Revision on the genus Sergetes (Decapoda: Dendrobranchiata: Sergestidae): Taxonomy and Distribution

Extensive Danish collections of sergestid shrimp taken during the “Dana I” (1920-22), “Dana II” (1928-30) and “Galathea” (1950-52) Expeditions have been examined. These 1409 examined samples comprise a total of 20,544 specimens: 9,022 males and 11,522 females. All the 29 hitherto known valid species plus 6 new species (Sergestes antarcticus, S. mepae, S. oleseni, and S. vinogradovi, S. cylindricus and S. sirenkoi) are considered. A new species group is established for S. cornutus and S. mepae. Briefly considered are: (1) the history of the genus; (2) development; (3) biomass, feeding, predators and their role in communities; (4) growth; (5) locomotion, (6) illumination and behaviour; (7) pelagic and benthopelagic modes of life; (8) vertical distribution; (9) geographical distribution; (10) generic morphology, and (11) generic taxonomy. Keys to species groups and species within each species group are provided. Five species are synonymised: S. erectus with S. coalitus, S. curvatus with S. corniculum, S. nipponensis with S. seminudus, S. extensus with S. armatus and S. geminus and S. gibbilobatus with S. orientalis. The genus Sergestes is divided into 7 species groups: S. corniculum (8 species), S. arcticus (3 species), S. atlanticus (only species), S. cornutus (2 species), S. sargassi (8 species), S. vigilax (7 species), and S. orientalis (6 species). Each species group is diagnosed. Division is mainly based upon structure and shape of: (1) the carapace, (2) the male clasping organ, (3) the scaphocerite, (4) maxillipeds I & III, (5) pereopods II-III, (6) the posterior pleurobranch on somite XII; (7) the uropodal exopod, (8) the petasma and (9) the organs of Pesta. All species are described in a uniform manner with special attention paid to the petasma and maxilliped III; numerous morphometric characters are given. The description of each species is provided with a synonymy, list of material, species diagnosis, remarks on confusion in synonymy, and interspecific morphological similarities and differences; data on geographical distribution, and a brief record of vertical range and the species’ mode of life are given. Illustrations of lateral carapace view, male clasping organ, petasma, and distribution maps are provided for each species; figures of other characters are included if appropriate. Dr. K. Stephensen’s watercolours, made during the “Dana I” Expedition, are herein reproduced in colour for the first time