Caribbean Algocetus

Caribbean algocetus (Xenalgocetus diodon)
Order: Algocetuses (Algocetiformes)
Family: Algocetuses (Algocetidae)
Habitat: Caribbean Sea.
Herbivorous sea mammals in human epoch were presented by sirenian order – not numerous group of sluggish aquatic mammals. These animals bred slowly and differed in poor ingenuity. It made them very vulnerable for hunting, and their number began to reduce even in early historical time. Despite of strict protection, residual populations of these animals had not gone through human epoch. In Neocene various groups of vertebrates competed for a role of sea herbivores. In Tanganyika passage algal turtles (Thalassotestudo algophaga) live, but they did not manage to become dominant herbivores of seas – their distribution is limited only to warm waters of passage. Descendants of South American rodent coypu (Myocastor coypus) have achieved the much greater success. At coast of South America the representatives of new group of mammals descended from them very fast to evolutionary measures; these ones are algocetuses, herbivorous animals permanently living in sea. The majority of algocetuses does not cross equators and is settled only in coastal waters of South America and Antarctica. Only one species managed to step to the north, to Caribbean Sea. Thickets of sea spinach (Thalassolatucca crystallophylla), floating aquatic plant, are the basic source of food for Caribbean algocetus, heat-loving species of herbivorous water mammals.
Caribbean algocetus is a second-largest species in order after Falkland paralgocetus. The body length of adult individual reaches 5 – 6 meters. Layer of blubber at this species is thin – it is a consequence of life in tropics. However the blubber layer is necessary for it serving as an adaptation facilitating swimming. Caribbean algocetus spends a significant part of life at the surface of water. At this species the extra adaptations were developed, allowing the improving of heat radiation: skin is covered with the numerous cross wrinkles increasing its surface. Tail fin is wide with rounded flukes – it is not only swimming organ, but also the adaptation for heat emitting. Caribbean algocetus swims slowly and dives only to depth of about 20 – 30 meters only in case of extreme danger, for example, in storm. At its way of life speed and ability to dive deeply become almost excessive, because its forage is always on surface of water.
Rear limbs of this animal had disappeared completely –only rudiments of sacrum and hip remained from them. But front flippers of this species are very mobile – they are rather long and can bring food to mouth. Front limbs keep mobility in elbows and even prehensile function is kept partly at them. The second and third fingers of forward limb are covered with the common skin cover, are separated from the fourth and fifth fingers by small interval and can move independently of them. Due to this feature the limb capable to grasp food is formed. On second and third fingers large claws are advanced.
Caribbean algocetus eats mostly sea spinach – floating species of aquatic plants living on surface of Caribbean Sea. This plant lives in stable conditions and always gives plentiful growth, therefore groups of these animals are always provided with habitual forage. Caribbean algocetus, however, does not leave far in sea – it is possible to find only separate males at great distance from the coast. The basic population prefers to be fed in thickets of sea spinach above depths up to 100 meters. This animal may be seen frequently in shallow waters; it swims there for thickets of sea spinach carried by wind, and also for aquatic plants growing on shoaliness. In silent weather this animal occasionally comes to edges of mangrove forests and in high inflow browses leaves of mangrove trees. Feeding on branches of mangrove trees, Caribbean algocetus swims in shallow water, lies sideways and drags branches of mangrove trees to mouth by forelimb. In outflow this animal tries to swim to deeper places. Occasionally the careless animal can get in a trap among mangrove trees: when passages become too shallow, animal stays on shoaliness and may die from heatstroke or choke under weight of its own body.
Soft vegetative food had resulted in significant changes of dental system of this species. Molars are lack completely, and they are replaced with corneous plates with ribbed chewing surface. Incisors in top jaw had turned to tusks similar to tusks of walrus or dugong, but shorter, rather than their ones. They are used in tournament fights of males. Female tusks are smaller. In lower jaw incisors are reduced completely.
Once in two years female gives rise to one large cub. Once in ten – fifteen cases of birth twins may be born. The one and a half meters long cub quickly grows, eating fat milk. Till two months of life it doubles its initial weight and gradually passes to feeding on plants though it is fed with milk almost up to one-year-old age. At four-year-old age the young animal is ready for breeding.
Caribbean algocetus lives in herds under the leadership of large female. Usually such herd totals up to 20 – 30 adult females and their posterity of the first years of life. Young males stay in herd up to their sexual maturity. Adult males form large barchelor herds which break up in breeding season. The female ready to pairing emits with urine the substance which taste helps males to find her out. In courtship season male behaves aggressively relatively to contenders. Battling for the female, males snap each other’s flippers and tail flukes. Battling with the help of tusks, they strike each other lateral impacts by head. Tusk points are used only for protection against predatory fishes.
Life expectancy of Caribbean algocetus reaches 35 – 40 years. Sharks are main enemies of these animals, but these mammals are more often suffer from the parasitic invertebrates boring into skin. Animals escape from them, coming into fresh water where parasites perish. With the same purpose during the inflow algocetuses scratch against roots and trunks of mangrove trees.