Reproduction
   
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  Copulation, egg release, & larval stages: genera P-R
  This topic is divided into a section dealing with genera Pachycheles, Pachygrapsus, Paralithodes, Petrolisthes, Pugettia, and Rhinolithodes, presented here, and sections on CANCER and GENERA A-L. presented elsewhere.
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Pachycheles

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Research study 1
 

drawings of larval and post-larval stages of crab Pachycheles rudisCulture of eggs from ovigerous females of Pacycheles rudis collected at La Jolla, California provides details of larval development.  Only 2 zoeal stage are passed through to the post-larval megalopa stage, the first taking 10d and the second, 14d at 15-18oC (see drawings). Knight 1966 Crustaceana 10: 75. Photo courtesy Dave Cowles, Walla Walla University, WA wallawalla.edu.photograph of crab Pachycheles rudis courtesy Dave Cowles, Walla Walla U


NOTE
  a second species Polyonyx quadriungulatus is included in the study but not shown here.  It lives in Chaetopterus tubes and subtidally, and is not so common as the intertidal-inhabiting P. rudis

 
Research study 2
 

drawings of zoeae larvae of porcelain crab Pachycheles pubescensdrawing of glaucothoe (megalopa) larva of porcelain crab Pachycheles pubescens
A characteristic feature of zoea larvae of F. Porcellanidae are long rostral and posterior spines.  A study on 2 species Pachycheles pubescens and P. rudis collected north of San Francisco provides information on their
larvae for identification purposes.  The drawings on the Left show 1st and 2nd zoeae, and on the Right, the glaucothöe (=megalopa), of P. pubescens. Zoea larvae of the 2 species are similar and can be distinguished only by the setation of the endopodite of 1st maxillipeds.  MacMillan 1970 Biol Bull 142: 57.

NOTE  the author notes that ovigerous females are kept in the laboratory for almost 50d (at 14oC) before the eggs hatch

 
Research study 3
 

histogram of proportion of crabs Pachycheles rudis infested with bopyrid isopods in relation to carapace width of the hostBopyrid isopods are common parasites of crabs and shrimps.  The parasites, depending on species, reside in the abdominal region or branchial chamber of its host, and feed on its host’s hemolymph using piercing and sucking mouthparts.  The abdominal type of bopyrid usually (or always?) castrates its host and, while this does not occur in the branchial-chamber type, there may still be deleterious effects on both reproduction and growth. The effect owes to loss of nutrients and energy to the parasite in the form of hemolymph, and perhaps to inhibition of gas exchange.  In the San Simeon area of southern California the anomuran Pachycheles rudis hosts females of graph showing effect of parasitism by bopyrid isopods on clutch size in crabs Pachycheles rudisthe branchial-chamber inhabiting isopod Aporobopyrus muguensis

The incidence of parasitism may reach 50% in mid-sized crabs (average 35%, with little difference between male and female hosts; see histogram above Right). Immature bopyrids occur in small hosts, while mature ones occur in large hosts.  Note in the histogram that crabs larger than about 8mm carapace width are much less infested, but many display empty but distended branchial chambers symptomatic of previous infestation. The graph on the Left shows that clutch size in parasitised female Pachycheles is significantly reduced in comparison with unparasitised crabs.  Although clutch sizes may be reduced by as much as 50-75% depending upon crab size, this bopyrid species is unique in causing only partial reduction in reproductive effort and growth of its host.  Van Wyk 1982 Parasitology 85: 459.

NOTE  many research studies are made less convincing by small sample sizes but, with an N value of 4327 to produce the histogram, there is no doubt about these data

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The author speculates on reasons for decreased infestation in large Pachychelis rudis.  Think about the possibilities listed below, then CLICK HERE to see explanations.

Parasitised crabs experience higher mortality than non-parasitised ones. 

The hosts lose their parasites as they grow larger. 

Growth of parasitised crabs is stunted. 

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Pachygrapsus

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Research study 1
 

graph showing seasonality of breeding in female crabs Pachygrapsus crassipesphotograph of shore crab Pachygrapsus crassipes courtesy Jackie Soanes, Bodega Marine Laboratory, CaliforniaOn beaches around Hopkins Marine Station, Pacific Grove, California female Pachygrapsus crassipes carry eggs between Mar-Aug.  Boolootian et al. 1959 Physiol Zool 32: 213. Photo courtesy Jackie Soanes, Bodega Marine Laboratory, California.

