Summary ⁵

Panulirus argus, the Caribbean spiny lobster, is a species of spiny lobster that lives on reefs and in mangrove swamps in the western Atlantic Ocean.

Biology ⁶

Young lobsters start off at just 2.5 cm and adults are typically about 10 cm from the tip of the antennae to the tail. It takes about 7 years to get to this size. Very few make it to 20 years old but these may reach 45 cm and weigh 4.5 kg.Because they have hard shell (exoskeletons) spiny lobsters have to shed them to grow. During this molt the lobster bulks up with water to expand the new exoskeleton. This then firms up and becomes hard within a week. Spiny lobsters molt about 4 times per year.

Description ⁷

The carapace of Panulirus argus is subcylindrical and bears many strong, forward-facing spines. A pair of rostral horns projects forward over the stalked eyes. Whip-like antennae are longer than the body and are studded with small spines and setae. Antennules are also elongate, extending approximately 2/3 body length. The abdomen is notched along its lateral margins, but is otherwise smooth. Each segment of the abdomen has a transverse groove that is disrupted at the midline. The central telson is flanked by 2 pairs of biramous uropods. Body color is varied, but is generally a gray or tan base color mottled with shades of green, red, brown, purple, or black. The second and sixth segments of the abdomen have large yellow or white ocelli, with smaller ocelli scattered dorsolaterally along the abdomen. Legs are striped longitudinally in a dull blue color. Dactyls of the walking legs are setose. Pleopods are bright orange and black. The endopodites in female pleopods are well developed and hook-like, bearing many setae. In juveniles, antennae and pereopods are banded with white; and a broad white stripe runs the length of the dorsal midline across both the carapace and abdomen. Panulirus argus is sexually dimorphic, with females distinguished from males by differences in the sternum, legs and genital openings. In males, the sternum is somewhat broader and lacks the striations that are commonly found in females. The second pair of walking legs in males is more elongate than the other legs, and bears longer, curved dactyls. Females have small chelae on the dactyls of the fifth pair of walking legs. The raised genital openings of males are located ventrally, on the bases of the fifth pair of walking legs. In females, the gonopores are set at the bases of the third pair of walking legs. II . HABITAT AND DISTRIBUTION

Distribution ⁸

The Caribbean Spiny Lobster (Panulirus argus) occues in the Western Atlantic from Bermuda and North Carolina (U.S.A.) to Rio de Janeiro (Brazil), including the entire Gulf of Mexico and the Caribbean Sea. It has been reported twice from West Africa (Ivory Coast). (Holthuis 1991)

Size ⁹

Panulirus argus reaches a maximum length of approximately 45 cm (1.47 feet), but is more commonly found at lengths of approximately 20 cm (7.9 inches). Growth in the first year averages 5 cm (1.5 inches), with growth thereafter averaging approximately 2.5 cm (1 inch) per year. Male and female growth rates are approximately equal in south Florida nursery areas (Davis and Dodrill 1980). Females tend to grow somewhat more slowly than males (Little 1972; Olsen and Koblick 1975) and do not achieve as large a size (Williams 1984).Spiny lobsters molt an average of 2.5 times per year, with most molting occurring from March - July, or from December - February in Florida (Williams 1984). Growth characteristics are correlated with age, with molt frequency and increment of growth at molting tending to decline with age (Aiken 1980). Variability in food quality and abundance, population density, water temperature, as well as rates of predation and injury, all affect growth rates in local populations. Eldred et al. (1972) estimated average growth rates in wild populations of Panulirus argus as 5 mm (0.2 inches) per month for the first 9 -10 months post-settlement in Biscayne Bay, Florida. Tagging studies in the same area showed that mean growth rates in 40-85 mm (1.6 - 3.3 inches) lobsters averaged 1.8 mm (0.07 inches) per month, with physical condition having a significant impact on growth rates. Davis (1981) reported that individuals having no injuries grew approximately 2.2 mm (0.09 inches) per month, while those missing legs and antennae grew only 1.3 mm (0.05 inches) per month. In Florida Bay, however, growth rates for injured and uninjured lobsters were approximately equal, at 3.3 mm (0.12 inches) per month (Davis and Dodrill 1980). In Key West, tagged lobsters 49-83 mm (1.9 - 3.3 inches) in length grew approximately 3.1 mm (0.12 inches) per month (Little 1972).Witham et al. (1968) reared pueruli of Panulirus argus under laboratory conditions over 7 months. During this time pueruli averaging 6 mm (0.2 inches) carapace length (CL) grew to an average of 34 mm (1.33 inches), with growth rates ranging from 3.8 - 4.2 mm (0.14 - 0.16 inches) per month. Other laboratory populations grew considerably more slowly, with Lewis et al. (1952) and Sweat (1968) reporting monthly growth rates less than 2 mm (0.07 inches) per month. Assuming a post-settlement growth rate of 4.0 mm (0.16 inches) per month, Panulirus argus likely reaches legal harvest size in 20 - 40 months, depending on location and degree of injury (Little 1972; Davis and Dodrill 1980).

Diagnostic description ¹⁰

The Caribbean Spiny Lobster (Panulirus argus) has an antennular plate with 4 large spines arranged in a square; there are no scattered small spinules. The third maxilliped has an exopod with a flagellum. The transverse grooves of the abdominal somites have margins that are straight, not crenulated, where interrupted, they gradually narrow toward the middle of the body, rather than end abruptly. The color of the abdominal somites is reddish, brownish, or sometimes greenish, without transverse colour bands. A large eyespot of whitish or yellowish, surrounded by a dark colour, is present over the anterior end of the base of the pleura of abdominal somite 2; a similar (even slightly larger) spot is present on the anterolateral parts of somite 6. The tail fan has a broad transverse reddish band along or just before the posterior margin. (Holthuis 1991)

Look alikes ¹¹

Panulirus argus closely resembles a related species, the smoothtail spiny lobster, P. laevicauda, whose range is sympatric. The two are easily distinguished based on 2 characters: P. laevicauda lacks dorsal grooves on abdomen, but possesses a series of small white spots that run along the lateral margins of the abdomen.

