Grass Shrimp
Palaemonetes pugio
Summary 2
Palaemonetes pugio (daggerblade grass shrimp) is small, transparent shrimp with yellow coloring and brownish spots. It can be found throughout the western Atlantic Ocean and Gulf of Mexico. Palaemonetes pugio has a smooth carapace and abdomen, as well as three pairs of legs. The second pair is the strongest, while the third pair lacks chelae (claws). It reaches a length of around 5 cm (2.0 in), and has a life span of around one year.
Physical description 3
Palaemonetes pugio has a smooth carapace and abdomen. Grass shrimp also have three pairs of legs. The second pair is the strongest, while the third pair lacks chelae (claws). A well-developed rostrum (horn-shaped structure between the eyes) possessing dorsal and ventral teeth is present in this species, located between its compound eyes on its head. P. pugio has a tail with two pairs of spines, on pair located dorsally, the other located posteriorly (Anderson, 1996). The pleura (side plates) of the second abdominal somite (section) overlap the pleura of the first and third abdominal somite (Zimmerman, 2000). The abdominal pleura are rounded in this species (Anderson, 1996).
Male adults reach an average length of 23.5 mm. Female adults bearing eggs are usually about 30.0 mm while those without eggs are usually about 26.2 mm. The females undergo a period of growth just before their breeding season in the summer. (Daiber, 1982) The adults rarely grow beyond 50 mm. P. pugio are transparent with yellow coloring and brown spots. (Anderson, 1996)
Size 4
Adult Palaemonetes pugio reach a length of around 5 cm (Kaplan 1988). The life span of P. pugio is 6 to 13 months (Alon and Stancyk 1982).
Look alikes 5
Palaemonetes pugio may be confused with several co-occuring shrimp species. The relatively small size and the lack of chelae (claws) on the third pair of walking legs is sufficient to distinguish the caridean shrimps (including P. pugio) from the familiar penaeid shrimp species.Members of the genus Palaemonetes can be differentiated from other palaemonid shrimp (e.g., Palaemon, Macrobrachium) by the absence of mandibular palps, although this usually requires detailed examination beyond the scope of amateur naturalists (Anderson 1985). Likewise positive differentiation of P. pugio from co-occurring congeners requires close examination of subtle differences in the chelae, rostra, antennules, and other external features (see included figure, adapted from Anderson 1985).
Reproduction 6
Palaemonetes pugio reproduces annually when the water warms up. Females bearing eggs have been demonstrated to be in much greater supply at 30 degrees Celsius and above. The females continuously produce eggs during the breeding season. Fertilized eggs take between 15-20 days to mature and new eggs are produced 1-2 days after the hatching of a previous group. Larger females tend to produce bigger eggs and larger quantities of eggs. (Daiber, 1982) Females can produce anywhere between 250-450 eggs in a season. (Anderson, 1996)
Before spawning, the ovaries in the female become more dense and visible. Additional setae are developed that will later hold the fertilized eggs. The female molts before mating can occur and the males do not stay with or guard females. Instead, the male must make contact with the female's exoskeleton to realize that mating is possible. Mating must occur within seven hours of the molt. (Anderson, 1996)
During copulation, the male and female move their genital regions to close proximity. The male inserts a spermatophore into the female's genitals where it remains until the eggs are ready for fertilization, usually within seven hours after the spermatophore has been inserted. Then through enzyme action, part of the spermatophore dissolves, allowing the sperm to fertilize the eggs. The fertilized eggs are then secured to the body by the setae. The female holds the eggs until the larvae are ready to hatch. The larvae break free from the egg membrane through their struggling, osmotic swelling of the inner membrane, and ventilatory movements by the mother. (Anderson, 1996)
Link to Access Genomic Data 7
http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=221654&lvl=0
Link to Access Genomic Data 7
http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=221654&lvl=0
Sources and Credits
- (c) Mike Gigliotti, some rights reserved (CC BY-NC), uploaded by Mike Gigliotti
- Adapted by matbio from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Palaemonetes_pugio
- Adapted by matbio from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18663916
- Adapted by matbio from a work by (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11526583
- Adapted by matbio from a work by (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11526580
- Adapted by matbio from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18663917
- (c) Emily Rose Sharkey, all rights reserved
