Pacific Salamanders, these giant, sturdy pacific salamanders have an enormous head, properly developed eyes, and giant, properly developed limbs. Fore and hind limbs fail to overlap when adpressed to the trunk in D. copei in addition to in some people of the opposite species, however overlap barely by as many as 4 costal folds within the different species. The tail is comparatively brief, all the time a lot shorter than head plus physique size, and it’s laterally compressed with a definite keel. Metamorphosed adults are darkish in coloration, usually attractively mottled or marked with totally different shades of grey. Larvae are considerably flattened dorsoventrally and are darkly pigmented. The comparatively brief, sturdy tail is considerably flattened on the base however then turns into laterally compressed with a modest fin. The fin terminates on the base of the tail, properly behind the pelvis. Gills of larvae are brief and comparatively inconspicuous in larvae residing in small, quickly flowing streams, however can change into giant and filamentous in larvae residing in lakes and bigger streams.
Evolution and systematics
These giant salamanders occupy a considerably enigmatic place phylogenetically. They lengthy have been thought to be allied with mole salamanders (Ambystomatidae) and torrent salamanders (Rhyacotritonidae) and have been categorized in a single household, Ambystomatidae, however there are not any uniquely derived traits shared by these three teams. Despite the truth that every incorporates solely a single genus, at current three households are sometimes acknowledged. Some molecular proof means that dicamptodontids and ambystomatids are sister taxa. Some latest classifications place the dicamptodontids and rhyacotritontids in a single household, Dicamptodontidae, however there isn’t a morphological or molecular proof in help of a sister-group relationship of these two distinct lineages. Dicamptodontids differ from most ambystomatids in having a larval stage that lasts for a couple of 12 months, however there are species in each households that by no means metamorphose and breed as completely gilled varieties. Dicamptodontids additionally differ from ambystomatids in having comparatively a lot bigger and extra closely ossified skulls, with extra cranium bones; within the anatomy of the tongue skeleton; and in having trunk vertebrae that aren’t pierced by the spinal nerves. Members of each households have species that attain the most important measurement of any metamorphosed, terrestrial salamander (one plethodontid is as almost as giant), however dicamptodontids are extra huge. Dicamptodontids differ from rhyacotritontids in being a lot bigger and in having much less properly developed skulls and limbs. The single genus, Dicamptodon, consists of 4 species (D. aterrimus, D. copei, D. ensatus, and D. tenebrosus). No subfamilies are acknowledged.
The household is narrowly distributed and is restricted to the Pacific Northwest area of North America. An remoted group of populations of D. ensatus happens on the central and southern San Francisco peninsula in California. The species are roughly constantly distributed within the coastal ranges from north of San Francisco to the northern finish of the Olympic Peninsula in Washington, and from the southern Cascade Mountains of Oregon into the coastal mountains of southwestern British Columbia (however not on Vancouver and neighboring islands). One species, D. aterrimus, is disjunctly distributed and happens within the mountains of northern Idaho and northwestern Montana, west of the Continental Divide.
Dicamptodontids are restricted to wooded areas which have clear, everlasting streams through which their larvae dwell. Typically they dwell in coniferous woodlands which are in comparatively steep terrain. They do particularly properly in areas dominated by Douglas fir and coast redwood. Larvae do finest in small, troutless streams, however bigger larvae could dwell in rivers (such because the Willamette) and small lakes. Occasionally they’re caught on hook and line by fishermen.
Adults are incessantly discovered strolling by day in darkish, moist forests, however extra sometimes they’re nocturnal. Large people will be aggressive and have interaction in head-butting and taillashing. They are able to inflicting a harmful chew as a result of they’ve robust jaws and small however quite a few and properly developed enamel. Nothing is understood regarding courtship and mating, however fertilization is inner by way of a spermatophore, in all probability deposited in a terrestrial web site, and eggs are deposited singly however in giant teams of 80 or extra underneath giant rocks and logs in headwater streams. Adults are able to vocalizing. They produce a pointy “bark,” however the operate of this conduct is unknown.
Feeding ecology and weight-reduction plan
The larvae are opportunistic feeders of benthic larvae of bugs (these discovered on the backside of the stream or river), however in addition they take different stream-dwelling organisms. Because the larvae develop to giant measurement, they feed on bigger prey as properly, together with larvae of ambystomatid salamanders and small fish. They are thought of to be probably the most considerable vertebrate predators in headwater streams all through their vary. Adults show a variety of sizes. As small adults they eat a big selection of terrestrial invertebrates, which they catch with their protrusible tongue. As they develop bigger they prey on vertebrates, corresponding to slender salamanders, lizards, shrews, mice, and even snakes, which they seize with their robust jaws. They forage broadly and climb vegetation as excessive as 6.5 ft (2 m) on tree trunks.
Relatively little is understood in regards to the replica of dicamptodontids. Courtship has not been noticed, however most probably it’s aquatic as a result of D. copei sometimes reproduces as a gilled kind. Eggs are onerous to discover. The few discoveries have been underneath giant rocks and logs in or on the fringe of streams. Eggs develop slowly, and hatching doesn’t happen for a lot of weeks. Newly hatched larvae have giant quantities of stomach yolk and in all probability don’t feed for a number of weeks. The larval stage is not less than two years and could also be so long as 4 years often. Metamorphosis is uncommon in D. copei. Reproductive larvae have been reported within the different species, however courting and egg laying has not been noticed, and the gravid larvae could metamorphose earlier than reproducing.
Pacific big salamanders are depending on forests and clear, unpolluted streams. Areas through which they happen have been and at the moment are present process nice habitat modification because of forestry practices, highway constructing and different development, and urbanization. Salamanders are most considerable in outdated progress forests, however they survive following logging and even improve in density as long as streams stay comparatively unsilted. Eventually their numbers decline, and because the forest regrows they seem not to recuperate, and their populations in second progress forests are a lot decrease than in main forests. These salamanders could spend most of their lives as stream-dwelling larvae, so stream high quality is a significant component of their long-term survival. Different species are protected to some extent in numerous preserves, together with nationwide and state parks, and not one of the species is susceptible to extinction at current.