Reproduction
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  Copulation, egg release, & larval stages: genera A-L
  This topic is divided into a section dealing with genera Acantholithodes, Chionecetes, Emerita, Fabia, Hemigrapsus, Lopholithodes, and Lophopanopeus, presented here, and sections on CANCER and GENERA O-R, presented elsewhere.
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Acantholithodes
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Research study 1
 

drawings of developmental stages of the lithode crab Acantholithodes hispidusThe lithode crab Acantholithodes hispidus has 4 zoeal larval stages and one megalopal stage.  The following observations come from culture of larvae at the West Vancouver Laboratory, British Columbia.  The larvae hatch to Zoea I stage after 15d at 9oC, and are fed on newly hatched brine-shrimp Artemia salina nauplii. After about 31d from the appearance of Zoea I, the larvae moult to the spiny megalopa stage.  The authors do not rear the megalopa to the juvenile stage.  Hong et al. 2004 Invert Repr Develop 47: 101.

NOTE  the eggs are hatched from berried females and are of unknown ages

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Carcinus

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Research study 1
 

drawing of zoea larva stage I of crab Carcinus maenasResearchers at California State University, Fresno provide drawings and a dichotomous key for zoeal larval stages of crabs in San Francisco Bay.  The survey includes 13 species, of which Carcinus maenas is shown here (stage I zoea only).  Rice & Tsukimura

NOTE  other Cancer, Eriocheir, Fabia, Hemigrapsus (2 spp.), Lophopanopeus, Pachygrapsus, Pinnixa, Pyromaia, and Rithropanopeuscan be found in their own sections in the ODYSSEY.  Separating them in this way is not so handy, but interested readers can use the links provided here to navigate from one to the other. The key requires too much photograph of crab Carcinus maenasdetailed anatomy to be included here. Most species are described from the literature, but a few are cultured from gravid females2007 J Crust Biol 27 (1): 74. Photograph courtesy Fred Uglow, University of Hull, England.


This aggressive European native arrived on west-coast shores in
the late 1980s and has proven to
be a successful coloniser 0.5X

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Chionecetes

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Research study 1
 

photograph of tanner crab Chioneocetes bairdiTanner crabs Chionoecetes bairdi are fished commercially in Alaska but little is known of their natural behaviour.  In the fishery, only males are harvested, and the effect of their removal on fecundity has not previously been investigated.  Laboratory studies in Seward, Alaska on mating in C. bairdi show that sperm may remain viable in the female for up to 2yr.  Female tanner crabs, unlike the males, reach terminal size with a maturity moult and then produce an annual egg clutch without further moulting.  Males continue to moult annually over the duration of their 6-yr life span from sexual maturity.  A female’s first mating occurs after her maturity moult while the carapace is still soft.  Prior to that time the gonopore is sealed and inflexible.  Females forced to use stored sperm to fertilise 3 successive annual layings produce no viable eggs in the third year.  During the first 2yr after copulation a female produces up to 280,000 viable eggs in each clutch.  With a life span of about 6yr after sexual maturity, a female will produce at least 4 clutches, and thus will have to mate at least twice to continue to produce viable eggs.  The author notes that the ability of C. bairdi to store sperm for 2yr provides the species with at least some protection from a fishery-related reproductive failure (e.g., over-harvesting of males).  Paul 1984 J Crust Biol 4: 375.

NOTE  sperm are stored in paired spermathecae located at the proximal ends of the vaginas

 
Research study 2
 

schematic showing mating status of laboratory-held population of tanner crabs Chionoecetes bairdi over time
Further studies on mating and egg viability in tanner crabs Chionoecetes bairdi in Alaska show that even though a batch of females have reached their “maturity moult”, it may take up to a month or more before most are producing viable eggs (white portion of graph). For whatever reason, a small percentage of females in this laboratory population, even though apparently mated, fail to produce viable eggs (black portion of graph).  Given that males may in short supply and the fertile period of the female ranges from 1-28d, the results of the study may have implications for commercial fisheries.  Paul & Adams 1984 J Crust Biol 4: 589.

