Blue King Crab Paralithodes Platypus Research Articles

Синий краб Paralithodes platypus – востребованный объект крабового промысла в северо-западной части Охотского моря (в Северо-Охотоморской подзоне)

The history of the study and fishing, the main biological indicators of the blue king crab Paralithodes platypus, living in the north-western part of the Sea of Okhotsk, are considered. Based on the materials collected in 2003-2022, the course of fishing and catching of this crab is analyzed. It is shown that the prospects of industrial development of this valuable object in the coming years do not cause concerns.

Size of maturity for blue king crab Paralithodes platypus in the northern part of the Sea of Okhotsk

We determined the size of sexual maturity of male and female blue crabs in the northwestern part of the sea (zone of cold core action), as well as in the northeastern part of the sea and the local cluster near the Iona bank (zone of comparatively warm waters). Morphological 50% maturation of males in the northwestern part of the Sea of Okhotsk was observed at the carapace width of 73.3 mm. Similar width were demonstrated for the northeastern part of the sea and for the Iona Bank area – respectively 88.5 mm and 91.0 mm. Females in samples from the northwestern part of the sea reached functional 50% maturity at the carapace width of 71.7 mm, from the northeastern part – of 79.4 mm, and from the Iona Bank – of 81.0 mm. Comparison with available literature data showed that blue crab in the northwestern part of the Sea of Okhotsk has probably the slowest growth rate, and the crabs have the smallest size at maturity compared to individuals in the other areas.

Growth Features of Blue King Crab Paralithodes platypus in the Northern Part of the Sea of Okhotsk

Growth Features of Blue King Crab Paralithodes platypus in the Northern Part of the Sea of Okhotsk

Dynamics of indices of the state of the blue king crab stock in the western part of the Bering Sea in 2005–2021

The aim of the research is a retrospective analysis of the stock of the blue king crab Paralithodes platypus inhabiting the western part of the Bering Sea, to show the prospects of using the relative abundance index (I%N) as an assessment characterizing the state of the stock of this species. Material and methods. It is based on the data of direct accounting of P. platypus during trawl and trap surveys in 2005–2021. For each year, an index of relative abundance was established, expressed as a percentage of the maximum number of crabs noted in the retrospective period. The I%N index was determined for different functional groups of the crab separately and for combined size and age groups. New data. The use of the relative abundance index I%N in quartiles makes it possible to apply a four-zonal evaluation characteristic of the stock status of P. platypus: the stock condition is good, satisfactory, uncertain and depressive. This indicative method displays the dynamics of the state of the stock in the studied period and visualizes its variability in the historical period. In the West Bering Sea population of P. platypus, there has recently been a decrease in the number, which is less than 40 % of the maximum number observed during the study period. In all functional groups of P. platypus, the estimate of abundance (stock) is currently characterized as uncertain. Practical significance. The retrospective dynamics of the relative abundance index I%N is an additional operational indicator in making a management decision when developing P. platypus as a commercial reserve unit in the western part of the Bering Sea.

Relative abundance index as an operational assessment of the state of the king blue crab stock in the Shelikhov Bay of Okhotsk Sea

The material of spring registration surveys of the blue king crab Paralithodes platypus conducted in the Shelikhov Bay of the Okhotsk Sea from 2007 to 2019 is presented. It is proposed to use the relative abundance index (I%N) for a quick assessment of the characterizing state of the stock of the exploited population. The index I%N is defined as the ratio of the number of a separate functional group of the crab to the maximum number for this group of crab in the study period, expressed as a percentage. A similar algorithm was used to determine the index of the relative density of the distribution of crabs (I%P) and the index of the relative average daily catch of fishing vessels for the first half of the year (I%M). When comparing the relative indices I%N, I%P, I%M, the most convincing was the relative population index I%N. To assess the stock status of the studied functional group of crabs in the values of the index I%N, it was proposed to distinguish 4 quartiles (interval 25 units): 1st quartile (Q1) I%N <75 stock condition is good; 2nd quartile (Q2) I%N = 51–75 stock condition is satisfactory or relatively stable; 3rd quartile (Q3) I%N 26–50 stock status uncertain; 4th quartile (Q4) I%N ≤25 stock status is unsatisfactory or depressive. The boundary values between quartiles Q1–Q2, Q2–Q3, and Q3–Q4 are I%N values of 75, 50, and 25, respectively. The dynamics of the I%N index in the studied time period reflects the real process taking place in the fishing unit of the stock based only on empirical data.

