The polychaete species typically referred to as Capitella capitata
is actually comprised of a large group of unnamed sibling species with
diverse life history and reproductive attributes (Grassle and Grassle 1976,
Grassle, 1980, Petraitis 1985). Detailed examination reveals only slight
morphological differences between species, even though life history and
reproductive modes differ dramatically (Grassle and Grassle 1976).
Capitella capitata is a small benthic polychaete belonging to Family
Capitellidae. The body is flexible, slender, elongated, and usually blood
red in color. The conical, shovel-shaped head and reduced parapodia with
chetae in both rami are useful diagnostic features. There is a single
genital pore between chaetigers eight and nine, surrounded by cross spines
Potentially Misidentified Species
Capitella capitata is morphologically similar to a number of
infaunal polychaetes, and positive identification to species level is
generally beyond the scope of amateur naturalists.
HABITAT AND DISTRIBUTION
Capitella capitata is generally considered to be a cosmopolitan
species in coastal marine and estuarine soft sediment systems. Grassle and
Grassle (1976) used electrophoretic enzyme analysis to determine that the
global population is actually made up of several genetically distinct (and
apparently genetically isolated) sibling species whose distributions
overlap such that local C. capitata populations actually consist of
a number of co-occurring sibling species.
Capitella capitata occurs throughout the soft sediment communities of the IRL.
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Capitella capitata is a small polychaete worm. Specimens may reach 10 cm, but more often they are around 2 cm.
Infaunal polychaetes such as Capitella capitata can be extremely
abundant, generally ranging between several hundred and several thousand
individuals per square meter. Sears and Mueller (1989) report a peak
seasonal numerical abundance of 22,000 individuals/m2 in a
Galveston, TX, mixed-species assemblage consisting primarily of C.
capitata, Streblospio benedicti, and Scoloplos foliosus.
At other times during the study, abundance declined to a low of around
Male Capitella species I are capable of developing as
simultaneous hermaphrodites, and they do so at greater
frequency when females are scarce within the population
(Petraitis 1985). Hermaphroditism in Capitella has
been hypothesized to be an adaptation to conditions of low
faunal density. However, since females do not become
hermaphroditic and hermaphrodites don't self-fertilize,
Petraitis (1985) suggests hermaphroditism in Capitella
is an adaptation to reduce mate competition in small local
Animals reach sexual maturity at about 4 months in temperate
waters, and somewhat faster in warmer areas (Warren 1976,
Qian and Chia 1994). In the laboratory, animals became mature
in 31-48 days at temperatures ranging around 12.6-22°C
(Tsutsumi and Kikuchi 1984). Female produces from 100-1,000
Somewhat similar to the polychaete Streblospio benedicti,
Capitella capitata exhibits both pelagic and non-pelagic
(direct-developing) larval development strategies (Henriksson 1969,
Forbes and Calow (2002) indicate that the Type M and Type I sibling C.
capitata species are lecithotrophic (briefly planktonic), while the
Type S sibling species is direct-developing. Lecithotrophic larvae are
brooded during part of their development within the adult burrow tube
(Grassle and Grassle 1974)
Planktonic-developing Capitella capitata transition over several
hours to several days through two distinct free-swimming larval stages
(trochophore, metatrochophore) before undergoing metamorphosis and
settlement to the benthos as a crawling worm (Biggers and Laufer 1996).
This process can be accelerated in the laboratory within the span
of an hour or less by exposing larvae to methyl farnesoate which has been
shown to be stimulatory to early postembryonic larval stages of crustaceans
as well (Laufer and Biggers 2001).
Dubilier (1988) demonstrated that newly hatched Capitella species I
could be induced to settle onto organic-enriched sediments in as little as
30 minutes. The addition of sulphide to experimental sediments delayed
settlement by several hours as larvae apparently tried to avoid settling
into sulphide-rich areas. Presented alone, however, sulphide induced
settlement, in keeping with earlier findings by Cuomo (1985) that sulphide
is a positive settlement cue associated with areas of nutrient enrishment.
