donovan, 1808 en H. midae Linnaeus, 1758 aangetoon. Twee nuwe spesies, naamlik M. spadiceae sp. nov. en M midae sp. nov. is beskryf. Verteenwoordigers van die genus Mantoscyphidia speel op hul beurt gasheer vir siliofore van die genus Caliperia Laird, 1953, wat ook as 'n nuwe spesie beskryf is, naamlik Caliperia perlemoenae sp. nov. Tydens die studie is 'n perlemoen-akwakultuur fasiliteit, "Danger Point Abalone Farm", besoek. Haliotis midae individue is ondersoek en daar is gevind dat hulle dieselfde sessiele siliofoor (M midae) en Caliperia spesie, as H. midae van die De Hoop Natuur Reservaat op hul kieue het. Tydens die huidige studie is massiewe infeksies van redia, serkarië en metaserkariestadiums, sowel as 'n paar volwasse digenetiese trematode in die verteringskiier asook op die kieue van H. spadicea gevind. Ten einde lig te werp op die simbiont/gasheer verwantskappe, is veldeksperimente sowel as histopatologiese ondersoeke uitgevoer. Hieruit is daar tot die gevolgtrekking gekom dat die gasheer/sessiele siliofoor assosiasie heelwaarskynlik nie parasities van aard is nie. Geen duidelike bewyse is gevind wat daarop kon dui dat die verteenwoordigers van die genus Caliperia patogenies vir hul sessiele siliofoor gashere is nie. Daarenteen kan die trematood potensieel patogenies wees omdat hulle weefselvernietiging kan veroorsaak en die voortplantingsorgane van die gasheer nadelig kan affekteer.