Dimarcusidae is a
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of
triclad
Planarians (triclads) are free-living flatworms of the class Turbellaria, order Tricladida, which includes hundreds of species, found in freshwater, marine, and terrestrial habitats.pp 3., "Planarians (the popular name for the group as a whole ...
s found mostly in freshwater habitats of
cave
Caves or caverns are natural voids under the Earth's Planetary surface, surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance undergrou ...
s, although at least one species, ''
Rhodax evelinae'', occurs in surface waters.
Currently the family contains only seven species distributed in five genera, although the total number of species is thought to be much higher.
Description
The morphological features uniting species of Dimarcusidae are related to the
reproductive system
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are al ...
. Their ovaries are located more posteriorly than in most triclads, which usually have them close to the brain. The penis in species of Dimarcusidae contains glandular elements and the common ovovitelline duct is perpendicular to the female genital duct.
Taxonomy
The family Dimarcusidae was erected in 1972 by Mitchell and
Kawakatsu to include a new species, ''Dimarcus villalobosi''. However, the same species had been briefly described by Benazzi in the same year as ''
Opisthobursa mexicana'' and this name had priority, with ''Dimarcus villalobosi'' becoming a junior synonym. As a result, the family is called Dimarcusidae despite the absence of a valid genus ''Dimarcus''.
Phylogeny
Historically, species of Dimarcusidae have been classified as members of the suborders
Maricola
Maricola is a suborder of triclad flatworms including species that mainly inhabit salt water environments. However, some species are also known from freshwater or brackish waters.Ball, I. R. 1974. La Faune Terrestre de l'Ile de Saint Hélène: T ...
(marine triclads) or Paludicola (freshwater triclads). They received their own suborder, Cavernicola, in 1990, although their relationship to other triclads had not been settled.
Recent molecular studies, however, suggest that Cavernicola is the sister group of Maricola, thus being more closely related to marine than to freshwater triclads.
The Dimarcusidae family, within the order Tricladida, has been the subject of phylogenetic studies to elucidate its evolutionary relationships. A comprehensive analysis by Sluys (1990) examined the phylogenetic relationships among genera within Dimarcusidae, highlighting the monophyletic grouping of certain genera.
Additionally, molecular analyses using genes such as COI and ITS-1 have been employed to resolve taxonomic statuses and infer phylogenetic positions within the family.
Genera
Currently the family Dimarcusidae includes the following five genera:
*''
Balliania''
Gourbault, 1978
*''
Kawakatsua''
Sluys, 2019
*''
Novomitchellia''
Özdikmen, 2010
*''
Opisthobursa''
Benazzi, 1972
*''
Rhodax''
Marcus, 1946
References
{{Authority control
Cavernicola (worm)