 
Research study 3
 

Another fisheries-related question tested in an earlier paper by the authors is whether a small male Chinoecetes bairdi has sufficient sperm to fertilise a full egg clutch.  Tests show that for males within a range of 65-140mm carapace width the answer is ‘yes’, with enough sperm left over to fertilise additional clutches.  This means that the minimum size limit enforced by the fisheries for male crabs, namely, 135-140mm, is set correctly to ensure that males of reproducing size are always available to sustain population growth.  Adams & Paul 1983 Int J Invert Repr 6: 181.

 
Research study 4
 

schematic showing reproductive timing in tanner crabsLike other crabs, tanner crabs Chionecetes bairdi engage in a premating embrace (amplexus) prior to moulting.  Copulation takes place after moulting, and eggs are extruded within 48h and brooded externally.  The timing of extrusion and length of brooding varies depending upon whether it is a female’s first reproduction (primiparous) or whether she has brooded eggs before (multiparous).  A study by a researcher at the National Marine Fisheries Service in Kodiak, Alaska show that first-brooding females actually extrude and begin to incubate eggs several months ahead of second- or later-brooding females (see schematic), and thus the overall incubation period is much longer in the former group.  During development the eggs of tanner crabs enter a “rest” or diapause period at the gastrula stage, which may last for several months.  Because the diapause period is longer in eggs of primiparous females than in multiparous ones (6mo vs. 3mo), hatching of the eggs occurs more-or-less simultaneously in both groups in April-May.  Another difference between the 2 reproductive modes is that primiparous females produce only about two-thirds as many eggs as multiparous ones.  Female tanner crabs undergo a terminal moult at about age 5yr, and afterwards they either mate while hard-shelled or use stored sperm (good for about 2yr) to fertilise subsequent clutches.  The author notes that researchers rarely indicate (or perhaps know) whether the crabs they are providing data on are first- or later-brooders, so the study provides useful data relating to this.  The study is the first to show a developmental diapause in tanner crabs, and the first to compare its duration between the 2 reproductive modes.  The author suggests that the different diapause lengths function to synchronise embryo development and hatching among the 2 groups, but this begs the question of how the difference evolved in the first place.  Swiney 2008 J Crust Biol 28(2): 334.  

NOTE  data based on laboratory-held individuals.  Hatching times in this study are similar to those provided by other researchers

NOTE this is termed “eclosion” by the author, a word usually used to describe the emergence of adult insects from their pupal cases

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Emerita

 
Research study 1
 

photograph of mole crabs Emerita analoga
Male sand crabs Emertia analoga are much smaller than the females.  During mating time, which in southern California occurs in late spring/early summer, males will gather round a female that is ready to mate and attach to her using special sucker pads on the dactyli of their 4th legs.  The males are persistent and will follow a gravid female for several days, burying with her in the sand and following her about in the surf.  One to several males may attach sperm packets to a female’s gonopores, and the timing of this does not depend upon moulting as in other decapod crustaceans.  The sperm, contained in packets, are attached by a thick, ribbon-like mucus.  As the eggs are released from the gonopores, they are fertilised as they pass through the sperm-laden mucous mass.  The eggs are sticky and are manipulated by the female onto the 3 pairs of pleopods, where they stay for several weeks until hatching.  MacGinitie 1938 Am Midl Nat 19: 471.



Two Emerita analoga at the Monterey Bay
Aquarium, possibly a male and female 2X

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Research study 2
 

drawings of larval stages of sand crab Emerita analogaSand crabs Emerita analoga have 5 zoeal stages.  Culture of zoea stage I larvae and collections of zoeal stages II-V in plankton tows 240-290km off the California coast from San Luis Obispo to San Diego yield the views shown here. The authors provide considerable detail on appendage morphology for E. analoga and also give comparative material on 2 other less common sand-crab species, not shown here.  Johnson & Lewis 1942 Biol Bull 83: 67.

