New records of Stylasteridae (Hydrozoa: Hydroida) from the Galapagos and Cocos Islands

20 Pages·1991·9.9 MB·English

PROC. BIOL. SOC. WASH.
104(2), 1991, pp. 209-228
new records of stylasteridae
(hydrozoa: hydroida) from the
galApagos and cocos islands Jill 1
>l
Stephen D. Cairns
Abstract.—Based on the collections ofthe Johnson-Sea-Link I submersible,
new records of 14 stylasterid species are reported from the Galapagos Islands,
includingone newspecies: Lepidopora concatenata. Five stylasteridspeciesare
reported from Cocos Island, including two new species: Pliobothrusfistulosus
and Stylaster cocosensis. These are the first records ofstylasterids from Cocos
Island, three ofthe five species also shared with the Galapagos Islands. These
specimens are also the first records ofthe genera Lepidopora and Pliobothrus
intheeasternPacific, fromtheGalapagosandCocosIslands, respectively. Both
theGalapaganandCocos Islandstylasteridfaunaeareconsideredtobederived
from the western Pacific, having no affinity with the shelfand slope fauna of
the American continents in the eastern Pacific.
A rich fauna offourteen stylasterid spe- (1986b)andisnotrepeatedhere. Oneofthe
cies, all endemic to the Galapagos Islands species previously reported, Stenohelia ro-
and all based on only sixAlbatross stations busta Boschma, 1964a, is herein synony-
made at the turn of the century, was re- mized with Stenohelia concinna Boschma,
viewedbyCairns(1986b). Therefore, itwas 1964a, and one new species is described,
anticipated that a more intensive collecting which maintains the number of species
effort (27 stations in the Galapagos and 8 known from the Galapagos at 14. The ad-
offCocos Island) using more efficient and ditional specimens collected by the John-
selectivecollectingmethods(amannedsub- son-Sea-Link I, however, did: allow an ex-
mersible) would certainly yield many more tension ofthe geographic, bathymetric, and
species. Although stylasterids were sighted temperature ranges of all species; provide
on every submersible dive and collected at information on the range of variation of
21 ofthe27 sitesintheGalapagos, inwhich various morphological characters; and es-
all 14 previouslycollectedspecieswererep- tablish maximum colony sizes for half of
resented,onlyonespecimenofonenewspe- the species.
cies was collected. This surprising result StylasteridswerealsoabundantoffCocos
might be explained by assuming that all of Island,beingcollectedfrom fouroftheeight
the Galapagan stylasterid species are uni- stations. Since no stylasterids had previ-
formlyandabundantlydistributedthrough- ously been reported from Cocos Island, the
outthearchipelago, suchthatevenacursory five species reported herein are all new rec-
sampling would have a high probability of ords for this island, including two new spe-
collecting most ofthe resident species. This cies.
hypothesis would explain both the paucity Materialandmethods.—Thenewrecords
of new species and the re-collection of all onwhich this report isbased originated pri-
previously known species. marily from collections ofthe R/VSeward
The history ofour knowledge ofthe Ga- Johnson andJohnson-Sea-Link Isubmers-
lapagosstylasteridfaunawasgivenbyCairns ible expedition to the Galapagos and Cocos
210 PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
Table 1.—List oiJohnson-Sea-LinkI(JSL) stationsatwhichstylasteridswerecollected(Fig. 32).
