Keith Philippe Louse Symbionts Among Right Whales Final

Louse (PHTHIRAPTERA) Symbionts Among Right Whales (Eubalaena spp.) _______________________________________________________________________ _ Keith Philippe Undergraduate, University of Minnesota, April 2007 Marine Biology, Prof. Peter W. Sorensen

key words: cyamid (louse), right whale (Eubalaena sp.), parasite

There is little known about symbionts of Cetaceans (Miggnucci-Giannoni et al.,1998). Existing literature indicate that certain species of whales are well known for harboring conglomerates of parasites (Kim, 1985). Parasitic populations of lice occupying specific body parts of their host have definite organization. These include species richness, population density, and microhabitat selection. Lice community organizations result from successive invasion and colonization in which parasitic arthropods, in this instance, cyamid-whale reciprocity, continually interact among themselves and their hosts.

This article describes parasitic occurrence of lice (cyamid amphipods) on three species of right whales: (i) The North Atlantic (Eubalaena glacialis); (ii) The Southern (Eubalaena australias); and (iii) a poorly known remnant population, Eubalaena japonica. To help accomplish its objective, this review will focus primarily on: (i) evolutionary trends of right whales and lice; (ii) microhabitat selection of lice on right whales; and (iii) intraspecific host transfer of whale lice.

Louse (pl. lice) are small creatures usually less than 5mm long. Their first instar nymphs (a phase between two periods of molting in the development of an insect larva or other invertebrate animal.) are less than 1mm long. Lice are dorsoventrally1 flattened and 1

axis joining the dorsal and ventral surfaces

Philippe

1 of 7

possess many short setae2. With little variation in color, lice are generally off-white with a few having brownish or reddish hues. They generally remain near the surface of the skin where they feed, copulate, and lay eggs. Most lice have large claws on their tarsi in which they use to lodge on hosts (Marquardt et al., 2000).

Although various forms of social symbiosis exist between whales and lice, right whales and their louse symbionts appear to share both commensalic (relationship in which one party gains some benefit, whilst the other suffers no serious disadvantage) and phoretic (an animal attaching to another for transportation, especially that of arthropods) relationships.

Most cetaceans carry populations of benign ectoparasites called cyamids (whale lice), also known as amphipod crustaceans (Caprellidea; Cyamidae) (Seger, 2005). Other ectoparasites of cetaceans include ascarids, diatoms, ciliates, cirrepeds, copepods, isopods, lampreys and remoras (Kim, 1985). Cyamids spend all life stages 3 on whales, feeding on the outer surface of their host’s epidermis. They roam widely on their hosts, but because they have no free-swimming stage they can migrate only between whales engaging in physical interaction. Literature indicates that the ecological universe of a cyamid population is well defined and sharply bounded, consisting of many virtually identical and constantly moving habitat islands (whales) that occasionally replace them selves through a simple birth-and-death process (Seger, 2005). Right and grey whales (Eschrichtius robustus) are unusual in that each carries large populations of three cyamid 2

a stiff hair like or bristle like structure, esp. in an invertebrate.

3

The life stages of louse include three phases: (i) the egg or nit; (ii) the nymph; and (iii) the adult louse.

Philippe

2 of 7

representatives that are not common among other cetaceans. Grey whale cyamids (Cyamus ceti, Cyamus kessleri, Cyamus scammoni) are distantly related to right whale cyamids. Right whale cyamids are traditionally referred to as Cyamus ovalis, Cyamus gracilis and Cyamus erraticus. Every adult right whale carries populations of all three cyamid species. On a typical adult, the callosities4 provide about 0.5 m2 of substrate for C. ovalis which is by far the most abundant of the three species with about 5000 adults per adult right whale, based on an estimated density of roughly one adult cyamid per cm2 according to photographic and defined-area census data (Seger, 2005).

The Cyamids of Right Whales occupy ecologically suitable regions of whale hosts. The details on such selectivity are not fully understood. Cyamus ovalis ,for example, blankets the callosities (raised patches of roughened skin on the head); and their white bodies make the callosities far more pronounce against the black skin of the whale’s head and back. Each right whale has distinct callositive patterns that can be identified in photographs; owing to the visual contrast and sharp delineation of callosity boundaries created by a living blanket of Cyamus ovalis. Cyamus gracilis occupies pits and grooves between the elevated patches of callosity tissue. Adults of this species are smaller and thinner than adult Cyamus ovalis. Cyamus. erraticus occupies smooth skin in the genital and mammary slits; it is highly mobile and opportunistically colonizes wounds and other areas of reduced water flow not occupied by the other two species; it also ‘blooms’ on the heads of young calves, but these concentrations disappear within a few months (Seger, 2005).

4

a thickened and hardened part of whale skin; a callus.

Philippe

3 of 7

Morphological and behavioral adaptations of parasitic arthropods are strongly correlated with mammalian skin type. The mammalian skin provides numerous microhabitats for different parasitic arthropods to reside and obtain food (Kim,1985). There is much speculation on what whale lice feed on when attached to their hosts. Some suggest cyamids feed on shedding integument. Others indicate neither Anoplura nor Mallophage (blood sucking lice) are found on cetaceans (Kim,1985)..

Some cyamids occur on more than one cetacean species, but few cetaceans normally host more than one species of cyamid at a given period. The slow-swimming right whales and grey whale (Eschrichtius robustus) are unusual in that each carries large populations of three cyamid species that do not occur regularly on any other cetaceans. The grey whale cyamids (Cyamus ceti, Cyamus kessleri, Cyamus scammoni) are only distantly related to each other and to the right whale cyamids, and vice versa (Seger, 2005).