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Research study 3
 

graph showing reproductive state of female sand crabs Emerita analoga through the yearOn beaches around Hopkins Marine Station, Pacific Grove, California female sand crabs Emerita analoga are ovigerous from Apr-Oct.  Boolootian et al. 1959 Physiol Zool 32: 213.

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Research study 3.1
 

drawings of developmental stages of a sand crab Emerita rathbunaeA researcher at Scripps Institution of Oceanography, California provides a description of larval development of sand crabs Emerita rathbunae.  Eggs removed from a single female are cultured at 19-29oC using newly hatched brine shrimps Artemia salina as food.  As in other species of Emerita, the number of zoeal stages passed through to the megalopa is variable; for E. rathbunae the laboratory average is 8.  Larvae collected from the plankton and compared in size with the ones cultured in the laboratory are found to be somewhat larger in size (see graph), suggesting better conditions in the plankton.  Overall, larval development takes 5-6wk under the variable temperature conditions imposed here.  The author provides a detailed description of each developmental stage and ends the presentation with a comparison with Emerita analoga as presented in Research Study 2 above.  Knight 1967 Pac Sci 21: 58.graph comparing sizes of zoea larvae of sand crabs Emerita rathbunae in laboratory culture and from the plankton

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Research study 4
 

drawing of diminutive male sand crab Emerita analoga readying itself to deposit a spermatophore on a femaledrawing of precocious male sand crab Emerita rathbunae in the process of attaching spermatophores to a femaleAs noted in Research Study 1 above, female sand crabs Emerita analoga are larger than males, by about a factor of about 2-3.  Collections of E. analoga from 22 beaches between Ensenada, Baja California and Tofino, British Columbia, however, disclose that some males actually mature in the first summer at a size of just 6mm carapace length. The megalopae themselves are just 4mm in size.  These males will mate with females from the same recruitment cohort and also with ones from the previous year.  The males grow no larger than 10-12mm in length in their first summer and most die by springtime of their second year.  The “copulation” involves attachment of sperm packets by the male close to the genital pores on the 3rd walking legs of the female as shown in the accompanying drawings. As the eggs are released they pass through the sperm packets and become fertillised.  The generally small size of reproductive males in several west-coast Emerita species, including E. analoga, suggests to the author that neoteny in males may be a general characteristic of sand crabs. However, later researchers (see the following Research Study X) have proposed that sand crabs may actually be protandric hermaphrodites, that is, starting off male and then changing to female at a larger size.  Efford 1967 Crustaceana 13: 81.

NOTE  these drawings show male behaviour at copulation for a related Mexican species Emerita rathbunae.  Males of this species mate at a much smaller relative size than do males of E. analoga (2-3mm vs. female sizes of 30-40mm carapace length)

NOTE defined by the author as “a precocious sexual maturity” or “a relative retardation in the rate of development of the body (soma) as compared with the reproductive glands (germen)”.  Another definition of neoteny is “retention of larval characteristics into the adult stage” and, while the present author argues in support of certain larval features being retained, the males actually appear to have a juvenile adult form when they mature, which may reflect sexual dimorphism, rather than neoteny

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Research study 5
 

graph showing percentage female sand crabs Emerita analoga in relation to size in a populationA 2-yr study of sand crabs Emerita analoga on beaches around Santa Barbara, California reveals a spring/summer mating season leading to continual summer release of pelagic zoea larvae.  The zoeae pass through 5 moults before returning to the shore as megalopae beginning in September and continuing through the following winter and spring.  By mid-November the reproducing females from summer have disappeared, suggesting an annual cycle for the species.  The author notes a general absence of small females coupled with a progressive seasonal increase in proportion of females in the larger size classes in the population, and suggest that E. analoga undergoes sex transformation during development (see graph).  This protandric hermaphrotidism seems not to have been reported by other authors for this species and probably needs to be confirmed.  Barnes & Wenner 1968 Limnol Oceanogr 13: 465.

NOTE a comment in a much earlier study that male E. analoga are smaller than females, and that only the larger individuals in a population carry eggs may, in fact, be the first reference to possible protandry in the species.  Weymouth 1919 Calif Fish Game 5: 171.

