Glanapteryginae

Taxobox
name = Glanapteryginae
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Siluriformes
familia = Trichomycteridae
subfamilia = Glanapteryginae
subfamilia_authority = Myers, 1944
type_genus = "Glanapteryx"
type_genus_authority = Myers, 1927
subdivision_ranks = Genera
subdivision = "Glanapteryx"
"Listrura"
"Pygidianops"
"Typhlobelus"

Glanapteryginae is a subfamily of catfishes (order Siluriformes) of the family Trichomycteridae. It includes four genera, "Glanapteryx", "Listrura", "Pygidianops", and "Typhlobelus".cite journal|url=http://digitallibrary.amnh.org/dspace/bitstream/2246/5665/1/N3496.pdf|title=New and Noteworthy Venezuelan Glanapterygine Catfishes (Siluriformes, Trichomycteridae), with Discussion of Their Biogeography and Psammophily|first=Scott A.|last=Schaefer|coauthors=Provenzano, Francisco; de Pinna, Mario; Baskin, Jonathan N.|journal=American Museum Novitates|issue=3496|pages=1–27|date=November 29, 2005|format=PDF]

Phylogeny

Monophyly of the subfamily is supported by five synapomorphies involving reductions in the fins, caudal skeleton, and laterosensory system. It has been proposed that the sister-group to this subfamily is the Sarcoglanidinae. "Listrura" is the sister group to the remainder of the subfamily. "Glanapteryx" is sister to a clade formed by the sister taxa "Pygidianops" and "Typhlobelus".

Distribution

"Glanapteryx", "Pygidianops", and "Typhlobelus" are distributed in the Orinoco and the Amazon River. "Listrura" species are from Brazil, outside of the Amazon River basin. However, the distribution of glanapterygines may be greater than previously thought.

Description

Most of the subfamily is constituted by "miniaturized" species. Though miniaturized fish usually refers to fish that do not reach 25.4 millimetres (1.0 in) SL, "Glanapteryx" and "Typhlobelus" have been considered "elongate miniatures" due to their paedomorphic features and small head sizes, despite their lengths exceeding 25.4 mm.cite journal|url=http://digitallibrary.amnh.org/dspace/bitstream/2246/5105/1/N2950.pdf|title=A New Sarcoglanidine Catfish, Phylogeny of Its Subfamily, and an Appraisal of the Phyletic Status of the Trichomycterinae (Teleostei, Trichomycteridae)|first=Mario C. C.|last=de Pinna|journal=American Museum Novitates|issue=2950|pages=1–39|date=August 9, 1989|format=PDF]

"Pygidianops" and "Typhlobelus" are the most modified glanapterygines sharing extreme reduction or loss of pigmentation, fins, laterosensory system, and eyes; they are also miniaturized, yet retain the well-ossified skeleton comparable in both bone differentiation and degree of calcification to that observed in larger trichomycterids. All four of these genera are currently monophyletic.

Habitat

Glanapterygine phylogeny indicates that the evolution of the group followed a trend of decreasing dependence on leaf litter and increasing association with sand. "Listrura" occur in shallow-water leaf-litter deposits underlain by mud or deeper layers of leaf litter. Little is known about the habitats of the species of "Glanapteryx", but information available indicates that they have been collected in association with leaf litter underlain with sand. By contrast, "Pygidianops" and "Typhlobelus" are entirely disassociated from leaf litter, and occupy exclusively clear loose sand; some species have been found to live exclusively in the substratum of the sand (rather than on the sand surface or in the water column above the sand), which could be the first vertebrates identified to be part of the meiofauna of benthic organisms. The latter two genera are more specialized for this lifestyle than any other catfishes, as evidenced by their loss of morphological traits. These two species also have paired keels called metapleural keels; these keels, formed by long ridges of stiffened integument, extend along the entire ventral margin of the abdomen, ending posteriorly shortly posterior to the anus. These keels probably serve to stabilize the body while moving in sand.

References