Morphology, habitats and distribution of species of the albifrons group (, ) in Finland

I. HAAHTELA

Department of Zoology, University of Oulti

Jaera specimens of the albifrons group (J. ma­ information on the occurrence of the species in rina (Fabr.)) are common in the seas surroun­ Finland, I examined all available museum ding Europe and on the east coast of North samples. Unfortunately, these consisted mainly America, where they are found in shallow water of females, so, since the identification of the under stones and among seaweeds. They are fre­ species is based on males, additional collections quently reported in bottom samples too (p. 311). were also made. FORSMAN (1949) divided J. albifrons Leach into The aim of the present paper is to present four distinctive races; J. a. albifrons, J. a. basic information, while more material is being ischiosetosa, J. a. praehirsuta, and J. a. posthir- collected for further study. suta. BOCQUET (1950) described two additional races J. a. syei (the Baltic form of J. a. albifrons, the characteristics of which FORSMAN (1949) Identification had already observed), and J. a. forsmani, fi­ The species may be identified by the secon­ nally elevating the species J. albifrons to the rank dary sexual characters on the male peraeopods. of a superspecies and the subspecies (races) to The adult males are clearly smaller than the species. BOCQUET retained the trinominal specific females. The abdomen of a female is more names, but a leaning towards the binominal pointed or curved than that of a male (Fig. form is to be seen in the recent study of BOCQUET 1). Beneath the pleotelson, the first pair of & PRUNUS (1963). Because at least some of pleopods join to form a T-shaped praeoper- these forms are sympatric, they will be regarded culum in the male. The female does not possess here as sibling species. The systematic position this first pair of pleopods, but the second pair of J. a. syei seems, however, to be somewhat forms a broad operculum (Fig. 2). The praeoper- obscure (LECHER 1964, NAYLOU & HAAHTELA culum is an important systematic character. All 1965), and it will be regarded here as a subspecies species of the J. albifrons group have similar of J. albifrons (J. a. albifrons in BOCQUET 1953). praeopercula, but they differ from all the other A comparable situation arose when SEGER- species of the genus, and these respectively STRALE (1947) and SPOONER (1947, 1951) split from each other, in the shape of this organ (see the amphipod species Gammarus zaddachi Sex­ KESSELYAK 1938). ton into three (see KINNE 1954). It might be A key to the Finnish species (Jaera albifrons group along the Fin­ but the inner margin of the ischiopodite bearing a distinctive row of long and slender, curved bristles nish coast (Fig. 4). In order to obtain further (Fig. 3 C) J. ischiosetosa Forsman 1949 310 /. Haahtela

A B Fig. 1. Jaera ischiosetosa Forsman from Rymattyla. A = young ovigenous female, B = adult male.

In the Finnish samples of J. ischiosetosa I of peraeopod VI was often almost as long as found that the morphological characters always that of peraeopod VII. In France (BOCQUET corresponded well with the descriptions of FORS­ 1953) and Britain (NAYLOR & HAAHTELA 1965) MAN (1949) and BOCQUET (1953). In J. a. syei in specimens of that species the carpopodial the carpopodial lobe of peraeopods VI and VII spine of peraeopod VI is much shorter than that often had only about 15 bristles, the maximum of peraeopod VII, a character which in those being 22. For four males (l.u

B Fig. 2. Jaera ischiosetosa Fnrsman from Rymattylft. A = female operculum, B = male praeoperculum.