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Research study 6
 

photograph of ventral view of sand crab Emerita analogaThe latter part of the 1960's decade seems to have been a popular time for research on reproduction in sand crabs Emerita analoga.  In this third Research Study from this period, researchers from San Diego State College follow the reproductive status of Emerita over a 20mo period on beaches near La Jolla, California.  Ovigerous females are present from late winter (Feb-Mar) through the summer.  Eggs are carried for about 3wk.  Observation of females in the field and laboratory suggest that large individuals may have several successive broods.  Cox & Dudley 1968 Ecology 49: 746. Photograph courtesy Lovell & Libby Langstroth and CALPHOTOS.


 

Ventral view of gravid female Emerita analoga.
The animal is facing to the left. Eggs are
visible under the folded abdomen flap 3X

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Research study 7
 

Sand crabs Emerita analoga have a variety of carotenoid pigments in their ovaries, eggs, and hemolymph.  Experiments at the Hopkins Marine Station, Pacific Grove, California show that 14C-labelled carotenoids in the green seaweed Ulva, when fed to Emerita, are taken up, metabolised, and incorporated into various body tissues, including eggs, which are orange-coloured.  Female Emerita increase their uptake of carotenoids during the breeding season.  The authors could find no evidence for metabolic utilization of the carotenoids during embryonic development, yet reason that they likely play a role in reproduction, as found in other crustaceans.  Gilchrist & Lee 1972 Comp Biochem Physiol 42B: 263.

NOTE  carotenoids identified are ∞-carotene, ß-carotene, echinenone, canthaxanthin, zeaxanthin, diatoxanthin, alloxanthin, and astaxanthin

 
Research study 8
 

graph of size of mole crabs Emerita analoga at different locations north and south of Point Conception, California
A detailed study of life-history characteristics of sand crabs Emerita analoga in California over a period of several years reveals strong latitudinal effects on size at reproductive maturity for both sexes. As an example, female size at maturity increases from south to north, as shown in the accompanying graph.  Overall, sizes of crabs are 1.5-3 times greater in northern than in southern populations.  Crabs from southern sites thus reproduce at smaller sizes and younger ages than crabs from northern sites.  Multiple linear-regression analyses show that overall size is positively dependent upon food availability, but not upon beach morphodynamics (e.g., sediment sizes, beach slope).  Life-history features, including settlement, growth, and survival, are remarkably consistent from yea- to-year at the different beaches.  Dugan et al. 1991 J Exp Mar Biol Ecol 150: 63; Dugan et al. 1994 J Exp Mar Biol Ecol 181: 255.

NOTE  ovigerous females of 3.5cm carapace length have brood sizes of 45,000 eggs

NOTE  5 years of data (1983-87) are included in the graph

 
Research study 9
 

map showing 4 headlands used in the studyA recent idea relating to recruitment of sand crabs Emerita analoga, proposed by researchers from the University of California Davis, is that the larvae are retained near headlands during upwelling, when the graph showing settlement of sand crabs Emerita analoga at different distances from headlands in Californiapredominant alongshore flow is equatorward.  During relaxation of the upwelling winds, when the alongshore flow reverses and moves in a northwards direction, the larvae are redistributed to the north of the headlands.  In support of their idea, the authors are able to correlate a decreasing magnitude of Emerita recruitment with distance north of 4 headlands along 800km of the California coast during 1998, a year of photograph of beach where sand crabs Emerita analoga are sampledmoderate upwelling; thus, recruitment falls off with increasing distance (see pink line on graph).  Exceptions to this prediction are found, but only during the second year of the study (1999), a year of anomalously high upwelling intensity (see blue line on graph).  Thus, when upwelling and wind-stress are within long-term average levels, recruitment is as predicted.  The authors conclude that Emerita along the California coast may be characterised by discrete populations separated by major headlands that tend to enhance population persistence.  Diehl et al. 2007 Mar Ecol Progr Ser 350: 1.

