Observations on the ontogenetic and intraspecificchanges in the radula of Polycera aurantiomarginataGarcía and Bobo, 1984 (Gastropoda: Opistobranchia)from Southern Spain

SCIENTIA MARINA 70 (2) June 2006, 227-234, Ba celona (Spain) ISSN: 0214-8358 Obse a ions on he on ogene ic and in aspeci ic changes in he adula o Polyce a au an ioma gina a Ga cía and Bobo, 1984 (Gas opoda: Opis ob anchia) om Sou he n Spain INES MARTÍNEZ-PITA, JOSE M. GUERRA-GARCÍA, ANA I. SÁNCHEZ-ESPAÑA and FRANCISCO J. GARCÍA Labo a o io de Biología Ma ina, Depa amen o de Fisiología y Zoología, Facul ad de Biología, Uni e sidad de Se illa, A da. Reina Me cedes 6, 41012 Se illa, Spain. E-mail: [email p o ec ed] SUMMARY: Polyce a au an ioma gina a Ga cía and Bobo 1984 has a s able popula ion in he in e idal a ea o El Po il beach (Huel a, SW Spain). This ac allowed specimens o di e en sizes o be collec ed om Ma ch 2001 o Decembe 2003. In his pape , he on ogene ic a ia ions o he adula o P. au an ioma gina a a e s udied. The adulae o 141 specimens we e exam- ined, 138 om El Po il and 3 om La He adu a (G anada, SE Spain). Specimens o 1.5-2 mm in leng h lack he ypical adu- la desc ibed o P. au an ioma gina a. They ha e he so called p e- adula whose ee h a e di e en in size and shape om he ypical adula o he adul s. In he specimens o 3 and 4 mm he p e- adula coexis s wi h he cha ac e is ic adula, which is he single s uc u e p esen in he specimens la ge han 4 mm. The ollowing ea u es o he adula a e included in his s udy: adu- la leng h, numbe o ee h ows and leng h o he ou e la e al ee h. Acco ding o he h ee measu ed a iables, he a ini ies among specimens wi hou a p e- adula we e es ablished h ough clus e analysis, which de ined h ee di e en g oups (4-10 mm, 11-22 mm and 23-48 mm). Co ela ions be ween specimen leng h and adula leng h, numbe o ows and mean leng h o ou e la e al ee h we e signi ican . Feeding s a egies could be ela ed o he di e en mo phology o he adula es ablished by he Clus e analysis. Keywo ds:Polyce a au an ioma gina a, Opis hob anchia, Gas opoda, adula, on ogene ic a ia ion. RESUMEN: CAMBIOS ONTOGENÉTICOS E INTRAESPECÍFICOS OBSERVADOS EN LA RÁDULA DE POLYCERA AURANTIOMARGINATA GARCÍA AND BOBO, 1984 (GASTROPODA OPISTHOBRANCHIA). – Polyce a au an ioma gina a Ga cía y Bobo, 1984 mues a una población es able y en la localidad de El Po il (Huel a, SW de España), lo que ha pe mi ido la ecolección, desde ma zo de 2001 has a diciemb e de 2003, de un al o núme o de ejempla es de odos los amaños. En el p esen e es udio se ha ex aído la ádula de 141 animales, 138 ecogidos en la zona in e ma eal de El Po il y 3 en La He adu a (G anada). Los amaños de los animales han osci- lado en e 1.5 mm y 48 mm. Se ha podido obse a en los indi iduos de en e 1.5 y 2 mm la exis encia de una p e- ádula cuyos dien es son mo ológicamen e di e en es a los de la ádula de los indi iduos mayo es; sin emba go, en los ejempla es de 3 y 4 mm es a p e- ádula coexis e con la ádula ípica, siendo es a es uc u a la única p esen e en indi iduos de longi ud igual o mayo a 4 mm. A cada una de las ádulas ex aídas, an o con p e- ádula o sin ella, se le ha medido la longi ud o al de la cin a, la lon- gi ud del dien e la e al ex e no y el núme o de ilas de dien es. Conside ando los es pa áme os medidos, las a inidades en e los ejempla es sin p e- ádula se es ablecie on a pa i de análisis de Clus e , que de inie on es g upos dis in os (4-10 mm, 11-22 mm y 