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First extant records of mermithid nematode parasitism of Auchenorrhyncha in Europe
Journal of Invertebrate Pathology 99 (2008) 351–353
Contents lists available at ScienceDirect
Journal of Invertebrate Pathology journal homepage: www.elsevier.com/locate/yjipa
Short Communication
First extant records of mermithid nematode parasitism of Auchenorrhyncha in Europe Alvin J. Helden * School of Biology and Environmental Science, University College Dublin, Dublin, Ireland Department of Life Sciences, Anglia Ruskin University, Cambridge, UK
a r t i c l e
i n f o
Article history: Received 27 April 2008 Accepted 1 May 2008 Available online 9 July 2008 Keywords: Mermithidae Delphacidae Cicadellidae Parasitism
a b s t r a c t Parasitic nematodes of the family Mermithidae were found within four specimens of Auchenorrhyncha from two families (Cicadellidae and Delphacidae). This appears to be the the first extant example of mermithid parasitism of Auchenorrhyncha in Europe. The insect hosts were collected from agricultural grassland field margins at three locations in Ireland during a farmland biodiversity study in 2007. Ó 2008 Elsevier Inc. All rights reserved.
1. Introduction Nematodes of the family Mermithidae are obligate parasites of invertebrates. Poinar (1975) gives details of their structural characteristics, biology, host range, effects on their hosts, as well as a key to the genera and information about the associated literature. Most mermithids have been found to be parasites of insects but they are also found in spiders, crustaceans, leeches, molluscs and other nematodes (Poinar, 1975). Within the sub-phylum Hexapoda, mermithids have been found in most groups including the springtails (Collembola), fleas (Siphonaptera) and true bugs (Hemiptera). They have been found in many families within the Hemiptera but acording to Poinar (1975) most of these are probably accidental infections. There are records of mermithid parasitism of Auchenorrhyncha from various areas of the world but, with the exception of an example discovered fossilised in Baltic amber, not in Europe (Poinar, 2001). In this paper the first extant examples of mermithid infection of Auchenorrhyncha in Europe are described. 2. Materials and methods During the summer of 2007 a multi-site survey of farmland biodiversity was carried out in three regions of Ireland: County Cork, County Offaly and the counties Sligo and Leitrim region. As part of this work, samples of arthropods were taken from field margins of * Address: Department of Life Sciences, Anglia Ruskin University, Cambridge, UK. Fax: +44 1223 417712. E-mail address: [email protected]. 0022-2011/$ - see front matter Ó 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.jip.2008.05.005
agricultural grasslands using a Vortis suction sampler (Arnold, 1994). All arthropods were preserved in 70% ethanol prior to sorting into different arthropod orders.
3. Results and discussion While sorting samples from counties Sligo and Leitrim four adult Auchenorrhyncha specimens were discovered to contain parasitic nematodes of the family Mermithidae. The Auchenorrhyncha were of two species, the leafhopper Macustus grisescens (Zetterstedt), (family Cicadellidae), and the planthopper Javesella dubia (Kirschbaum) (family Delphacidae). In the M. grisescens and two of the J. dubia, the mermithids had partially emerged from the host, whilst in the other J. dubia the nematode was clearly visible through the abdominal wall of the insect. Further details of the four specimens are given as follows : Specimen 1 Host Date collected Location Description
Specimen 2 Host Date collected Location
Macustus grisescens (Cicadellidae) $ (Fig. 1a) 5.6.07 Ballinamore, County Leitrim, Ireland (H1112) Mermithid partially emerged from a relatively restricted exit point on the ventral side of abdominal segments three and four Javesella dubia (Delphacidae) # (Fig. 1b) 25.6.07 Collooney, County Sligo (G6823)
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A.J. Helden / Journal of Invertebrate Pathology 99 (2008) 351–353
Fig. 1. Mermithid nematodes found in specimens of (a) a female Macustus grisescens from Ballinamore, County Leitrim, (b) a male Javesella dubia from Collooney, County Sligo and (c and d) female J. dubia from Collooney, County Sligo (scale bars = 1 mm).
