Field Studies 6 (1986),517-529

SEA SPIDERS (PYCNOGONIDS) IN AND AROUNDMILFORD HAVEN(South West Sfales)

P. E. KING eNo R. M. CASEMarine Research Group, School of Biological Sciences, Uniaersity College of Swansea,

Singleton Park, Swansea S42 8PP, Wales, U.K.

ABsrRAcr

Thirteen ofthe 19 British species ofPycnogonids (sea spiders) have been recorded in

and around Milford Haven in southwest Vales. The sites from which each species has

been recorded are listed and maps are provided for the more widely distributed. The

influence of salinity and other estuarine factors affecting their penetration into the

Daucleddau (the joint estuary of the Eastern and rffestern Cleddau rivers) is discussed.

INrnooucrroN

THr Pycnogonida are a group of marine arthropods often referred to as sea spiders. Theirgeneral biology has been reviewed by Thompson (1909), Helfer and Schlottke (1935),Fage (1949) and King (1973). Their distribution in the Brit ish Isles recorded by Hodge(1864), Thompson (1909), Hodgson (1910), Halhed (1896), Carpenter (1905, l9l2),Bruce, Colman and Jones (1963), King, Wyer and Jarvis (1971) and King (1972,1976).Species occurring in Pembrokeshire were recorded by Crothers (1966) and King andCrapp (1971). Since that t ime the l ist has been extended and further studies havesuggested some changes in the relationship and validity of some species (Fry, 1978). King(1986) has revised the earlier keys and summarised the current position on taxonomy andnomenclature. The present study updates the pycnogonid records for Pembrokeshire anddescribes in more detail their distribution in Milford Haven.

DrsrRrsurroN rN $fESr Werns

King and Crapp (1971) listed eleven species from Pembrokeshire (now part of Dyfed).Since that time two more have been added, Endeis charybdaea and Anoplodactyluspetiolatus. Thus, 13 of the 19 British species have been recorded in the area. Using theclassification and terminology of King (1986), the records of pycnogonid distribution inPembrokeshire are as follows:

Family NympnoNro re ( Fig. 3 )Nymp hon gr acile Leach ( I 8 I 4)

Nymphon breoirostre Hodge (1863)

Family Acnlutoar (FiS. a)Achelia echinata Hodge (1864)

Milford Haven, Daucleddau, IJTest Angle,Freshwater East, Martin's Haven,Skokholm, Solva, Cwm-Eglys.Dale Fort Beach, Black Rock(Dale), Tenby, Ramsey Haven.

Sandy Haven, ufest Blockhouse Point, DalePoint, \Tatwick Bay, West Angle Bay inMilford Haven; Skokholm-Hog Bay andPeter's Bay, Skomer, Cwm-Eglys,Fishguard, St Brides Bay, Manorbier,Lydstep Point, Caldy Island, Tenby,Freshwater West, Ramsey.

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oSKOKHOLM MILFOED HAVEN

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FRESHWATERWEST M A N O R B I E R

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5 1 8 P. E. KrNc AND R. M. Cesr

The sites from which sea spiders have been recorded i::;;:ld .r*r, of pembrokeshire, outside Milford Haven.

A. longipes Hodge (1864) Solva, Little Haven, St Brides, Watwick,West Angle, Freshwater East, LydstepPoint, Caldy Island, Tenby.

A.laezsis Hodge (1864) Caldy Island.

Family AuuorunroRnPhoxichilidiumfemoratun (Rathke, 1799) Castlebeach Bay, Gann Flat, Skomer.

Family ENocroer (Fig. 5)Endeis spinosa (Montagu, 1808) Gann Flat, Musselwick Point, Dale Point,

Watwick, Martin's Haven, North Skomer,Mew Stone, Cwm Eglys, Fishguard,Ramsey, Solva St Brides, Manorbier,Caldy Island, Tenby.

Endeis charybdaea (Dohrn, l88l) Martin's Haven, Skomer.

Family PycNocoNrnnrPycnogonum littorale (Strom, 1762) Slip Pier Beach (Dale), Sandy Haven,

West Dale Bav. Skokholm.

