Signature information and individual recognition in the isolation calls of Amazonian manatees,Trichechus inunguis (Mammalia: Sirenia)

Acoustic signals are assumed to form the basis of manatee communication. Empirical evidence of individual vocal recognition has been reported. If manatees can recognize one another by acoustical means, it should be possible to identify individual vocal patterns. We recorded vocalizations of 14 individually housed Amazonian manatees and then digitized selected vocalizations, allowing seven variables to be measured and subjected to multivariate statistical treatment. Discriminant function analysis indicated that individuals can be separated on the basis of variables related to the fundamental frequency and signal duration. We observed significant differences in the vocal patterns between sexes and age classes. Females tended to have greater fundamental frequency and shorter note duration than males. Calves had shorter note durations and greater values for the fundamental frequency range than subadults and adults. An inverse relationship between total body length and fundamental frequency range suggests that the fundamental frequency becomes more defined as the animal ages. The similar individual patterns in the vocalizations of a mother and calf pair are discussed. Individual recognition by Amazonian manatees according to their vocal patterns is suggested through a preliminary playback experiment.     

Biology, conservation and status of the Amazonian Manatee Trichechus inunguis

The Amazonian Manatee Trichechus inunguis (Natterer, 1883) is the only exclusively freshwater sirenian and the smallest of the living species. Its inability to reduce peripheral heat loss limits its distribution to tropical waters. The species is endemic to the Amazonian region, being distributed throughout the Amazon basin, occurring mainly in calm waters and lakes. The species has been commercially exploited since 1542, with the meat and hide being the main products extracted. This commercial exploitation, combined with their very low reproductive rate, has seriously reduced the manatee population. Therefore the Amazonian Manatee is now considered an endangered species. Although it is protected by most of the countries where it occurs, there is no law enforcement, and the species is still captured throughout the Amazon. Data on general biology, physiology and management of the Amazonian Manatee, as well as its status and recommendations for its conservation, are presented.     

Heart rates and gas exchange in the Amazonian Manatee (Trichechus inunguis) in relation to diving

Unrestrained Amazonian manatees (Trichechus inunguis) maintained a constant heart rate during diving and exhibited a slight tachycardia during breathing. 'Forcing' the manatees to dive caused a marked bradycardia. They exhibited a more pronounced tachycardia during breathing after 'forced' dives and hyperventilated during recovery dives. Manatees are capable of dives exceeding 10 min duration without having to resport to anaerobic metabolism, and even after 10 min dives recover within 3-4 short dives. The ability of manatees to make long dives, in spite of relatively poor O2 stores, is due to their low metabolic rate, while the rapid recovery is aided by their high CO2 stores which minimizes CO2 storage in the body. In manatees the changes in alveolar O2 and CO2 pressure (PAO2 and PACO2) in relation to dive time are slower and more variable than in other marine mammals. The lower rate of change is probably due to the manatees' reduced metabolic rate, while the greater variability is due to their breathing pattern, in which both ventilation and body gas stores influence alveolar gases.     

Seroepidemiology of TmPV1 infection in captive and wild Florida manatees (Trichechus manatus latirostris)

In 1997, cutaneous papillomatosis caused by Florida manatee (Trichechus manatus latirostris [Tm]) papillomavirus 1 (TmPV1) was detected in seven captive manatees at the Homosassa Springs Wildlife State Park, Florida, USA, and, subsequently, in two wild manatees from the adjacent Homosassa River. Since then, papillomatosis has been reported in captive manatees housed in other locations, but not in wild animals. To determine TmPV1 antibody prevalence in captive and wild manatees sampled at various locations throughout Florida coastal regions, virus-like particles, composed of the L1 capsid protein of TmPV1, were generated with a baculovirus expression system and used to measure anti-TmPV1 antibodies in an enzyme-linked immunosorbent assay. Serologic analysis of 156 manatees revealed a TmPV1 antibody prevalence of 26.3%, with no significant difference between captive (n=39) and wild (n=117) manatees (28.2% and 25.6%, respectively). No antibody-positive wild animal showed PV-induced cutaneous lesions, whereas papillomatosis was observed in 72.7% of antibody-positive captive manatees. Our data indicate that Florida manatees living in the wild are naturally infected by TmPV1 but rarely show TmPV1-induced papillomatosis. Hence, it appears that the wild population would not be harmed in a case of contact with captive animals without visible lesions and productive infections, which could be thus released into the wild.     