Description
Specimen 3 Host Date collected Location Description Specimen 4 Host Date collected Location Description
Abdominal wall of delphacid partially disintegrated to reveal mermithid coiled within the abdomen Javesella dubia (Delphacidae) $ (Fig. 1c) 25.6.07 Collooney, County, Sligo (G6924) Abdominal wall intact but in places translucent, through which coiled mermithid clearly visible Javesella dubia (Delphacidae) $ (Fig. 1d) 27.6.07 Collooney, County, Sligo (G6924) Mermithid partly emerged from side of abdomen, which shows considerable damage around the emergence area
The M. grisescens and the J. dubia specimen 4 have both been placed in the Museum of Natural History, Dublin. The other two specimens have been retained by the author. The four specimens of mermithid parasitised Auchenorrhyncha appear to be the first modern examples reported from Europe, with the only previous record being from an Achilidae planthopper fossilised in Baltic amber (Poinar, 2001, 1975). Extant mermithid parasitism in planthoppers (Superfamily Fulgoroidea), the group which includes the Delphacidae, is particularly unusual. It has been found in Asia, the USA and Australia before but seems to occur much less frequently than in other Auchenorrhyncha (Poinar, 2001). Indeed Sperka and Freytag (1975), in their survey of Auchenorrhyncha hosts of mermithids in Kentucky, USA, found mermithids in only three species of Delphacidae but 26 species of Cicadellidae (Superfamily Cicadoidea). The leafhopper species they
listed included some from the sub-family Deltocephalinae, the same sub-family as the M. grisescens found in County Leitrim. Unfortunately due to the nature of the sampling methodology, the Auchenorrhyncha specimens were preserved in 70% ethanol almost immediately. Consequently the mermithids were preserved within or in the process of emerging from their hosts. This means that they were juveniles and not the adult stage which would be needed to identify the mermithid species (Poinar, 1975). Therefore it has not been possible to identify the mermithids to species. The three locations at which mermithid parasitism was discovered in Ireland were similar in character in that they were all damp, low-intensity grazed agricultural grasslands. All contained plants typical of damp conditions, such as Juncus effusus L., and meadowsweet (Filipendula ulmaria (L.) Maxim.). The soil was noticeably wet in places at Ballinamore and at the Collooney site, where J. dubia specimens 3 and 4 were found, and there were plants typical of marshland, with marsh bedstraw (Galium palustre L.), marsh ragwort (Senecio aquaticus Hill), flote grass (Glyceria fluitans (L.) R. Br.) and yellow iris (Iris pseudacorus L.) present at one or both sites. Moisture levels may be a particularly important factor in the incidence of mermithid infection as the eggs and adults, which both occur outside the host, are susceptible to desiccation (Poinar, 1975). The dampness of the sample sites, together with the normally relatively high level of annual precipitation in Ireland and the unusually high rainfall of the summer of 2007 (Met Éireann, 2008), may have combined to provide the ideal conditions to enable mermithid parasitsim in the Auchenorrhyncha collected. Perhaps the lack of previous records in Europe may reflect the rarity of such parasitism, although the lack of any specific effort to find it, and the relatively low-level of interest in Auchenorrhyncha more generally may also be factors. In their survey, Sperka and Freytag (1975) found a mermithid parasitism rate of only 0.3% from 60,000 Auchenorrhyncha specimens, which may be indicative
A.J. Helden / Journal of Invertebrate Pathology 99 (2008) 351–353
of its rarity. Their work also indicated that mermithid parasitism may not be very host specific. Poinar (1975) suggested that some mermithid species could be considered ecological-dependent parasites that parasitise insects of different families that occur within their environment. In other suction samples from Irish agricultural grasslands as part of the described farm survey and related previous samples since 2002, mermithids have been found not infrequently preserved in the process of emerging from spiders (Poinar, 1985) but never from insects. At the present level of knowledge it is not possible to know whether the mermithid parasitism of Auchenorrhyncha found in 2007 represented a regular parasitic association or was more of an opportunistic relationship, made more likely by the dampness of the sites and the unusually wet weather. Acknowledgments The author thanks George Poinar for confirming that the nematodes found were indeed mermithids and for his encouragement to produce this short communication. Thanks must also go to the
353
three farmers for allowing access to their land. Annette Anderson and Kristi Leydon formed part of the insect collecting team, Helen Sheridan both identified the plant species and, together with Barry McMahon, organised the site selection. The work, funded by the Irish Department of Agriculture, Food and Rural Development’s Research Stimulus Fund (2006), formed part of the Agri-Baseline Project (RFS 06 376). References Arnold, A.J., 1994. Insect suction sampling without nets, bags or filters. Crop Protection 13, 73–76. Met Éireann, 2008. The weather of 2007. Summary Report issued by the Climatology and Observations Division of Met Éireann on 2nd January 2008. www.met.ie/climate. Poinar, G., 2001. Heydenius brownii sp. n. (Nematoda: Mermithidae) parasitising a planthopper (Homoptera: Achilidae) in Baltic amber. Nematology 3, 753–757. Poinar, G.O., 1975. Entomogenous nematodes. A manual and host list of insect– nematode associations. E.J. Brill, Leiden. Poinar, G.O., 1985. Mermithid (Nematoda) parasites of spiders and harvestmen. Journal of Arachnology 13, 121–128. Sperka, C., Freytag, P.H., 1975. Auchenorrhynchus hosts of mermithid nematodes in Kentucky. Transactions of the Kentucky Academy of Science 36, 57–62.