Thus at the beginning of the summer the pop­ KEL has recorded specimens of the J. albifrons ulation comprises relatively numerous young, group as much as 7 mm long (according to KES- small individuals among the larger adults. To­ SELYAK 1938), but these are exceptions. Usually wards the autumn the former attain adult size, 5 mm is considered the maximum length (KES- and represent a group uniform in size, since the SELYAK 1938, GRUNER 1962, 1965). old individuals have apparently died. This could be seen in the Finnish material too. The measurements thus far carried out (from Habitats and geographical distribution the anteriormost visible margin of the head to the posterior margin of the pleotelson), showed With a few exceptions the samples studied that the species did not differ much in size. The by the author originated from the S and SW mean length of J. a. syei $$ from Rymattyla, coasts of Finland, usually from under stones in in August 1964, was 2.n mm (12 spec, ranging shallow water. There were some records of Jaera from 1.6 to 2.i mm). J. ischiosetosa S3 of the from depths below 10 m, the deepest being at same sample measured I.T mm (104 spec, l.i- 38 m from Korppoo (BAGBE et at. 1965). Recently 2. o mm), and from Pyhtaa commune, in August LAAKSO (1965) has found specimens from depths 1955, l.« mm (21 spec, l.«-2.o mm). J. between 18 and 24 m, but considers that thy praehirsuta SS from Maakrunni, in January might have drifted there in algae from shallow 1964, measured 2.i mm (6 spec, l.e-1.4 mm), water. In the Skagerrak specimens belonging to and from Pyhtaa commune, Harvasaari, in Au­ the J. albifrons group have been recorded at 55 m gust 1955, 1.7 mm (8 spec, l.e-l.» mm). (GRUNER 1962, 1965). With such records it is In a pure J. ischioselosa population from very difficult to conclude whether the Espoo, Lehtisaari, in June 1889, the mean length are actually from weeds or from the substratum of the ovigerous ?? was 3.J mm (37 spec, 2.a - itself. 3.s mm), in the sample of J praehirsuta from J. ischiosetosa was very abundant under Harvasaari mentioned above 2.7 mm (7 spec, stones at depths of less than 0.5 m, the popula­ 2.5 - 3.o mm). tions usually consisting of that species only. The largest specimens were collected from HAAHTELA (1964) has found one specimen at a depth of 38 m at Lohm, Korppoo (see below) 23 m near Ulkokrunni in the Bothnian Bay. in May 1960. The sample consisted of six J. tischiosetosa was only occasionally found females from 3.s to 4.? mm in length. They amongst weeds. The preference for stones along were relatively broad and the hairs on the body the beach has been reported by FOHSMAN (1949, margin were long, but, having no males in the 1956), BOCQUET (1953), and NAYLOR & HAAH- sample, I could not identify the species. KUN- TELA (1965). The two latter studies mention the 312 /. Haahtela

Fig. 3. Row A; Jaera praehirsuta Forsman, peraeopods II, VI and VII of a male, 2.6 mm, from Askainen, SW Finland. - Row B: Jaera praehirsuta Forsman, peraeopods II, VI and VII of a male, 2.0 mm, from Maakrunni, NW Finland. -Row C: Jaera ischiosetosa Forsman, peraeopods II, VI and ischio- and meropodite of peraeopod VII of a male, 1.9 mm, from Rymattyla, SW Finland. - Row D: Jaera albifrons ssp. syei Bocciuet, carpopodite of peraeopod VI of a male, 2.1 mm, from Rymattyla, SW Finland (left); peraeopod VI (middle) and carpopodite of peraeopod VII (right) of a male, 2.imm, from Tvarminne, SW Finland. — The length of eacli scale line is O.a mm. Ann. Zool. Fenn. 2. 