Reproductive isolation and morphological divergence between cryptic lineages of the copepod Acartia tonsa in Chesapeake Bay

The systematics of the subfamilies Salmoninae and Coregoninae of recently glaciated regions are reviewed. Interrelation between systematics and fisheries biology are stressed, pointing out the abundance of intraspecific genetic diversity of some salmonid fishes manifested in ecological and behavioral specializations, but not necessarily by morphological divergence. Innate, reproductive homing behavior of salmonid fishes may allow closely related populations to exist in sympatry and maintain reproductive isolation. Examples are cited to support the contention that many sympatric "sibling species" have evolved from a common ancestor in postglacial times. Closely related, sympatric populations are a major taxonomic problem, but this phenomenon which allows a species to consist of genetically discrete units with reproductive isolation between the stocks is of great significance for fisheries management. Postglacial salmonid communities are typically fragile and highly susceptible to disruption or destruction by introductions, eutrophication, and exploitation. Every effort should be made to protect the genetic diversity of a species.

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Attachment of the peritrich epibiont Zoothamnium intermedium Precht, 1935 (Ciliophora, Peritrichia) to artificial substrates in a natural environment

Brazilian Journal of Biology ◽

10.1590/s1519-69842008000400013 ◽

2008 ◽

Vol 68 (4) ◽

pp. 795-798 ◽

Cited By ~ 4

Author(s):

LRP. Utz

Keyword(s):

Chesapeake Bay ◽

Natural Environment ◽

Acartia Tonsa ◽

Artificial Substrates ◽

Copepod Species ◽

Field Observations ◽

Marine Environments ◽

Eurytemora Affinis ◽

Free Swimming ◽

Living Organisms

Peritrich ciliates are commonly found as epibionts, colonizing living organisms, or attached to non-living substrates in freshwater, estuarine and marine environments. Several species of peritrich epibionts are obligate, which means that they are able to only colonize other organisms, while others are facultative attaching to living or non-living substrates. The peritrich Zoothamnium intermedium is commonly found as epibiont on the copepod species Acartia tonsa and Eurytemora affinis in Chesapeake Bay, USA. Previous studies demonstrated that Z. intermedium is not able to attach to non-living substrates in the laboratory; with free-swimming stages (telotrochs) dying when living substrates are not available for colonization. The present study investigated the ability of Z. intermdium to colonize artificial substrates in the field. Observations were carried out while the peritrich ciliate was colonizing copepods in Rhode River, a tributary of Chesapeake Bay. Results demonstrated that four species of Zoothamnium were recovered from artificial substrates, but none of them was Z. intermedium. At the same time, Z. intermedium was colonizing adults and copepodites of E. affinis and A. tonsa during the whole study period. These results, in addition to laboratory observations, suggest that Z. intermedium is an obligate epibiont.

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