NOTE  the crabs are sampled by corings taken at 4 sand-beach sites located approximately 10, 50, 100, and 200km north of each of the 4 headlands

Gaviota State Beach, just south of Point Conception, California
where sand crabs Emerita analoga were sampled. Beach photo
courtesy the authors; crab photo courtesy G. Jensen

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Eriocheir

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Research study 1
 

drawing of zoeal larval stage of mitten crab Eriocheir sinensisResearchers at California State University, Fresno provide drawings and a dichotomous key for zoeal larval stages of crabs in San Francisco Bay.  The survey includes 13 species, of which Eriocheir sinensis is shown here (stage I zoea only).  Rice & Tsukimura 2007 J Crust Biol 27 (1): 74. Photograph courtesy Marine Biological Association U.K.

NOTE  other genera Cancer (3 spp.), Carcinus, Fabia, Hemigrapsus (2 spp.), Lophopanopeus, Pachygrapsus, Pinnixa, Pyromaia, and Rithropanopeus can be found in their own sections in the ODYSSEY.  Separating them in this way is not so handy, but photograph of the woolly handed crab Eriocheir sinensisMBAUKinterested readers can use the links provided here to navigate from one to the other. The key requires too much detailed anatomy to be included here. Most species are described from the literature, but a few are cultured from gravid females 


The woolly-handed or mitten crab Eriocheir
sinensis
is an introduced species from Asia 0.6X

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Fabia
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Research study 1
 

photograph of crab Fabia subquadrata courtesy Dave Cowles, Walla Walla University, WashingtonIn San Juan Islands, Washington the pinnotherid crab Fabia subquadrata lives symbiotically with horse clams Modiolus modiolus and other bivalves.  Mostly the crabs live one per host.  During mating time in late May the crabs leave their hosts, swarm to the surface, and copulate in open water.  At this time both males and females are only in Stage I of development, so insemination is precocious.  Following copulation, the female returns to a host and continues its development through to Stage V over the following 3-4wk.  Most males also return to a host.  Egg-bearing females are first noted in November, with eggs hatching in February.  Development in the plankton proceeds through 5 zoeal stages to the megalopa, with the latter seeking out an appropriate host at this time.  By installing a window in the shell of a Modiolus photograph of mussel showing damage caused by parasitic crab Fabia subquadratahost, the author is able to view the crab’s in situ feeding behaviour.  It mainly involves picking mucous food strings from the food grooves of the host’s ctenidia.  The crab usually sits on one of the demibranchs, often resulting in serious damage to the tissues. The relationship is therefore best described as a parasitism, although some authors commonly refer to it as commensalism or mutualism.  Pearce 1966 Pac Sci 20: 3. Photograph of Fabia courtesy Dave Cowles, Walla Walla University, Washington wallawalla.edu.

NOTE  these include Mytilus californianus, M. trossulus, Tresus capax, and Saxidomus spp.  Modiolus in the San Juan archipelago may be 80% infected with Fabia

NOTE  the author provides considerable detail of the different developmental stages for both sexes, including moulting, but does not include any drawings

Dissected mussel shows damage caused to the left
ctenidial demibranch from the activity of the parasitic crab
Fabia subquadrata.
The steel pointer shows the split ctenidia

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Research study 2
 

drawings of zoeal I larval stage of crab Pinnixa sp.Researchers at California State University, Fresno provide drawings and a dichotomous key for zoeal larval stages of crabs in San Francisco Bay.  The survey includes 13 species, of which Fabia subquadrata (as a representative of F. Pinnotheridae) is shown here (stage I zoea only).  Rice & Tsukimura 2007 J Crust Biol 27 (1): 74.

photograph of crab Pinnixa sp. within ctenidia of a mussel Mytilus californianusNOTE  other genera Cancer (3 spp.), Carcinus, Eriocheir, Hemigrapsus (2 spp.), Lophopanopeus, Pachygrapsus, Pinnixa, Pyromaia, and Rithropanopeus can be found in their own sections in the ODYSSEY.  Separating them in this way is not so handy, but interested readers can use the links provided here to navigate from one to the other. The key requires too much detailed anatomy to be included here. Most species are described from the literature, but a few are cultured from gravid females 