23-48 mm). Las co elaciones exis en es en e la longi ud de los indi iduos y la longi ud de la ádula, el núme o de ilas y la longi ud media de los dien es ue on signi ica i as. Las di e encias mo ológicas econocidas en los g upos conside ados pod í- an es a elacionadas con dis in as es a egias alimen a ias. Palab as cla e:Polyce a au an ioma gina a, Opis hob anchia, Gas opoda, ádula, a iación on ogené ica. sm70n2227-2025 25/5/06 16:02 Página 227 INTRODUCTION The mo phology o he adula ee h, including aspec s such as he numbe o ee h ows and ee h pe hal - ow, has o en been used o di e en ia e species o opis hob anchs. Ne e heless, he in aspeci ic and on ogene ic adula a ia ions in he opis hob anchs ha e been p o ed in some species. Bleakney (1989) e ealed a mo phological a ia ion o he adula o Placida dend i ica (Alde and Hancock, 1843), compa ing popula ions om he Paci ic and A lan ic. Be sch (1976, 1978a, 1978b) s udied he adulae o Discodo is e elinae Ma cus, 1955 and se e al gene a o Ch omo- do ididae, concluding ha he e is a mo phological a ia ion be ween he newly o med ee h, si ua ed in he newe ows, and he o he ee h, si ua ed in olde ows. Fu he mo e, he numbe o ee h ows inc eases wi h he leng h o he animal. P u o -Fol (1926) desc ibed he p esence o a “p e- adula” o dis inguish he i s ee h ows om he emaining ows, du ing he ju enile s age o he police id nudib anch Polyce a quad ilinea a (Mülle , 1776). Focusing on he amily Polyce a idae, Fe ei a (1977) epo ed di e en adula pa e ns be ween ju enile and adul s in species o he genus T iopha Be gh, 1880. Recen ly, Ocaña e al. (2004) p o ided da a on he on ogene - ic a ia ion in numbe and mo phology o adula ee h in se e al species o genus Tambja Bu n, 1962, compa ing ju enile and adul s ages. This pape examines in aspeci ic adula a ia- ions o Polyce a au an ioma gina a Ga cía and Bobo, 1984 om sou he n Spain, and p o ides da a on he a ia ion in numbe and mo phology o ee h ows in specimens a di e en s ages, be ween 1.5 and 48 mm in leng h. MATERIAL AND METHODS The p esen s udy was conduc ed using speci- mens om El Po il beach (Huel a, SW Spain) (37º12´40´´N, 7º7´50´´W) and La He adu a (G anada, SE Spain) (36º44´N, 3º43´W) (Fig. 1). Th ee animals we e collec ed in La He adu a and 138 o hem in El Po il om Ma ch 2001 o Decembe 2003. The specimens we e ca ied ali e o he labo a o y, whe e hey we e measu ed and ixed in 4% o malin. The adulae o all he specimens we e s udied by using op ic mic oscopy and hose o he ju eniles we e also pho og aphed using SEM. The leng h o he adula, he numbe o ows and he leng h o he ou e la e al oo h we e measu ed wi h a mic ome e ocula . To de e mine he size o he adula ee h we conside ed he leng h o he ou e la e al oo h, om he apical cusp o he base (Fig. 2). The a ini ies among specimens acco ding o he h ee measu ed a iables ( adula leng h, numbe o ows and he mean alues o oo h leng h) we e es ab- lished h ough Clus e analysis using he UPGMA me hod (Unweigh ed Pai G oup Me hod using A i hme ic a e ages) (Snea h and Sokal, 1973), based on Euclidean dis ance. Fo hese analyses he ou specimens wi h a p e- adula we e no included. Once he g oups o specimens we e es ablished h ough he Clus e analysis, he possible di e ences o he h ee SCI. MAR., 70(2), June 2006, 227-234. ISSN: 0214-8358 228 • I. MARTÍNEZ-PITA e al. IBERIAN PENINSULA EL PORTIL LA HERRADURA FIG. 1. – Map o Spain showing he sampling loca ions. FIG. 2. – Ou e la