NWT RESEARCH DATABASE

Tags: biology, fish, genetics, biological evolution

Objective(s): To collect a total of about 30 larvae at least 60 mm in total length for each of the two species from localities where adults of each species are known, describe their gross morphology and pigmentation and produce an identification key.

Project Description: The purpose of this study is to know more about the lampreys of NWT. It is part of a larger scale study of lampreys of the genus Lethenteron across the northern hemisphere (Eurasia and North America). In the Northwest Territories (NWT) part of the study our objectives are: 1- To collect a total of about 30 larvae at least 60 mm in total length for each of the two species from localities where adults of each species are known, describe their gross morphology and pigmentation and produce an identification key. A total of about 10 adults of each species would also be desirable to corroborate the identity of the larvae. 2- Compare the DNA sequences between the two lamprey species. The tissue samples will be taken from the same specimens as in objective 1. The project team has done preliminary work based on a single mitochondrial gene on samples from Japan (L. camtschaticum) and Alaska (L. alaskense) and found no differences (Lang et al. 2009). The research team wishes to examine more genes, including nuclear ones, on samples of both species from NWT to further test these results. This collaborator, Dr. Margaret F. Docker at the University of Manitoba and her graduate student, Youyang Li will be conducting the molecular analyses. 3- Perform a histological examination of lamprey larvae of different sizes (5 larvae per 10-mm increments from 30 mm up to 120 mm total length) for the two species to follow the development of their ovaries and determine if they contain one or two generations of eggs. This gives a combined total for the two species of 90 larvae. 4- Perform an analysis of the genes that are expressed in each of the two lamprey species during development to determine if their different developmental pathways (i.e., as parasitic or nonparasitic) are controlled by differences in the timing or extent of gene expression rather than by differences in the gene sequences themselves. As lamprey larvae spend most of their time buried in the streams bottoms, the most efficient way of collecting them is with a backpack electrofisher that stimulates them to leave their burrows, at which point they are scooped up with a fine-mesh dipnet. The research team will be using a Smith-Root Model 12-A POW (programmable output waveforms) backpack electrofisher. Lamprey larvae are most effectively collected with low pulse frequencies (< 10 Hz). This electrofisher has two settings under 10 Hz (i.e., 1 and 5 Hz), and therefore, these are the ones that will be used. Low pulse frequencies cause just enough irritation for the larvae to emerge from their burrows in the sediment, whereas high pulse frequencies (> 30 Hz) cause immobilization in the burrows by producing muscle tetanus. High pulse frequencies (30-120 Hz) are the ones associated with injuries in bony fishes. According to Porter et al. (1974) the conductivity of the water in the Martin River varies from 289-426 µmhos/cm. According to the Government of the Northwest Territories Drinking Water Quality Database (2012), the conductivity of the raw water at Fort Simpson, Fort Providence, Hay River, and Fort Smith is respectively, 230, 219, 233, and 229 µmhos/cm. The voltage setting recommended for medium water conductivities (i.e., 200-400 µmhos/cm or µSiemens/cm) is 400-700 volts. Electrofishing, however, is biased towards the collection of larger larvae as smaller larvae swim unhindered through the electrical field while the larger ones are attracted to the anode. Therefore, limited additional sampling may be needed to collect the smaller larvae that are required for the histological component of the study. This will be achieved by using a shovel to remove some sandy-silty substrate and using a sieve to retrieve the smaller larvae. Upon collection, the lamprey will be euthanized with an overdose of MS-222 (i.e. 100 mg/L of river water). A small piece of tissue will be removed and put in a small Eppendorf vial containing 95% ethanol for subsequent DNA analysis (Objective 2); subsamples of the gonad (or 5-mm thick whole body sections in small larvae) and head will be preserved in RNA Later for subsequent gene expression analysis (Objective 4). The rest of the body will be wrapped in cheesecloth and placed in double-layered plastic bags containing 4-5% formalin for the morphological component of the study (Objective 1) and in Bouin solution for the histological component of the study (Objective 3). Lamprey larvae have long been used as effective bait to catch sport fishes in Europe as well as in North America. Nursall and Buchwald (1972) reported them as being eaten by Burbot, Northen Pike, and Walleye. Perhaps they could also be used as bait in the NWT subject to the controls and regulations of the Department of Fisheries and Oceans. The research team is interested in giving presentations on lampreys and producing posters to hand out when visiting the communities of Fort Simpson, Fort Providence, Hay River, and Fort Smith. The team would also be interested in an exchange of information on the local presence of lampreys. In the near future, the team will be contacting the various community contacts in the Deh Cho and South Slave regions as given in the Guide for Researchers of the Aurora Research Institute and any other contact suggested. Once this study is complete, the team will send the results to these communities and remain available to answer any questions that might arise. The results will be disseminated through email, fax, regular mail, videoconference or whatever other means are most suitable for individuals and communities and the team will do this best to accommodate these requests. The fieldwork for this study will be conducted from June 20, 2012 to July 10, 2012.