First record of new rickettsia-like organism in the blue king crab Paralithodes platypus from the Sea of Okhotsk: Distribution, morphological evidence and genetic analysis

An infection caused by a rickettsia-like organism (RLO) was detected in the blue king crab Paralithodes platypus from the eastern Sea of Okhotsk. The external signs of the disease are lethargy and an empty gastrointestinal tract. Dissection of infected individuals revealed that their hepatopancreas was light yellow in color. The causative agent of infection is Gram-negative rod-shaped bacterium targeted exclusively at hepatopancreas tissues. In the cytoplasm of infected cells, the bacteria are enclosed in parasite vacuoles or located immediately in cytosol. An ultrastructural analysis showed two main morphological types corresponding to the life cycle stages in the RLO: the vegetative stage of intermediate bodies, characterized by growth and division processes, and the infection stage of elementary bodies, which are spore-like non-dividing short rods surrounded by a multilayered membrane and having an osmiophilic inclusion body. At the terminal stage of infection, as a result of lysis of the infected cells, the RLO enters the lumen of the hepatopancreatic tubules which contributes to the spread of infection. According to genetic analysis based on 16S rRNA gene sequences, the RLO from P. platypus is most closely related to the Candidatus Hepatobacter penaei, NCBI #JX981946 (94.7% similarity) and NCBI #KY363553 (94.1% similarity). The high level of genetic differences (more than 5%) of the studied pathogen, along with the structural features, allows characterizing the RLO isolated from P. platypus as a new species of the genus Candidatus Hepatobacter paralithodi nov. sp., NCBI #MK928971.

Pitanie sinego kraba Paralithodes platypus v zalive Babushkina Okhotskoe more v iyule 2011 g

Pitanie sinego kraba Paralithodes platypus v zalive Babushkina Okhotskoe more v iyule 2011 g

A herpes-like virus in king crabs: Characterization and transmission under laboratory conditions

A herpes-like virus was found infecting the antennal gland and bladder epithelium in the blue king crab Paralithodes platypus from the eastern area of the Sea of Okhotsk. Electron microscopic analysis of antennal gland samples from blue king crabs with histologically confirmed signs of disease revealed virus particles, which were mostly hexagonal in shape and located primarily in the nucleus; these particles were rarely observed in the cytoplasm of infected cells. Most virus particles ranged in size from 115 to 125nm. Hemocytes of the red king crab Paralithodes camtschaticus in cell culture could be experimentally infected with virus from thawed antennal gland samples of the blue king crabs with histologically confirmed signs of viral infection. Clear signs of infection were observed in hemocyte cultures at 3–4days post-inoculation as small foci of highly vacuolated formations. These formations included several nuclei and were surrounded by a halo of small cytoplasmic bubbles containing actin and tubulin. As demonstrated by electron microscopic studies, no virus-like particles were found in the cells 1day post-inoculation, but particles become abundant at 7days post-inoculation. We developed a consensus primer PCR method for amplification of a region of the herpesviral DNA-directed DNA polymerase. Primers were designed to target sequences encoding highly conserved amino acid motifs covering a region of approximately 800bp. Thus, macroscopic, histological and ultra-structural examinations of blue king crabs infected with a virus and the molecular identification of the pathogen revealed the presence of herpesviruses. The frequency of the herpes-like viral infection in natural populations of blue king crabs in the Sea of Okhotsk ranged from 0% to 3% in different years.