 
Research study 2
 

photograph of a gravid crab Pachygrapsus crassipesOn shores around Pacific Grove, California female Pachygrapsus crassipes copulate at least once per year and may do so a second time in preparation for a winter brood.  Copulation is mainly at night and, according to the author, the copulatory position is assumed rapidly by the receptive partners.  The male lies on his back below the female, grasping her with his walking legs.  At this time the abdominal flaps are open and pressed together.  The author notes that with the crabs in this position it is difficult to see the movements of the copulatory penes as they transfer the sperm-containing spermatophores to the female’s gonopores.  Female shore crabs Pachygrapsus crassipes copulate at least once per year and may do so a second time in preparation for a winter brood.  Eggs are borne in April-September or, for some females, over winter.  An average clutch of 50,000 eggs is extruded 16-25d from copulation and is incubated by the female for 26-31d.  The eggs are attached to 4 pleopods on the female’s abdomen.  The pleopods bear setal tufts on either side, making 8 clusters of eggs in total.  However, because the eggs are so tightly packed they usually appear as one cluster.  Males are sexually mature 7mo from hatching (12mm carapace width) and females at 12mo (15mm CW).  Hiatt 1948 Pac Sci 2: 135.

NOTE  the author provides a large amount of information on the biology of P. crassipes in this paper

   
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Research study 3
 

Some additional features of copulatory behaviour in Pachygrapsus crassipes are given in a study done at Hopkins Marine Station, Pacific Grove, California.  The main feature to add to what is described in Research Study 2 above is a copulatory ‘dance’, initiated by the male, and later reciprocated by the female.  In their dance, the crabs touch chelae and move one another back and forth, sometimes stopping and swaying without walking.  The behaviour culminates with the male rolling backwards and the female walking over him to adopt an uppermostl copulatory position.  Bovbjerg 1960 Pac Sci 14: 421.

   
 
Research study 4
 

Studies in La Jolla, California show that the crustacean moulting hormone crustecdysone also acts as a sex pheromone.  Close proximity to a moulting female Pachygrapsus crassipes induces typical precopulatory behaviour in mature male conspecifics, presumably leading to amplexus.  The hormone is effective at extremely low concentrations in P. crassipes (10-13 M).  It also has interspecific effects: for example, female Pachygrapsus will induce precopulatory behaviour in males of Cancer antennarius (at 10-11 M) and males of C. anthonyi (10-8 M).  Other interspecific interactions include female C. productus and male C. magister.  The authors remark that theirs may be the first description of a pheromone in a marine invertebrate.  Kittredge et al. 1971 Fish Bull 69: 337.

NOTE  a non-ionic polar lipid that induces moulting in crabs

NOTE  in fact, there is an earlier report of a male-attracting pheromone in the urine of premoult female crabs Portunus sanguinolentus in Hawaii.  Ryan 1966 Science 151: 340.

   
 
Research study 5
 

drawing of first zoeal stage of shore crab Pachygrapsus crassipes
drawing of fifth zoeal stage of shore crab Pachygrapsus crassipesThe shore crab Pachygrapsus crassipes is distributed from mid-Oregon to Baja California, and lives as well in Japan and Korea.  Ovigerous females can be collected at Seal Beach, California throughout the year.  In laboratory culture the 5 zoeal stages are passed through in 95d (at 16oC), although other observers have recorded much shorter times (around 40d). No megalopae are obtained in the study.  Schlotterback 1976 Crustaceana 30: 184.

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Paralithodes

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Research study 1
 

photograph of Alaska king crab Paralithodes camtschaticusBy enclosing male king crabs Paralithodes camtschaticus with multiple females in undersea cages, scientists in Alaska confirm that males can mate repeatedly.  However, for some sizes and shell-ages, after a male has mated 7-9 times, egg fertility and fullness of the brood in the females declines precipitously.  The study has fitness implications with respect to fisheries management.  Powell et al. 1974 Fish Bull 72: 171.