This small crab Fabis subquadrata is commonly found with sea
mussels Mytilus californianus, tucked within the ctenidial area 3X

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Hemigrapsus

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Research study 1
 

drawings of megalopa and first juvenile developmental stages of grapsoid crab Hemigrapsus nudusdrawings of zoeal stages of development of grapsoid crab Hemigrapsus nudusAn early description of development in Hemigrapsus nudusby a researcher at the Pacific Biological Station, Nanaimo. British Columbia includes drawings of 5 zoeal, megalopa, and first juvenile stages.  In Departure Bay, British Columbia berried females are present in April-May.  Hart 1935 Can J Res 12 (4): 411.

NOTE  the author also includes a description of H. oregonensis but, as its development is similar to that shown for H. nudus and as it is featured in Research Study 5 below, it is not included here

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Research study 1
 

graph showing reproductive cycle of female grapsid crabs Hemigrapsus nudus in the region of Pacific Grove, CaliforniaOn beaches near the Hopkins Marine Station, Pacific Grove, California female Hemigrapsus nudus carry eggs between Oct-May.  Boolootian et al. 1959 Physiol Zool 32: 213.

 
Research study 2
 

schematic showing reproductive cycle of shore crabs Hemigrapsus nudus in Puget Sound, WashingtonStudies on the reproductive cycle of Hemigrapsus nudus in southern Puget Sound, Washington show that oogenesis occurs in autumn-winter, copulation in Dec-Jan, egg release in Jan-Mar, and hatching in May-Jun.  Less than 1% of mature females carry a second seasonal brood. 

drawing showing copulation ritual in shore crabs Hemigrapsus nudusphotograph of shore crab Hemigrapsus nudusAmplexus does not occur in H. nudus.  Copulation is quick and without preamble.  It involves some preliminary grappling and positioning of the female by the male, then the male rolls over backward, opens the female’s abdomen flap, and inserts his copulatory appendages for insemination. The mean number of eggs in each brood is 13,000.  Knudsen 1964 Pac Sci 18: 3. Photo courtesy Ron Long, SFU.

 
Research study 3
 

schematic showing reproductive cycle of shore crab Hemigrapsus oregonensis in Puget Sound, Washington
The reproductive cycle of Hemigrapsus oregonensis in Puget Sound is similar to that described for H. nudus, save for details of timing.  One difference of note is that many H. oregonensis females (70%) carry a second brood commencing in late spring.  Mean number of eggs in a brood is 4500, but in a large female with 2 broods the total number can reach 22,000.  Knudsen 1964 Pac Sci 18: 3.photograph of egg-bearing shore crab hemigrapsus oregonensis

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Research study 4
 

A later study provides a description of copulatory behaviour of shore crabs Hemigrapsus oregonensis in laboratory and field situations, the latter at Coose Bay, Oregon.  Prior to copulation the male straddles a standing female and cages her in outspread legs and chelipeds, then falls over backwards bringing the female with him.  Copulation ensues with the male on his back and the female above him, sternum to sternum.  There is no courtship dance as described for other decapod species. Lindberg 1980 Crustaceana 39: 263.

NOTE unfortunately, the author does not provide graphical illustration of this interesting behaviour. Over 20 other behaviours are described, mostly relating to burrow possession

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Research study 5
 

drawing of zoeal larval stage I of crab Hemigrapsus nudusdrawing of zoeal larval stage I of crab Hemigrapsus nuResearchers at California State University, Fresno provide drawings and a dichotomous key for zoeal larval stages of crabs in San Francisco Bay.  The survey includes 13 species, of which Hemigrapsus nudus and H. oregonensis are shown here (stage I zoeae only).  Rice & Tsukimura 2007 J Crust Biol 27 (1): 74.

