Dactylopodolidae

Dactylopodola baltica, from Todaro & Rocha (2003). Scale bar = 50 µm.

Belongs within: Gastrotricha.

I can’t think of a clever title involving gastrotrichs
Published 27 August 2007
Macrodasyidan (left) and chaetonotidan gastrotrichs, from Hochberg & Litvaitis (2000).

In this section, we dive underwater and scrabble in the mud in search of the gatrotrich family Dactylopodolidae. Just kind of rolls off the tongue, doesn’t it?

Gastrotrichs are minute (usually less than 1 mm) aquatic ‘worms’ that are one of those horribly obscure animal phyla that usually get allocated half a page in hidden corners of the textbooks, if they’re lucky. They are inhabitants of the interstitial—they live among and between the grains of sand and mud, where they hunt down microscopic algae and protozoa by crawling about on their ciliated bellies. There are two distinct orders of gastrotrichs; the illustration above from Hochberg & Litvaitis (2000) shows an idealised representative from each. The animal of the right belongs to Chaetonotida, which have a fairly consistent bowling pin shape, covering of spined scales and two long posterior furcae each bearing a single adhesive tube. The more varied Macrodasyida, on the left, generally have a more elongated body shape and a greater number of adhesive tubes. The Macrodasyida are simultaneous or alternating hermaphrodites whereas Chaetonotida have a higher diversity of reproductive strategies, including a number of parthenogenetic species. Macrodasyida are almost exclusively marine, with only a couple of exceptions; Chaetonotida are both marine and freshwater.

The Dactylopodolidae are members of the Macrodasyida. Phylogenetic studies using both morphological and molecular data agree that the Dactylopodolidae are the basalmost family of macrodasyids, which makes them potentially very significant for gastrotrich phylogeny (Hochberg & Litvaitis 2000, 2001; Todaro et al. 2003). They seem to have a fairly generalised body-plan—no extravagant ornamentation, relatively short body with a deeply lobed posterior, while the adhesive tubes are generally restricted to the posterior part of the body (Hummon 1974). Their basal position is indicated by a plesiomorphic musculature and monociliated epidermis (Hochberg & Litvaitis 2001).

Dactylopodola typhle, from the Senckenberg Forschungsinstitut und Naturmuseum.

The Dactylopodolidae contains three to five genera (depending on whether or not the contentious genera Xenodasys and Chordodasys are included). The largest genus is Dactylopodola. The picture above comes from the Senckenberg Forschungsinstitut und Naturmuseum and shows Dactylopodola typhle; the linked site also has a close-up of its head that I recommend taking a look at. Get a good look—these appear to be the only images of Dactylopodolidae sensu stricto available on the web!

Systematics of Dactylopodolidae
<==Dactylopodolidae
|--+--Dendropodola Hummon et al. 1993HL01
| `--Dendrodasys Wilke 1954HL01
| |--D. affinis Wilke 1954R-M86
| |--D. gracilis Wilke 1954R-M86
| |--D. pacificus Schmidt 1974R-M86
| `--D. ponticus Valkanov 1956R-M86
|--+--Chordodasys Schöepfer-Sterrer 1969HL01
| | `--C. riedli Schöepfer-Sterrer 1969R-M86
| `--Xenodasys Swedmark 1967HL01
| `--X. sanctigoulveni Swemark 1967R-M86
`--Dactylopodola Strand 1929HL01
|--D. baltica Remane 1926R-M86
|--D. cornuta Swedmark 1956R-M86
| |--D. c. cornutaR-M86
| `--D. c. brevis d’Hondt 1966R-M86
|--D. indica Rao & Ganapati 1968R-M86
|--D. mesotyphle Hummon, Todaro et al. 1998TBT02
|--D. roscovita Swedmark 1967R-M86
`--D. typhle Remane 1927 [incl. D. weilli d’Hondt 1965]R-M86

*Type species of generic name indicated

References

Hochberg, R., & M. K. Litvaitis. 2000. Phylogeny of Gastrotricha: a morphology-based framework of gastrotrich relationships. Biological Bulletin 198 (2): 299–305.

[HL01] Hochberg, R., & M. K. Litvaitis. 2001. Macrodasyida (Gastrotricha): a cladistic analysis of morphology. Invertebrate Biology 120 (2): 124–135.

Hummon, W. D. 1974. Some taxonomic revisions and nomenclatural notes concerning marine and brackish-water Gastrotricha. Transactions of the American Microscopical Society 93 (2): 194–205.

[R-M86] Renaud-Mornant, J. 1986. Gastrotricha. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 86–109. E. J. Brill/Dr W. Backhuys: Leiden.

[TBT02] Todaro, M. A., M. Balsamo & P. Tongiorgi. 2002. Marine gastrotrich fauna in Corsica (France), with a description of a new species of the genus Tetranchyroderma (Macrodasyida, Thaumastodermatidae). Sarsia 87: 248–257.

Todaro, M. A., D. T. Littlewood, M. Balsamo, E. A. Herniou, S. Cassinelli, G. Manicardi, A. Wirz & P. Tongiorgi. 2003. The interrelationships of the Gastrotricha using nuclear small rRNA subunit sequence data, with an interpretation based on morphology. Zoologischer Anzeiger 242 (2): 145–156.

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