Hannan (1981) used collection jars to sample water column availability of
C. capitata larvae and demonstrated that larval availability does
not determine observed benthic settlement patterns. The author suggested
that larval substratum choice and environmental hydrodynamic processes must
also be considered when predicting or interpreting recruitment patterns.
Although it is now largely cosmopolitan in its distribution (excluded only
from the tropics), Capitella capitata may have originated from cold
marine environments. Wu et al. (1988) collected animals at sea water
temperatures of -2° that harbored mature oocytes indicating
reproductive activity even under these extreme conditions.
Examination of NOAA NBI collection records indicate Capitella
capitata have been collected from Florida waters ranging in salinity
from 41.5 ppt to nearly fresh water.
Capitella capitata exhibits a relatively high tolerance for sediment
hypoxia, hydrogen sulphide concentration, and other sediment conditions
avoided by many infauna (Henriksson 1969). Forbes and Lopez (1990)
experimentally demonstrated that reduced oxygen concentrations
(pO2 = 20 mm Hg or less) led to decreased C. capitata
growth rates and cessation of burrowing and feeding activity even when an
abundance of food was provided. The authors hypothesize that animals rely
solely on anaerobic metabolism once this threshold is crossed. Magnum and
van Winkle (1973) similarly observed that C. capitata oxygen uptake
ceased when pO2 fell to between 0-34 mm Hg. The fact that
experimental worms lost body mass under these conditions supports the
contention that full aerobic metabolism cannot be sustained at very low
ambient oxygen conditions despite a very high affinity of C.
capitata hemoglobin for oxygen. The
critical pO2 threshold is higher for larger worms.
Dense Capitella capitata populations are frequently located in areas
with greatly elevated organic content, even though eutrophic sediments are
often anoxic and highly sulfidic (Tenore 1977, Warren 1977, Tenore and
Chesney 1985a, Bridges et al. 1994).
Concentrations of more than 300 individuals/m2 were found to occur in a
self-sustaining population in proximity to a south Australian lead-zinc
smelting facility (Ward and Hutchings 1996).
Capitella capitata is a deposit-feeding detrital consumer
(Henriksson 1969, Levin et al. 1996). Individuals feed by everting a
papillose sac-like proboscis to gather detrital deposits. Feeding is
primarily non-selective, but gut contents usually include significant algal
material, suggesting that some selection may occur (Fauchald and Jumars
Tenore and Hanson (1980) demonstrated that detrital materials from
different sources were of unequal nutritional value to C.
capitata, with decay-resistant Spartina detritus being less
available than periphyton or macroalgal detritus. Nutritional value of
all types of detritus increased with aging, suggesting that microbial
enrichment is an important aspect of benthic detrital energetics.
Capitella capitata thrive in the absence of intraspecific
competition as early colonizers to benthic habitat patches that have been
disturbed or otherwise defaunated as a result of environmental stress
(Grassle and Grassle 1974, McCall 1977).
While space may at times be a limiting factor, some experimental evidence
exists suggesting that dietary resources are generally not limiting in most
infaunal estuarine habitats (Wilson 1990, Bridges 1996).
An array of benthic fish and invertebrate predators rely on infaunal
polychaetes as a seasonally variable dietary resource (Marsh and Tenore
1990). Nelson and Capone (1990) experimentally demonstrated that specific
predators impact various infaunal polychaete populations differently,
depending on predator foraging strategy and prey species-specific
Capitella capitata is a component of a great many marine soft
sediment communities, including vegetated and unvegetated benthic
habitats as well as those with elevated nutrient loads or excess levels
of other types of pollutants. It resides within mucus-lined burrows
within the substratum (Henriksson 1969, Rosenberg 1976, Forbes and
Lopez 1990). NOAA NBI ollections have revealed the presence of this species at depths ranging from inertidal to
This polychaete is a prototypical 'r-adapted' species, i.e., an
opportunistic species with high growth, reproduction, and mortality rates.