 

 

 

 

Alaska king crab Paralithodes camtschaticus
in Oregon Coast Aquarium, Newport 0.4X

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Research study 2
 

graph showing ovarian indices in crabs Paralithodes platypus over a 2-yr periodphotograph of blue lithodid crab Paralithodes platypus courtesy NOAA, Alaska Fisheries Science CenterPrior to the mid-1980s the red king-crab Paralithodes camtschaticus dominated commercial catches of lithodid crabs in Alaska, but when this article was written the blue king crab P. platypus was dominant.  While the former species reproduces each year, the latter does so only every other year.  Studies in the Pribilof Islands, Alaska show that the period of embryonic development in P. platypus is about 15mo and eggs are produced at 2-yr intervals (see graph showing ovarian indices over a 2-yr period).  A large female P. platypus of 14cm carapace length produces about 180,000 eggs vs. about 230, 000 eggs for an equivalent-sized P. camtschaticus.  Egg size is about 20% greater in P. platypus than in P. camtschaticus, and larval size and perhaps larval survival is correspondingly longer. Adult life span is estimated to be longer in the former species (13-17yr vs. 10yr, respectively).  These features may compensate for the relative infrequent spawning in P. platypus.  Somerton & MacIntosh 1985 J Crust Biol 5: 365. Photograph courtesy NOAA, Alaska Fisheries Science Centre.

NOTE  calculated as live ovary mass over live body mass, the latter estimated from a regression equation for whole body mass over carapace length

   
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Research study 3
 

A laboratory study at the Kodiak Fisheries Research Center, Alaska on reproduction in red king-crabs Paralithodes camtschaticus compares primiparous (first brood) and multiparous  (2nd or later brood) females.  Results show: 1) primiparous females extrude their eggs 2mo earlier than multiparous ones, 2) eggs of primiparous females hatch about 2wk earlier than multiparous ones,  3) complete embryonic development of primiparous females is 365d, about  5wk longer than multiparous ones.  Mean number of larvae released is about 107,000, similar for both reproductive types.  Stevens & Swiney 2007 J Crust Biol 27 (1): 37. 

NOTE  average seawater temperature of 7oC

   
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Research study 4
 

graph showing size-fecundity for blue king-crabs Paralithodes platypusA study of blue king-crabs Paralithodes platypus in the Bering Straits by University of Alaska researchers provides information on fecundity and other features of reproduction.  The authors report that mean fecundity is 63,000 eggs with principal hatching in spring and summer.  The authors note that theirs is the first study to document life-history information for Bering-Strait blue king-crabs.  Herter et al. 2011 J Crust Biol 31(2): 304; for information on temperature effects on embryonic development of P. platypus in laboratory settings see Stevens 2006 J Crust Biol 26 (4): 495 and Stevens et al. 2008 J Shellf Res 27(5): 1255.

NOTE  the authors maintain gravid crabs in the laboratory for up to 13mo to obtain information on hatching times, but the data are not included here

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Petrolisthes

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Research study 1
 

graph showing seaonality of egg-bearing in the crab Petrolisthes cinctipesphotograph of juvenile porcelain crab Petrolisthes cinctipesOn beaches around Hopkins Marine Station, Pacific Grove, California, porcelain crabs Petrolisthes cinctipes appear to be reproductive through most of the year.  Boolootian et al. 1959 Physiol Zool 32: 213.

 
Research study 2
 

schematic showing reproductive cycle of porcellain crabs Petrolisthes eriomerus in Puget Sound, Washington
In southern Puget Sound, Washington the reproductive cycle of porcelain crabs Petrolisthes eriomerus follows the schedule shown in the diagram.  Mean brood size is 620 eggs.  A second brood is common, so total fecundity of most females is over 1200 eggs. Knudsen 1964 Pac Sci 18: 3. Photo courtesy Dave Cowles, Walla Walla University, Washington wallawalla.edu.photograph of porcellain crab Petrolisthes eriomerus Dave Cowles, Walla Walla U

