8142

• UCREFRP Catalog Number: 8142
• Author: Horn, M. J.
• Title: Nutritional Limitation of Recruitment in the Razorback Sucker ‎(
• USFW Year: 1996.
• Copyright Material: NO

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64

n. Methods

1. Processing of Larvae

Experimental procedures and design followed the outline given in Chapter 1.

Lipid extractions follow the methods of Reznick and Braun (1987) and Horn (1990). The

procedure allowed for gravimetric estimation of lipid values for individual larvae.

Larvae were sacrificed prior to first feeding on each sampling date to minimize

gut contents, as food would bias estimates of lipids and weight. Larvae sampled in early

evening from Lake Mohave often had food in their intestine making gut evacuation

necessary. Larvae were measured to the nearest 0.1 nun total length (TL) with dial

calipers. Foods were evacuated from the gut by gently sliding a needle down the ventral

surface of larvae, forcing gut contents from the anus.

After measuring, individual larvae were placed on pre-weighed foil squares in a

glass scintillation vial and dried at 500C for 24 hr. Following drying, larvae and vials

were cooled to room temperature for 1-2 hr in a closed container containing desiccant,

then weighed. Larvae and foil were weighed together to the nearest 0.00001 gm, and

both foil and larvae were placed back in to vials containing 10 to 15 ml of anhydrous di-

ethyl ether and vials tightly capped. Ether was selected as a solvent because it is selective

for non-polar lipids such as triglycerides and does not affect polar structural lipids, thus

giving a relatively unbiased indication of storage products (Reznick and Braun 1987).

Vials and larvae were placed in a fume hood and lipids allowed to extract for 24 hr (Horn

1990). Following extraction, the ether was decanted and the larvae again dried for 24 hrs