Botrylloides leachii ( Savigny, 1816 )

Botrylloides leachii ( Savigny, 1816) View in CoL

( Figures 4 View Figure 4 , 3B, C View Figure 3 )

Botryllus leachii Savigny, 1816: p. 199 View in CoL –200, pl. 4, fig. 6.

Botryllus leachi: Michaelsen, 1922: p. 479 View in CoL ; Brewin, 1946: p. 111 –112; Brunetti, 2009: p. 19 –21, pl. 1a–d. For synonymy see Brunetti, 2009: p. 19.

Material examined

New Records: Thompson Sound , Crayfish Heights (45° 13.182’S, 166° 58.656’E, 15 m, 30 January 2006, NIWA 49980 View Materials , eight colonies); Crooked Arm, Doubtful Sound (45° 25.121’S, 166° 56.00’E, 20 m, 2 February 2006, NIWA 49999 View Materials ) GoogleMaps ; Breaksea Sound , First Cove (45° 34.74’S, 166° 44.43’E, 18 m, 2 February 2009, NIWA 49970 View Materials , NIWA 49971 View Materials ) GoogleMaps ; Nine Fathom Passage , Dusky Sound (45° 44.237’S, 166° 53.199’E, 16 m, 1 February 2009, NIWA 49950 View Materials ) GoogleMaps ; The Narrows , Long Sound (46° 02.335’S, 166° 44.16’E, 17 m, 28 January 2009, NIWA 49939 View Materials ) GoogleMaps ; Long Sound , Only Island (45° 57.652’S, 166° 52.241’E, 16 m, 28 January 2009, NIWA 49937 View Materials ) GoogleMaps ; Caswell Sound , Paua Bay (45° 01.01’S, 167° 08.4’E, 15 m, vertical rock wall, coll. M. Page, 3 February 2009, NIWA 49986 View Materials ) GoogleMaps .

Previously recorded: (see Kott 1985): Australia; West Indian Ocean; Red Sea; South Africa; British Isles; North Sea; Mediterranean, Adriatic and Black Seas.

Description

Colonies are predominantly thin, encrusting dead black coral trees and rock walls, often overgrowing brachiopods and coralline algae. As is common in this genus, colony colour can vary greatly from red-purple (RP 4/4, NIWA 49999, Figure 3B View Figure 3 ), mustard (Y 8/12, NIWA 49986, Figure 3C View Figure 3 ) to white, almost transparent in colour (NIWA 49971). Zooids form branching meandering double row systems, and pear-shaped terminal ampullae are usually found at the growing edge of the colony. The zooids have a wide atrial opening with a large spatulate atrial languet, exposing much of the branchial sac ( Figure 4A View Figure 4 ). The branchial sac has 11 rows of stigmata, the second row being incomplete. A distinctive flask-shaped stomach has eight continuous folds enlarged into lobes at the gastric end ( Figure 4B View Figure 4 1 View Figure 1 ). There is a small inconspicuous gastric caecum, slightly lobed at its distal end, located halfway down the pyloric region of the stomach. The typhlosole lies in an open space between the first and eighth stomach folds and extends into the intestinal loop ( Figure 4B View Figure 4 2 View Figure 2 ). The testis follicles have a ‘mulberry-like’ appearance (see Kott 1985) and are located ventral and adjacent to developing eggs that lie in a brood pouch extending from each side of the body wall ( Figure 4C View Figure 4 ).

Remarks

The current species can be distinguished from other Botrylloides by the morphology of the gastric region and the location of the egg in a brood pouch at the posterior dorsal-lateral corner of the peribranchial cavity ( Brunetti 2009). Conspicuous lobes at the cardiac end of the stomach folds and a small caecum with a slightly swollen tip are common only to Botrylloides leachii and Botrylloides nigrum Herdman, 1886 . The present specimens of B. leachii however, can be separated from B. nigrum by eggs located in a brood pouch dorsal, and posterior to the testis follicles ( Figures 5A, B View Figure 5 ), as figured for B. leachii by Brunetti (2009) from the Red Sea (p. 23, pl. 1a), a condition not described for B. nigrum from Guadaloupe ( Monniot 1983). Furthermore, B. nigrum is a tropical and subtropical species unlikely to be found in the cool water of Fiordland. The distribution of B. leachii throughout Fiordland, however, is consistent with the broad biogeographic range occupied by this species both in New Zealand and worldwide. It has been suggested that this species is opportunistic and possibly introduced ( Kott et al. 2009). Certainly, it is common in fouling communities on ship hulls and artificial substrata in ports and harbours, and may have been introduced into Fiordland by early whalers and sealers.