Contents lists available at ScienceDirect
Journal of Invertebrate Pathology journal homepage: www.elsevier.com/locate/yjipa
Short Communication
First extant records of mermithid nematode parasitism of Auchenorrhyncha in Europe Alvin J. Helden * School of Biology and Environmental Science, University College Dublin, Dublin, Ireland Department of Life Sciences, Anglia Ruskin University, Cambridge, UK
a r t i c l e
i n f o
Article history: Received 27 April 2008 Accepted 1 May 2008 Available online 9 July 2008 Keywords: Mermithidae Delphacidae Cicadellidae Parasitism
a b s t r a c t Parasitic nematodes of the family Mermithidae were found within four specimens of Auchenorrhyncha from two families (Cicadellidae and Delphacidae). This appears to be the the first extant example of mermithid parasitism of Auchenorrhyncha in Europe. The insect hosts were collected from agricultural grassland field margins at three locations in Ireland during a farmland biodiversity study in 2007. Ó 2008 Elsevier Inc. All rights reserved.
1. Introduction Nematodes of the family Mermithidae are obligate parasites of invertebrates. Poinar (1975) gives details of their structural characteristics, biology, host range, effects on their hosts, as well as a key to the genera and information about the associated literature. Most mermithids have been found to be parasites of insects but they are also found in spiders, crustaceans, leeches, molluscs and other nematodes (Poinar, 1975). Within the sub-phylum Hexapoda, mermithids have been found in most groups including the springtails (Collembola), fleas (Siphonaptera) and true bugs (Hemiptera). They have been found in many families within the Hemiptera but acording to Poinar (1975) most of these are probably accidental infections. There are records of mermithid parasitism of Auchenorrhyncha from various areas of the world but, with the exception of an example discovered fossilised in Baltic amber, not in Europe (Poinar, 2001). In this paper the first extant examples of mermithid infection of Auchenorrhyncha in Europe are described. 2. Materials and methods During the summer of 2007 a multi-site survey of farmland biodiversity was carried out in three regions of Ireland: County Cork, County Offaly and the counties Sligo and Leitrim region. As part of this work, samples of arthropods were taken from field margins of * Address: Department of Life Sciences, Anglia Ruskin University, Cambridge, UK. Fax: +44 1223 417712. E-mail address: [email protected]. 0022-2011/$ - see front matter Ó 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.jip.2008.05.005
agricultural grasslands using a Vortis suction sampler (Arnold, 1994). All arthropods were preserved in 70% ethanol prior to sorting into different arthropod orders.
3. Results and discussion While sorting samples from counties Sligo and Leitrim four adult Auchenorrhyncha specimens were discovered to contain parasitic nematodes of the family Mermithidae. The Auchenorrhyncha were of two species, the leafhopper Macustus grisescens (Zetterstedt), (family Cicadellidae), and the planthopper Javesella dubia (Kirschbaum) (family Delphacidae). In the M. grisescens and two of the J. dubia, the mermithids had partially emerged from the host, whilst in the other J. dubia the nematode was clearly visible through the abdominal wall of the insect. Further details of the four specimens are given as follows : Specimen 1 Host Date collected Location Description
Specimen 2 Host Date collected Location
Macustus grisescens (Cicadellidae) $ (Fig. 1a) 5.6.07 Ballinamore, County Leitrim, Ireland (H1112) Mermithid partially emerged from a relatively restricted exit point on the ventral side of abdominal segments three and four Javesella dubia (Delphacidae) # (Fig. 1b) 25.6.07 Collooney, County Sligo (G6823)
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A.J. Helden / Journal of Invertebrate Pathology 99 (2008) 351–353
Fig. 1. Mermithid nematodes found in specimens of (a) a female Macustus grisescens from Ballinamore, County Leitrim, (b) a male Javesella dubia from Collooney, County Sligo and (c and d) female J. dubia from Collooney, County Sligo (scale bars = 1 mm).