Functional properties of hemoglobin and whole blood in an aquatic mammal,the Amazonian manatee (Trichechus inunguis)

• 1. Hematocrit (43%) and O₂ binding capacity (18.8 ml O₂/100 ml blood) ofTrichechus inunguis blood are low compared to the values for other diving mammals but are similar to those for land mammals.
• 2. Stripped manatee Hb is similar to human Hb A in its sensitivity to pH, 2,3-diphosphoglycerate and CO₂, but less sensitive to temperature and more prone to dissociate into dimers.
• 3. The unique Hill plots exhibit no cooperativity below 30% O₂-saturation indicating a highly stabilized T or low-affinity state(s); such asymmetric Hill plots together with biphasic O₂-binding kinetics could mean chain heterogeneity.
• 4. The pH dependence of oxygen binding by the apparent T state, hemoglobin as seen in the Hill plots, is enhanced by 2,3-diphosphoglycerate but eliminated by CO₂.

     

Phylogeography and population genetics of the endangered Amazonian manatee, Trichechus inunguis Natterer, 1883 (Mammalia, Sirenia)

We used mitochondrial DNA control region sequences to examine phylogeography and population differentiation of the endangered Amazonian manatee Trichechus inunguis. We observe lack of molecular differentiation among localities and we find weak association between geographical and genetic distances. However, nested clade analysis supports restricted gene flow and/or dispersal with some long-distance dispersal. Although this species has a history of extensive hunting, genetic diversity and effective population sizes are relatively high when compared to the West Indian manatee Trichechus manatus. Patterns of mtDNA haplotype diversity in T. inunguis suggest a genetic disequilibrium most likely explained by demographic expansion resulting from secession of hunting and enforcement of conservation and protective measures. Phylogenetic analysis of T. manatus and T. inunguis haplotypes suggests that T. inunguis is nested within T. manatus, effectively making T. manatus a paraphyletic entity. Paraphyly of T. manatus and recent divergence times of T. inunguis and the three main T. manatus lineages suggest a possible need for a taxonomic re-evaluation of the western Atlantic Trichechus.     

Activity patterns and spatial use of facility by a group of captive female manatees (Trichechus manatus latirostris)

As a means to compare and contrast to free‐ranging Florida manatees, we examined the behavior and movement patterns of nine adult‐female captive manatees at Homosassa Springs Wildlife State Park (HSWSP). HSWSP has a unique manatee exhibit that consists of a natural river and a man‐made pool. Because the manatees are exposed to a natural environment including natural food resources, the study of various aspects of behavioral and physiological parameters of the captive manatees is especially valuable with this group. We determined activity pattern and spatial use of the facility by manatees over three allotted periods of a day (noon, mid‐afternoon, and late‐afternoon) and three seasons (winter, spring, and summer). Behavioral strategies of the manatees were: 1) to remain “inactive,” probably to conserve energy, during the day while the park provisioned food; 2) to alter locations during the course of the afternoon, apparently with the direction of the sun, possibly to assist with thermoregulation; and 3) to change location seasonally where and when food resources became abundant, showing a strong interest in natural vegetation as it became available. Spatial use and activity pattern of the HSWSP captive manatees apparently were influenced by energy constraints and nutrient intake by provisioned food availability over the day and natural vegetation over the study period. The behavior of the female group of manatees may have been affected by the single‐sex living arrangement. In addition, these manatees are subject to a largely invariable temperature (ca. 23°C) that may have created thermal stress and immunological suppression over time. This study demonstrated that for these captive manatees the activity patterns and spatial use were comparable to that of free‐ranging manatees in relation to the availability of food resources. Zoo Biol 0:1–17, 2006. © 2006 Wiley‐Liss, Inc.     

Evaluation of adrenocortical function in Florida manatees (Trichechus manatus latirostris)

The study objectives were to determine the predominant manatee glucocorticoid; validate assays to measure this glucocorticoid and adrenocorticotropic hormone (ACTH); determine diagnostic thresholds to distinguish physiological vs. pathological concentrations; identify differences associated with sex, age class, female reproductive status, capture time, and lactate; and determine the best methods for manatee biologists and clinicians to diagnose stress. Cortisol is the predominant manatee glucocorticoid. IMMULITE 1000 assays for cortisol and ACTH were validated. Precision yielded intra‐ and inter‐assay coefficients of variation for serum cortisol: ≤23.5 and ≤16.7%; and ACTH: ≤6.9 and ≤8.5%. Accuracy resulted in a mean adjusted R²≥0.87 for serum cortisol and ≥0.96 for ACTH. Assay analytical sensitivities for cortisol (0.1 µg/dl) and ACTH (10.0 pg/ml) were verified. Methods were highly correlated with another IMMULITE 1000 for serum cortisol (r=0.97) and ACTH (r=0.98). There was no significant variation in cortisol or ACTH with sex or age class and no correlation with female progesterone concentrations. Cortisol concentrations were highest in unhealthy manatees, chronically stressed by disease or injury. ACTH was greatest in healthy free‐ranging or short‐term rehabilitating individuals, peracutely stressed by capture and handling. Cortisol concentrations ≥1.0 µg/dl were diagnostic of chronic stress; ACTH concentrations ≥87.5 pg/ml were diagnostic of peracute stress. In healthy long‐term captive manatees, cortisol (0.4±0.2 µg/dl) and ACTH (47.7±15.9 pg/ml) concentrations were lower than healthy free‐ranging, short‐term rehabilitated or unhealthy manatees. Capture time was not significantly correlated with cortisol; ACTH correlation was borderline significant. Cortisol and ACTH were positively correlated with lactate. Zoo Biol 30:17–31, 2011. © 2010 Wiley‐Liss, Inc.     