 
Research study 3
 

photograph of porcelain crabs Petrolisthes eriomerus and Petrolisthes cinctipes courtesy Charles Lowe, UBCA detailed description of courtship behaviour is provided for 4 species of porcelain crabs Petrolisthes collected around La Jolla, California, including P. cinctipes and P. eriomerus, which also extend north into Washington and British Columbia.  The descriptions of behaviour are similar for the 4 species.  Basically, all 4 species hold territory during courtship.  About 1-2h before copulation the males nudge the females into mating position with chelae and walking legs.  Species-specific behaviours through courtship include antennae lashings; chelae hunching, lifting, rocking, grasping, exploration, probing, and shoving; walking-leg contact; and other behaviours such as approaching, fast and slow retreating, swimming, grooming, feeding, and moulting. Several other behaviours are exhibited by males and females, separately and together.  In addition to describing these many small details of behaviour in the 4 species, the author notes that such non-communicatory acts of feeding and swimming are typically anomuran in nature. In contrast, various communicatory acts performed with the chelae resemble acts performed by brachyurans that possess chelae modified for display (e.g., fiddler crabs Uca).  Molenock 1975 Behaviour 53: 1. Photo courtesy Dave Zitten, UBC.

NOTE  Infraorder Anomura in the Order Decapoda includes diverse forms such as porcelain crabs, hermit crabs, stone crabs, and sand crabs; Infraorder Brachyura includes the "true" crabs

A distinguishing feature for these 2 species (at least
in British Columbian specimens) is colour of antennae:
straw for eriomerus and burgundy for cinctipes 1X

 
Research study 4
 

photograph of porcelain crab Petrolisthes cinctipes
graph of clutch size of porcelain crabs Petrolisthes cinctipes with changing live mass Petrolisthes cinctipes
in Sonoma County, California have broods up to 1200, but only in the largest females.  A plot of clutch size against female size gives a regression slope equivalent to 346 eggs . g live mass-1. Donahue 2004 Mar Ecol Progr Ser 267: 219.

 

 

 

 

Petrolisthes cinctipes, sex unknown 2.5X

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photograph of porcelain crab Petrolisthes eriomerus taken from a video

CLICK HERE to see a video of a female porcelain crab Petrolisthes eriomerus ventilating its pleopods by flapping its abdomen. The bristly pleopods within the abdomen form a basket that receives the eggs when they are released from the gonopores. The eggs are sticky and attach to the bristles.

NOTE  the video replays automatically

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Research study 5
 

 

 
Many marine invertebrates release their larvae coincidentally with springtime plankton blooms, thus ensuring the availability of food if their larvae feed on phytoplankton or, in the case of zoea larvae of crabs, ensuring the availability of small zooplankters, such as other larvae, as food.  Other factors, such as tidal/lunar cycles and water temperature, may also be involved.  The question of hatching induction in porcelain crabs Petrolisthes cinctipes is investigated by scientists from the University of Victoria at 3 sites in Clayoquot Sound, British Columbia in relation to tidal cycles, water temperature, and chlorophyll levels (see map).  Results indicate that a major hatching occurs during a new-moon period characterised by seasonally high nighttime ebbing tides (11-12 July, see histogram below).  map of Vancouver Island showing study sites for porcelain-crab larval-release study
Neither phytoplankton content nor water temperature seem to have been involved, although the sites where these parameters are measured are a puzzlingly far distance from the 3 crab-sampling locations (see map ).  The single data point of the  report represents a good start but, in the words of the authors, further study will be required.  Kerr & Duffus 2006 Crustaceana 78 (9): 1041. histogram showing proportion of porcelain crabs bearing eggs during summer
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Pugettia
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Research study 1
 

graph showing proportion of gravid female kelp crabs Pugettia producta through the yearphotograph of kelp crab Pugettia productaOn beaches around Hopkins Marine Station, Pacific Grove, California, kelp crabs Pugettia producta are reproductive throughout most of the year.  Boolootian et al. 1959 Physiol Zool 32: 213.

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Rhinolithodes
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Research study 1
 

drawing of Stage I zoea of crab Rhinolithodes wosnessenskiiphotograph of rhinoceras crab Rhinolithodes wosnessenskii courtesy Dave Cowles, Walla Walla UniversityA description is provided for Stage I zoeae of the lithodid Rhynolithodes wosnessenskii reared in the laboratory.  The author includes keys for distinguishing zoea larvae of 10 species, and megalopae of 7 species, of west-coast lithodids.  Haynes 1984 Fish Bull 82: 315. Photograph courtesy Dave Cowles, Walla Walla University, Washington wallawalla.edu.

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