Reproduction & recruitment
   
 

Sexes are separate in most or all shrimps.  Copulation involves the extrusion and application by the male of a sticky sperm-filled spermatophore onto the genital opening of the female.  As the eggs pass out of the female’s gonopore, they pass through the sperm mass and are fertilised.  The eggs are sticky and cling to bristles on the pleopods of the female.

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  Mud & ghost shrimps
  Reproduction in shrimps & relatives is separated into 2 subsections: mud and ghost shrimps here, and "true" shrimps below.
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Research study 1
 

drawings of larval and post-larval stages of a mud shrimp Upogebia pugettensisA study done at the Pacific Biological Station, British Columbia on mud shrimps Upogebia pugettensis indicates that females bear eggs in December through to April, and larvae occur in the plankton from February-May.  There are 3 larval stages before the post-larval one (see drawings).  The author provides considerable morphological detail on the larval stages, but nothing on duration of the different stages in culture or other features of larval life.  Hart 1937 Can J Res 15 (10): 179.

NOTE  the author gives details of larval stages of several hermit crabs, not included here.  In large part the paper is intended to provide a means for differentiating the various, similarly shaped, larvae of mud shrimps and anomurans

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Research study 2
 

map of Salmon River Estuary, Oregon showing distributions of adult populations of ghost shrimps Neotrypaea californiensisThe Salmon River estuary in Oregon hosts abundant populations of ghost shrimps Neotrypaea californiensis (see map). When the zoeae hatch in late spring/early summer do they stay in the estuary or move out to sea?  By measuring current velocities, temperature/salinity profiles, and larval abundances during 8 weekly tidal cycles, and by employing surface drogues, researchers determine that the Zoea I larvae are flushed out to sea in springtime, spend 6-8wk feeding in the plankton, and enter the estuary as megalopae on flood tides in August.  Johnson & Gonor 1982 Estuar Coast Shelf Sci 14: 501.

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Research study 3
 

photograph of ghost shrimp Neotrypaea californiensis courtesy Dave Cowles, Walla Walla U, Washington
photograph of mud shrimp Upogebia pugettensis Dave CowlesIn Willapa Bay and Grays Harbor, Washington “berried” female mud shrimps Upogebia pugettensis are present during Oct-May (ghost shrimps Neotrypaea californiensis: Apr-Aug).  After several weeks the eggs hatch to zoea larvae that spend 6-8wk feeding in near-shore areas.  Mud and ghost shrimps pass through 3 and 5 zoeal stages, respectively, before moulting to the juvenile stage.  Dumbauld et al. 1996 J Crust Biol 16: 689; Feldman et al. 2000 Estuaries 23: 141. Photos courtesy Dave drawing of bristles on a swimmeret of a ghost crab Neotrypaea calirorniensis Cowles, Walla Walla University, Washington wallawalla.edu.

NOTE the photo of U. pugettensis (above Right) shows the presence of a not uncommon parasitic clam Neaeromya (Pseudopythina) rugifera attached to an anterior pleopod

 

Bristles on a pleopod (swimmeret) of Neotrypaea californiensis
onto which the sticky eggs cling after being released from female;
from MacGinitie 1934 Amer Midl Nat 15: 166)
500X

 

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Research study 4
 

map of Willapa Bay, Washingto showing study sites for work on mud shrimps Upogebia pugettensis and ghost shrimps Neotrypaea californiensis

In Willapa Bay, Washington average fecundities are 7100 eggs for mud shrimps Upogebia pugettensis and 3900 eggs for ghost shrimps Neotrypaea californiensis.  The authors estimate that females invest 30-40% of their body mass annually in egg production.  The species differ in their seasonal timing of reproductive cycle, with Upogebia extruding eggs in October, eyed embryos appearing in December, and hatching of zoeae in Feb-May.  In comparison, Neotrypaea extrudes eggs in March-July, with hatching in June-August.  Dumbauld et al. 1996 J Crust Biol 16: 689.

