Two new cryptic and sympatric species of the king crab parasiteBriarosaccus(Cirripedia: Rhizocephala) in the North Pacific

Abstract

Rhizocephalan barnacles have been reported to parasitize a wide range of king crab species (Lithodidae). So far all these parasites have been assigned to a single species, Briarosaccus callosus Boschma, 1930, which is assumed to have a global distribution. Here we investigate Briarosaccus specimens from three different king crab hosts from the fjord systems of Southeastern Alaska: Lithodes aequispinus Benedict, 1895, Paralithodes camtschaticus (Tilesius, 1815), and Paralithodes platypus (Brandt, 1850). Using molecular markers and by morphological comparison we show that Briarosaccus specimens from these three commercial exploited king crabs are in fact morphologically distinct from B. callosus, and further represent two separate species which we describe. The two new species, Briarosaccus auratum n. sp. and B. regalis n. sp., are cryptic by morphological means and were identified as distinct species by the use of genetic markers (COI and 16S). They occur sympatrically, yet no overlap in king crab hosts occurs, with B. auratum n. sp. only found on L. aequispinus, and B. regalis n. sp. as parasite of the two Paralithodes hosts.

Spatial variability in size at maturity of golden king crab (Lithodes aequispinus) and implications for fisheries management

“…Another possible explanation that may be influencing golden king crab growth is the parasite B. auratum , previously identified as B. callosus , a parasitic barnacle that suppresses growth, feminizes and castrates male crabs and sterilizes female crabs [ 41 ]. This parasite has a root system (interna) that runs through the inside of its host taking over their body and produces multiple egg sacs (externa) under the abdominal flap [ 39 ].…”

“…Female CL was measured and pleopods inspected to determine maturity during 1998-2015 (n = 14 242). Crabs that were visually infected with Briarosaccus auratum (n = 448) were excluded from the analysis, because they are known to suppress growth, potentially hindering maturity [39][40][41]. Observer coverage included at least one trip in one of the seven management areas in Southeast Alaska each year (figure 1).…”

Infestation of parasitic rhizocephalan barnaclesSacculina beauforti(Cirripedia, Rhizocephala) in edible mud crab,Scylla olivacea

“…Even if copulation successfully occurred between a normal male and abnormal female, the copulated female is unable to secure her fertilized eggs onto her reduced pleopods. In addition, the sterilisation effect onto infected hosts by rhizocephalan parasites are well documented ( Isaeva, Dolganov & Shukalyuk, 2005 ; Noever, Olson & Glenner, 2016 ; Yang et al, 2014 ), even in sacculinids ( Høeg, 1995 ). Further studies on the histology and mating of abnormal crabs are recommended to validate these hypotheses.…”

The bigger, the better? Volume measurements of parasites and hosts: Parasitic barnacles (Cirripedia, Rhizocephala) and their decapod hosts

“…This trend is further highlighted in the king crab rhizocephalan Briarosaccus , which is closely allied to Peltogaster [ 64 ]. This parasite, which reaches enormous sizes for rhizocephalans [ 65 , 66 ], has been reported with up to 500,000 larvae being released in one single spawning event [ 67 ].…”