5 1 9Sea sbiders around Milford Haaen

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Frc. 3.Records ofNyzp hon gracile and, N. breairos*e

F amily CALLTIALLENTDAEC allip allene br eair osnis (Johnston, I 837)

F amily ANopLoDAcryLrDAE (Fig. 6)Anoplodactylus angulatus (Dohrn, 188 I )

Anoplodactylus pygmaeus (Hodge, 1864)

Anoplodactylus petiolatus (Kroyer, 1884)

Ramsey Haven.

Pembroke Ferry, Slip Pier Beach (Dale),Sandy Haven, St Brides, rVest Angle.Stack Rock, Sandy Haven, Black RocksFlat (Dale), Tenby, Cwm-Eglys.Milford Haven.

Distribution within Milford HavenPycnogonids occur over a wide bathymetric range, though species occurring in the

littoral zone are subjected to greater fluctuations of temperature and salinity than thosefrom greater depths. Species vary in their ability to tolerate these conditions, as shown forAchelia echinata and Nymphon gracile (El-Hawawi and King, 1978). The distribution ofspecies within estuaries indicates the range of tolerances, though availability of food and a

Sea spiders around Milford Haven 521

Frc .4 .Records of lclrelia echinata, A. longipes nd A. laeais

suitable substratum must also be considered. Little work on this aspect of pycnogoniddistribution has been published. Volff (1976) described the distribution of pycnogonidsin the estuarine area of the south-western part of the Netherlands. No detailed study ofthe distribution within the Haven has been made and since data regarding the environmentare available (Nelson-Smith, 1965; Will iams and Jolly, 1975) it was considered of interestto investigate the distribution in this estuary. Records in the present study have beenaugmented from Crothers (1966) and King and Crapp (1971).

Littoral collections were made during summer months of 1972 and 1974 during springtides at a number of sites within Milford Haven and along the Daucleddau. Circa-littoralcollections were made at different depths by diving, mainly in the Daucleddau, during1977 and 1978 (Fie.7) .

C allipallene br etsir o s tri sNot previously recorded in Milford Haven. Daucleddau specimens were recovered

from Neyland upstream to Castle Reach. Wolff (1976) observed greater numbers in thelittoral than sublittoral zone in the Oosterschelde estuary but in British waters the converse

522 P. E. KrNc aNo R. M. Cnsn

F r c . 5 .

Records of-Erdeis spinosa and E. charybdaea

is usually true (King, 1974). Tlr,e distribution shown in Table I indicates a sublittoraldistribution in the Daucleddau, typically below the algal belt. Specimens were notnumerous (13) but males carrying eggs were collected at Bridge (12.10.77), \Warrior

(8.6.78) and Cosheston (8.7.78).

Achelia echinata (Fig. 8)The most abundant species recorded, though it showed no depth preference. Their

distribution is shown in Fig. 8. They occur further up the Daucleddau in deeper waterthan in the littoral zone. Wyer and King (1974) recorded them feeding on detritustrapped in moribund areas of Bugula colonies. Species of Bugula occur regularly in theDaucleddau. King (1974) reported this species in association with the hydroid Dynamenepumila and the bryozoan Flustrafoliacea. F. foliacea does not occur in the Daucleddauand D. pumila rarely occurs sublittorally other than on algal substrates, which suggests analternative food source. Specimens were collected associated with poriferans: Dysideafragilis, Halichondria panicea, Haliclona oculata, Raspailia hispida, Stelligera stuposa;coelenterates: Hgdrallmania falcata, Nermertesia antennina, Nermertesia ramosa;

Sea spiders around Milford Hazten 523

F r c . 6 .

Records of lnoplodactglus angulatus, A. petiolatus nd A- plgmaeus.

Table 1. Vertical distibution o/ Callipallene brevirostris enthe Daucleddau

Metres Bridge $Tarrior Cosheston Castle R

057 .5

l 012 .51 5

XX

XXXXX XXX

molluscans: Ostrea edulis; bryozoans: Bugula plumosa, Alcyonidiumtunicates: Dendrodoa grossularia, Styela clazta. Some of which mayfood source.

cf. gelatinosum andprovide a suitable

524 P. E. KrNc RNo R. M. Cnsn

The l9?2 and 197.1 collection sites within Milford Haven "ra,fL

O"o.f.aaau. Neyland 1l;, Bridge (2), Pembroke Ferry (3),

Warrior (4), Burton-Cliff (5), Cosheston (6), Mil l Bay (7), Whalecum (8), Lawrenn-v (9), Castle Reach (10), Garron Poinr (l l),Beggars Reach (12), and Black Tar (13).