Habitat and ecology ¹²

Habitat and Ecology

• Marine

Behaviour ¹³

Caribbean spiny lobsters are social animals and live in groups. When attacked the whole group will come together in a defensive pod and stick their spiny antennae straight up at the predator. This makes it difficult to pick off any one lobster.When they move their antennae the base rubs against a ‘file’ on their body, making a rasping noise to repel predators. Spiny lobsters are the only animals that make sound in this way.They are fussy when it comes to selecting den-mates and will shun any diseased individuals. Remarkably, they can tell if a lobster is infected even before it shows signs of being sick.These animals are famous for their migratory marches. During autumn they head for deep water in long processions, single file. They are one of the few invertebrates capable of true navigation and may use ‘maps’ of the Earth’s magnetic field to do this.

Reproduction ¹⁴

Panulirus argus reach sexual maturity at lengths of approximately 70 - 80 mm (2.8 - 3.2 inches) (Witham et al 1968. Olsen et al 1975, Davis 1979). Adult male and females often inhabit estuaries, bays, and lagoons; but spawning typically occurs in nearshore and offshore reef fringes and other hardbottom areas from late spring through summer in Florida waters (Davis 1975; Kanciruk and Herrnkind 1976; Lyons et al. 1981). Annual variation in peak spawning period is dependent on water temperature. Lyons et al. (1981) reported spawning begins when water temperatures reach 24º C in deeper reef areas. In Florida, there is little evidence that spiny lobsters spawn more than once per year; however, in Bermuda, evidence supports multiple spawning (Sutcliffe 1952). Mating follows short courtships that involve signals being given by both sexes. In copulation, males hold females sternum to sternum and extrude a spermatophore which is adhered to the female's sternum, and will remain until the time of spawning. Sperm may be viable for as long as a month (Marx and Herrnkind 1986). Spawning occurs when females flex the abdomen under the carapace, spreading the telson and uropods, as well as the pleopods. Eggs are shed onto the abdomen, while the female scratches at the spermatophore to liberate sperm and fertilize eggs as they are extruded. Fecundity varies with body size. Females 71-75 mm (2.8 - 3 inches) in length carry approximately 230,000 eggs; while females over 100 mm (3.9 inches) carry more than 700,000 eggs (Mota-Alves and Bezerra 1968). Williams (1984) reported females 23 cm (9.1 inches) with 500,000 eggs, 30 cm (11.8 inches) with 1.18 million eggs, and 38 cm (15 inches) with 2.6 million eggs. Using the Index of Reproductive Potential (IRP) Lyons et al. (1981) estimated that female Panulirus argus in the upper Florida Keys measuring 76-85 mm (3.0 - 3.3 inches) carapace length (CL) contribute 48% of all egg production in the population. Females over 85 mm (3.3 inches) CL comprise approximately 20% of the female population, but contribute 41% of egg production. Females smaller than 76 mm (3.0 inches) comprise approximately 25% of all females, but contribute 11 % of all eggs. Minimum spawning size has declined in Florida Panulirus argus females, perhaps as a response to intense fishing pressures. In 1922, minimum spawning size of females was reported to be 76mm (3.0 inches) (Crawford and De Schmidt 1922). Recent surveys have revealed reproductive females as small as 65 mm- 71 mm (2.6 - 2.8 inches) in south Florida (Warner et al. 1977; Lyons et al 1981). However, unfished populations in the Dry Tortugas area show the minimum size in egg-bearing females to be 78 mm (3.1 inches) (Davis 1975). Suggested reasons for this decline in minimum spawning size have been genetic selection; modified sexual behavior when large females become rare; and reduced growth rates (Davis 1975; Warner et al. 1977; Lyons et al 1981). Decline in size of mature females has caused a marked reduction in reproductive potential, with Lyons et al. (1981) estimating that egg production in Florida Keys spiny lobsters was only 12% of that expected from a similarly sized, unfished population (Lyons et al. 1981).

Link to Access Genomic Data ¹⁵

http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=6737&lvl=0

Sources and Credits

1. (c) Zach Putnam, some rights reserved (CC BY-NC-SA), http://www.flickr.com/photos/35484985@N00/3403215992
2. (c) Roberto Arreola Alemón, all rights reserved, uploaded by Roberto Arreola Alemón
3. (c) Grant Bishop, some rights reserved (CC BY-NC-SA), https://www.flickr.com/photos/64609422@N04/8388945314/
4. (c) Maniacduhockey, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/b/bd/Homard3.jpg
5. Adapted by Emily Rose Sharkey from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Panulirus_argus
6. Adapted by Emily Rose Sharkey from a work by (c) Natural History Museum, London, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/12496638
7. Adapted by Emily Rose Sharkey from a work by (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11526595
8. Adapted by Emily Rose Sharkey from a work by (c) Shapiro, Leo, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/17763460
9. Adapted by Emily Rose Sharkey from a work by (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11526600
10. Adapted by Emily Rose Sharkey from a work by (c) Shapiro, Leo, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11289872
11. Adapted by Emily Rose Sharkey from a work by (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11526598
12. Adapted by Emily Rose Sharkey from a work by (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/28249458
13. Adapted by Emily Rose Sharkey from a work by (c) Natural History Museum, London, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/12496637
14. Adapted by Emily Rose Sharkey from a work by (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11526599
15. (c) Emily Rose Sharkey, all rights reserved

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