e al oo h. The ba shows he measu ed leng h o de e mine he size o he ee h. sm70n2227-2025 25/5/06 16:02 Página 228 measu ed a iables be ween g oups we e es ed using he non-pa ame ic K uskal-Wallis es , a e es ing he da a o no mali y using he Kolmogo o - Smi no es and Le ene’s es o homogenei y o a iances. Mul i a ia e analyses (clus e ) we e ca - ied ou using he PRIMER package (Cla ke and Go ley, 2001) and o uni a ia e analyses (mean com- pa ison h ough K uskal Wallis) he BMDP was used (Dixon, 1983). RESULTS Mo phological a ia ion o he adula ee h The adula o P. au an ioma gina a is de ined as ha ing he o mula 8-15 x 4.2.0.2.4 (Figs. 3E, F). The ou ma ginal ee h a e quad angula , wi hou cusps and he size dec eases ou wa ds (Fig. 3F; Fig. 4C). The wo in e nal ee h a e hama e, as he inne SCI. MAR., 70(2), June 2006, 227-234. ISSN: 0214-8358 ONTOGENETIC AND INTRASPECIFIC RADULAR CHANGES OF P. AURANTIOMARGINATA • 229 FIG. 3. – SEM pho og aphs o he adula and p e- adula in di e en specimens o P.au an ioma gina a. A. Olde po ion o he adula in an indi idual 1.5 mm long. B. De ail o a bi id oo h in he adula o an indi idual 1.5 mm long. C. Radula and p e- adula o a specimen 4 mm in leng h. D. De ail o he p e- adula po ion om a ju enile 4 mm in leng h. E-F. Adul adula. sm70n2227-2025 25/5/06 16:02 Página 229 oo h is smalle and hinne han he second one; hey ha e an apical cusp and a spu app oxima ely in he middle o he oo h (Figs. 3E, F; Figs. 4G, J). The e is no achidian oo h. This adula pa e n, conside ed as he adul ype o he species, appea s in almos all he specimens s udied. Howe e , some mo phological di e ences a e seen in specimens smalle han 4 mm in leng h. Specimens o 3-4 mm in leng h ha e he adula di ided in o wo po ions, wi h mo phological a i- a ions o he ee h. The an e io ee h ows, which a e he oldes , ha e he ma ginal ee h p o ided by an enla ged basal pa and a ilamen ous cusp (Fig. 3D; Fig. 4B); he la e al ee h ha e he adul mo - phology, al hough he spu s a e e y small (Figs. 4E, I). The newe ows ha e he adul pa e n desc ibed be o e (Fig. 3C; Figs. 4F, J). In his si ua ion, he an e io po ion o he adula is conside ed as a p e- adula, acco ding o P u o -Fol (1926). Specimens smalle han 3 mm lack he adul adula pa e n (Fig. 3A), o i only appea s in he las ows o he ibbon. The ma ginal ee h a e ilamen ous, lacking SCI. MAR., 70(2), June 2006, 227-234. ISSN: 0214-8358 230 • I. MARTÍNEZ-PITA e al. FIG. 4. – On ogene ic a ia ions in he adula and p e- adula. A, B and C, a ia ion o he ma ginal ee h in animals smalle han 3 mm (A), 3-4 mm in leng h (B) and bigge han 4 mm (C). D, E, F and G, a ia ion in he ou e la e al oo h in animals smalle han 3 mm (D), 3-4 mm in leng h in he p e- adula po ion (E) and adula po ion (F) and indi iduals bigge han 4 mm (G). H, I and J, a ia ion o he inne la e al oo h in animals smalle han 3 mm (H), 3-4 mm in leng h (I) and indi iduals bigge han 4 mm (J). The alue o he scale ba s a e 10mm in H, 20mm in A, B, D, E and I, 100mm in F and 200mm in C, G and J. sm70n2227-2025 25/5/06 16:02 Página 230 he basal enla ged po ion; some ma ginal ee h ha e he ip bi id (Figs. 3A, B; Fig. 4A). The ou e la e - al ee h lack he spu and he cusp is p o ided by a longi udinal u ow (Fig. 4D). The inne la e al ee h ha e he adul mo phology, bu he spu s a e e y small (Fig. 4H). Rela ion be ween he leng h o he animal and he size o he adula and ee h Figu e 5 shows he ela ion be ween he leng h o he