A New Hemichordate, Saccoglossus bromophenolosus (Hemichordata, Enteropneusta, Harrimaniidae), From North america

8 Pages·1994·2.3 MB·English

by  G M King

PROC. BIOL. SOC. WASH.
107(2), 1994, pp. 383-390
A NEW HEMICHORDATE,
SACCOGLOSSUS BROMOPHENOLOSUS
(HEMICHORDATA: ENTEROPNEUSTA: HARRIMANIIDAE),
FROM NORTH AMERICA
Gary M. King, Cem Giray, and Irv Komfield
Abstract.—Anew species, S. bromophenolosus, isdistinguishedfrom its con-
gener, S. kowalevskii (Agassiz 1873), on the basis ofthe following morpholog-
ical, biochemical, and genetic criteria: placement ofgill pores; prominence of
the dorsal ridge; structure ofthe proboscis skeleton; presence ofbromophenols
or bromopyrroles; relative electrophoretic mobility ofallozymes (e.g., super-
oxidedismutase);molecularweightsoffragmentsfromrestrictionendonuclease
digestion of mitochondrial DNA. S. bromophenolosus occurs from southern
Maine,U.S.A.,toNovaScotia, Canada,withanadditionalrecordfromWillapa
Bay, Washington, U.S.A.
Three families of enteropneusts (Hemi- tionsaboutthe taxonomic status ofthe spe-
chordata: Enteropneusta: Harrimaniidae, cies (King 1986, Woodin et al. 1987). Spe-
Ptychoderidae, and Spengeliidae) occur cifically, animals collected in Maine and
along the coasts of North America (Milne northward typically accumulate high con-
& Milne 1973, Bullock 197.S, Ruppert & centrations oftwo secondary products, 2,4-
Fox 1988). The best known species belong dibromophenol andadibromoindole (King
to the genus Saccoglossus (Harrimaniidae), 1986, unpubl. data), while animals from
which occurs on both the Atlantic and Pa- other locales accumulate 2,3,4-tribromo-
cific coasts (Milne & Milne 1973, Bullock pyrrole (King, unpubl. data, Woodin et al.
1975). Ofthe several saccoglossids, S. ko- 1987). Thedifferentialaccumulationofthese
walevskii(Agassiz 1873) has beendescribed haloaromatics does not appear to correlate
in greatest detail. Various aspects ofits dis- with any major environmental variables or
tribution, biology and ecology have been gradients. Further, the presence ofa given
reportedsubsequentto Agassiz's(1873)ini- haloaromatic phenotype appears to be a
tial description (e.g., Bateson 1886, Bullock fixedtraitassociated with populations from
1940, Tweedell 1961, Colwin & Colwin specific regions.
1962, Barrington 1965, King 1986, Woodin We now report that the genus Saccoglos-
et al. 1987, Balser & Ruppert 1990, Carey sus consists ofat least two distinct species
& Mayer 1990). S. kowalevskii has been along the Atlantic coast ofNorth America.
considered the only memberofitsgenus on These two species are readily differentiated
the Atlantic coast of North America, and by gross external morphological characters,
hasbeennotedinintertidalcollectionsfrom the accumulation of halogenated aromatic
Nova Scotia to Georgia (Dorjes 1972, compounds, morphology of the proboscis
Bromley 1979). Although there are certain skeleton, electrophoretic mobilities ofsev-
characteristics common to all saccoglossids eral enzymes, and the sequence composi-
along this range, a comparison ofbiochem- tion ofthe mitochondrial DNAs (mtDNA).
icalattributesreportedforpopulationsfrom We propose the name S. bromophenolosus
Maine and South Carolina has raised ques- forthe newspeciesoccurringfrom southern
384 PROCEEDINGS OFTHE BIOLOGICALSOCIETY OFWASHINGTON
Mainenorthwardandpossessingfeaturesas boscides was irritated with the syringe nee-
detailed below. S. kowalevskii occurs from dle prior to sample collection in order to
southern Maine southward, as noted by stimulatemucusandhaloorganicexcretion.
