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Phylum Annelida
Class Oligochaeta
Family Tubificidae
Subfamily Phallodrilinae

Phallodriloides macmasterae (Erséus, 1986)



Synonomy: Phallodrilus macmasterae Erséus, 1986

Taxonomic Characterization: Phallodriloides macmasterae is almost colorless and transparent when alive. The prostomium is conical and rounded. Inconspicuous secondary annulation is present. There are somatic setae bifid with upper tooth somewhat thinner and shorter than lower and with thin subdental ligament. There is 1 penial setae on each side that are somewhat sigmoid, and ectally single-pointed and hooked. The male pores are paired in line with ventral setae. There are spermathecal pores paired in lateral lines, anteriorly in an X. The pharyngeal glands are poorly developed in available material. In the male, the vas deferens are 5-8 micrometers wide, coiled, and several times longer than the atrium, entering apical end of atrium. The vas deferens has distinct muscular lining along the ectal part. The atruim is small and spindle-shaped with thick outer lining of muscles and a granulated and ciliated inner epithelium. The posterior prostate gland is attached to the middle-to-ectal part of the atrium. Both prostates are small and compact. The spermatacae is slender with short indistinct ducts opening into small invaginations of body wall. The sperm are random in ampullae (Erséus, 1986).

Disposition of Specimens: Type specimens have been deposited in the United States Museum of Natural History: male holotype (USNM 98777) and paratype (USNM 98778).

Ecological Classification: Stygobitic

Size: Total body length of adult male greater than 3.7 mm with more than 29 segments.

Number of Species in Genus: At least 4

Genus Range:

  • Bermuda: Phallodriloides macmasterae Erséus, 1986
  • Surinam: Phallodriloides lobatus

Species Range: Known only from Prospero's Cave near Castle Harbour, Bermuda (Erséus, 1986).

Closest Related Species: Phallodriloides macmasterae was originally assigned to P. exiguus, but can be distinguished from that species by its heavily muscular male ducts and lateral position of the spermathecal pores. This new species is also closely related to P. lobatus, known from the continental slope off Surinam. The three aforementioned species are similar in that they all have penial setae of the same appearance and number (1-2 at each side of worm), and their spermathecae are very slender. P. macmasterae is distinct as it has thick muscular lining on its vas deferentia and atria (Erséus, 1986).

Habitat: Anchialine limestone caves

Ecology: P. macmasterae specimens were collected from extremely fine clay interspersed with macroscopic clumps of delicate filamentous blue-green algae and debris at 12 m water depths in Prospero's Cave. This cave is artificially illuminated with a salinity of 35.9 ppt, and a pH of 8.05. The water of the cave has subterranean connections with the sea.

Evolutionary Origins: The closely relationship between P. macmasterae and the deep water P. lobatus gives further support to the view that there are significant ties between the marine cave faunas and those of the deep sea.

Conservation Status: This species is listed as critically endangered (IUCN, 1996).

References:

  • Erséus, C. 1986. A new species of the Phallodrilus (Oligochaeta, Tubificidae) from a limestone cave on Bermuda. Sarsia, 71:7-9, 1 figure.
  • Hart, C.W. Jr., R.B. Manning and T.M. Iliffe. 1985. The fauna of Atlantic marine caves: evidence of dispersal by sea floor spreading while maintaining ties to deep waters. Proceedings of the Biological Society of Washington, 98:288-292.
  • IUCN, 1996. The 1996 IUCN Red List of Threatened Animals. Gland, IUCN, 368 pages.

Links:

Contributor: Christopher Erséus, Swedish Museum of Natural History


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