1965 313 preference for the upper tidal zone. In rock-pools J. ischioseiosa has been recorded in -weeds only (FORSMAN 1951). J. ischiosetosa occurs along the south coast of F'inland, and in addition there is one record from the Bothnian Bay (see p. 309) (Fig. 4). FORSMAN (1956), BOCQUET (1953) and NAYLOR & HAAHTELA (1965) consider the species to be very euryhaline. Thus its occurrence in a very diluted medium (see HAAHTELA 1964) is not surprising. General distribution: Finland, Sweden, Norway, Russia, Poland, Germany, France and Britain. J. a. syei was seldom found at depths of less than 0.5 m, but the deepest record was from 3 m only. FORSMAN (1956) has found J. a. syei in Sweden at a depth of 15 m. Rather than stones it preferred weeds, especially Pucus vesiculosus and some red or green algae. On the Baltic coast of Sweden J. a. syei lives both in algae and under stones along the beach (BOCQUET 1953, FORSMAN 1956), BOCQUET (1953) has explained that the wide range of microhabitats of ,/. a. syei results from lack of competition with closely related species; such species are absent from the areas where J. a. syei occurs. In Finland, how­ ever, there are several records of it with J. ischio­ Fig. 4. The outermost localities of linds or the entire Jaera setosa and J. praehirsuta in the same sample, albi/rons group (squares) and all those of the species (circles); J. a. sget (white), J. ischiosetosa (black) and ./. praehir­ usually in algae, but sometimes from under suta (hatched) in Finland. The sectors in the circles do not stones, too. indicate abundance. 1. Ykskivi (NOBDQVIST 1890), 2. Ronn- skar (K. M. Levander), 3. Eekero (HELLEN & EHHSTEOM All records of J. a. syei were from the south 1919), 4. Soderskar (SJOBLOM 1955), 5. Haapasaari com­ mune (SUOMALAINEN 1939), 6. Ulkokrunni (HAAHTELA 1964), coast of Finland (F'ig. 4). The record near Kotka, and Maakrnnni (T. Valtonen), 7. Askainen (L. von Haart- man), 8. Rymattyla (I. Haahtela), B. Karppoo (P. Tulkki), where the salinity is about 4 o/oo, suggests that 10. Tvarminne (FORSMAN 1949 and Anon, coll.), 11. Espoo as far as salinity is concerned, J. a. syei might, (K. M. Levander), and Helsinki (A. Nordman), 12. Kymi and Pyhtaa commune (T. TJlvinen). be found in the Gulf of Bothnia as well. General distribution: The Baltic (Finland, Sweden, Po­ land, Germany). J. a. syei has only recently been J. praehirsuta is common on the south recorded from the Atlantic side of Europe: Brit­ coast of Finland. The record in the Bothnian ain (NAYLOR, SLINN & SPOONER 1961), Norway Bay at Maakrunm is the northernmost in the (HUSSEY 1964), Germany, the Netherlands, Baltic, and marks a new distribution area (Fig.4). France and the east coast of North America This record is not surprising, because the species (LECHER 1964). is regarded as very euryhaline (BOCQUET 1953, J. praehirsuta was found at the same depths F'ORSMAN 1956, NAYLOR & HAAHTELA 1965). as the previous species and in similar weeds. The General distribution: Finland, Sweden, Norway, deepest record was at a depth of 3 m. The spe­ Germany, Britain, W Greenland and the east cies seldom occurred under stones. FORSMAN coast of North America. (1956) has recorded J. praehirsuta at a depth In general, the data are too scanty to give a of more than 30 m and exclusively among algae. conclusive idea of the distribution of the species. BOCQUET (1953) has confirmed the preference There are only a few samples from waters more for algae, and has found the species only in the than a few metres deep or from other than shel­ lower part of the intertidal zone. In estuarine tered shores. The salinity and temperature re­ conditions in South Wales a wider range has quirements of the species of the ./. albifrons been observed (NAYLOR & HAAHTELA 1965). group also need much more investigation. 314 /. Haahiela