Verrill (1873) and Gosner (1979). The samples were analyzed by direct injec-
tion into a gas chromatograph. Details of
the extraction and analytical procedures
Materials and Methods
have been reported elsewhere (King 1986,
Saccoglossids were collected from the in- 1988). The proboscideal skeletons of 5 in-
tertidal zones ofsites ranging from Halifax, dividuals from Lowes Cove and York,
Nova Scotia, to Georgetown, South Caro- Maine, were examined after dissection of
lina, by excavating sediments to a depth of live animals.
about 10 cm at low tide. The proboscis,
collarandanteriorportionsofthetrunkwere Saccoglossus bromophenolosus,
obtained readily by removing the animals new species
directly from the substrate, but complete Figs. 1-4, Table 1
specimensweredifficulttocollectduetothe Saccoglossussp. Bullock 1975, p. 619; Koz-
fragilityofthe posteriorregion ofthetrunk.
loff 1987, p. 478.
Specimens were examined in the field for Saccoglossus kowalevskii.—Milne & Milne
external morphological characteristics (see 1973, (p.p.): 230; Bromley 1979, p. 533.
below)andthenplacedindividuallyin small Saccoglossus kowalewskyi.—Brinkhurst et
vials (20 ml) containing local seawater; the
al., 1976, p. 156.
animals were subsequently transported to
Saccoglossus kowalevskyi.—¥Ang, 1986, p.
Walpole, Maine, for further processing.
257.
MtDNA was extracted from live animals —
Saccoglossuskowalewskii. Linkletteretal.
using procedures modified from Lansman
1977, (p.p.): 42, Gosner 1979, p. 265;
letabaol.ra(t1o9r8y1.)Awimthiinni2m4u-m48ofh1o0frleivteuranntiomatlhse Meinkoth, 1981, (p.p.): 726; Carey &
Mayer, 1990, p. 79.
from Lowes Cove and York, Maine
(69°34'N, 43°56'W; 43°09'N, 70°39'W) and Diagnosis.—Saccoglossus bromopheno-
from Portsmouth, New Hampshire losusattains a length up to 20 cm. It has an
(43°06'N, 70°42'W) were also homogenized elongate proboscis thatextends 1.5-2 cm in
for electrophoretic analyses of enzymes at narcotized specimens. The proboscis has a
the following loci using standard methods shallow dorsal groove and a single pore at
(Murphy et al. 1990): glucose phosphate the base of the proboscis. Concretions fill
isomerase (GPI; E.C. 5.3.1.9), malate de- the primary shaft ofthe proboscis skeleton.
hydrogenase (MDH; E.C. 1.1.1.37), phos- Hexaneextractsoftheprobosciscontain2,4-
phoglucomutase (PGM; E.C. 2.7.5.1), and dibromophenol andadibromoindole; these
superoxidedismutase(SOD; E.C. 1.15.1.1). compounds account for the characteristic
Analyses of haloorganic contents utilized "bromoform" odor oflive specimens. The
extracts ofanimalsthat were extractedwith collar is diiferentiated into 4-5 zones, and
hexane immediately aftercollection and re- is generally rectangular from above with an
moval of adhering sediment. In addition, aspectratioofabout 3:5 (width length). The
:
animals used for mtDNA and allozyme trunk is differentiated into distinct bran-
analyses were "halotyped" by collecting 1- chial and hepatic-genital regions. Dorsolat-
2-jLtl samples of the seawater immediately erally placed gill pores appear ellipsoid in
adjacent to the proboscis with a 10-jul gas relaxed and ventilating specimens, with the
chromatography syringe (Hamilton Inc., majoraxis oriented vertically: the gill pores
Reno, Nevada). The epidermis ofthe pro- do not occur in folds and vary from about
VOLUME 107, NUMBER 2 385
60-110 pair per individual. Esophageal dorsolaterally, beginning at thejunction of
pores, which occur slightly posterior to the collar and trunk. Slightly posterior to the
gill pores vary from about 4-8 pairin num- terminal gill pores, 4 pairs ofdorsal esoph-
ber. Gonads begin at the terminus of the ageal pores were observed; they formed an
branchial region in both sexes, and are dor- angleofabout30°openingtowardthetrunk.