NOTE  newly extruded eggs are yellow in Upogebia and red in Neotrypaea

 

 

 

Map of Willapa Bay, Washington showing some of the collecting sites

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Research study 5
 

histograms showing recruitment success of ghost shrimps Neotrypaea californiensis on different types of substrata

Studies in Grays Harbor, Washington show that a dense covering of bivalve shells over the mud surface significantly reduces recruitment of ghost shrimps Neotrypaea californiensis. Overall recruitment success is found to be a combination of larval selection for mud habitat, postlarval selection for mud substrata, and loss by predation to young-of-the-year juvenile Dungeness crabs Cancer magister.  Note in the histogram the absence of selection of shell habitat by the larval ghost shrimps in August when the larvae are beginning to settle.  Ten months later, juvenile shrimps have colonised areas where the shell cultch has sunk under the mud surface (“subsurface shell”).  The study is part of a larger “shell mitigation” programme in Grays Harbor aimed at enhancing recruitment success of Dungeness crabs by addition of oyster and other bivalve shells to mud habitats.  Feldman et al. 1997 Mar Ecol Progr Ser 150: 121.

  Research study 6
 

Zoeae larvae of estuarine crustaceans often exhibit vertical migratory behaviours that enhance their seaward transport from the estuary.  Once the open ocean is reached, currents enable long-distance transport up and down the coast and, at the end of the planktonic stage, there may be other behaviours to facilitate re-entry into the estuary.  Whether this happens with ghost crabs Neotrypaea californiensis is investigated by researchers from Washington State University by collecting larvae from specific depths in Willapa Bay, Washington at different times of day and at different tides.  Results are suggestive enough for the authors to conclude that Stage I zoeae are most abundant during ebb tides and tend to stay higher in the water column, both behaviours potentially enhancing seaward transport.  Breckenridge & Bollens 2011 Estuaries & Coasts 34: 1255.

NOTE  the authors include pinnotherid or pea crabs in their study, but these are not identified to species and are not included in this summary

NOTE  samples are collected every 3h during ~24h periods in May and October over a 1.5y period at 3 depths (1m above bottom, mid-depth, and 1m below surface).  Water-column depth during the study varies from 6-10m.  In Willapa Bay May is spawning time and October is recruitment time

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  "True" or caridean shrimps: pandalids, hippolytids, crangonids
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Research study 1
 

photograph of pandalid shrimp Pandalus danaeAn early account from the Pacific Biological Station, DFO, Nanaimo describes copulatory behaviour in coon-stripe shrimps Pandalus danae.  Copulation occurs only after the female has moulted to full reproductive form, a state that includes the presence of long, fringe-bearing pleopods to which the eggs will later attach. At this time the female's ovaries are packed with blue-green eggs, visible through the exoskeleton. When a male is placed with a newly moulted female, he undertakes tentative exploration with his antennae, then swings himself up and under the female, such that his abdomen is immediately beneath her thorax.  This places his copulatory appendages close to the female’s gonopores.  In the next few moments the male deposits spermatophores between the bases of the last 2 pairs of walking legs of the female.  Eggs are released 1-2d after the female moults. They are fertilised as they pass over the spermatophores. The sperm are thumbtack shaped with sharp points, and these hook onto the eggs as they pass by. The points penetrate the eggs, the contents of the sperm pass into the eggs, and the sperm are left as collapsed shells. The During egg release the female stands tippy-toe on her 3rd pair of walking legs, supported by tail and telson.  The 4th and 5th walkings legs move constantly, perhaps helping the eggs move down the oviducts.  The eggs pass in a steady stream between the walking legs to the abdomen where, under field conditions, they would stick to the setal fringes of the pleopods.  The eggs are surrounded by clear membranes of "egg cement", and threads from these attach the eggs to each other and to the pleopodal fringes. The process takes about 30min under lab conditions.  Needler 1931 Can Field Nat 45: 107. Photograph courtesy Dave Cowles, Walla Walla University, Washington www.wallawalla.edu.