As with most such opportunistic species, C. capitata populations
often show variable densities, including pronounced seasonal shifts in
abundance (McCall 1977). Rapid growth and reproduction during periods of
high food availability appear to push localized populations above carrying
capacity, resulting in rapid population declines when resources become
scarce and the needs of the population cannot be met. (Chesney and Tenore
A large amount of trophic energy is transferred from Capitella
capitata and other infaunal detritivores to benthic consumer levels
(Marsh and Tenore 1990). Additionally, Capitella capitata is
commonly employed as a pollution indicator species in environmental
assessment studies (Reish 1957, Henriksson 1969).
Biggers WJ and H Laufer. 1996. Detection of juvenile hormone-active
compounds by larvae of the marine annelid Capitella sp. I. Archives
of Insect Biochemistry and Physiology 32:475-484.
Bridges TS, Levin LA, Cabrera D, and G Plaia. 1994. Effects of sediment
amended with sewage, algae, or hydrocarbons on growth and reproduction in
two opportunistic polychaetes. Journal of Experimental Marine Biology and
Bridges TS. 1996. Effects of organic additions to sediment, and maternal
age and size, on patterns of offspring investment and performance in two
opportunistic deposit-feeding polychaetes. Marine Biology 125:345-357.
Chesney EJ and KR Tenore. 1985a. Oscillations of laboratory populations of
the polychaete Capitella capitata (type I): Their cause and
implications for natural populations. Marine Ecology Progress Series
Chesney EJ and KR Tenore. 1985b. Effects of predation and disturbance on
the population growth and dynamics of the polychaete Capitella
capitata (type I). Marine Biology 85:77-82.
Cuomo MC. 1985. Sulphide as a larval settlement cue for Capitella
sp I Biogeochemistry. Vol.1(2): pp. 169-181.
Dublilier N. 1988. Hv2S: A Settlement cue or a toxic substance for
Capitella sp. I larvae? Biological Bulletin, Vol. 174(1) pp. 30-38.
Fauchald K and PA Jumars. 1979. The diet of worms: A study of polychaete
feeding guilds. Oceanography and Marine Biology Annual Review 17:193-284.
Forbes VE and P Calow. 2002. Population growth rate as a basis for
ecological risk assessment of toxic chemicals. Philosophical Transactions:
Biological Sciences, Vol. 357 (1425), Population Growth Rate: Determining
Factors and Role in Population Regulation. pp. 1299-1306.
Forbes TL and GR Lopez. 1990. The effect of food concentration, body size,
and environmental oxygen tension on the growth of the deposit-feeding
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(7) pp. 1535-1544.
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systems in marine benthic polychaetes. Marine Research, 32:253-284.
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in suspended jar collectors and in the adjacent natural habitat in Monterey
Bay, California. Limnology and Oceanography, Vol. 26(1) pp. 159-171.
Henriksson R. 1969. Influence of pollution on the bottom fauna of the sound
(Oresund). Oikos, Vol. 20(2) pp. 507-523.
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farnesoate for invertebrate reproduction and post-embryonic development.
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response experiments. Ecological Applications, Vol. 6(4) pp. 1295-1313.
Magnum CP and W van Winkle. 1973. Response of aquatic invertebrates to
declining oxygen conditions. American Zoologist 13:529-541.
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benthos of Long Island Sound. Marine Research 35:221-266.
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Petraitis P. 1985. Females inhibit males' propensity to develop into
simultaneous hermaphrodites in Capitella species I (Polychaeta).
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Qian PY and FS Chia. 1994. In situ measurement of recruitment,
mortality, growth, and fecundity of Capitella sp. (Annelida:
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capitata (Fabricius), to waste discharges of biological origin. United
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Rosenberg R. 1976. Benthic faunal dynamics during succession following
pollution abatement in a Swedish estuary. Oikos, Vol. 27(3) pp. 414-427.
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and Big Reef, Galveston, Texas. The Southwestern Naturalist 34:150-154.
Tenore KR. 1977 Growth of Capitella capitata cultured on various
levels of detrit.us derlved from different sources. Limnology and
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and ages to a polychaete macroconsumer, Capitella capitata.
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species composition in polluted intertidal and subtidal marine sediment
near a lead smelter, Spencer Gulf, South Australia. Marine Ecology Progress
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