Description
Specimen 3 Host Date collected Location Description Specimen 4 Host Date collected Location Description
Abdominal wall of delphacid partially disintegrated to reveal mermithid coiled within the abdomen Javesella dubia (Delphacidae) $ (Fig. 1c) 25.6.07 Collooney, County, Sligo (G6924) Abdominal wall intact but in places translucent, through which coiled mermithid clearly visible Javesella dubia (Delphacidae) $ (Fig. 1d) 27.6.07 Collooney, County, Sligo (G6924) Mermithid partly emerged from side of abdomen, which shows considerable damage around the emergence area
The M. grisescens and the J. dubia specimen 4 have both been placed in the Museum of Natural History, Dublin. The other two specimens have been retained by the author. The four specimens of mermithid parasitised Auchenorrhyncha appear to be the first modern examples reported from Europe, with the only previous record being from an Achilidae planthopper fossilised in Baltic amber (Poinar, 2001, 1975). Extant mermithid parasitism in planthoppers (Superfamily Fulgoroidea), the group which includes the Delphacidae, is particularly unusual. It has been found in Asia, the USA and Australia before but seems to occur much less frequently than in other Auchenorrhyncha (Poinar, 2001). Indeed Sperka and Freytag (1975), in their survey of Auchenorrhyncha hosts of mermithids in Kentucky, USA, found mermithids in only three species of Delphacidae but 26 species of Cicadellidae (Superfamily Cicadoidea). The leafhopper species they
listed included some from the sub-family Deltocephalinae, the same sub-family as the M. grisescens found in County Leitrim. Unfortunately due to the nature of the sampling methodology, the Auchenorrhyncha specimens were preserved in 70% ethanol almost immediately. Consequently the mermithids were preserved within or in the process of emerging from their hosts. This means that they were juveniles and not the adult stage which would be needed to identify the mermithid species (Poinar, 1975). Therefore it has not been possible to identify the mermithids to species. The three locations at which mermithid parasitism was discovered in Ireland were similar in character in that they were all damp, low-intensity grazed agricultural grasslands. All contained plants typical of damp conditions, such as Juncus effusus L., and meadowsweet (Filipendula ulmaria (L.) Maxim.). The soil was noticeably wet in places at Ballinamore and at the Collooney site, where J. dubia specimens 3 and 4 were found, and there were plants typical of marshland, with marsh bedstraw (Galium palustre L.), marsh ragwort (Senecio aquaticus Hill), flote grass (Glyceria fluitans (L.) R. Br.) and yellow iris (Iris pseudacorus L.) present at one or both sites. Moisture levels may be a particularly important factor in the incidence of mermithid infection as the eggs and adults, which both occur outside the host, are susceptible to desiccation (Poinar, 1975). The dampness of the sample sites, together with the normally relatively high level of annual precipitation in Ireland and the unusually high rainfall of the summer of 2007 (Met Éireann, 2008), may have combined to provide the ideal conditions to enable mermithid parasitsim in the Auchenorrhyncha collected. Perhaps the lack of previous records in Europe may reflect the rarity of such parasitism, although the lack of any specific effort to find it, and the relatively low-level of interest in Auchenorrhyncha more generally may also be factors. In their survey, Sperka and Freytag (1975) found a mermithid parasitism rate of only 0.3% from 60,000 Auchenorrhyncha specimens, which may be indicative
A.J. Helden / Journal of Invertebrate Pathology 99 (2008) 351–353
of its rarity. Their work also indicated that mermithid parasitism may not be very host specific. Poinar (1975) suggested that some mermithid species could be considered ecological-dependent parasites that parasitise insects of different families that occur within their environment. In other suction samples from Irish agricultural grasslands as part of the described farm survey and related previous samples since 2002, mermithids have been found not infrequently preserved in the process of emerging from spiders (Poinar, 1985) but never from insects. At the present level of knowledge it is not possible to know whether the mermithid parasitism of Auchenorrhyncha found in 2007 represented a regular parasitic association or was more of an opportunistic relationship, made more likely by the dampness of the sites and the unusually wet weather. Acknowledgments The author thanks George Poinar for confirming that the nematodes found were indeed mermithids and for his encouragement to produce this short communication. Thanks must also go to the
353
three farmers for allowing access to their land. Annette Anderson and Kristi Leydon formed part of the insect collecting team, Helen Sheridan both identified the plant species and, together with Barry McMahon, organised the site selection. The work, funded by the Irish Department of Agriculture, Food and Rural Development’s Research Stimulus Fund (2006), formed part of the Agri-Baseline Project (RFS 06 376). References Arnold, A.J., 1994. Insect suction sampling without nets, bags or filters. Crop Protection 13, 73–76. Met Éireann, 2008. The weather of 2007. Summary Report issued by the Climatology and Observations Division of Met Éireann on 2nd January 2008. www.met.ie/climate. Poinar, G., 2001. Heydenius brownii sp. n. (Nematoda: Mermithidae) parasitising a planthopper (Homoptera: Achilidae) in Baltic amber. Nematology 3, 753–757. Poinar, G.O., 1975. Entomogenous nematodes. A manual and host list of insect– nematode associations. E.J. Brill, Leiden. Poinar, G.O., 1985. Mermithid (Nematoda) parasites of spiders and harvestmen. Journal of Arachnology 13, 121–128. Sperka, C., Freytag, P.H., 1975. Auchenorrhynchus hosts of mermithid nematodes in Kentucky. Transactions of the Kentucky Academy of Science 36, 57–62.