Evidence Of Molt Research Articles

Growth marks in eyestalks of Portunus trituberculatus: A development of technique and evidence of molting

Growth marks in eyestalks of Portunus trituberculatus: A development of technique and evidence of molting

Correction: Evidence of molting and the function of "rock-nosing" behavior in bowhead whales in the eastern Canadian Arctic.

[This corrects the article DOI: 10.1371/journal.pone.0186156.].

Evidence of molting and the function of "rock-nosing" behavior in bowhead whales in the eastern Canadian Arctic.

Bowhead whales (Balaena mysticetus) have a nearly circumpolar distribution, and occasionally occupy warmer shallow coastal areas during summertime that may facilitate molting. However, relatively little is known about the occurrence of molting and associated behaviors in bowhead whales. We opportunistically observed whales in Cumberland Sound, Nunavut, Canada with skin irregularities consistent with molting during August 2014, and collected a skin sample from a biopsied whale that revealed loose epidermis and sloughing. During August 2016, we flew a small unmanned aerial system (sUAS) over whales to take video and still images to: 1) determine unique individuals; 2) estimate the proportion of the body of unique individuals that exhibited sloughing skin; 3) determine the presence or absence of superficial lines representative of rock-rubbing behavior; and 4) measure body lengths to infer age-class. The still images revealed that all individuals (n = 81 whales) were sloughing skin, and that nearly 40% of them had mottled skin over more than two-thirds of their bodies. The video images captured bowhead whales rubbing on large rocks in shallow, coastal areas—likely to facilitate molting. Molting and rock rubbing appears to be pervasive during late summer for whales in the eastern Canadian Arctic.

Performance and physiological responses of combined t-bar and PIT tagged giant mud crabs (Scylla serrata)

Mud crabs (Scylla spp.) are intensively caught throughout South-East Asia and support a very substantial commercial, recreational fishing and aquaculture industry. Identification of individual animals is important to improve understanding and management of this species. However, tagging of crustaceans is difficult as they frequently molt and internal tags can pose a hazard to consumers. In this pilot study we tested a new method combining passive integrated transponder tags and t-bar tags externally. 45 giant mud crabs (Scylla serrata) were captured from the wild and kept in tanks for a maximum of 10 months. We inserted tags into the abdomen of 35 giant mud crabs and tested a modified method where the combined t-bar/PIT-tag was inserted into the muscle tissue of the rear leg between the dorsal carapace plate and the top of the abdominal flap. Tagged crabs with the modified method showed 85% tag retention for molting crabs. We tested the same method in the field where 852 individuals were tagged with combined t-bar/PIT-tags of which 82 were recaptured showing 100% tag retention but without any evidence of molting having occurred. The tested method of combined t-bar/PIT-tags in giant mud crabs can further improve monitoring for wild and aquaculture populations and can be deployed widely with low cost.

BODY MOLT OF MALE LONG-TAILED DUCKS IN THE NEAR-SHORE WATERS OF THE NORTH SLOPE, ALASKA

We examined the timing and intensity of body molt in relation to stage of remige growth for postbreeding adult male Long-tailed Ducks (Clangula hyemalis) off the coast of northern Alaska. During this period, remige and rectrix feathers are molted simultaneously with body feathers during the prebasic molt, which results in a period of increased energetic and nutritional demands. We collected birds from late July through mid-August and recorded intensity of molt in eight regions: head and neck, back and rump, greater coverts, lesser coverts, flank and sides, breast, belly, and tail. Using nonlinear regression, we estimated the peak intensity and variation for each region in relation to ninth primary length. We found little evidence of molt in the head and neck region. The greater and lesser coverts, and back and rump reached peak molt intensities earliest and were followed by tail, breast, and belly. Molt intensity in the flank and side region was highly variable and indicated a more prolonged molting pattern in relation to other regions. While body molt occurs simultaneously with wing molt, we found that molt among regions occurred in a staggered pattern. Long-tailed Ducks may employ this staggered molting pattern to minimize the energetic and nutritional requirements of molt.

The Relationships of Sparrows in the Genera Ammodramus, Passerherbulus, and Ammospiza with a Description of a Hybrid Le Conte's × Sharp-Tailed Sparrow

THE first and second editions of the A.O.U. Check-list (1886, 1895) list the Henslow's Sparrow (now Passerherbulus henslowii) and the Le Conte's Sparrow (now Passerherbulus caudacutus) in the subgenus Coturniculus of the genus Ammodramus with the Grasshopper Sparrow (now Ammnodramus savannarum). When Ridgway (1901) raised the subgenera (Passerculus, Centronyx, Coturniculus, and Ammodramus) of Ammodramus to generic rank, he separated the Henslow's and Le Conte's Sparrows from the Grasshopper Sparrow and placed them with the former members of the subgenus Ammodramus, the Sharp-tailed Sparrow (now Ammospiza caudacuta) and the known Seaside Sparrows (now Ammospiza maritima and nigrescens), a treatment later followed by the A.O.U. (1903). The Ammodramus group remained intact, despite being renamed Ammospiza (Oberholser, 1905) and then Passerherbulus (Stone, 1907), until Oberholser (1917) split the group into four genera: Thryospiza for the Seaside Sparrows, Ammospiza for the Sharp-tailed Sparrow, Passerherbulus for the Le Conte's Sparrow, and Nemospiza for the Henslow's Sparrow. Subsequently the A.O.U. (1931) recognized the genus Ammospiza containing the Sharp-tailed and Seaside Sparrows, the genus Passerherbulus containing the Le Conte's and Henslow's Sparrows, and the genus Ammodramus, containing the Baird's (A. bairdii) and Grasshopper Sparrows. No changes have been made since, and as yet no diagnoses exist for these genera as presently constituted. More recently Tordoff and Mengel (1951) questioned the present classification when they discovered that the prealternate molt of the Le Conte's Sparrow was extensive and thus more like that of the Sharp-tailed Sparrow than that of the Henslow's Sparrow. Graber (1955) actually transferred the Le Conte's Sparrow to Ammospiza on the basis of the similarity of the juvenal plumages of the Le Conte's and Sharp-tailed Sparrows. With the discovery of a hybrid between the Le Conte's and Sharp-tailed Sparrows (described below), it seems appropriate to consider the evidence of molt, plumage, and voice bearing on the relationships of these species. Molt.-The descriptions of the molts of the species being considered are generally incomplete or erroneous. Detailed studies for most species have yet to be made. The best that can be done now is a brief comparison of what is known.