Phylogeography and Sex-Biased Dispersal across Riverine Manatee Populations (Trichechus inunguis and Trichechus manatus) in South America

Phylogeographic patterns and sex-biased dispersal were studied in riverine populations of West Indian (Trichechus manatus) and Amazonian manatees (T. inunguis) in South America, using 410bp D-loop (Control Region, Mitochondrial DNA) sequences and 15 nuclear microsatellite loci. This multi-locus approach was key to disentangle complex patterns of gene flow among populations. D-loop analyses revealed population structuring among all Colombian rivers for T. manatus, while microsatellite data suggested no structure. Two main populations of T. inunguis separating the Colombian and Peruvian Amazon were supported by analysis of the D-loop and microsatellite data. Overall, we provide molecular evidence for differences in dispersal patterns between sexes, demonstrating male-biased gene flow dispersal in riverine manatees. These results are in contrast with previously reported levels of population structure shown by microsatellite data in marine manatee populations, revealing low habitat restrictions to gene flow in riverine habitats, and more significant dispersal limitations for males in marine environments.     

Tactile discrimination of textures by Florida manatees (Trichechus manatus latirostris)

Two male Florida manatees (Trichechus manatus latirostris) demonstrated sensitive tactile discrimination in a two‐alternative forced choice task, using a modified staircase method. Stimuli were acrylic plates with vertical gratings of ridges and grooves. The standard stimulus, present on every trial, had 2 mm gratings and the comparison stimuli had wider gratings. The blindfolded subjects were trained to demonstrate discrimination by pressing the target with wider gratings. Discrimination thresholds (75% correct) for the subjects were 2.05 mm and 2.15 mm, corresponding to Weber fractions of 0.025 and 0.075, respectively. These results indicate thresholds on similar stimuli comparable to humans (index finger tasks) and better than harbor seals, Phoca vitulina, and the closely related Antillean manatee, Trichechus manatus manatus. Memory for the tactile task was quite stable for both subjects, over 2 yr in the case of one of the subjects. Video analysis of responses indicated that bristle‐like hairs, perioral bristles, and skin on the oral disk were involved in the discrimination response.     

The primary structure of the hemoglobin of the Brazilian manatee (Trichechus inunguis, Sirenia)

The hemoglobin of the Brazilian Manatee (Trichechus inunguis, Sirenia) consists of one component. We present the primary structures of the alpha- and beta-chains which have been separated by chromatography on carboxymethyl-cellulose CM-52. The sequences have been determined by automatic Edman degradation with the film technique, using the native chains, tryptic peptides and the C-terminal prolyl-peptide obtained by acid hydrolysis of the Asp-Pro bond of the alpha-chains. Compared to the corresponding human chains we found 27 substitutions in the alpha- as well as in the beta-chains. Three heme contacts and four alpha 1/beta 1 contacts between the subunits are affected by exchanges. The hemoglobin of Trichechus inunguis is compared with those of Elephas maximus, Loxodonta africana, and Procavia habessinica and the monophyletic origin of the superorder Paenungulata is discussed.     

Nephrolithiasis and pyelonephritis in two West Indian manatees (Trichechus manatus spp.)

Two West Indian manatees (Trichechus manatus spp.) were reported with severe emaciation. One animal was a Florida manatee from the Everglades; the other was an Antillean manatee from Cuba. On necropsy, both animals had nephrolithiasis, pyelonephritis, and moderate to severe renomegaly. Histopathology revealed multifocal to diffuse pyelonephritis, interstitial nephritis, and nephrocalcinosis. The stones were analyzed and consisted primarily of calcium carbonate. Serum chemistry values for the Florida animal revealed no renal abnormalities. The mechanism of calculus formation remains unclear in manatees. In horses, another hindgut fermenter, the most common urolith is also calcium carbonate. Urinalyses performed on manatees are very similar to those of horses (i.e., alkaline urine, low specific gravity, and calcium carbonate crystals). Formation of uroliths in manatees may have a pathogenesis similar to equine urolithiasis.     

The former southern distribution of New World manatees (Trichechus spp.)