animals and he leng h o he adula. The ela ion be ween he leng h o he specimens and he mean alue leng h o he ee h is shown in Figu e 6. Bo h g aphs show a s a is ically signi ican posi i e co e- la ion. The leng h o he adula inc eases wi h he g ea e leng h o he animal (Fig. 5). This line is desc ibed by he equa ion Y = 0.69 + 0.04x, wi h he coe icien o co ela ion ( ) equal o 0.91 (n = 141, P <0.001). The leng h o he ou e la e al oo h (con- side ed he mean alue leng h o all ows o each spec- imen) inc eases as he leng h o he animal inc eases (Fig. 6). The eg ession line is Y = 154.36 + 5.99x; = 0.92 (n =137, P <0.001). Va ia ion o oo h size along he adula wi h p e- adula Besides he on ogene ic mo phological a ia ion, he ee h o he p e- adula pa di e in size om he adul pa . Figu e 7 shows he size o he ou e la e al ee h along he adula ibbon in specimens up o 4 mm in leng h. The ee h along he p e- adu- la ows a e no ably smalle han he ee h p esen in adul ows. Specimens wi h only p e- adula ee h ha e all he ou e la e al ee h clea ly smalle han hose ani- mals wi h adul ee h. In specimens wi h p e- adula and adul adula ows, he size o he ee h inc eas- es quickly om he olde ows (p e- adula po ion) o he newe ows (wi h adul ee h pa e n). In ani- mals 4 mm in leng h he p e- adula may be p esen o absen . When only adul ee h ows a e p esen , he size o he ee h coincides wi h hose o la ge specimens. Radula di e ences be ween he numbe o ows and he leng h o he specimens Figu e 8 shows he ela ion be ween he numbe o ows and he leng h o he animals. In his g aph- ic i is possible o see ha specimens smalle han 4 mm ha e mo e ee h ows han la ge specimens. SCI. MAR., 70(2), June 2006, 227-234. ISSN: 0214-8358 ONTOGENETIC AND INTRASPECIFIC RADULAR CHANGES OF P. AURANTIOMARGINATA • 231 Animal leng h (mm) 0 102030405060 Radula leng h (mm) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Y=0.69+0.04X FIG. 5. – Rela ion be ween he animal’s leng h and he leng h o he adula. Animal leng h (mm) 0 102030405060 Mean ee h leng h (µm) 100 150 200 250 300 350 400 450 500 Y=154.36+5.99X FIG. 6. – Rela ion be ween he animal’s leng h and he mean leng h o he ou e la e al oo h. Row 0 5 10 15 20 25 30 35 Tee h leng h (µm) 0 20 40 60 80 100 120 140 160 180 1.5 mm 2 mm 3 mm 4 mm 4 mm´ 4 mm´´ FIG. 7. – Size o he ou e la e al oo h in each ow o he adula ib- bon in specimens up o 4 mm in leng h. The a ow indica es he beginning o he adula pa . Indi iduals 4 mm in leng h wi hou a p e- adula a e included. sm70n2227-2025 25/5/06 16:02 Página 231 The e is a signi ican dec ease in he numbe o ows in specimens la ge han 4 mm, and a e his, he numbe o ows inc eases e y slowly wi h inc eas- ing animal size. The sudden dec ease coincides wi h he disappea ance o he p e- adula in he animal. On ogene ic a ia ion o he adula in P. au an ioma gina a Figu e 9 shows he esul o clus e ing he speci- mens using he UPGMA me hod and Euclidean dis- ance. The h ee measu ed a iables ( adula leng h, numbe o ows and he mean alues o oo h leng h) we e used o es ablish he a ini ies among speci- mens. Animals wi h a p e- adula we e no included in his analysis. Clus e analysis dis inguished h ee g oups, which ep esen h ee animal sizes: 4-10 mm, 11-22 mm and 23-48 mm in leng h. The non- pa ame ic K uskal-Wallis es showed s a is ically signi ican di e ences among he h ee g oups o he h ee measu ed a iables (Table 1). Figu e 10 shows ha he mean alues o he ou e la e al oo h o each adula ow e eal ha he h ee g oups ha e di e en in e al sizes, which a e la g- SCI. MAR., 70(2), June 2006, 227-234. ISSN: 0214-8358 232 • I. MARTÍNEZ-PITA e al. Adul leng h (mm) 1 10 100 Row numbe 0 5 10 15 20 25 30 Row 0123456789101112 Tee h leng h (µm) 100 150 200 250 300 350 400 4-10 mm 11-22 mm 23-48 mm FIG. 8. – Rela ion be ween he leng h o he animal and he numbe o ows p esen in he ibbon, he loga i hmic scale has been used o he leng h o he animal. 