Bottomtemperature
Station Latitude longitude(°W) Depth(m) Date (°C)
1911 0°32.7'S 90°07.0' 426^62 12 Nov 1986 8.3-10.3
1912 0°21.9'S 90°15.7' 713-806 14 Nov 1986 5.9-6.7
1913 1°32.7'S 90°25.8' 84-227 14 Nov 1986 13.5-14.5
1914 1°17.3'S 90°17.4' 166-172 15 Nov 1986 14.3-14.4
1915 1°17.2'S 89°48.7' 650-652 15 Nov 1986 7.4-10.8
1916 1°18.7'S 89°48.8' 545-562 16 Nov 1986 7.3-10.8
1920 1°46.6'S 89°30.8' 64-104 17 Nov 1986
1921 0°17.0'N 89°59.8' 680-720 18 Nov 1986 6.0-6.7
1922 0°23.7'N 90°26.3' 475-578 19 Nov 1986 7.3-8.9
1923 0°23.7'N 90°32.3' 348-384 19 Nov 1986 9.9-10.0
1924 0°03.9'N 90°19.2' 373^30 20 Nov 1986
1925 0°14.9'S 90°32.5' 415-447 20 Nov 1986 8.9-9.3
1927 0°10.5'S 90°53.3' 708-784 21 Nov 1986 5.6-6.5
1928 0°15.2'S 91°06.9' 720-813 22 Nov 1986 5.0-7.5
1929 0°14.7'N 91°36.5' 806 23 Nov 1986 5.7-9.3
1931 0°10.3'S 91°24.7' 441-525 24 Nov 1986 7.9-8.0
1932 0°15.1'S 9r27.7' 313-315 24 Nov 1986 10.4-12.2
1933 0°17.1'S 91°40.2' 663-788 25 Nov 1986 6.0-7.0
1935 0°15.2'S 91°27.9' 252-308 25 Nov 1986 7.8-9.0
1936 0°40.7'S 9r24.0' 182-224 26 Nov 1986 12.5-14.4
1937 0°59.8'S 91°27.1' 315-316 27 Nov 1986 11.2-12.6
1940 5°34.6'N 87°04.3' 546-631 1 Dec 1986 9.0
1942 5°34.6'N 87°04.3' 606-628 2 Dec 1986 6.7-7.1
1943 5°26.rN 87°08.0' 303-333 2 Dec 1986 11.9
1944 5°28.1'N 87°08.0' 293-576 3 Dec 1986 7.7-8.3
IslandsinNovemberandDecemberof1986. The following abbreviations are used in
Stylasterids were collected at 25 of the 35 the text:
submersible sites (Table 1). The use of a CDRS Charles Darwin Research Station,
manned research submersible allowed se-
Santa Cruz, Galapagos
lective collection of deep-water inverte- H:W Height-to-width ratio ofa gastro-
brates and in situ observation and photog-
style
rraepchoymmeofndelidvifnogr tchoeralc,ollaecntdionisofhidgeehpl-y JSL Johnson-Sea-Link I, a 4-man re-
search submersible owned by the
water benthic invertebrates in areas ofrug-
Harbor Branch Oceanographic In-
ged topography.
stitution, Inc., Fort Pierce, Rorida
Definitions ofthe terms used in the de- USNM
Collections of the United States
scriptions are reviewed and illustrated by National Museum (now housed at
Cairns (1983b, 1986a). Synonymies are not
the National Museum of Natural
always complete; where they are not, they
History), Smithsonian Institution,
includeareferencetoacompletesynonymy.
Washington, D.C.
All type and most nontype specimens are
deposited at the USNM; a synoptic collec- Zoogeography.—Cairns(1986b)reported
tionisalso depositedatthe Charles Darwin that all 14 stylasterid species known from
Research Station. The scanning electron the Galapagoswere endemic. Furthermore,
photomicrographs were done by the author he stated that, at the generic level, the af-
on a Cambridge Stereo Scan 100. finities of the Galapagos stylasterids were
VOLUME 104, NUMBER 2 211
withthewestern Pacificandless sowiththe pagos Islands), 680-720 m, 1 colony and
western Atlantic, not at all with the eastern SEM stub 698, USNM 84697.
Pacific. The deep-water Equatorial Under- Description.—Colony uniplanar and rel-
mm
currentwassuggestedasapossibledispersal ativelysmall, theholotype20.4 talland
mm
mechanism for larvae. The collections of 30.2 broad, with a basal branch di-
the Johnson-Sea-Link I expedition rein- ameter of 3.2 mm. Branching sparse, di-
force this interpretation. At the species lev- chotomous, and equal, resulting in a fairly
el, three Galapagan species are now known symmetrical branching pattern. Branches
from Cocos Island and one, Crypthelia cy- circularin cross section, terminating in tips
mm
mas, isknownfromoflfNewZealand(Cairns about 1.8 in diameter; nobranchanas-
1991c). This observation, along with the tomosis. Coenosteum white and reticulate-
discovery ofLepidopora in the Galapagos imbricateintexture. Coenostealstripsbroad
(a widespread genus but not known else- but variable in width, ranging from 0.11 to
mm
where in the eastern Pacific) reinforces the 0.20 across and separated by a series
hypothesis ofa western Pacific origin ofthe ofquite broad (about 66 ft wide), elliptical
Galapagan stylasterid fauna. to elongate coenosteal pores and shallow
Five stylasterid species are known from grooves. Platelet structure poorly defined
offCocos Island, belonging to three genera: (Fig. 6), the platelets being only 18-35 n
Pliobothrusfistulosus, Errina macrogastra, wide.
