Page 79 - The Toxicology of Fishes

Toxicokinetics in Fishes 59

TABLE 3.1 (cont.)
Generalized Structural, Functional, and Environmental Differences between Fish and Mammals
Characteristic Fish Mammals
Lymphatics No Yes
Secondary circulation Yes No
Blood pressure and flow Low High
Red blood cells Nucleated Non-nucleated
Plasma proteins Lower levels Higher levels
Blood pH Higher that mammals Lower than fish
Kidney
Nephron Less complex. SW—no distal More complex, including glomerulus,
tubule; aglomerular. FW, distal tubule and loop of Henle
SW—modified loop of Henle
Blood supply Renal artery and renal portal Renal artery
Hematopoiesis Many fishes NA
Waste excretion Minor site Primary site
Fluid balance Primary site Primary site
Ion balance Secondary site Primary site
Acid–base balance Secondary site Primary site
Liver
Functional unit Tubule, with no triads or zonal Lobule, with triads and zonal
relationships arrangement
Gallbladder May or may not be present May or may not be present
Bile flow Slower than mammals Faster than fish
Biotransformation rates Slower than mammals Faster than fish
Gastrointestinal tract
Structural divisions Gradual transitions Clear delineations
Gastric stomach Absent in 15% of species Present
Absorptive surface Longitudinal folds Villi
Lipid absorption Primarily into blood Size dependent into lymph
Change in temperature Change in length/morphology NA
Skin
Epidermis Living, moist Dead, dry, keritinized
Mucous Present Absent

Intraperitoneal
Feces Kidney Bladder Urine

Renal
Gastointestinal
Tract Portal
Intramuscular
Hepatic Muscle
Portal
Fat
Bile Liver Skin Internal
Blood Surfaces

Secondary
Circulation

Gill Water
Ingestion Intravenous Inhalation Dermal
FIGURE 3.1 Pathways for absorption, distribution, and elimination of xenobiotic compounds in fish.