0 1 2 3 4 5 4 -10 mm Euclidean dis ance 11 - 22 mm 23 - 48 mm FIG. 9. – The h ee di e en g oups esul ing om he clus e ing using he UPGMA me hod and he Euclidean dis ance. Animals wi h a p e- adula a e no included. FIG. 10. – Mean alues o he ou e la e al ee h wi h he s anda d e o o he mean in each adula ow along he ibbon in he h ee di e en g oups. sm70n2227-2025 25/5/06 16:02 Página 232 e in he animals 23-48 mm in leng h. Howe e , he size cu es along he ibbon a e simila o he h ee g oups. Thus, he oldes ee h a e smalle because o wea ; he size o he ee h inc eases owa ds he newe ows, wi h a maximum leng h in he six h o eigh h ows. The las ows o he adula (which a e he mos ecen ly o med) ha e smalle ee h, which a e s ill de eloping. DISCUSSION Al hough he opis hob anchs ha e a ce ain wide ange in he numbe o ee h pe ow, his pa ame e is equen ly used as a diagnos ic ea u e a a speci ic le el. Some a icles ha e been published ha aim o examine he in aspeci ic a iabili y ela ed o he adula o mula (i.e. Beeman, 1963; Be sch, 1976; Fe ei a, 1977). All o hem desc ibed a di ec co e- la ion be ween he size o he body and he numbe o adula ows. Howe e , we ha e ound in P. au an- ioma gina a ha he co ela ion is no obse ed i specimens smalle han 4 mm a e conside ed, because in animals up o 3-4 mm he numbe o adula ows is no ably highe han ha o specimens la ge han 4 mm. Simila si ua ions we e desc ibed in he species o Polyce a idae T iopha ca alinae (Coope , 1863), T. macula a MacFa land, 1905, Tambja ceu ae Ga cía- Gómez and O ea (1988) and T. ma bellensis Schick and Ce e a, 1998 (Fe ei a, 1977; Ocaña e al., 2004). Fo bo h species o T iopha, Fe ei a (1977) desc ibed he p esence o a di ec unc ion be ween he size o he adul specimens and he numbe o ows. Howe e , his au ho indica ed ha e y small specimens (smalle han 10 mm in leng h) ha e a much g ea e numbe o ows han he adulae o ma u e indi iduals (Fe ei a, 1977). In Tambja ceu ae and T. ma bellensis he numbe o adula ows is also highe in specimens smalle han 10 mm long (Ocaña e al., 2004). P u o -Fol (1926) desc ibed he p esence o he so called p e- adula o dis inguish he i s ee h ows o Polyce a quad ilinea a om he es o he ows de eloped du ing he ju enile s age. The shape o he ee h o he p e- adula is di e en om he adul ee h o he adula ibbon.The species o Tambja s udied by Ocaña e al. (2004) also show some changes which coincide wi h he idea o he p esence o a di e en de elopmen al pa e n o he adula in ela ion o he size (o age) o he speci- mens. Du ing he de elopmen o animals om he ju enile o adul s ages he adula changes in he numbe o ows and he shape o he ee h, inde- penden ly o he species. This pa e n o adula wi h p e- adula, coincides wi h ha ound in P. au an- ioma gina a. Acco ding o he idea o P u o -Fol (1926), who desc ibes a p e- adula in Polyce a quad ilinea a, he obse a ions o Fe ei a (1977) and Ocaña e al. (2004) in he T iopha, and Tambja species espec i ely, and in P. au an ioma gina a (p esen pape ), i is possible o suppose ha in Polyce a idae he e is a ansi ion in adula mo - phology om young o adul animals ha akes place apidly. This a ia ion could be ela ed o a change o die no con i med ye by analysis o s omach con en s. Finally, based on ou s udy he ollowing conclu- sions can be made abou P. au an ioma gina a: 1) The leng h o he adula inc eases wi h he leng h o he specimen. 