ON RECENT SPECIES OF SPIRASERPULA REGENHARDT, 1961 



99 



Spiraserpula minuta (Straughan, 1967) 

 (Figs. 32, A-Q; 3, N) 



Synonymy: Pseudoserpula minuta Straughan, 1967, p. 216, 

 Fig.6, h-1. 



Material examined. 



Queensland (Australia): 1. Port Douglas, sheltered side of 



rocks, near LWM, legit D. Straughan, 17. i. 1963 (HOLO- 



TYPE AM W4062). 2. Same locality and date, legit D. 



Straughan: (25 studied out of numerous specimens, AM 



W4059). 



TYPE LOCALITY. Port Douglas, Queensland (Australia). 



Description. According to the original description, the 

 tubes are white, round, and may have a pink tinge. An 

 operculum or pseudopercula ( = rudimentary opercula) are 

 absent, there are 5 pairs of radioles, the number of thoracic 

 chaetigers is 7 or 8, and bayonet collar chaetae have 2 or 3 

 blunt teeth on the basal boss (Straughan, 1967). Vide discus- 

 sion on the taxonomy which follows this description. 



The holotype (AM W4062) was examined by the second 

 author in 1979. Upon removal of the worm from its tube, it 

 lacked a branchial crown and its abdomen consisted of 48 

 segments, the last 6 with capillaries. However, the present 

 study revealed that AM W4059, which was collected from the 

 same locality and on the same date by Straughan, contains 

 several well-preserved specimens, and the following descrip- 

 tion is based on 25 of them. 



TUBES: Whitish in juveniles, with a very faint overall pinkish 

 tinge in adults but, unlike S. lineatuba (Straughan), lacking a 

 pair of pink longitudinal bands. They occur in aggregations of 

 a few to several individuals which are mutually bonded at 

 their bases (Fig. 32, C). Their anterior ends are often free and 

 erect (Fig. 32, A). A very fine granular overlay is present 

 (Fig.32,A). 



ITS, located in the first formed parts of the tube, consist of 

 an unserrated dorsal ridge, which is somewhat T-shaped in 

 cross-section, along its convex wall, and a serrated ridge 

 along the opposite side (Figs. 32, B,C; 3, N). The posterior 

 end of the abdomen often shows a short mid-dorsal longitudi- 

 nal groove, into which the unserrated dorsal ridge of the tube 

 fits (Fig. 32, D). The serrated ventral ridge of the tube fits into 

 a mid-ventral longitudinal groove in the abdomen (Fig. 32, 

 D). 



worms: Out of the 25 specimens only 1 1 are complete. Three 

 have total lengths of over 10 mm, three between 8.0 and 

 10.0 mm, and five between 6.4 and 8.0 mm. Measurements 

 and meristic data of the longest and two smallest specimens 

 are presented in Table 23: 



Quite in contrast to the original description, nineteen 

 specimens with complete anterior ends all possess a pair of 



Table 23 S. minuta (Straughan). Measurements and meristic data 

 of three specimens. 



Table 24 S. minuta (Straughan). Meristic and other data. 



Specimen 



Total 



Thoracic 



Length of 



No. of 



Capillaries 



no. 



length 



width 

 (mm) 



abdomen 

 (mm) 



segments 



on 



1 



13.7 



0.5 



11.3 



82 



11 



2 



7.5 



0.5 



5.5 



48 



8 



3 



6.5 



0.5 



5.2 



78 



10 



No. of specimens (n= 19) 

 No. of radioles 



2 

 6/5 



14 



5/5 



3 



5/4 









No. of specimens (n=20) 

 No. of tnor. chaetal tufts 



1 

 9/8 



2 

 9/7 



8 

 8/8 



4 

 8/7 



2 

 8/6 



2 1 

 7/7 7/6 



No. of specimens (n= 17) 

 Thor. membranes end 



2 

 6/5 



3 

 6/4 



5 

 5/4 



6 



4/4 



1 



4/3 





rudimentary opercula (Fig. 32, D-F). A fully formed opercu- 

 lum is absent. The length of the radioles. ranges between 

 1.0 mm and 1.3 mm, and they end in short pinnule-free tips 

 which are about as long and as thick as the pinnules (Fig. 32, 

 D-F). Some meristic data on the population are given Table 

 24. 



The thorax is somewhat wider in specimens that had been 

 accidentally removed from their tubes prior to fixation 

 (Fig. 32, G,H). Two clusters of prostomial ocelli are present. 

 Ventral thoracic glands were not discernible. 



The numbers of bayonet chaetae in 8 collar fascicles from 

 different specimens, including a developing one deep within 

 are: 4 in 1 , 5 in 6, and 6 in 1 . Their blades are moderately long 

 and faintly serrated. The unserrated notch is about 1/3 the 

 length of the blade. The tooth counts in the above 40 bayonet 

 chaetae are: 3 in 18 (Fig.32,I,L), 4 in 17 (Fig. 32, J,M), 5 in 1 

 (Fig. 32, K), and indeterminate in the remaining 4. The usual 

 number of teeth is, therefore, 3 or 4. In some chaetae two 

 teeth may be large, while the third is much smaller (Fig. 32,1). 



Thoracic uncini (Fig. 32, N) bear 4-5 teeth in a single row. 

 Anterior abdominal uncini (Fig. 32, O) are similar, with 4-6 

 teeth. Posterior abdominal uncini bear 1-3 teeth in a single 

 row anteriorly, followed by a rasp-shaped cluster of smaller 

 teeth posteriorly (Fig. 32, Q). In the intermediate region 

 there is a gradual reduction of the number of anterior teeth in 

 the single row and a corresponding increase in the posterior 

 cluster (Fig.32, P). 



Etymology. Renamed after its discoverer, D. Straughan. 



Habitat and distribution. 5. minuta occurs in shallow 

 water, where it may form 'dense mats on the sheltered side of 

 vertical rocks near L.W.M.' (Straughan, 1967). 



It has hitherto been reported only from the type locality, 

 Port Douglas, Queensland. 



DISCUSSION 



Spiraserpula Regenhardt 1961 differs from the remaining 

 genera of its clade, namely Serpula Linnaeus 1758, Hydroides 

 Gunnerus 1768 and Crucigera Benedict 1887, with regard to 

 an important character, namely, the presence of ITS. In 

 addition, the worm lacks an apron. The tubes of the other 

 three genera lack ITS and, with a few exceptions, their worms 

 possess an apron. 



Straughan (1967) erected the the genus Pseudoserpula for 

 P. rugosa (type species) and P. minuta, believing an opercu- 

 lum to be absent in both, and distinguished between them on 

 the grounds that the former possessed a pair of pseudoper- 

 cula (= rudimentary opercula) which were said to be absent 

 in the latter. Ten Hove and Jansen-Jacobs (1984:162-165) 