solateral in placement. The hepatic-genital region ofthe trunk ex-
Material examined.—YioXoiypt (USNM tended about 23 mm, measured from the
168049) and 3 paratypes (USNM 168050- terminationofthegillporestoapointwhere
168052)fromLowesCove, Maine(69°34'N, genital structures were not observable. Na-
43°56'W), collected by G.M. King 20 Oc- scent grayish egg masses were visible dor-
tober, 1993. solaterallyjust beneath the epidermis. The
Description.—The holotype is a sexually hepatic-genital region was grayish-brown
immature female with the following char- dorsallyandyellowish-brownlaterally. The
acteristics observed while the animal was posterior-most region of the trunk was 34
mm
relaxed in a solution of7% MgCl2. The in- inlength, yellowish-brown incolorand
mm
complete specimen was 82 in length; characterized by pairs of carmine-colored
mm
an additional 60-70 of the posterior- spots located dorsally.
most region ofthe trunk was lost unavoid- General dimensions for 3 male paratypes
ably during collection. The posterior-most with maturing gonads were similarto those
section ofthe trunk was extremelythin and oftheholotype. However,gillporenumbers
fragile; in color and diameter, it resembled ranged between 68-101 and esophageal
the fecal coils present at the sediment sur- pores numbered 4-6. The sperm sacs were
face. The relaxed and extended proboscis dorsolateral and pink in color.
was creamy white in color with a shallow Remarks.—AXihou^ the range of body
dorsal groove running from the base to the size, coloration, location and appearance of
proboscistip. Striationsperpendiculartothe the gonads, and external features ofthe col-
major axis ofthe proboscis were observed larandproboscisof-S. bromophenolosusand
at low power on a dissecting microscope. S. kowalevskii are very similar, gill pore
mm
The proboscis was 16 in length and 3 placementandthemorphologyofthedorsal
mm
at the base. The basal-most region was ridge allowdiscrimination ofthe species by
arustorangeincolor. Theorangecollarwas visual inspection in the laboratory or field
mm mm
5 in length and 2.5 and 3 in di- (Fig. 1, 2). In contrast to S. bromopheno-
ameter at the anterior and posterior ends, losus, the dorsal ridge of S. kowalevskii is
respectively. Both ends of the collar were relatively broad and flattened immediately
distinctlythickened,withaprominentlight- posterior to the collar, covering >50% of
er-colored ridge circlingthe posteriorofthe the dorsal area. The dorsolateral gill pores
collar.Thebranchialregionofthetrunkwas ofS. kowalevskiioccurwithinlateralgrooves
mm
about 2.5 in diameter where it joined that can be closed, thereby obscuring them
the posterior of the collar. A prominent, from view (Fig. 2). This state is typical of
raised dorsal ridge began immediately pos- specimens preserved without prior relaxa-
terior to the collar and ran the length ofthe tion. Inadditionto external morphology, S.
branchial region, terminating just anterior bromophenolosusand S. kowalevskiican be
totheesophagealpores. Nearthe collar, the distinguished by other diagnostic charac-
mm
dorsal ridge was about 1 in width with teristics requiring dissection orvarious lab-
mm
a central groove about 0.5 in width. oratory analyses (Fig. 3, Table 1). Collec-
Thisregion ofthetrunkwaspinkish-orange tionstodateindicatethatS. kowalevskiiand
to orange and about 14 mm in length. A S. bromophenolosusexistsympatrically only
total of 61 pairs ofgill pores were located within a narrow range around the mouth of
386 PROCEEDINGSOFTHE BIOLOGICALSOCIETY OFWASHINGTON
Fig. I. A. Dorsolateral view of relaxed, sexually immature female of 5. hroniophenolosus. new species
illustratingsuperficialfeaturesoftheproboscis(P),collar(C,limitsindicatedbyarrows)andtrunk(T);gillpores
(gp, indicated by arrow) are evident immediately posterior to the collar. B. Detailed view ofthe posterior
proboscis, collar, and anteriorofthetrunk, illustratingtheprominent, raised dorsal ridge (DR)and gill pores.
