Age and Sexual Maturity Estimation of Stranded Striped Dolphins, Stenella coeruleoalba, Infected with Brucella ceti

Abstract

Age parameters in cetaceans allow examining conservation and studying individuals with growth affection. The age and sexual maturity of 51 stranded Stenella coeruleoalba striped dolphins from the Eastern Tropical Pacific (ETP) of Costa Rica, most suffering brucellosis (95.6%), were assessed. In order to ascertain the dolphins’ ages, we measured the length and growth of dentin-layer group counts (GLGs) and assessed flipper bone radiography without (FBSA) and with a formula (FBF). Sexual maturity was determined through gonadal histology and sexual hormone serum levels. Compared with a model based on S. coeruleoalba ages estimations in other latitudes, the striped dolphin studied displayed deficient growth parameters, with considerable variability in length, teeth, and flippers bone development. Close to 43% (n = 15) of GLGs’ measurements were below the body length average ranges for the predicted age, suggesting developmental abnormalities. Likewise, 34.4% and 31.2% of the dolphins assessed by FBSA and FBF were also below the body length based on age prediction curves, also indicating developmental abnormalities. This information is supported by the poor correlation between GLGs, FBSA, and FBF. Inconsistencies between sexually mature males and females related to GLGs, FBSA, and FBF were evident. Although the different oceanic settings of the ETP, such as contamination, food access, diseases, and other parameters, may influence size variation, our data also suggest that long-lasting debilitating brucellosis may account for detrimental growth in the ETP striped dolphins. Our study highlights the possible deleterious consequences of chronic infectious diseases in the cetacean populations already confronting distressful conditions.

The First Report of Pennella (Crustacea: Copepoda) Infesting Stenella coeruleoalba Stranded in Malta: Morphological and Genetic Analyses

“…Just as parasites, including Pennella balaenoptera, may benefit from a weakened host, the parasites themselves may be carriers of infectious pathogens, such as Brucella ceti, which, in turn, may have long debilitating effects on the dolphin, potentially facilitating further parasite infestation. At the same time, other diseases, such as Cetacean morbillivirus (CeMV), may also coinfect or activate various other latent infections, weakening the dolphin in various life-threatening ways [32,34,[46][47][48][49][50].…”

“…However, other research publishing a growth curve for Mediterranean striped dolphins shows the maximum body length to be 205 cm from around 11 years of age, while specimens at 200 cm body length would be around 7 years of age [30]. This may, however, vary according to population genetics, distribution, and general health, with unhealthy dolphins remaining smaller in size [31][32][33]. The dolphin under study had an empty stomach, except for a couple of cephalopod beaks, and its dorsal blubber thickness was 1.5 cm.…”

Brucella ceti Infection in Striped Dolphins from Italian Seas: Associated Lesions and Epidemiological Data

“…The highest frequency of B. ceti infection was confirmed in adults, and this observation seems in accordance with the results obtained in a previous study on marine mammals of the genus Stenella stranded in Brazil [ 26 ]. Additionally, more than a half of the animals showed a poor body condition, and almost all animals had empty stomachs at necropsy, suggesting an impairment in their foraging ability, likely caused by the disease and impairment of neurological functions [ 16 , 17 , 84 ].…”