The genus Troglocyclops
diverged early from the cyclopid lineage and, according to Rocha & Iliffe (1994), it represent "the most primitive member of the Halicyclopinae because of the presence of 15-segmented antennules, mandibular palp reduced to 3 setae, one of them quite long and plumose, a bisegmented maxillary endopodite, and 3-segments in the maxillipede endopodite". The genus is also characterized by the presence of a supplementary seta on the male leg 5, but this character is shared with representatives of the "caridophilus-group" of Halicyclops (left: T. janstocki).
These copepods possess the first pediger still distinct, being partially enclosed dorsally and laterally by a carapace-like extension of the posterior margin of the dorsal cephalic shield. This latter character represents a plesiomorphic state shared with the primitive cyclopinids and, within the Cyclopidae, only with the Euryteinae.
The present taxon is the only known species of Halicyclopinae having two apical spines on the terminal segment of the exopodite of legs 2 to 4, and the intercoxal sclerites of the legs 1 and 2 sexually dimorphic.
In Bahamian anchialine caves, its further evolution involved developing characteristic features such as the inner apical spine on the terminal segment of exopodite of legs 2-4 and the sexual dimorphism in the armature of the intercoxal sclerites of the legs 1 and 2, while retaining several primitive characters" (Rocha & Iliffe, 1994).
The most outstanding features of the genus relate to the structure and armature of the mouth parts, which are the most modified among the Cyclopidae.
SERGIOSMIRNOVIA Monchenko, 2007
This genus exhibits very modified conditions not known in the other Cyclopidae for the structure of the maxilla, maxilliped, etc. The first one is characterized by the prehensile type with only 1 apical and subapical setae or spine on the distal joint and without the distal endit of the sympod with its armature; the second one is strongly reduced to only one small joint with 2 weakly developed setae (in other general minimal setae) (left: S. reducta).
Monchenko, V.I., 1977. Smirnoviella reducta gen. et sp. n. (Crustacea, Copepoda) from Dniester river liman (Black Sea basin). Zool. Zhurn., v.56, N 9: 1402-1406 (in Russian with English Abstract).
Monchenko, V.I., 1982. The genus Smirnoviella (Crustacea, Cyclopidae) in the Caspian Sea with the description of a new species. Vestnik Zool., v.16, N 3: 12-15 (in Russian with English Abstract).
Monchenko, V.I., 2007. Sergiosmirnovia, a replacement name for Smirnoviella Monchenko (Copepoda, Cyclopoida). Crustaceana.
Vol. 80, No. 7. (2007), pp. 891-892.
Characteristic of the genus Prehendocyclops is an antennal prehensile device formed by a stout curved spine on the third segment, and the three proximalmost appendages of the terminal segment modified into stout, heavily serrate spines; the distalmost spine of these is claw-shaped. Additionally, on the praecoxal arthrite of the maxillule the two outermost apical spines are curved towards a strong, straight, pointed spine inserted on the inner surface of the arthrite (left: P. boxshalli).
The close relationship of the more derived
genera Prehendocyclops, Smirnoviella, and
Colpocyclops seems undeniable. The development of
of prehensile device on the antenna of these
genera, allied to the characteristic modifications
in the structure of their mouthparts, allow the assumption
that these genera are able to exploit some hosts.
Prehendocyclops and sister genera Smirnoviella and Colpocyclops, which evolved in esturaries connected to the Caspian and Black Sea, were linked in the past as part of the Tethys Sea. Considering that the three genera have similar mouthparts and antenna, they are probably derived from one or more ectoparasitic Halicyclops-like ancestral forms (Rocha et al., 2000).
Attempts towards some level of
ectoparasitism in Halicyclopinae have occurred from one
or more Halicyclops-like ancestral forms, leading to the
differentiation of the 3 above genera:
Prehendocyclops, with 3 species, nowadays apparently
confined to Mexican cenotes, whereas Smirnoviella and
Colpocyclops, with 2 species each would have evolved
in estuaries connected to the Caspian and Black Sea. It
is noteworthy that these areas were linked in the past,
forming part of the ancient Tethys Sea.
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