Summary

Three forms of the Jaera albifrons group, of less than 0.5 m under stones, with one ex­ viz. J. ischiosetosa Forsman, J, albifrons ssp. ceptional deep-water specimen, J. a. syei and syei Bocquet and J. praehirsuta Forsman, have J. praehirsuta were both generally found below been recorded in Finland. The morphological a depth of 0.5 m and preferred weeds to stones. features of the first-mentioned species corre­ All three species are common on the south spond well to those presented by other authors, and southwest coast of Finland, J. ischio­ but the remaining two show a reduction in the setosa and J. praehirsuta also occurring in the number of certain spines or bristles character­ northern part of the Bothnian Bay. izing them. The species do not differ much in size, but it should be noted that the mean size Acknowledgements. I am grateful to Prof. SVEN G. SE- of members of a population changes rapidly, GERSTHALE (Mus. Zool. Helsinki), Mr. P. TULKKI (Mar. Biol. Station, Univ. Turku) and Mr. T. ULVINEN (Univ. Oulu) owing to the short life-span and breeding season. for sending material, to the first-mentioned and to Dr. E. NAYLOH (Univ. College of Swansea, Wales) tor helpful J. ischiosetosa was usually recorded at depths discussions.

References

BAGGE, P., K. JUMPPANEN, E. LEPPAKOSKI and P. TULKKI, KINNE, O., 1954: Die Gammarus-Arten der Kieler Bucht. - 1995: Bottom fauna of the Finnish southwestern archi­ Zool. Jahrb,, Abt. Syst. 82, 405-424. pelago. III. The Lohm area, - Ann, Zool. Fenn. 2, LAAKSO, M,, 1965: The bottom fauna in the surroundings 38 - 52. of Helsinki. - Ann. Zool, Fenn. 2, 18-37. BOCQUET, C, 1950: Le probleme taxonomique des Jaera LECHEH, P., 1964: Recherches complementaires sur le poly­ marina Fabr. (J. albifrons Leach). - Compt. Rend. typisme de la super-espece Jaera albifrons Leach = Acad. Sci. 230, 132 - 134. Jaera marina (Fabricius), III. — Etude chromosomique - • ~ 1953: Recherches stir le polymorphisme naturel des de differentes populations de Jaera (albifrons) svei Boc­ Jaera marina (Fabr.) (Isopodes Asellotes). - Arch, Zool. quet. - Bull. Biol. France et Belg. 98, 415-431. exper, gen. 90, 187-450. MARGALEF, R., 1952: Une Jaera dans les eaux douces des - • - & G. PRUNUS, 1903: Recherches complementaires sur Baleares, Jaera balearica nov. sp. (Isopoda ). le polytypisme de la super-espece Jaera albifrons Leach - Hydrobiologia 4, 209 - 213. = Jaera marina (Fabricius). I, - Redescription de NAYLOB, E. & 1. HAAHTELA, 1965: Habitat preferences and l'espece Jaera (albifrons) posthirsuta Forsman. — Bull. interspersion of species within the superspecies Jaera Biol. France et Belg. 97, 343 - 353. albifrons Leach (Crustacea: Isopoda). - Journ. Anim. FORSMAN, B„ 1944: Beobachtungen tiber Jaera albifrons Ecol. (in press). Leach an der schwedischen Westkiiste. - Ark. f. Zool. NAYLOK, E., D. J. SLINN & G. M. SPOONER 1961: Observa­ 35 A; 11, 1 -33. tions on the British species of Jaera (Isopoda: Asellota). - Journ, Mar. Biol. Ass. U. K. 41, 817-828. - « - 1949: Weitere Studien iiber die Rassen von Jaera albi­ NORDQVIST, O., 1890: Bidrag till kannedomen om Bottniska frons Leach. - Zool. Bidr. Uppsala 27, 449-463. vikens och norra Ostersjens evertebratfauna. - Medd, -• - 1951: Studies on Gammarus duebeni Lillj., with notes Soc. F. Fl. Fenn. 17, 83-128. on some rock pool organisms in Sweden. - Ibid. 29, SCHULZ, E., 1954: Jaera petiti nov. spec, ein neuer Isopode 215 - 237. von der franzosischen Mittelmeer-Kuste. - Vie et milieu - • - 1956: Notes on the invertebrate fauna of the Baltic. - 4, 59 - 64. Ark. f. Zool. 9, 389 - 419. SEGEHSTRALE, S. G., 1947: New observations on the distribu­ GRUNER, H.-E., 1962: Jaera albifrons (Crustacea, Isopoda) tion and morphology of the amphipod, Gammarus zad- mid ihre Unterarten an den deutschen Kilsten. - Abh. dachi Sexton, with notes on related species. - Journ. Verh. Naturwiss. Ver. Hamburg 6, 197-208. Mar. Biol. Ass. U. K. 27, 219-244. —»— 1965: Krebstiere oder Crustacea. V. Isopoda, 1. Liefer- SJOBLOM, V., 1955: Bottom fauna - G. GRANQVIST, The ung, — Die Tierwelt Deutschlands und der angrenzenden summer cruise with M/S Aranda in the northern Baltic Meeresteile 51, 1 — 149. 1954. - Merentutk.lait. julk. 166, 37-40. HAAHTELA, I., 1964: Havaintoja Perameren selkarangat- SPOONER, G. M., 1947: The distribution of Gammarus species tomista. - Luonnon Tutkfja 68, 162- 166. in estuaries, I. - Journ. Mar. Biol. Ass. U.K. 27, 1 - 52. HELLEN, W. & K. E. EHRSTROM, 1919: Zur Kenntnis der — » - 1951: On Gammarus zaddachi Segerstrale. - Ibid. 30, Isopoden-Fauna Finlands. - Medd. Soc. F. Fl. Fenn. 45, 129-147. 124-131, SUOMALAINEN, H., 1939: Beitrage zur Kenntnis der Ver- HUSSEY, B., 1964: A note on Jaera albifrons (Leach) in breitung der marinen Bodentierwelt im ost lichen Teil Olderfjorden (Ttoms Coanty). - Astarte 24, 1-4. des finnischen Meerbusens. - Ann. Zool. Soc. 'Vanamo' KESSELYAK, A., 1938: Die Arten der Gattung Jaera Leach 6:6, 1-13. (Isopoda, Asellota), - Zool. Jahrb., Abt. Syst. 71, SYE, C. G., 1887: Beitrage zur Anatomic und Histologic 21B - 252. von Jaera marina. — 37 pp. Univ. of Kiel, Thesis.

Received 10. VIII. 1965 Printed 1. XII. 1965

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