Pennella balaenopterae

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Geographic Range

Pennella balaenopterae is found in the Antarctic seas and the Western and Northern Pacific Ocean. (Dallay and Vogelbein, 1991)

Habitat

The definitive hosts for Pennella balaenopterae are the Sei and Minke Whales (Balaenoptera borealis and Balaenoptera acutorostrata, respectively) of the Antarctic and North Pacific regions of the world. There have been some intermediate hosts found for species of the Pennellidae family that are important for the life cycle of the species. Although the intermediate host of Pennella balaenopterae is not known, this is not the case with all other copepodids. (Bliss, 1982; Dallay and Vogelbein, 1991; Uchida, et al., 1998)

Physical Description

Pennella balaenopterae may reach up to 30 centimeters long, and thus is one of the largest species of copepods within its family. Adult females are characterized by a loss of external segmentation and obscuration of swimming appendages. Pennella species are recognized by the branched outgrowths on the posterior part of their trunks. The mandibles are prolonged, forming a sucking tube for the mouth through which the species feed. Adults also have paired, segmented sensory antennae. Five pairs of thoracic legs are found in the species, which are more modified in females than males. After attaching to the host the parasite undergoes diphasic growth. The first phase of this type of growth occurs in the copepod's anterior body portion. During the second phase of growth, the posterior portion, designated primarily for reproductive processes, begins to grow extremely rapidly, and is soon larger than the anterior portion. (Bliss, 1982; Roberts and Janovy, Jr., 2000)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    30 (high) cm
    11.81 (high) in

Development

The life cycle of Pennellidae species has not been fully studied. However, the typical copepodid life cycle is comprised of several stages, where there is a free-living stage within which the copepod undergoes several series of molts until the infective immature stage is reached. Also characteristic of this order is the existence of an intermediate host in the life cycle, usually a fish of some sort, but sometimes other vertebrates are used. The early development of the larvae takes place in the egg sac while it is still attached to the female copepodid, which then develops more and is ultimately released into the water possessing a full set of cephalic appendages and three pairs of thoracic legs. The copepod then finds its intermediate host where it remains until it reaches its later copepodid stages. After development of the attachment mouthparts, the copepod finds its definitive host where it then permanently attaches. Engorged females can produce from 300 to 700 eggs in each of her paired egg sacs. (Bliss, 1982; Roberts and Janovy, Jr., 2000)

Reproduction

Both sexes differ. Females have distinctive anchoring processes that extend from the anterior end of the parasite. Mating occurs after both sexes have reached full sexual maturity. After copulation, the copepod male dies early on in the cyclopodid stage of the life cycle. The female then loses all external segmentation and grows drastically in size. Both temperature and salinity are important factors to ensure successful reproduction. (Bliss, 1982; Roberts and Janovy, Jr., 2000)

  • Parental Investment
  • pre-fertilization
    • provisioning

Behavior

Pennella balaenopterae is a solitary species with no social behavior with others of its species, except during mating. Once it has attached to its host, it no longer moves around, except in the case of the male when searching for the female to mate. The female attaches to the host after the development of two cephalic anchoring appendages. One of the pairs develops from the posterior corners of the cephalothorax and the second from the ventral surface of the cephalon. As the female further develops, the processes expand and bifurcate allowing the female to deeply extend herself permanently into the whale's blubber. The egg sacs are thus carried externally and the nauplii are then released into the water, thus starting another series of life cycles. (Bliss, 1982)

Communication and Perception

Adults also have paired, segmented sensory antennae. Crustaceans in general have various sensory resceptors, mainly setae over the body. Photoreceptors are also generally present. (Brusca and Brusca, 2003; Roberts and Janovy, Jr., 2000)

Food Habits

Pennella balaenopterae is an ectoparasite of whales. It feeds by siphoning blood from the host through its elongate mandibles, which are the parasite's primary mouthparts. (Dallay and Vogelbein, 1991; Roberts and Janovy, Jr., 2000)

  • Animal Foods
  • blood
  • body fluids

Predation

This free-living stage of this species is likely eaten by fish or other copepod predators. Eggs and younger stages have a high mortality probably due to not reaching a suitable host.

Ecosystem Roles

The definitive hosts for Pennella balaenopterae are the Sei and Minke Whales (Balaenoptera borealis and Balaenoptera acutorostrata, respectively) of the Antarctic and North Pacific regions of the world. There have been some intermediate hosts found for species of the Pennellidae family that are important for the life cycle of the species. Although the intermediate host of Pennella balaenopterae is not known, this is not the case with all other copepodids. (Bliss, 1982; Dallay and Vogelbein, 1991; Uchida, et al., 1998)

Species Used as Host

Economic Importance for Humans: Negative

Although the Pennellidae species do not have a direct effect on humans, they do have an impact on the whaling industry as they affect the exterior, and sometime the interior, parts of the whales. Infested whales tend to have scars and legions on the surface of their blubber. (Bliss, 1982; Dallay and Vogelbein, 1991; Uchida, et al., 1998)

Contributors

Nagla Fetouh (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.

Glossary

Antarctica

lives on Antarctica, the southernmost continent which sits astride the southern pole.

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

motile

having the capacity to move from one place to another.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sanguivore

an animal that mainly eats blood

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

References

Bliss, D. 1982. The Biology of crustacea. New York: Academic Press.

Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Cressey, R. 1982. The Biology of Crustacea, Pathobiology. New York: Academic Press.

Dallay, M., W. Vogelbein. 1991. Parasite Fauna of Three Species of Antarctic Whales with Reference to Their Use as Potential Stock Indicators. Fishery Bulletin, 89(3): 355-364.

Roberts, L., J. Janovy, Jr.. 2000. Foundations of Parasitology. U.S.: McGraw Hill.

Uchida, A., Y. Kawakami, S. Yuzu, S. Kishikawa, T. Kuramochi. 1998. Prevalence of Parasites and Histopathology of Parasitisation in Minke Whales from the Western North Pacific Ocean and Southern Sea of Okhotsk. Report of the International Whaling Commission, 48: 475-479.