Nyntphon gracile and Nyrnphon breoirostre (Fig.9)During the summer months this species migrates on shore, particularly males carrying

eggs on their ovigers, which may account for its absence in the sublittoral abovePembroke Ferry. lrI. breviroste was recorded between Neyland and Black Tar at all depthsand particularly below the algal belt. King (1974) recorded this species in associationwith tubularians, Halichondria panicea and Irlermertesia sp. Each of these was,presentin the Daucleddau samples, often occurring together in the same faunal assemblage.

Anoplodactylus pygftiaeus, Anoplodactylus angulatus and, inoptodactyluspetiolatus (Fig. t0)

A. pygmaeus has been recorded at the mouth of the Flaven. A. angulatu.s penetratesfurther with a specimen collected from Pembroke Ferry (Crothers, 1966). In the present

Achel ia echi nata recorded

not recorded

Subl i t toral records

Sea spiders around Milford Hazten

Frc .8 .Littoral and sublittoral records of I chelia echinata in Milford Haven and the Daucleddau.

F rc .9 .Littoral and sublittoral records of Nl,mphon gracile nd Nymphon breairostre in Milford Haven and the Daucledciau

525

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526 P. E. KrNc aur R. M. Cesn

Records of ln oplrdorrylr, .p..i.l L il,,ro.o "r".r

and the Daucleddau.

study specimens of A. petiolatus were collected as far upstream as Beggar's Reach in theDaucleddau. This suggests that within this genus there is a difference in the degree oftolerance to environmental stresses. A. pygmaeus and A. angulatu.s were collected inthe littoral zone but A. petiolatus from sublittoral samples, where it may avoid adversesalinit ies.

Although information is incomplete, A. petiolaras, with a recorded distribution fromNorway to the Mediterranean, may be better suited to the temperatures in the Haventhan A. angulatus with a more southerly distribution. El-Hawawi and King (1978)showed the effects of temperature and salinity tolerance in pycnogonids.

Endeis spinosa and Pycnogonurn littorale occur in the mouth of the Haven.

There is considerable confusion arising from the available salinity data for theDaucleddau and their interpretation. It is apparent that the general mixing of fresh waterand sea water, and the greatest fluctuations in surface salinities, occur well above theconfluence of the Eastern and Western Cleddau. Data on vertical stratification have beenrecordetl by Nelson-Smith (1965) and Will iams and Jolly (1975) in warers betweenLawrenny and Landshipping (Fig. 1l). Maximum stratification occurs at low water of anebb neap tide, particularly between Cosheston and Garron Point. Evidence suggests thatthe estuary is well mixed for the first sixteen kilometres from the mouth, which is definedby a line drawn between St Ann's Head and Studdock Point. IJpstream of this there is asteepening longitudinal (horizontal) salinity gradient between Neyland and Landshipping.In the present study salinity readings were taken between Pembroke Ferry and Llangwm

Sea spiders around Milford Haaen 527

F I G . 1 I ,

Range ofsurface and bottom salinities (%m NaCl) in the upper reaches ofMilford Haven and the Daucleddau obtained during the

present study. Scale in miles.

during March 1978 using a N l0 MC5 salinometer-conductivity cell. This period coincidedwith large spring tides, a generally wet winter and recent heavy precipitation. Hence the

salinity values were lower than those of both Nelson-Smith (1965) and Williams and Jolly( re75) (F ig. 1 l ) .

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s15.9 b22.6

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528 P. E. KrNc eNn R. M. Cass

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Frc. l2Salinities at different tide levels and zones within N{ilford Haven and rhe Daucleddau (Nelson-Smith, 1965).