Substrate preferences and redistribution of blue king crab Paralithodes platypus glaucothoe and first crab on natural substrates in the laboratory

Despite the importance of blue king crab (BKC) to the Bering Sea fishery, there has been no detailed study of juvenile habitat preferences. Such information is critical for understanding life history and for development of stock enhancement programs. The aims of this study were to determine the natural substrata that glaucothoe prefer to settle on, and whether they or subsequent crab 1 stage (C1) redistribute to different habitats over time. A laboratory experiment was performed in 24 round containers divided in four equal quadrants each filled with one of the following natural substrata: beach sand, gravel, shells and cobble. Containers were assigned to 8 groups of 3 replicates each and were kept at ~ 6–8 °C. Twenty five glaucothoe were released in each container on day 0, and one group of three replicates was removed for examination at each of the following intervals: 24 h, 7, 14, 21, 28, 35, 42 and 49 days. Numbers of swimming and settled specimens on each substrate and period were recorded. Glaucothoe began to settle immediately after being released since no swimming larvae were found during any sampling periods. Substrata complexity was important for the habitat selection and distribution of blue king crab glaucothoe and crab 1 stage. During the glaucothoe stage, beach sand was rejected and cobble, shell and gravel were chosen equally. After glaucothoe molted to crab 1 stage and became bigger, animals preferred cobble and shell instead of gravel and beach sand. Understanding habitat selection is useful not only for management of crab populations, but also for assessing the potential of various habitats for stock enhancement of blue king crabs.

Thermal Effects on Embryonic Development and Hatching for Blue King Crab Paralithodes platypus (Brandt, 1850) Held in the Laboratory, and a Method for Predicting Dates of Hatching

Climate change may affect crab populations via thermal effects on embryo development and hatching. To test this, we measured the duration of development and hatching for the embryos of 11 blue king crabs Paralithodes platypus held at 2.3 ± 0.45, 4.3± 0.31, and 6.1± 0.61C. Embryo area, length, and width, eye length and width, and percent yolk were measured biweekly from digital images, and hatching larvae were collected daily from individual crabs. Data were compared between eggs of identical age (weeks since fertilization). Temperature did not have a significant effect on embryo measurements, but did affect development indices (percent yolk and eye size). Hatching was significantly delayed at colder temperatures with about a 46-day difference from 2.3C to 6.1C. Length of development was related to temperature via a power function, and ranged from 410 ± 8 days at 6.1 Ct o 434 ± 11 days at 2.3C. Length of hatching increased from 40 ± 4.6 days at 2.3 Ct o 55± 6.2 days at 6.1C. A model for predicting hatching dates from an eye index was developed using a quadratic equation. Embryo development at 4.3 and 6.1C was arrested between weeks 35 and 50; this evidence, plus other behavioral observations, suggests that crabs may be able to adjust development rates to partially compensate for temperature changes.

Survival of blue king crab Paralithodes platypus Brandt, 1850, larvae in cultivation: effects of diet, temperature and rearing density

Blue king crab (Paralithodes platypus) larvae were cultivated to test the effects of diet, temperature and rearing density. Dietary treatments included no feeding (unfed), Artemia nauplii enriched with diatoms Thalassiosira nordenskioeldii (THAL), unenriched Artemia fed in addition to Thalassiosira (A+THAL) and a control diet of Artemia enriched with frozen Isochrysis paste (ISO 6). Trials were conducted at 6 °C, and a rearing density of 10 zoea L−1, with six replicates per treatment. The ISO 6 diet was also tested at 3 °C (ISO 3) and 9 °C (ISO 9), and at densities of 20 (ISO 20) and 40 (ISO 40) zoea L−1. Survival of zoea larvae fed the A+THAL diet (91.7%) was significantly higher than all others, whereas unfed zoea larvae died within 2 weeks. Temperature and rearing density had no significant effects on survival. Time required to reach stage C1 was significantly greater at 3 °C (109 days) than at 6 °C (70 days), but did not decrease further at 9 °C. After reaching the postlarval (glaucothoe) stage, half of the replicates in the ISO 20 and ISO 40 treatments were fed continuously, but survival did not differ significantly from unfed glaucothoe. We conclude that blue king crab larvae are not lecithotrophic and can be cultivated with high survival using the proper diet. These techniques can be used to produce large numbers of juvenile crab for laboratory research, or could be modified for use in stock-enhancement programmes.

