Philometra

 

Contents

 

Rev: 10/03/2023

  Classification Biology and Ecology
Morphology and Anatomy Life Cycle
Return to Philometra Menu Ecosystem Functions and Services
Distribution Management
Return to Philometridae Menu Feeding  References
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Classification:

Chromadorea
  Chromadoria
   Rhabditida
Spirurina
              Dracunculoidea
               Philometridae

Philometra Costa, 1845

A genus of parasites reported from the ovaries and musculature of marine fish.

 

Originally this genus was described under the name of Filaria globiceps by Rudolphi, 1819, and later was transferred to Ichthyonema by Diesing, 1861. In 1845, Costa described a worm from Uranoscopus scaber which he named Philometra reticulatum. The type species, Filaria globiceps, being identical with Costa's worm, was synonymised with it by Railliet in 1916.  The name of the type species of the genus should have become Philometra reticulatum. However,  the type species name was specified as Philometra reticaudata by Railliet (1916) (note the change in species name). There was some confusion about whether there may have been a misprint in the species name and that it should be recticaudata.  However, P. reticaudata continues to be generally accepted usage.  (Rasheed, 1963).

A huge number of species of this genus (and of other gerera of fish parasites) have been described by Dr. Frantisek Moravec  of the Institute of Parasitology, Biology Centre of the Czech Academy of Sciences.

    Synonyms:
     

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Morphology and Anatomy:

Species identification of the genus  Philometra has been problematic as it was usauslly based on the morphology of large-sized females. However, scanning electron microscopical examinations of small philometrid males made the identification more reliable and indicated considerable species diversity in these nematodes (Moravec et al., 2016).

 

  • Body cylindrical with blunt, rounded or slightly tapering extremities.
  • Cuticle smooth.
  • Head with cephalic papillae. Outer circle arranged in groups of two, fused or double. Internal circle when present consists of four submedian papillae.
  • Esophagus with an anterior swelling, with oesophageal gland, with or without the ventriculus or the appendix.
  • Intestine terminating blindly.
  • No anus or vulva.
  • Ovaries opposed, uterus continuous.
  • Viviparous.
  • Body lengths range fro 3 to 30cm
  • Parasites of marine or fresh-water fishes.

 

 

Body size range for the species of this genus in the database - Click:

   

Males:  

  • In many of the species of the genus, males are unknown.
  • Equal or subequal spicules.
  • Gubernaculum present or absent.
  • Cloaca terminal.
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Distribution:

Gonad-infecting species of Philometra are widely distributed in the world's oceans. Many of the gonad-infecting species exhibit a high degree of host specificity (Moravec et al., 2016).. They sometimes also occur in brackish water.

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Feeding:

Parasites of marine fish. Species have been described from the gonads and intestinal cavities of host fish,  Parasitism of gonads may affect reproductive success of hosts. At least 27 species of Philometra are known as gonad parasites.

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Biology and Ecology:

Large-sized females of various species may range from a few cm to 1 m long, while males are much smaller, (2-5mm) (Moravec and Justine, 2008)

 

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Life Cycle:

All philometrids are ovoviviparous and after fertilization, females become very large as first stage larvae fill their uteri. In fully gravid females the vulva and anus atrophy in most philometrid genera. The first stage juveniles are dispersed nhen the female body bursts in contact with water.

Philometrids exhibit a marked  sexual dimorphism in which females are highly modiied  and considerably larger than the males. While males are usually 2-4 mm long, the conspeciic gravid  females may be several centimetres long and even and a length of  more than 1 meter has been reported for one unidentiied species of Philometra (Moravec and de Buron, 2013).

For Ecophysiological Parameters for this genus, click 
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Ecosystem Functions and Services:

 

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Management:

 
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References:

Moravec, F. and Justine, J-L. 2008. Some philometrid nematodes (Philometridae), including four new species of Philometra, from marine fishes off New Caledonia. Acta Parasitologica 53:369-381.

Moravec, F., de Buron, I., Baker, T.G., Gonzalez-Solis, D. 2008. Some gonad-infecting species of Philometra (Nematoda, Philometridae) from offshore fishes of South Carolina and Georgia, USA, including Philometra charlestonensis sp. nov. from the scamp Mycteroperca phenax. Acta Parasitologica, 54:382-391

Moravec, F. and Justine, J-L. 2009.. New data on dracunculoid nematodes from fi shes off New Caledonia, including four new species of Philometra (Philometridae) and Ichthyofi laria (Guyanemidae). Folia Parasitologica 56:129-142.

Moravec, F. Chaabane, A., Justine, J-L., Neifar, L. 2016. Two gonad-infecting species of Philometra (Nematoda: Philometridae) from groupers (Serranidae) off Tunisia, with a key to Philometra species infecting serranid gonads. Parasite 23,8 DOI: 10.1051/parasite/2016008

Moravec, F., de Buron, I.  2013. A synthesis of our current knowledge of philometrid nematodes, a  group of increasingly important  ish  parasites. Folia Parasitologica 60:81-101.

Rasheed, S. 1963. A revision of the genus Philometra Costa, 1845. J. Helminthol. 37:89-130..

 

 

Copyright 1999 by Howard Ferris.
Revised: October 03, 2023.