Geology topics

Christine Densmore

Publications and source records attributed to Christine Densmore.

5 recordsLinked to original sources

USGS2025

Two new species of Henneguya Thélohan, 1892 (Cnidaria: Bivalvulida: Myxobolidae) infecting gill of blue catfish, Ictalurus furcatus (Rafinesque) (Siluriformes: Ictaluridae) from the Tallapoosa River and Chesapeake Bay tributaries

We herein describe 2 new species of Henneguya Thélohan, 1892 (Bivalvulida: Myxobolidae), Henneguya auburnensis Ksepka and Bullard n. sp. and Henneguya chesapeakensis Ksepka, Walsh, and Bullard n. sp., infecting the inter-lamellar epithelium of cultured blue catfish ( Ictalurus furcatus [Valenciennes, 1840] [Siluriformes: Ictaluridae]) from Saugahatchee Creek (Tallapoosa River; Auburn, Alabama) and the inter-lamellar epithelium of invasive blue catfish captured in Chesapeake Bay tributaries, respectively. Henneguya auburnensis resembles Henneguya mississippiensis Rosser, Griffin, Quiniou, Khoo, Greenway, Wise, and Pote, 2015 , and Henneguya sutherlandi Griffin, Pote, Wise, Greenway, Mauel, and Camus, 2008 , which both infect channel catfish ( Ictalurus punctatus [Rafinesque, 1818] [Siluriformes: Ictaluridae]) in Mississippi, but differs from these species by having more polar tubule coils (10–12 vs. 8–9 and 6, respectively). Henneguya chesapeakensis resembles Henneguya longicauda Minchew, 1977 , which infects channel catfish in Mississippi, but differs from this species by having shorter polar capsules (6.0–7.0 vs. 7.0–9.0). A phylogenetic analysis of the small subunit (SSU) rDNA recovered ictalurid-infecting Henneguya spp. as monophyletic, with H. auburnensis sister to a clade of Henneguya spp. that, except for H. chesapeakensis , infect the gill or adipose fin of channel catfish. Henneguya chesapeakensis was recovered sister to Henneguya ictaluri Pote, Hanson, and Shivaji, 2000 . Histological sections of infected gill filaments revealed that the plasmodia of both new species developed within the inter-lamellar epithelium. The new species comprise the second and third species of Henneguya reported from blue catfish.

Journal of Parasitology↗

USGS2024

Invasive blue catfish in the Chesapeake Bay: A risk to realizing Bay restoration investments

Introduction The partners of the Chesapeake Bay are investing billions of dollars in the restoration of critical habitats to improve conditions for people and living resources throughout the Bay and its watershed. However, the recent proliferation of invasive Ictalurus furcatus (blue catfish) in the Chesapeake Bay’s major rivers has the potential to disrupt these restoration efforts and limit the full potential improvement of the ecosystem. The U.S. Geological Survey can help respond to this management challenge in the Nation’s largest estuary by leveraging its leadership and technical capabilities to work with resource managers, academics, and other stakeholders.

Chesapeake Bay↗

USGS1999

Non-lethal sampling for the detection of Myxobolus cerebralis in asymptomatic rainbow trout

We have described in previous reports (Schill et al., 1998) the development of a polymerase chain reaction (PCR) amplification of 18S ribosomal RNA for the detection of Myxozoan parasites. Oligonucleotide primers were developed by multiple alignment of Myxozoan sequence information and analysis by a custom-written computer program (PRIM). Candidate pairs of primer sequences were then analyzed for specificity by BLAST (Basic Local Alignment Search Tool). From these, a set of promising primers (MYXFWD and MYXREV) was chosen for further testing. These were chosen because they should direct detection of a number of Myxozoan species (Table 1). PCR using MXYFWD and MYXREV proved to be robust and relatively free of artifact products. Further, we were able to routinely detect Myxobolus cerebralis in fish tissues (Figure 1).

Book↗

USGS1999

Preliminary effects of water hardness on triactinomyxon production and development from eastern tubifex worms infected with Myxobolus cerebralis

Whirling disease is caused by Myxobolus cerebralis and requires an intermediate oligochaete host identified as Tubifex tubifex (Wolf, Markiw, and Hiltunen, 1986). M. cerebralis spores ingested by the tubifex worms develop into triactinomyxons (tams) that are eventually released into the water column to infect salmonid fish. There may be many environmental parameters, biotic or abiotic, that may affect the development of waterborne tams in eastern tubifex worms. This study will focus on one of those environmental parameters, total water hardness. Total water hardness is defined as the concentration of calcium and magnesium in a water sample expressed in milligrams per liter of equivalent CACO 3 (Boyd, 1990). This study will address whether different levels of water hardness affect the development and production of tams released by infected tubifex worms.

Book↗

USGS1999

Influence of temperature and substrate on infection rate, triactinomyxon production, and release duration from eastern tubifex worms infected with Myxobolus cerebralis

Salmonid whirling disease is caused by Myxobolus cerebralis , a metazoan parasite with a two host life cycle involving salmonid fish a an aquatic oligochaete, Tubifex tubifex (Wolf, Markiw and Hiltunen, 1986). Whirling disease has been reported in 22 U.S. states with the greatest losses occurring in the salmonid fisheries of western and Midwestern states. Although whirling disease is endemic in the eastern United States, serious documented losses to wild populations have not been reported. Two high priority research needs identified in 1996 were a better understanding of how worm and parasite populations might differ from different geographic areas and how environmental factors affect the various stages of whirling disease. To begin to address these research needs we established "eastern" populations of worms, parasite and fish hosts. This abstract will present data on the effects of temperature and substrate upon eastern T. tubifex worms infected with an eastern isolate of M. cerebralis . The influences of these abiotic factors upon the ability to infect the worms and subsequently their ability to produce waterborne triactinomyxons.

Book↗