2) The leng h o ou e la e al ee h inc eases wi h he leng h o he animal. Fu he mo e, he ee h along he p e- adula ows a e clea ly smalle han adul ee h. 3) Specimens smalle han 4 mm wi h a p e- adu- la ha e mo e ee h ows han hose la ge han 4 mm. 4) In specimens wi hou a p e- adula, he numbe o ee h ows inc eases as he leng h o he animal inc eases. 5) Acco ding o he on ogene ic a ia ions obse ed in he adula o P. au an ioma gina a, ou g oups o specimens a e dis inguished, which ep e- sen di e en animal sizes: smalle han 4 mm wi h a p e- adula, 4-10 mm, 11-22 mm and 23-48 mm. SCI. MAR., 70(2), June 2006, 227-234. ISSN: 0214-8358 ONTOGENETIC AND INTRASPECIFIC RADULAR CHANGES OF P. AURANTIOMARGINATA • 233 TABLE 1. – Resul s o he K uskal Wallis es o he h ee measu ed a iables: he adula leng h, numbe o ows and mean leng h o he ee h in he h ee g oups es ablished h ough he Clus e analysis. Mean ± S anda d de ia ion K uskal Wallis 4-10 mm 11-22 mm 23-48 mm (S a is ic) Radula leng h 0.94 ± 0.16 1.46 ± 0.22 2.00 ± 0.27 805.8*** Numbe o ows 8.93 ± 0.77 10.00 ± 0.96 11.20 ± 1.27 45.1*** Mean leng h o he ee h 178.55 ± 36.69 261.49 ± 26.88 333.61 ± 26.08 104.9*** *** p<0.001 sm70n2227-2025 25/5/06 16:02 Página 233 The e is no clea eason o explain he clus e sepa- a ion o he di e en g oups; howe e , ou own obse a ion leads us o hink ha his sepa a ion could be ela ed o eeding s a egies o ood ype. P obably, he e is a change in die in P. au an- ioma gina a du ing i s g ow h, which would be ela ed o he ype o adula ee h p esen . The smalles specimens (1.5 o 4 mm in leng h) we e ound on he b yozoan Sessibugula ba osoi López de la Cuad a and Ga cía-Gómez, 1994 (pe s. obs.), which leads us o hink ha his species could be i s p ey die . Howe e , he la ge specimens (which include he h ee emaining clus e g oups) we e ound ea ing he b yozoan Bugula ne i ina (Linnaeus, 1758) and T icella ia occiden alis (T ask, 1857). ACKNOWLEDGEMENTS We wish o exp ess ou g a i ude o Au o a Mon e o who helped us o ex ac mos o he adu- lae. We also hank D . Sánchez Tocino and D . Ocaña o p o iding he specimens om La He adu a and SEM pho og aphs. REFERENCES Beeman, R.D. – 1963. Va ia ion and synonymy o Phyllaplysia in he No heas e n Paci ic (Mollusca: Opis hob anchia). Velige , 6(1): 43-46. Be sch, H. – 1976. In aspeci ic and on ogene ic adula a ia ion in opis hob anch sys ema ics (Mollusca: Gas opoda). Sys . Zool., 25: 117-122. Be sch, H. – 1978a. The Ch omodo idinae nudib anchs om he Paci ic coas o Ame ica. – Pa II. The genus Ch omodo is. Velige , 20(4): 307-327. Be sch, H. – 1978b. The Ch omodo idinae nudib anchs om he Paci ic coas o Ame ica. – Pa III. The gene a Ch omolaichma and Mexich omis. Velige , 21(1): 70-86. 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The p inciples and p ac ique o nume ical classi ica ion. WWH F eeman and Company, San F ancisco. Scien . ed.: J.D. Ros Recei ed No embe 9, 2004. Accep ed No embe 4, 2005. SCI. MAR., 70(2), June 2006, 227-234. ISSN: 0214-8358 234 • I. MARTÍNEZ-PITA e al. sm70n2227-2025 25/5/06 16:02 Página 234