Organ Weights and Growth Profiles in Bottlenose Dolphins (<I>Tursiops truncatus</I>) from the Northwestern Gulf of Mexico

Abstract

Systematic necropsies were performed on 63 bottlenose dolphins (Tursiops truncatus), and data on organ mass, standard body length (SBL), body mass (BM), gender, sexual maturity, and age were measured and/or estimated. Animals were extremely fresh and recovered from along the Texas and Louisiana coastline in the northwestern Gulf of Mexico. Organ reference tables were established for this species to facilitate comparisons with other bottlenose dolphins and to provide a baseline for other cetacean species. Organs examined included lungs, adrenal glands, kidneys, testes, ovaries, heart, liver, pancreas, brain, pituitary, thyroid, thymus, and spleen. Individuals were separated into three size classes: < 175 cm, 175-225 cm, and > 225 cm, based on SBL to further facilitate comparisons. Growth rates of length and mass were described using Gompertz nonlinear models as a function of gender. No sexual dimorphism was identified in BM or organ weights, and SBL was only significantly larger for older mature males. SBL and BM were strongly correlated with age when all animals were included in analyses, although this is not an accurate predictor of age, especially in older individuals. Organ weights were significantly correlated with both SBL (except thymus and spleen) and BM (except left ovary, spleen, and thymus). Age was significantly correlated with all organ weights (except thymus, thyroid, and ovaries). There were no significant differences in the weight of any paired organs (adrenal glands, kidneys, lungs, ovaries, testes), and all were significantly correlated with BM. These data on organ weights of bottlenose dolphins, when interpreted with SBL, BM, and age, are significant tools for pathologists and veterinarians interpreting animal health status.

Early physical maturation of female common bottlenose dolphin Tursiops truncatus in the eastern Levantine Basin

“…Size sexual dimorphism of western North Atlantic coastal CBD, with males being slightly larger, was described by almost all investigators employing large enough series (Sergeant 1973;Read et al 1993;Tolley et al 1995;Fernandez & Hohn 1998;Stolen et al 2002;Mattson et al 2006;Turner et al 2006;McFee et al 2010;Neuenhoff et al 2011). Asymptotic lengths of males in the southern US Atlantic coast and Gulf of Mexico range between 10 and 20cm (4-8%) higher than those of females, and this relationship seems to hold for the population hereby reported.…”

“…Goodness of fit of all curves, acquired by least squares iterations, was judged by R 2 values, residual sum of squares and Akaike's Information Criterion (AIC) values. Correlation with regional primary productivity To this end, we could only find four other studies that fitted single Gompertz curves to a point database from dead CBD and reported G and g constants for both genders: three from the coast of Texas (Fernandez & Hohn 1998;Turner et al 2006;Neuenhoff et al 2011) and one from the Indian River Lagoon, Florida (Stolen et al 2002). The values of the first three studies were averaged and the three regional sets of male and female G and g values were log transformed and correlated (Pearson's product correlation coefficient) to corresponding log transformed regional mean annual primary productivity rates obtained from the literature.…”

“…Most authors who reported on smaller samples used a single sigmoid curve for the entire sample (i.e. Stolen et al 2002;Turner et al 2006;Neuenhoff et al 2011), some (Read et al 1993;Fernandez & Hohn, 1998) avoiding the stage 1 issue by initiating the curves at the age of one year, and others (Neuenhoff et al 2011) acknowledging the fact that a single-stage model cannot account for the high growth rate observed in young dolphins, particularly when late fetal growth was considered. Mattson et al (2006) applied two-staged sigmoid curves with the intersection points at the age of about eight years for CBD from Mississippi Sound and got satisfactory results; however, they too had to exclude non-neonate animals younger than one year for part of the calculations.…”

Comparison of Dolphins' Body and Brain Measurements with Four Other Groups of Cetaceans Reveals Great Diversity

“…The smallest adult La Plata dolphin, Pontoporia blainvillei , may weigh as little as 15-20 kg [Kamiya and Yamasaki, 1974;Pirlot and Kamiya, 1975] while the largest blue whale, Balaenoptera musculus , may approach 200,000 kg [Lockyer, 1976]. It is obvious from many studies that brain size does not vary strictly with body size [Pilleri and Gihr, 1970;Pirlot and Kamiya, 1975;Miyazaki et al, 1981;Ridgway and Brownson, 1984;Worthy and Hickie, 1986;Marino et al, 2004;Turner et al, 2006;Connor, 2007;Montgomery et al, 2013;Gingerich, 2015;Mallette et al, 2016]. Data on brains of cetaceans of known maturity have been sparse.…”

Report of the Working Group on Taxonomy and Stock Identity of bottlenose dolphins in the Southwest Atlantic Ocean

“…In addition, offshore specimens of T. truncatus in the western North Atlantic seem to be larger than those found along the coast (e.g. Hohn, 1980;Turner et al, 2006 Herein, we compile the information of total body length (TL) and condylobasal length (CBL) measurements of bottlenose dolphins from different geographic locations along the SWAO (Tables 1 and 2). Nevertheless, these data should be viewed with caution because the sample includes immature and mature individuals of both sexes.…”