NOTE  the author remarks that in the laboratory the eggs lack the sticky coating necessary for them to attach to the fringes, and they tend to fall off

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Research study 2
 

photograph of spot prawns Pandalus platycerosdrawing of Stage V post-larval prawn Pandalus platycerosDevelopment from egg to post-larva is presented in this study on spot prawn Pandalus platyceros from reared from eggs from gravid females collected in Hood Canal, Washington.  Developmental stages are fed on newly hatched brine shrimp Artemia salina and maintained for 83d (at temperatures of 7-14oC) in the laboratory. Nine stages are passed through during this time, at about 9d per stage.  One stage in development is shown here, the Stage V first post-larval stage.  Price & Chew 1972 J Fish Res Bd Can 29: 413.

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Research study 3
 

photograph of shrimp Crangon nigricauda courtesy California Academy of Sciences ResearchAn investigation of reproduction in crangonid shrimps by researchers at  Oregon State University shows that spawning season for both Crangon nigricauda and C. franciscorum in Yaquina Bay, Oregon is Dec-Aug.  The former species seems to prefer higher-salinity waters (25ppt) than the latter (15ppt).  Both species exhibit bimodal spawning periods with larger females spawning first.  Fecundity is similar in both species, with egg counts per brood ranging from 3500-4000.  The authors note maximum ages of 1.5yr for females of both species an 1yr for males, but rather than dying off, it is more likely that the males undergo sex transformation as described by later authors (see Research Study 8 below).  Supporting evidence for this includes maturation of males at 28mm total length and maturation of females at about 48mm length.  Krygier & Horton 1975 Northwest Sci 49 (4): 216.  Photograph courtesy California Academy of Sciences Research.

NOTE  sexes cannot be differentiated at sizes <22mm total length (tip of rostrum to tip of telson) for C. nigricauda  and at sizes <26mm for C. franciscorum

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Research study 4
 

photograph of broken-back shrimp Heptacarpus brevirostris courtesy Dave Cowles, Walla Walla University, WashingtonThere are over a dozen thoridid (hyppolitid) shrimps on this coast, one of the smallest being Heptacarpus sitchensis at 1.3mm carapace length from southern California.  The species breeds through all seasons except autumn and has an 18-mo life span.  Interestingly, the females are multiple breeders and have more than one set of developing eggs in their ovaries at a time.  Shortly after the larvae hatch, and after a moult, the females copulate again.  Males appear to respond to a non-diffusible substance present on the exoskeleton of the newly moulted female.  There is no prelonged pre-copulatory behaviour.  After touching the female with his antennae,the male climbs onto the female (see series of drawings below), momentarily adopts a straddle position, then dips below the female in crosswise orientation.  

This brings the male and female reproductive openings into juxtapostion. Meantime, the male has extruded a spermatophore or sperm packet from its gonopores in the shape of a “W”, as shown in the drawings below. Note that the spermatophore, comprised of mucous gel with embedded thumbtack-shaped spermatozoa, is formed by fusion of the 2 ropey gonopore emissions.  It is sticky, and when pressed to the gonopore region of the female by the male’s gonopods, adheres there during the period of egg extrusion.  The female extrudes eggs within a few moments after mating, each being fertilised as it passes through the spermatophore. Bauer 1976 J Nat Hist 10: 415.  Photograph courtesy Dave Cowles, Walla Walla University, Washington www.wallawalla.edu.

NOTE  formerly known as pictis; shown in photo:the related broken-back shrimp Heptacarpus brevirostris from northern Washington

   
 

drawings of copulatory behaviour in broken-back shrimps Heptacarpus sitchensisAfter first contact, the male climbs onto the female,

drawings of copulatory behaviour in broken-back shrimps Heptacarpus sitchensis
straddles her temporarily
drawings of copulatory behaviour in broken-back shrimps Heptacarpus sitchensis
then dips below her in crosswise orientation.
 
drawings of copulatory behaviour in broken-back shrimps Heptacarpus sitchensis
This orientation juxtaposes the reproductive openings, in proper orientation for copulation.
drawings showing spermatophore formation in a shrimp
The male forms a single spermatophore. It is extruded from the gonopores located on the bases of the 5th walking legs. The 2 extrusions fuse together to form a W-shape. The actual sperm are thumbtack- shaped and are embedded in the mucus comprising the spermatophore.
drawing of female shrimp showing spermatophore recently deposited by male during copulation
The male places the spermatophoreon top of the female gonopores, such that the eggs pass through it on release.
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Research study 5
 