NOTE  other genera Cancer (3 spp.), Carcinus, Eriocheir, Fabia, Lophopanopeus, Pachygrapsus, Pinnixa, Pyromaia, and Rithropanopeus can be found in their own sections in the ODYSSEY.  Separating them in this way is not so handy, but interested readers can use the links provided here to navigate from one to the other. The key requires too much detailed anatomy to be included here. Most species are described from the literature, but a few are cultured from gravid females 

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  Hyas
 
Research study 1
 

drawings of developmental stages of spider crab Hyas lyratusA researcher at the Royal British Columbia Museum in Victoria provides detail of early development of the spider crab Hyas lyratus.  In southern British Columbia eggs hatch in February-March to a short-lived prezoeal stage, leading to 1st and 2nd zoeal stages and a megalopa stage.  On a diet of newly hatched brine shrimp Artemia salina, this last is reached in laboratory culture after 5wk.  Hart 1960 Can J Zool 38: 539.

NOTE  the temperature in the culture flasks is not givenphotograph of spider crab Hyas lyratus
Spider crab Hyas lyratus with sponge and colonial tunicate
decorations 0.7X

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Lopholithodes

 
Research study 1
 

drawing of early zoea larva of Puget-Sound king crab Lopholithodes mandtiiphotograph of Puget-Sound king crab Lopholithodes mandtii
A description of early zoea larvae for Lopholithodes mandtii captured in southern Baranof Island, Alaska is provided. The author comments on not seeing any prezoeal stage.  Haynes 1993 Fish Bull 91: 379.

 

 

 

Juvenile Puget-Sound king crab Lopholithodes
mandtii
1X. Photo courtesy Ron Long, SFU

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Research study 2
 

drawings of several larval stages of the lithode crab Lopholithodes mandtii in Puget Sound, WashingtonA single ovigerous female collected in Puget Sound, Washington and cultured at the Shannon Point Marine Center, Washington (at 11oC) provides further information on development of the lithode crab Lopholithodes mandtii.  After undergoing a brief prezoeal stage, development proceeds through 4 zoeal stages and a megalopal stage to the first juvenile stage (3 zoeal stages are shown in the drawings).  Zoea larvae are provided with newly hatched brine-shrimp larvae Artemia as food.  Sizes of zoea I larvae in this study are comparable to those reported for Alaskan L. mandtii in Research Study 1 above.  The authors terminate their culture after the second juvenile stage is reached.  Crain & McLaughlin 2000 Invert Reprod Dev 37: 43.

NOTE  in the present study the rostral spine is included in measure of overall length, while in Research Study 1 above it is not

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Research study 3
 

drawings of zoeal and glaucothoe stages of development of a box crab Lopholithodes foraminatusCulture of zoeae of box crabs Lopholithodes foraminatus at the University of Victoria, British Columbia provides details on larval, glaucothoe, and early juvenile stages.  There is a single prezoeal stage, 4 feeding zoea larval stages that last for about 4wk in culture at 11oC, and one non-feeding glaucothoe stage (equivalent to megalopa, lasting for 3.5wk; see accompanying drawings).  The zoeae are lively swimmers.  The glaucothoe swims a bit for a day or two after moulting and then seeks out a solid substratum to cling to, which may be other glaucothoe.  Juveniles walk about the aquarium photograph of box crab Lopholithodes foraminatus courtesy Will Duguid & Dave Cowles, Walla Walla University, Washingtontank. The life-history character of non-feeding in the glaucothoe stage has been termed secondary lecithotrophy.  It is widespread among lithodid crabs and is also present in pagurid hermit crabs.  Stored reserves for development  are visible as lipid droplets in the digestive glands of late zoeal stages and early glaucothoe stage.  During the glaucothoe stage the mouthparts have noticeably reduced armature.  Duguid & Page 2009 J Mar Biol Assoc UK 89: 1607. Photograph courtesy Will Duguid & Dave Cowles, Walla Walla University, Washington wallawalla.edu.

