HCNSO Student Theses and Dissertations

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Defense Date

1996

Document Type

Thesis - NSU Access Only

Department

Oceanographic Center

First Advisor

Charles G. Messing

Second Advisor

Patricia Blackwelder

Third Advisor

James B. McClintock

Abstract

Seasonal variations were examined in the biochemical and energetic composition of two bathyal stalked crinoids, Neocrinus decorus and Endoxocrinus parrae (Isocrinidae). Three individuals of each species were collected in May, August and November, 1993, and April, 1994 (SW of Little Bahama Bank in 400-430 m), then frozen, lyophilized, and separated into crown, stalk and cirri. Three subsamples of each body part were burned at 500°C for 4h to determine % ash. Soluble protein and carbohydrate were determined colorimetrically. Lipid was measured gravimetrically. Insoluble protein was calculated by subtraction. All biochemical data are given in % dry weights. Ash constitutes the greatest percent of all body parts and comprises similar proportions of stalks and cirri of both species (87-91 %). However, the N. decorus crown contains significantly less ash (68-73%) than that of E. parrae (80-82%). Protein is the major organic component in all body parts. Soluble protein ranges are 9-1S% in crowns, 1-3% stalks, and 0.5-2% in cirri of both species. While insoluble protein content is also similar in the stalk and cirri of both species, the N. decorus crown always contains a greater proportion (7-16%) than that of E. parrae (3-7%). Lipids and carbohydrates show similar trends at lower levels. Changes observed in organic constituents for both species suggest: 1) short-term nutrient storage, 2) reproductive activity, although no ripe individuals were observed, and/or 3) seasonally higher food quality.

Total protein contributes the most to the energetic content of both species. Lipids contribute about the same energetic content to stalks and cirri of both species, but higher amounts to the crown of N. decorus. Mean total energetic content excluding ash of E. parrae is 1.7x that of N. decorus (21.7 vs. 12.9kJ) due to the former's larger crown. Both species invest >80% of their energy in the crown, reflecting its importance to reproduction, feeding and nutrient storage. Stalk and cirri are support structures that apparently require relatively small amounts of energy. Both species occur in locally high densities and may provide a substantial amount of energy to the biotic community. It remains unknown, however, what biota utilize this energy.

Gut contents were sampled from five specimens of each species in February, August, and October, 1991 and April, 1992 and the type and size of food items determined. Gut contents were quantified by determining area occupied by food items in a Neubauer counting chamber. Food composition is similar within and between species and does not vary with sampling month. Detritus is the major component (50-60%) by gut content area. Copepods, other crustacean parts and radiolarians together contribute 10-30%. Foraminifera, tintinnid ciliates, sponge spicules, ostracods, fecal pellets, diatoms, pollen grains and dinoflagellates each contribute 2% at most. Copepods are the main identifiable food item by area (40-60%) excluding detritus. Radiolarians are the most abundant food items (50-60%) by particle count (excluding detritus).

Mean size of ingested particles is ≤200μm (excluding detritus) with no significant differences between crinoid species. Ostracods are the largest identifiable particles and measure up to about 800J.lm wide, considerably larger than the ambulacral groove width of either species. The lack of significant differences in either size or composition of gut contents between species suggests that they do not partition food resources.

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