Records of New World manatees in 16th and 17th century literature extend the former distribution of Trichechus manatus to about 20° S. Early 19th century records confirm this range, but the species has since been exterminated from these southerly localities and is now rarely found to the south of Cayenne (French Guiana). Manatees probably did not occur at Rio de Janeiro or Santos, the Sao Vicente "monster" most likely being a pinnepede. The former distribution of T. manatus seems to have been bounded by the 24^° C mean annual isotherm.     

Social interactions in captive female Florida manatees

The Florida manatee (Trichechus manatus latirostris) is considered a semi‐social species with strong bonds developed primarily between mother and offspring. Some field studies suggest sociality may be more developed and such social relationships may facilitate survival. Seven facilities in Florida house manatees, many of which were brought into captivity because of injury or illness sustained in the wild. Decisions to release such manatees consider individual history and health. We examined social interactions in adult female captive manatees to assess level of association and implications for manatee care and release. We investigated the degree of contact among 20 manatees in captivity at four facilities housing two to nine adult female manatees. We used all contact behavior occurrences sampling and continuous recording for 180 continuous minutes per day over 3 consecutive days at each facility. Virtually all contacts were non‐aggressive. The number of contacts between manatees increased as the number of manatees per unit volume of water increased. Contacts did not fit a Poisson distribution, however, and were not random. When more than two manatees were present, manatees only associated with a subset of individuals in the aquarium. Relationships maintained in captivity indicate the potentially social nature of manatees, and suggest that further research is needed to examine the benefit of these relationships to the health and rehabilitation of manatees in captivity and conservation in the wild. Zoo Biol 24:135–144, 2005. © 2005 Wiley‐Liss, Inc.     

Alterations in blood and urine parameters in two florida manatees (Trichechus manatus latirostris) from simulated conditions of release following rehabilitation

In an effort to manage the existing population of the endangered Florida manatee (Trichechus manatus latirostris), as many individuals as possible are rehabilitated from illness or injury and released back into the waters of the state of Florida. It is not uncommon, however, for manatees recaptured for health assessment following release from rehabilitation to have elevated concentrations of serum creatinine. Although such elevated levels would be indicative of kidney failure in most other mammals, problems associated with renal function have not been evident in these recaptured manatees. To determine the possible cause(s) of the serum creatinine increase, two captive Florida manatees were manipulated to simulate many of the environmental and physical changes that occur during and shortly after release. Routine chemical analyses of serum and urine, complete blood counts, serum cortisol concentrations, and lymphocyte proliferation responses were measured. Serum creatinine concentrations increased significantly in response to decreased food intake and changes in food type. The increases differed depending on the salinity of the water in which the animals were maintained. It was found that significant changes in urinary creatinine and serum creatine kinase occurred as well, but serum cortisol concentrations were elevated only during simulated transport. Lymphocyte proliferation assays indicated that immune function was potentially impaired by extreme levels of dietary restriction and by changes in salinity. These results suggest that serum creatinine elevations and subsequent effects on the immune system might be minimized by adapting manatees undergoing rehabilitation to the diet and salinity they would encounter following release. Zoo Biol 22:103–120, 2003. © 2003 Wiley‐Liss, Inc.     

Early functional maturity of captive male northern elephant seals (Mirounga angustirostris)

A male northern elephant seal (Mirounga angustirostris) that was conceived in captivity was stillborn February 14, 1981, at Mystic Marinelife Aquarium in Mystic, Connecticut. Either of two males in the exhibit could have sired the pup. Both were only 3 yr at the time of conception.     

Seasonal reproduction and sexual maturity in Odontocymbiola magellanica (Neogastropoda, Volutidae)

Abstract. Members of Odontocymbiola magellanica (Volutidae, Odontocymbiolinae) inhabit Argentinean waters from 35°S to the Magallanes Strait. The reproductive biology of this potential fishery resource has not been studied before. Male individuals reach maturity at 80 mm and females at 90 mm, corresponding to ∼7 and 8 years of age, respectively. Mating was observed in the field in all seasons and females possess live spermatozoa in the bursa copulatrix all year round, suggesting that living sperm can be preserved for several months. Major oviposition events occurred July (winter) to December (summer) during the 5 years sampled, as characterized by aggregation of females coincident with increasing photoperiod from winter to summer solstices, and not, apparently, by increase in water temperature. Males showed gametogenic activity throughout the year. Gamete resorption occurred in both sexes. Ultrastructural studies showed that oocytes are attached to companion cells, which enables cell–cell communication and provides support until evacuation; males showed normal sperm cells and two types of parasperms. If populations of O. magellanica are commercially exploited in the future, we propose a minimum catch size of 100 mm, and a ban on the collection of females and egg capsules during the reproductive season.