Observations at Friday Harbor Laboratories, Washington of sex attraction in shrimps Heptacarpus paludicola show that males are especially attracted to newly moulted females with full ovaries.  If the ovaries are not full, the male’s attentiveness is greatly diminished.  The recognition mechanism appears to be through contact chemoreception via the second antennae.  Laboratory experiments suggest that a pheromonal substance released from the female increases the activity of the male.  The author suggests that it may be chemicals associated with hardening of the cuticle that are the contact pheromone involved in the sex recognition. This would be a good subject for reseach if it hasn't been done already. Bauer 1979 Mar Behav Physiol 6: 157.  

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Research study 6
 

Ovigerous Pandalus jordani collected off the coast of Oregon at 200m depth each bear 600-3000 eggs.  The eggs hatch to a series of 13 larval stages, with a final moult to a first juvenile instar.  The author provides no whole-body illustrations of the larvae, but does give sufficient detail of other body parts to differentiate the different stages from larvae taken in plankton tows.  Rothlisberg 1980 Crustaceana 38: 19.

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Research study 7
 

map showing disribution of crangonid shrimps in Californiadrawing of generalised crangonid shrimpThree major crangonid species, the sand or grass shrimp Crangon franciscorum, the black shrimp C. nigricauda, and the blue-spotted shrimp C. nigromaculata live in the shallow coastal areas of California from San Francisco south to Mexico.  Reproduction seems to occur all year-long in all 3 species, and females may carry several broods in a year.  Brood size of sand shrimps ranges from 1200-7000 eggs depending upon size of female.  Seven larval stages are passed through to metamorphosis.  The paper reviews aspects of life history, growth, and various environmental requirements of crangonids and, as such, may be useful for someone embarking on research on the group. Siegfried 1989 U.S. Fish & Wildl Serv Biol Rep 82 (11.125)  US Army Cops of Engineers, TR EL-82-4 18pp; Siegfried 1980 Biol Bull 159: 177.

NOTE  the first 2 species are found from Alaska to Mexico, while the third extends from the Gulf of Farrallons (north of San Francisco) to Baja California (see map)

NOTE in an earlier paper the author provides more detailed information on brood sizes in sand shrimps from the delta region of San Francisco Bay (see graph on Left)

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Research study 8
 

Research on sand shrimps Crangon franciscorum in Gray’s Harbor, Washington provides new insight into their reproductive patterns.  Prior to this work Crangon has been assumed to have separate sexes (gonochoristic), with the females outliving the males, reaching larger size than the males, and the males dying or emigrating after mating.  Observation of field and laboratory animals, however, suggests that the species is a protandric hermaphrodite, hatching first as a male and then transforming to female later in life (life span in the species is about 1.5yr).  The authors present evidence of ovarian development and vas-deferens atrophy in field individuals, and directly observe sex change in laboratory specimens.  Other supporting evidence comes from histological changes in the gonad and onset of female secondary sexual characters in individuals sampled monthly from Gray’s Harbor.  Other evidence shows that some individuals are born and mature as females.  These are termed primary females in contrast with the secondary females that go the sex-transformation route.  In conclusion, the authors propose that rather than being gonochoristic, with the males dying off or emigrating (i.e., “disappearing”) during their second year of life, C. franciscorum actually undergoes sex change.   Gavio et al. 2006 J Crust Biol 26(3): 295. Photograph courtesy monkeyfacenews.

photograph of shrimp Crangon franciscorumNOTE  lit. “first male” + “Greek deity Hermaphroditus”.  Because reproductive strategies in shrimps are so varied, a more explicit description for C. franciscorum is “partial protandric hermaphroditism with primary females”

NOTE  the authors provide useful morphological “indicators” for juveniles, mature males, transitional males, immature secondary females, mature secondary females, and also for immature primary females and mature primary females


Sand or grass shrimp Crangon
franciscorum
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