Stylastermarenzelleri, S. galapagensis, and Gastropores uniformly distributed on
5". cocosensis. At the species level, two of branch surfaces, circularin shape(0.31-0.33
mm
the five are known only from Cocos Island, in diameter), and flush with coenosteal
the remaining three also occurring in the surface (no gastropore lips). Gastropore
Galapagos Islands. All three genera have tubes cylindrical and deep, each bearing a
widespread distributions but do not occur diffuse ringpalisade composed ofblunt, cy-
in the eastern Pacific. Thus, although based lindrical elements up to 45 ju tall and 17 ix
onrelativelyfewspecimens,itwouldappear indiameter. Becauseonlyonespecimenwas
thattheCocosIslandfaunaisalsoprimarily available for study, a fragment was not sac-
influenced from the western, not eastern, rificed to examine and figure a gastrostyle;
Pacific. This is contraryto the indication of however, from gross external examination,
Briggs (1974), based on shallow-water in- gastrostyles appear to be elongate and slen-
vertebrates and shore fish, and Cairns der, probably with a relatively high H:W
(199la),basedonahermatypicScleractinia, ratio. Dactyloporesarrangedalong sinuous,
who both considered Cocos Island as an longitudinal or oblique ridges that occa-
extension ofthe Panamanian Province. But sionallyanastomoseintoareticulatepattern
it must be remembered that the Cocos sty- (Figs. 2, 5). Dactylopores circular to ellip-
lasteridfaunaisapredominantlydeepwater tical in shape: circular dactylopores about
one (e.g., 300-800 m) and therefore prob- 85 /u in diameter, elliptical ones up to 118
ably not influenced by the shallow water H in greaterdiameter. Ridges on which dac-
currents from the Panamanian mainland. tylopores occur quite tall (up to 0.5 mm)
andthin(25-30 wide),dactyloporecenters
ij, mm
New Records spaced every 0.5-0.8 along ridge. Dac-
tylopores are the most prominent sections
Family Stylasteridae Gray, 1847
of a ridge, the ridge connecting adjacent
Lepidopora concatenata, new species
pores sometimes slightly lower in height.
Figs. 1-7
Colony sexually immature and therefore
Records.-nololypQ-. JSL-1921, 0°17'N, sex and characteristics of ampullae un-
89°59.8'W (southwest of Genovesa, Gala- known.
212 PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
Figs. 1-4. Lepidopora concatenata, holotype, USNM 84697: 1, Holotypecolony, x2.3; 2, Branchtipillus-
trating tall dactylopore ridges and one gastropore, x25.5, stereo pair; 3, 4, Elongate ridges concatenating
(linking)dactylopores, x56, x62, respectively.
VOLUME 104, NUMBER 2 213
Figs. 5-7. Lepidoporaconcatenata, holotype, USNM 84697: 5, Branch segmentillustratingtwogastropores
andridgeslinkingdactylopores, x21,stereopair;6,Weaklyimbricatecoenostealtexture, x 180; 7,Branchcross
section revealing porous central core, two gastropores in cross section, and tall coenosteal ridges peripherally,
x38.
214 PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
Discussion.—Amongthe 25 valid species (Cairns 1991b); thus, this is the first record
of Lepidopora (see Cairns 1991c), L. con- ofthe genus for the eastern Pacific.
catenata is most similar to L. acrolophos
Cairns, 1983a, known only from the Scotia
Pliobothrusfistulosus, new species
Ridge west ofSouth Georgia (659-686 m).
Figs. 8-14
Both species have: similarly sized and
shapedcorallaandbranchingpattern; linked Records.-UoXoXype:JSL-1940, 5°34.6'N,
dactylopores; same sized gastro- and dac- 87°04.2'W (north coast of Cocos Island),
tylopores; and the same bathymetric range. 546-631 m, 9°C, 1 colony (ex SEM stub
USNM
Lepidopora acrolophos, however, differs in 699), 84696.