In an attempt to determine evolutionary patterns between cyamids and Right whales, researchers used nucleic material in cyamid and Eubalaena mitochondria. Their results indicated that one subspecies of Right whale (North Atlantic) have long been isolated from its southern counterparts. It was further suggested that the same species of louse occurred on both subspecies in lue of the long-term dissociation. Researchers questioned how a focal whale cyamid was able to migrate from the Northern Atlantic to the Southern Oceans. One possibility included a right whale migrating across the equator thousands of years ago allowing the lice to move from host to host. The challenges of this theory was

Philippe

4 of 7

the governing fact that the equator, being a major barrier to blubber-clad whales, can induce integument overheating (Bohannon, 2005).

Researchers believe that infestation of whale cyamid on host is mediated by: (i) social behavior of whales; (ii) interactions between whale heterospecifics and conspecifics; and (iii) delivery of calf. Melon-headed whales are highly social and usually travel in groups of 500 to 1,000 individuals. Occasionally, groups as large as 2,000 individuals have been observed (Wardle et al., 2000). Other scientists further believe that slow movements of whales serve as ideal conditions for lice shifts and relocation. Near shore drifting may also influence lice migration and subsequent habitation. Scheffer included a notable example of how mobility and drift location affect commensal transmission. Cyamids are host specific. Scientists indicate that this was expected considering the circumstances of their life history. Young whale-lice are released from the female brood pouch as miniature adults with no free-swimming stage(s). The adults have appendages that are adapted for swimming. In other amphipods these appendages are modified, often greatly reduced. The peraeopods or walking legs dig deeper into the whale skin as currents (or collectors) tend to pull the cyamid body away from the host. The probability of cyamid transmission from one host to another, apart from other restrictions of specificity, is mediated by bodily contact. There is contact between adult and calf at birth and in suckling, between adults during courtship and copulation; and accidental or occasional contact through closeness in migration, in play and in attack upon one another. Of these, only the latter accounts for transmission (Hurley, 1957).

Philippe

5 of 7

In their search to find out more about local interactions, large-scale movements and population histories of Right whales, researches have used Right whale cyamids as ‘replicated evolutionary experiments: DNA extraction, PCR, and sequencing; Polymorphism within and differentiating among populations; Gene tree estimates; and population sizes using equilibrium tests.

In recent years, human exploitation of Right whale populations has reduced whale and cyamid populations. While researchers have identified some cyamids of Right whales and developed relationships between the two, no single hypothesis completely explains the affinity of specific cyamids for Right whales.

In conclusion, whales and cyamids have a long history of commensalisms and phoresy. Not only are whale cyamids host specific, but, in the case of Cyamus ovalis and Cyamus gracilis on right whales, it appears as if lice selectively occupy bodily regions on whales. The most common methods of lice redistribution on right whales are through: (i) contact between adult and calf at birth and in suckling; (ii) contact between adults during courtship and copulation; (iii) sedated whale movements; and (iv) accidental contact through closeness in migration, in play and in attack upon one another. The redistribution of cyamids is apparently regulated by whale interactions. With such high dependency, cyamid redistribution is inherently risky.

Philippe

6 of 7

References Bohannan, John. Listening to Lice. Science Now. (September, 2005), p1-2, 2p, 1bw. http://search.ebscohost.com/login.aspx?direct=true&db=aph&AN=1834035 6&site=ehost-live Chung Kim, Ke. Evolutionary Relationships of Parasitic Arthropods and Mammals. Coevolution of Parasitic Arthropods and Mammals. New York, Whiley & Sons. (month n/a, 1985). pp. 21, 140, 236 Hurley and J. L. Mohr. On Whale-Lice (Amphipoda: Cyamidae) from the California Gray Whale, Eschrichtius glaucus. The Journal of Parasitology, Vol. 43, No. 3. (June, 1957), pp.352-357. Marquardt, W.C.; Demaree, R.S.; and Robert B. Grieve. Mallophaga and Anoplura: The Lice. Parasitology and Vector Biology. California, Harcourt Academic Press. (month n/a, 2000). p.549. Mignucci-Giannoni, A A; Hoberg, E P; Siegel-Causey, D; and Ernest H. Williams, Jr. Metazoan Parasites and Other Symbionts of Cetaceans in the Caribbean. The Journal of Parasitology, Vol. 84, No. 5. (October, 1998), pp.939-946. Seger J.; Kaliszewska, Z.A.; Rowntree, V.A.; Barco, S.G.; Benegas, R.; Best, P.B.; Brown, M.W.; Brownell Jr., R.L.; Carribero, A.; Harcourt, R.; Knowlton, A.R.; Marshalltilas, K.; Patenaude, N.J.; Rivarola, M.; Schaeff, M.C.; Sironi, M.; Smith, W.A.; and Tadusu K.Yamada. Blackwell Publishing, Ltd. Population Histories of Right whales (Cetacea: Eubalaena) Inferred from Mitochondrial sequence diversities and divergences of their whale lice (Amphipoda: Cyamus). Molecular Ecology (June, 2005) 14, 3439–3456 Scheffer, Victor B. Organisms Collected from Whales in the Aleutian Islands. The Murrelet, Vol. 20, No. 3. (SeptemberDecemeber, 1939), pp.67-69. Wardle, W.J.; Haney, A.T.; and Graham A.J. Worthy. New Host Record for the Whale Louse (Isocyamus Delphinii, AMPHIPODA, Cyamidae). Crustaceana. Koninklijke Brill NV, Leiden, (month n/a, 2000) 73 (5): pp.639-641

Philippe

7 of 7