NOTE  obtained from gravid females collected from the field and maintained in laboratory culture for several months

NOTE  the zoeae are fed on nauplii of brine-shrimps Artemia.  Little or no cannibalism is observed in the cultures


Box crab Lopholithodes foraminatus 0.33X

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Research study 4
 

Laboratory culture and field observations on reproduction in Lopholithodes foraminatus by researchers at the University of Victoria confirms that lithode crabs have a biennial (once every 2yr) cycle.  Specifically, after moulting, copulating, and extruding eggs by mid-summer, the females enter an 18mo brooding period that includes a 12mo diapause in embryogenesis at the gastrula stage.  Thus, larvae do not hatch out until late winter or early spring of the second year after fertilisation.  Note in the photo array below how little an egg changes from 13d post-extrusion to 11mo post-extrusion. Another feature is that eggs in a clutch, even ones in close proximity, are in different developmental stages during the 13-18mo post-fertilisation period.  Hatching, moreover, occurs over an extended 70d period, the longest known for any lithodid.  In these and other decapod species, extended hatching is thought by some researchers to be an adaptative strategy to ensure that at least some zoea larvae will be present coincidental with the spring plankton bloom. The authors discuss relative advantages and disadvantages of biennial reproduction.  Duguid & Page 2011 Invert Biol 130 (1): 68.

NOTE  lithode crabs apparently have no mechanism to store sperm, so these 3 events leading to egg extrusion happen in quick order

   
 
photograph of egg 4d after extrusion by a female lithode crab Lopholithodes foraminatus photograph of egg 1d after extrusion by a female lithode crab Lopholithodes foraminatus photograph of egg 1d after extrusion by a female lithode crab Lopholithodes foraminatus photograph of egg 1d after extrusion by a female lithode crab Lopholithodes foraminatus photograph of egg 1d after extrusion by a female lithode crab Lopholithodes foraminatus
Egg 4d post-extrusion 13d post-extrusion 11mo post-extrusion 15mo, note eye forming 18mo, note appendages
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Lophopanopeus

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Research study 1
 

drawings of zoea larval stages of xanthid crab Lophopanopeus bellusAn early investigation of larval development in crabs of British Columbia involves Lophopanopeus bellus  in Family Xanthidae.  The author, a reseacher at the Pacific Biological Station, Nanaimo  provides illustrations of 4 zoeae, megalopa, and first juvenile stages.  Eggs are carried in April, hatch May-August, and in laboratory culture the first juvenile crab is obtained 5wk after hatching.  Hart 1935 Can J Res 12 (4): 411.

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Research study 2
 

photograph of crab Lophopanopeus bellusA study on reproduction and larval behaviour in tiny pebble crabs (F. Xanthidae) in California reveals that there is no “prenuptial” pairing, and copulation is between 2 hard-shelled individuals in a front-to-front orientation. Thus, there is no waiting around for the female to moult. Ovigerous Lophopanopeus bellus bear between 1000-6000 eggs and are most common in the population Feb-Oct.  An interesting observation by the author is the eggs have hair-like attachments that wrap around the bristles of the female’s pleopods when they are released from the gonopores.  Attachment may be aided by a “sticky quality” of the extruded eggs.  Knudsen 1960 Pac Sci 13: 3.

NOTE  the featured species in the article are Lophopanopeus leucomanus and L. bellus, but also included are the less well-known Cycloxanthops novemdentatus and Paraxanthies taylori


Lophopanopeus bellus 1.8X

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Research study 3
 

drawings of zoeae larval stage I of crab Lophopanopeus bellusResearchers at California State University, Fresno provide drawings and a dichotomous key for zoeal larval stages of crabs in San Francisco Bay.  The survey includes 13 species, of which Lophopanopeus bellus is shown here (stage I zoeae only).  Rice & Tsukimura 2007 J Crust Biol 27 (1): 74.

NOTE  other genera Cancer (3 spp.), Carcinus, Eriocheir, Fabia, Hemigrapsus(2 spp.), Pachygrapsus, Pinnixa, Pyromaia, and Rithropanopeus can be found in their own sections in this larval part of the ODYSSEY.  Separating them in this way is not so handy, but interested readers can use the links provided here to navigate from one to the other. The key requires too much detailed anatomy to be included here. Most species are described from the literature, but a few are cultured from gravid females 

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