Overview

Comprehensive Description

General Description

The prostomium is wider than it is long, trapezoid in shape and bilobated anteriorly. There is a facial fold, a feature that connects the anterio-ventral side of the prostomium to the dorsal part of the mouth, which is visible only in specimens with an invaginated pharynx. The palps are biarticulated, and the palpophore is ovoid, flattened and slightly longer than it is wide. The palpostyle is conical and shorter than the palpophore. There are three antennae: paired antennae that are ciliated, conical and five times longer than wide basally and ca. same length as the palpostyle. The median antenna is very short and hardly visible, inserted on the dorsal posterior part of the prostomium. Median antenna furrows are absent. Eyes are absent. Nuchal organs are not visible. The prostomium has an entire posterior end. The prostomium and palpophores are densely covered with small tufts of short cilia. Papillose peristominal membrane and lip glands are absent. There is an eversible pharynx with a folded aperture and with three to four paired conical papillae that are located more deeply.

The noto- and neuropodial lobes and setae are absent on segments 1 and 2. Anterior dorsal cirri are present on segments 1 and 2 with cirrophores that are elevated and not fused. The ventral cirri and enlarged on segments 1 and 2. The following parapodia are subbiramous with a reduced notopodia bearing long and weakly segmented dorsal cirri, and two - three aciculae with slightly curved tip but without extending setae. Ther is a slight segmentation of the dorsal cirri, which is more visible and longer than wide distally. There are enlarged dorsal cirri in segments 1-5 or 1-4, which are irregular in length. The length of the posterior dorsal cirri is irregular, with some being very short and other being very long. This is likely to be linked to a regeneration process. The segments posterior to segment 2 have ventral cirri that are smaller than the parapodia and without a cirriphore. There are ciliated bands on the dorsal part of the segments.

The neuropodium are well developed, with a postsetal lobe that is rounded at the apex. There are four aciculae with slightly curved tips and a spreading fascicle of numerous (>90) compounded setae with long needle-shaped, serrated blades, varying in length. In the lower fascicle there are ca. 60 falcigers with shorter serrated blades that end with a terminal hood.

The anal cirri are ventral and well developed, but shorter than the anterior dorsal cirri. There are no pygidial papillae, and the anus is dorsal.

(Desbruyeres & Toulmond, 1998)

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Distribution

Types were found on the surface of ice-like methane hydrate mounds in the Gulf of Mexico at 538 m depth (27°44.77`N, 91°13.33`W) (Desbruyeres & Toulmond, 1998).

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Physical Description

Type Information

Holotype for Hesiocaeca methanicola Desbruyères & Toulmond, 1998
Catalog Number: USNM 182243
Collection: Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology
Preparation: Alcohol (Ethanol)
Collector(s): C. Fisher
Year Collected: 1997
Locality: Green Canyon site, exposed gas hydrate, Louisiana, United States, Gulf of Mexico, North Atlantic Ocean
Depth (m): 538 to 538
Vessel: Edwin Link R/V
  • Holotype: Desbruyères, D. & Toulmond, A. 1998. Cah. Biol. Mar. 39: 93-96, figs.1-5.
Creative Commons Attribution 3.0 (CC BY 3.0)

© Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology

Source: National Museum of Natural History Collections

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Ecology

Habitat

Depth range based on 4 specimens in 1 taxon.
Water temperature and chemistry ranges based on 2 samples.

Environmental ranges
  Depth range (m): 538 - 587.5
  Temperature range (°C): 7.150 - 8.336
  Nitrate (umol/L): 29.021 - 30.171
  Salinity (PPS): 34.899 - 34.984
  Oxygen (ml/l): 2.846 - 3.108
  Phosphate (umol/l): 1.891 - 2.041
  Silicate (umol/l): 16.797 - 18.986

Graphical representation

Depth range (m): 538 - 587.5

Temperature range (°C): 7.150 - 8.336

Nitrate (umol/L): 29.021 - 30.171

Salinity (PPS): 34.899 - 34.984

Oxygen (ml/l): 2.846 - 3.108

Phosphate (umol/l): 1.891 - 2.041

Silicate (umol/l): 16.797 - 18.986
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Wikipedia

Hesiocaeca methanicola

Methane clathrate deposits in the ocean floor have been found to be inhabited by polychaete worms of the species Hesiocaeca methanicola. The worms colonize the methane ice and appear to survive by gleaning bacteria which in turn metabolize the clathrate.

In 1997, Charles Fisher, professor of biology at Pennsylvania State University, discovered the worm living on mounds of methane ice at a depth of half a mile (~800 m) on the ocean floor in the Gulf of Mexico.[1] Fisher reported that experiments with live specimens showed that mature worms could survive in an anoxic environment for up to 96 hours. The experiments also showed that the larvae were dispersed by currents, and died after 20 days if they did not find a place to feed.

References[edit]

  1. ^ C. R. Fisher, I.'R. MacDonald, R. Sassen, C. M. Young, S. A. Macko, S. Hourdez, R. S. Carney, S. Joye & E. McMullin (2000). "Methane ice worms: Hesiocaeca methanicola colonizing fossil fuel reserves". Naturwissenschaften 87 (4): 184–187. doi:10.1007/s001140050700. PMID 10840806. 
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Source: Wikipedia

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