having a very different coenosteal texture Description.—Colony probably unipla-
(reticulate-papillose), small abcauline gas- nar, the only known specimen (the holo-
mm
tropore lips, dactylopores that are some- type) a colony fragment 11.0 tall and
mm
times not linked by ridges, and in lacking 10.5 broad, consisting of 3 terminal
ring palisades. branches. Branching dichotomous and ap-
Although less similar to L. concatenata, parently equal; branches circularto slightly
L.polystichoporaCairns, 1985(northofNew elliptical in cross section, having blunt to
mm
Zealand, 197-710 m) also sometimes has slightly clavate tips 1.8-2.2 in diame-
linked dactylopores as well as having equal ter. Coenosteumwhiteandlinear-imbricate
branching and primarily imbricate coenos- in texture. Coenosteal strips quite thin (21-
teal texture. ButL. polystichopora differs in 45 Ai wide), bordered by deep, elongate slits
having its dactylopores arranged in four to that are often equal to or wider than strip
sevendiscrete, longitudinal rows, the ridges width (e.g., up to 55 M wide). Slits traversed
uniting the dactylopores being quite low bynarrow(20-23mwide)coenostealbridges
(about 0.12 mm); having small, abcauline (Fig. 10). Platelets very poorly defined but
gastropore lips; and in lacking ring pali- present in a unilinear series on each strip.
sades. Gastropores uniformly distributed on all
In addition to L. concatenata, only one branch surfaces, circularin shape(0.37-0.39
mm
other species of Lepidopora has ring pali- in diameter), and flush withcoenosteal
sades: L. glabra (Pourtales, 1867), known surface. Gastroporetubescylindricalwitha
onlyfromtheStraitsofFloridaat267-1 170 slightly enlarged lower section, and bent
m
(see Cairns 1986a). L. glabra, however, about90°,thelowersectionrunningparallel
shares few other characters, differing in: to branch axis. Total length of gastropore
coenosteal texture; arrangement of gastro- tube 0.9-1.0 mm. No ring palisades or ta-
and dactylopores; havingunlinked dactylo- bulae present. Dactylopores also uniformly
pores; and in having quite large abcauline distributed on branch surfaces and circular
gastroporelips.Thecharacteroftall,slender inshape: 86-93nindiameter. Dactylopores
ridgesthatconsistentlylinkitsdactylopores elevated on cylindrical mounds as high as
is unique to L. concatenata. 0.2 mm, the thin walls ofthe mound 15-
Etymology.—The species name concate- 20)uthick,resultinginadactyloporemound
nata (Latin for "linked together") refers to diameter of0.12-0.13 mm.
the dactylopores ofthis species, which are Sex of holotype probably female. Am-
mm
linked together by tall, thin ridges. pullaeinternal, 0.3-0.4 indiameter,and
Distribution.—Species known only from communicatetocoenosteal surfacethrough
type locality. Lepidopora is a wide ranging aninconspicuous,spongyefferentporeabout
mm
genus known from throughouttheAtlantic, 0.10 in diameter.
Subantarctic, and South Pacific (New Zea- Discussion. —Four Recent species of
m
land region) from depths of 60-1874 Pliobothrus are known: P. tubulatus (Pour-
VOLUME NUMBER
104, 2 215
Figs. 8-12. Pliobothrusfistulosus, holotype, USNM 84696: 8, Holotype colony, x7.0; 9, Branch segment
illustratingone gastropore and two smallerdactylopores, x44; 10, Porous coenosteal texture with irregularly-
shaped efferent pore in center, x92, stereo pair; 11, Porous coenosteal texture (dactylopore in upper right),
X110; 12, Enlargementofcoenosteal texture, x 170.
216 PROCEEDINGSOFTHEBIOLOGICALSOCIETYOFWASHINGTON
USNM
Figs. 13, 14. Pliobothrusfistulosus, holotype, 84696: 13, Branch tip bearing a concave, ruptured
ampulla (left center), x20.5, stereo pair; 14, Longitudinal section ofa gastropore tube (above) and internal
ampulla(below), x46, stereo pair.
VOLUME 104, NUMBER2 217
tales, 1867) (Antilles, 419-718 m); P. sym- reportedfrom sixmorelocalities, extending
metricus Pourtales, 1868 (North Atlantic, its range into the western islands ofthe Ga-
80-1600 m); P. spinosus (Hickson & En- lapagos. Considerablylargerspecimenswere
gland, 1905) (Indonesia, 1089 m); and P. collected during the JSL expedition, the
echinatus Cairns, 1986a (Lesser Antilles, largest {JSL-\9\A) a uniplanar colony 7.7
164-708 m). Pliobothrus fistulosus differs cmtalland9.1 cmbroad,withabasalbranch
mm
fromallofthesespeciesinhavingextremely diameter of7.5 (Fig. 15). The tissue is
narrow coenosteal strips and much smaller a characteristic lightbrown; the corallum is
ampullae.Itsdactyloporemoundsareabout white. Branches are elliptical to flattened in
the same height as those ofP. symmetricus cross section; the distal, small-diameter
(0.2 mm), but considerably shorter than branches being flattened in the plane ofthe
those ofP. spinosus (1.2 mm), P. tubulatus colony. Although abcauline dactylopore
(0.8 mm), and P. echinatus (0.4 mm). It is spinesareclearlypresentonmostbranches,
further differentiated from P. symmetricus dactyloporespinesareoftenquitesmalland
by having less robust branches. low, and have very short, obscure dactylo-
Etymology.—The species namefistulosus tomes, thus sometimes superficially resem-
(Latin for "forming a pipe," "hollow," or bling species ofLepidopora.