Timing and Duration of Larval Hatching for Blue King Crab Paralithodes Platypus Brandt, 1850 Held in the Laboratory

Abstract Female blue king crab, Paralithodes platypus, were captured from the Pribilof Islands, Alaska, in July and October 2003 and shipped to the Kodiak Fisheries Research Center. Crabs were held in chilled seawater at 2, 3.5, or 4°C until hatching, and final counts were 4, 6, and 10 crabs in each treatment, respectively. Mean size of all crabs was 123.9 mm CL and did not differ significantly between treatments. Individual crabs required an average of 29 days for complete hatching, regardless of holding temperature. Earliest hatching began on or before 20 February 2004. Crabs captured in July and held at 4°C hatched significantly earlier, with a mean hatch date of 13 March 2004, than crabs captured in October and held at 2°C or 3.5°C, both of which groups hatched on a mean date of 18 April 2004. Crabs released an average of 416 ml of larvae, and 110,033 first stage zoeae. Excluding two crabs for which complete volumes were not obtained, there were no differences in volume or number of larvae released by...

Autotomy and regeneration of limbs in the male blue king crabParalithodes platypus from the Bering Sea and the Sea of Okhotsk

Limb loss and the frequency of regeneration was investigated in the male blue king crabParalithodes platypus collected in the Sea of Okhotsk and the Bering Sea. TheP. platypus population in the Bering Sea is characterized by an anomalously high proportion of crabs with missing limbs, which is largely due to the intensive fishing. The present approach to the exploitation of the Bering Sea population, in which large intact crabs are removed and injured crabs are left to recover to the normal state, may result in a decline in the reproductive potential of this population as early as this coming year.

Histopathology and host response in lithodid crabs parasitized by Briarosaccus callosus

Two red (Paralithodes camtschatica) and 26 golden (Lthodes aequispina) king crabs parasitized by the rhzocephalan Briarosaccus callosus were examined microscopically for histopathological effects of and host response to the parasite. Although numerous organs were invaded and tissues displaced, replaced or compacted, there was little necrosis or degeneration of tissues other than gonads. Host response to healthy B. callosus was negliqble, but degenerating rootlets of the parasite elicited heavy hemocytic response in a typical crustacean foreign-body reaction. Boschma (1962) described Briarosaccus callosus and suggested it may be a cosmopolitan parasite of lithodid crabs, reporting it from Lithodes aequispina in the Bering Sea, L. agassizii off southeastern United States, and L. antarcticus and Paralomis granulosa in the Antarctic and sub-Antarctic regions. Subsequently, Boschma & Haynes (1969) reported it from Pardithodes camtschatica in southeastern Alaska. Hawkes et al. (1985a) first reported B. callosus from Paralithodes platypus, again from southeast Alaska. Prevalences of infection have been investigated in blue king crab Paralithodes platypus (Hawkes et al. 1985a, b), red king crab P. camtschatica (Hawkes et al. 1986), and golden king crab Lithodes aequispina, as have gross observations on the effect on growth, reproduction and migratory behavior of parasitized crabs (Sloan 1984, 1985, Bower & Sloan 1985, Hawkes et al. 1986), but heretofore the histopathological effects have been only briefly mentioned (Sparks 1985, Sparks & Morado 1985). MATERIALS AND METHODS Two red king crabs Parahthodes camtschatica with Briarosaccus callosus externa were shipped alive to our laboratory where necropsies were performed and random samples of the major organ systems were O Inter-Research/Printed in F. R. Germany excised, fixed, and processed by standard histotechniques. All other crabs were collected during crab population surveys by the Resource Assessment and Conservation Engineering Division (RACE) of the National Marine Fisheries Service (NMFS) or Alaska Department of Fish and Game (ADF & G). Necropsies were performed aboard ship by personnel of our laboratory, the NMFS Kodiak Laboratory or the ADF&G. The fixed tissues were processed in our laboratory where microscopical observations were made on the histopathological effects of B. callosus and host response to the parasite in parasitized crabs.