Wolff (1976) stated that A. petiolatus, C. breairostris and A. echinata occur at salinitiesin excess of l5%o. During low water neap tides in Daucleddau, at the limit of penetrationby this species, the surface isohaline is l7o/oo though the bottom may be 8%o higher(Nelson-Smith, 1965). Values obtained by Will iams and Jolly (1975) were sornewhat lowerthan this. The figure obtained in the present study at the deepest point of penetrationagreed with the findings of Wolff (1976) who noted that N. breairostre penetrates furtherupstream than all other species and apparently tolerates salinities of ll-12%o. This is ingeneral agreement with the findings in this study. In the laboratory A. echinata has beenexposed to a range of salinity and temperature combinations and has shown negligibletolerance to constant exposure to salinit ies of 17o/oo, particularly at higher temperatures.

Nelson-Smith (1965) divided the Haven into four ecological zones) with each zonalboundary forming a critical region in the distribution of marine plants and animals upthe estuary (Fig. l2). Zone I is oceanic with sandy or rocky substrata. Zone II ismarine-polyhaline with mixed substrata, Zone III marine-mesohaline with rocky sub-strata and Zone IY polyhaline-mesohaline with muddy substrata. Zones I-III havesubstrata suitable for pycnogonids.

E. spinosa, P. littorale and A. pygmaeus do not penetrate beyond Zone I. In Zone II,A. echinata and N. gracile reach the limit of their littoral penetration and A. angulatusin the sublittoral. ln Zone III no species have been recorded from the littoral butN. breairostre, C. breairostis, A. echinata and A. petiolatus penetrate in the sublittoral.These species utilise the deep tongue of higher salinity warer.

Sea spiders around Milford Hazten 529

AcxNowrEncEMENTS

$7e would l ike to thank Professor E. W. Knrght-Jones and Professor J. S. Rylandin whose department the work was done and Dr A. Nelson-Smith for help andencouragement.

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Press.CenrrNtrR, G. l{. (1905). The marine fauna of the coast of Ireland, part 6. P,vcnogontda. Scientifrc Inaesti-

gations of the Fisheries BoardJor lreland,4, l-8.CRnleNrun, G. H. (1912). Pycnogonida. Clare Is land survey. Proceedings of the Royal l r ish Academy,3l , 1-4.CRorurRs, J H. (ed) (1966). Dale Fort Mar ine Fauna (2nd edn). Fie ld Sradies, 2 (suppl . ) i69 pp.Er-H.rwewr, A. S. N. and Krxc, P. E. (1978). Salinity and temperature tolerance tsy Nlntphon gracile (Leach')

and Achelia echinata (Hodge) (Pycnogonida). .lourndl of experinental narine biologj, and ecolog1,,33,2 t1 -222 .

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gonida. Re2ort o. f the Br i t ish Associat ionfor the Adz:ancement of Science,112.HELFER, H. and ScHrorTKE. E. (1935). Pantopoda. Brot tn 's Kl . Ordn. Tierre ichs,5, ( .1) , (2r .Hoocr, G. (186'{). List of the British P-vcnogonidae, q'ith descriptions of severai new species. Armals and

, \ Iagazine LtJ Naturul History,13, ser ies 3, 113-117.HoocsoN, T. V. i1Sl0l . The P1'cnogonida of Devonshire. Reporr o. l Transdct i<t t ts , T l te Det 'or t Associat ior t ,12,

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KrNc. P. E. (.1972). The marine flora and fauna of the Isies of Scill-v. P-vcnogoni da. Journal of Natural Histor1,,6,621 -624 .

Krxc, P. E. (1973). P1'cnogort ids. Hutchinson & Co., London, l - I ,14.Ktxc, P. E. i1971). Br i t ish sea spiders rArrhr t tpoCa:Pl ,cnogor ido).Krr- t andnotesfor the ident i f icat ion oJ rhe

specics. L innean Sociery Synopses of the Br i t ish Fauna No. 5,68 pp.Ktxc. P. E. (1976). The Marine Fauna of Lundy. Pycnogonida (Sea Spiders). Report oJ the Lundl Field Society,

1 1 1 1

I(tNc. i. E. (1986). Sea Spiders. A revised key to the adults of littoral Pycnogonida in the British Isles. FieldStudies.6. 503-526.

KIxc, P. E. and CnaRR, G. B. (1971)- L i t toral Pycnogonids of the Br i t ish Is les. Fie ld Studies,3,455-480.KrNc, P. E. , \ { 'vnn, D. and JeRvts, J. H. ( 1971). L i t toral Pycnogonids of Galwa-v Bay. I r ish Natural is t 's Journal ,

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