"porous") could be interpreted in any of Distribution. —Widespread throughout
three ways: forming a pipe, alluding to its Galapagos, including off: Femandina, Isa-
long axial gastro- and dactylopores, which bela, south ofMarchena, northeastofSanta
givethebranch averyporous cross section; Cruz, Espaiiola, and Floreana; 166-806 m;
hollow, referringtothenumerousaxialgas- 5.7°_14.4°C.
tro- and dactylopores and the numerous
rather large coenosteal pores that penetrate Distichopora laevigranulosa Cairns, 1986
the coenosteum; and "porous," as ageneral Fig. 16
designationforthehighlypermeable nature
ofthe coenosteum. Distichopora laevigranulosa Cairns, 1986b:
Distribution.—Knownonlyfromthetype 6-8, figs. 3A-I.
locality. Species of Pliobothrus are known
fromtheNorthAtlanticand Indonesian re- New records.—JSL Stations 1911, 1 fe-
m USNM
gion from depths of 80-1600 (Cairns malecolony, 84704; 1914, 2 female
USNM
1991b); therefore, this is the first record of colonies, 84705; 1916, 1 femalecol-
USNM
the genus from the eastern Pacific. ony, 84706; 1929, 2 female colo-
USNM
nies, 84707.
Lepidotheca macropora Cairns, 1986 Discussion.—Distichoporalaevigranulosa
Fig. 15 waspreviouslyknown from onlyonebranch
fragment(theholotype); sixadditionalspec-
Lepidotheca macropora Cairns, 1986b:4-6,
imens from four more localities are record-
figs. lA-G, 2A-C. edherein. Thelargest, andcomplete,colony
Newrecords.—JSLStations 1914, 16 col- is 31.0 mm tall and 3.95 mm broad, with
USNM mm
onies, 84698; 1924, 3 colonies, a basal branch diameter of 5.2 x 6.2
USNM
84699; 1929, 5 colonies and (/5'L-1929). It has equal, sparse branching,
USNM
branches, 84700; 1932, 3 colonies resulting in only 10 branch tips (Fig. 16).
USNM
and branches, 84701; 1933, 1 Tissue light brown; corallum white. The
USNM
branch, 84702; 1937, 1 colony, holotype has several gastropores on its an-
USNM
84703. terior face; however, the colony from JSL-
—
Discussion. Previouslyknownfrom only 1916 has numerous gastropores on its an-
two localities in the Galapagos, 29 addi- terior face in addition to those constituting
tional colonies ofL. macropora are herein the lateral edge pore row. Another point of
218 PROCEEDINGSOFTHE BIOLOGICALSOCIETYOFWASHINGTON
Figs. 15-18. 15,Lepidothecamacropora,75'L-1914,USNM84698, x0.81; 16,Distichoporalaevigranulosa,
JSL-1929, USNM 84707, female colony, xl.2; 17, Stylaster marenzelleri, JSL-1923, USNM 84730, male
colony, xO.8; 18, Stylastercocosensis, holotype, USNM 84734, x1.3.
variationisthatoneofthedactyloporerows Distribution.—OSKoca. Redonda, Santa
ofthe specimen fromJSL-1911 has almost Cruz, Espanola, and Floreana; 166-806 m;
completely degenerated, the opposite row 5.7°-14.4°C. Species of Distichopora are
appearingtobethe onlyfunctionaldactylo- common in the Indo-West Pacific (Bosch-
pores. The holotype, as well as all six spec- ma 1959) and western Atlantic (Cairns
imensreportedhere, are maturefemalecol- 1983a), but are conspicuously absent from
onies, thus male ampullae remain un- the Antarctic-Subantarctic region and east-
known. em Atlantic. Distichopora laevigranulosa is