Botrylloides sp.

Page, M. J., Willis, T. J. & Handley, S. J., 2014, The colonial ascidian fauna of Fiordland, New Zealand, with a description of two new species, Journal of Natural History (J. Nat. Hist.) 48 (27 - 28), pp. 1653-1688 : 1660-1662

Botrylloides sp. ( Figures 5 ; 3D, E )

Material examined

Records: Breaksea Sound, First Cove (45° 34.74’S, 166° 44.43’E, vertical rock wall, coll. M. Page, 20 m, 1 February, 2009, NIWA 49967 , four colonies); Bluff Harbour ,

Tiwai Point (46° 35.47’S, 168° 20.95’E, wharf pile, coll. M. Page, 8 m, 21 August, 2007, NIWA 68096 ) .

Description

The cushion-shaped colonies up to 50 mm in diameter and 20 mm high vary in colour from lavender (PB7/6) with white branchial apertures ( Figure 3D ), to cream (YR8/6) with purple pigment around the branchial apertures ( Figure 3E ). The test in lavendercoloured colonies from Fiordland is transparent and the zooid branchial sacs are clearly visible through the test, whereas colonies from Bluff are opaque. Double rows of zooids in ‘leachii-type’ systems ( Brunetti 2009) are tightly packed in a soft fleshy test. There are numerous common cloacal apertures, approximately 5 mm in diameter randomly distributed throughout the colonies.

The zooids are approximately 2 mm long and they have a branchial aperture on a narrow stout siphon and four large branchial tentacles interspersed with smaller tentacles of varying sizes. There is a large atrial opening with a wide spatulate languet exposing the majority of the branchial sac, extending one-third of the body length of the zooid ( Figure 5A ). The lower languet also extends out from the body and is equidistant from the upper languet. There are 12–13 rows of stigmata with 14–16 stigmata per half row. The second row of stigmata is dorsally incomplete on both sides of the branchial sac. The oesophagus is short and there is an oval stomach, with nine complete folds that extend the entire length of the stomach ( Figure 5B 1 , B 2 ). A typhlosole extends posterior to the stomach folds down the first tract of the intestinal loop. The ninth fold adjacent to the typhlosole is greatly reduced in size ( Figure 5B 1 ). A large pyloric caecum, 1.5 times the length of the stomach, curves in from the pyloric end to the gut loop. The gut forms a simple horizontal loop, and the rectum extends outside the atrial opening, ending in a bilobate anus adjacent to the eighth row of stigmata ( Figure 5A ). Left and right testes in the Fiordland specimen are round mulberry-like structures that sit adjacent and slightly anterior to the gut loop. Up to 25 testis vesicles are crowded into the testis, their convex outer edges forming the outside of the testis. No ovaries or larvae were present in specimens examined.

Remarks

Botrylloides magnicoecum from Australia described by Kott (1985) has predominantly conical, brightly coloured dark purple, white and yellow stalked lobed colonies with zooids in crowded double-row systems radiating from large terminal common cloacal apertures ( Kott 1985, Pl. VI a–d). A similar arrangement of zooids and colour was noted by Stocker (1985) for B. magnicoecum from Northland, New Zealand. Brewin (1951) also described purple and yellow colonies and zooids in irregularly branched systems from the Hauraki Gulf. The colonies collected from Fiordland and Bluff are not typical of the shape or colour described by these authors, but the zooids are arranged in leachii - type double row systems. The differences in morphology observed may be related to colony age or different environmental conditions in southern populations. Brewin (1958a) also noted the presence of B. magnicoecum in Stewart Island, but did not describe the colony morphology.

The arrangement of stomach folds and the shape and size of the caecum in Botrylloides sp. from Fiordland ( Figure 5 ) are the same as characters described by Brunetti (2010) for Hartmeyer’ s Botrylloides magnicoecum typus. Nine complete stomach folds, a very large curved caecum, a long typhlosole extending over the pyloric region of the stomach in towards the pole of the intestinal loop and a bilobate anus distinguish B. magnicoecum from Botrylloides israeliense ( Brunetti 2009) . Botrylloides anceps (Herdman, 1891) , another species with a long caecum, varies from B. magnicoecum having 10 stomach folds, spaces between folds, a typhlosole bent at right angles towards the pyloric end of the stomach, and fewer rows of stigmata.

The branchial sac in Botrylloides sp. has a dorsally incomplete second row of stigmata. Neither Kott (1985) nor Brewin (1951) noted this character in B. magnicoecum from the southern hemisphere. However, Monniot et al. (2001) in their description of B. magnicoecum from South Africa also found the second row of stigmata to be incomplete and noted a bilobate anus. The specimens from Fiordland and South Africa do not agree with Brunetti (2010) ’s redescription of Hartmeyer’ s typus and are clearly an undescribed species. Monniot et al. (2001) suggest that there are a number of species with a large caecum and conclude that the difference in descriptions is due to different species with a similar large caecum grouped together as B. magnicoecum . We agree with this hypothesis. It is likely that two magnicoecum - type Botrylloides species occur in New Zealand; a northern species Botrylloides magnicoecum , with lobate conical colonies and a complete second row of stigmata in the branchial sac, and the present species in southern waters, with low cushion-shaped colonies and incomplete stigmata in the second row. Extensive geographic collection and description of both species in reproductive condition is necessary for comparison. At present, we consider the species from Fiordland and Bluff to be the same as B. magnicoecum from South Africa as described by Monniot et al. (2001).

Figures

Figure 1. Map of Fiordland on the south-west coast of the South Island, New Zealand showing location of sampling stations.

Figure 2. Botryllus stewartensis (NIWA 49968): (A) part of a colony showing zooids arranged on sand-coated lobes; (B) zooid; (C) testis follicle; (D1, D2) parietal and mesial sides of the stomach. Scale bars: A, 10 mm; B, 1 mm; C, D 0.5 mm.

Figure 3. In situ images of: (A) Botryllus stewartensis (NIWA 49968); (B) Botrylloides leachii (NIWA 49998); (C) Botrylloides leachii (NIWA 49986); (D) Botrylloides sp. (NIWA 49967); (E) Botrylloides sp. (NIWA 68096); (F) Synoicum kuranui (NIWA 49977).

Figure 5. Botrylloides sp. (NIWA 49967): (A) zooid with a wide atrial opening and spatulate upper and lower atrial lips; (B1, B2) parietal and mesial sides of the stomach. Scale bars: A, 1 mm; B 0.5 mm.