VOLUME NUMBER
107, 2
Fig. 2. Anterior portion ofS. kowalevskii showing the broad, flattened dorsal ridge (DR), collar (C) and
proboscis (P); gill poresare obscuredby lateral folds (F, indicatedbyarrow). The "sole" (S) occurs ventrally.
the Piscataqua River, New Hampshire S. kowalevskii since GPI, MDH, and PGM
(43°06'N, 70°42'W); S. kowalevskii has not were fixed for alternative, diagnostic alleles
been observed north ofYork, Maine, while within each taxon; SOD was represented at
5". bromophenolosus has not been found 2 monomorphic loci in S. bromophenolo-
south ofPortsmouth, New Hampshire. sus, andbyasingle, differentmonomorphic
AUozyme analyses indicated substantial locus in S. kowalevskii. MtDNA analyses
divergencebetweenS. bromophenolosusand alsorevealedsubstantialdivergence(Fig. 4).
Table 1.—Diagnosticcharactersthatdistinguishamong 3 speciesofNorth Atlantic saccoglossids.
S.bromophenolosus S.kowalevskii S.ruber
Characteristic
Dorsal ridge raised, narrow broad, flattened raised, narrow
Gill pore placement central lateral central
Coloration'
(proboscis-collar-trunk) W/P-O/R-O W/P-O/R-O P/R/R-O
Halotype^ DBP/DBI TBPy DBP/TBP
Proboscis skeleton^ narrowcurve-co broadcurve-no co narrowcurve-co
' Colorcode:W/R,rangesfromwhitetopalepink;O/R, rangesfromorangetored;O,orange;P/R,palepink
to pale red.
^Compoundcode:DBP=2,4-dibromophenol;DBI=dibromoindole(positionsofbromineatomsuncertain);
TBP = 2,4,6-tribromophenol; TBPy = 2,3,4-tribromopyrrole.
' Co refersto concretionswithinthe proboscis skeleton.
1
388 PROCEEDINGS OFTHE BIOLOGICALSOCIETY OFWASHINGTON
B
Fig. 4. Autoradiogram offragments from the di-
gestionofpooledmtDNAfromspecimensof5.bromo-
phenolosus, new species (lanes 1, 3) or 5. kowalevskii
(lanes2,4)withtherestrictionendonucleasesHindIII
(lanes 1, 2) or Sty I (lanes 3, 4). Fragments were sep-
aratedafterdigestionbyagarosegelelectrophoresisand
radiolabelled with "S using a nick translation proce-
dure. Lane 5 containsa molecularweight standard (
kbladder, BRL); "a"and "b"indicate 5090and 1018
base pair fragments, respectively.
Fig. 3. A. Diagram oftheproboscideal skeleton of
5'. bwmophcnolosiis. new species; dark central region
consists ofconcretions as described forS. ruber(Bur-
don-Jones& Patil 1960). B. Diagram oftheproboscis
skeletonofS. kowalevskii;noteabsenceofcentralcon-
cretionsand more deeply curved skeletal arms.
VOLUME 107, NUMBER 2 389
No common DNAfragments werefoundin Grant for assistance with collections from
comparisonsofrestriction endonucleasedi- Nova Scotia; Drs. E. Ruppert and D. Hub-
gests ofthe mtDNA ofthe two taxa based bard for information about and assistance
on Hind III, Xba I, Nde I, Sty I, Stu I, Dra with collections from Georgetown, South
I or Ava I. In contrast, mtDNA haplotypes Carolina;A. LaursenandDrs. C. Planteand
for populations ofeach taxon were homog- G. Kozloff for information about and col-
enous. Forexample, an Xba I digestyielded lections of specimens from Willapa Bay,
the followingapproximate fragment molec- Washington. This work was partially sup-
ular weights: S. bromophenolosus—Sl50, ported by funds from the National Science
1075, 925, and 625, 5. kowalevskii-5000, Foundation, OCE-9203342 and EHR91-
3225, 2275, 1875, and 1000. 08766.
Etymology.—The species name is de-
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