Briarella doliaris, Salmen & Anton & Wilson & Schrödl, 2010

Briarella doliaris View in CoL spec. nov.

Material. Holotype (♀, ZSMA20092004 mounted on SEM stub) and paratypes (1♀ ZSMA20092005 , mounted on SEM stub and 1♀ ZSMA 20092006 in ethanol) partly damaged, collected together by Nerida Wilson , 9m, Amity , North Stradbroke Island , Moreton Bay, Queensland, Australia, 27°24'13.81"S, 153°26'11.49"E, 07 December 2002. Host: Ceratosoma trilobatum Gray, 1828 . 2♀♀ examined by SEM. GoogleMaps

Etymology. The Latin species name doliaris refers to the barrel-shaped body.

Description ( Figs 1-3 View Fig View Fig View Fig )

Female. Body length 3.0- 4.7 mm, (measurements were made from the anterior end of the cephalothorax to the posterior end of the abdomen, including the caudal rami and excluding antennae and the setae on caudal rami), width 1.1-1.4 mm, body stocky. Ratio of length to width about 1.71: 1. Parasites whitish, slightly translucent ( Fig. 1A View Fig ). Cephalothorax distinctly set off from trunk; thorax enlarged with five pairs of lateral processes; abdomen long and slender ( Fig. 1B View Fig ). Segmentation of all body parts unclear.

Cephalothorax consisting of head with five pairs of cephalic appendages and first thoracic segment bearing maxillipeds ( Fig. 1C View Fig , 3F View Fig ). Antennule ( Fig. 1D View Fig ) long and unbranched, indistinctly 4-segmented; first segment long, bearing nine setae, five short ones and four long ones; second segment with three long setae and one short one; third segment with two long setae; fourth segment with six long setae at apex. Antenna ( Fig. 1C View Fig , 3A View Fig ) unbranched, 3-segmented; first and second segment with small spine on proximal edge; third segment with at least five minute spines, apex with two subequal strong claws. Labrum ( Fig. 1C View Fig ) well developed, bilobate; lobes very long. Mandible ( Fig. 1E View Fig , 3B View Fig ) with broad and thick base, tapering into long and flat blade with thorns on both edges like a saw blade. Mandible palp very thick with blunt tip ( Fig. 1E View Fig , 3E View Fig ). Maxillule ( Fig. 1F View Fig , 3C View Fig ) thick, bearing two small spines at apex and a triangular bulge laterally. Maxilla ( Fig. 2A View Fig , 3D View Fig ) 2-segmented; first segment enlarged, second segment biramous, longer ramus with two apical elements. Labium tongue-shaped. Maxilliped posterior to maxilla ( Fig. 1C View Fig , 3F View Fig ).

Second thoracopod biramous, located on second thoracic segment, close to cephalothorax ( Fig. 1B View Fig ). Exopodite indistinctly 2-segmented with one strong spine at proximal edge of first segment; second segment with 4 strong spines increasing in size distally, one seta at level of longest spine, one seta at base of thoracopod ( Fig. 2B View Fig ). Endopodite about as long as exopodite, blunt apex bearing one seta. Third thoracopod biramous. Exopodite as in second thoracopod; endopodite longer than exopodite, apex split in two short elements; one seta at base of third thoracopod ( Fig. 2C View Fig ). No further thoracopods detected.

Thorax with deep transversal furrows demarcating four pairs of lateral processes. Processes shorter than whole body; stout with round tip. Fifth pair of lateral processes shorter than all others and more slender, situated posterior to enlarged part of thorax, slightly bent medially.

Abdomen long and slender with four indistinct constrictions; genital openings not detected; egg sacs slender, slightly bent with pointed tip. Caudal rami long and stout; each ramus with two pinnate setae laterally and four pinnate ones at apex, latter with small bulge bearing one long pinnate seta ( Fig. 2D View Fig ).

Male. Not found.

Biology

For the present study, no biological information on B. doliaris was available, e.g. on the specimens’ positions inside the host, or the colour of the egg sacs. Both parasites were damaged (see Fig. 1A,B View Fig ) during their incidental discovery; egg sacs were removed, fixed in ethanol, and given to the ZSM separately. No males were found, despite considerable effort dissecting the host specimen.

Remarks

The females resemble each other regarding the size and shape of the body. The morphology of mouthparts is nearly identical; differences only exist with regard to number and position of setae. Thoracopods were only detectable in one specimen, in the second one they were covered with host tissue. Genital openings could not be detected in both specimens, but it is likely that they are situated on the first slightly swollen abdominal segment as it is usual for copepods ( Gruner et al. 1993).

The specimens examined herein are members of the genus Briarella Bergh, 1876 . Diagnostic features refer to the morphology of the mouthparts, especially the long mandible, the two claws on the third segment of the antenna (see Fig. 3A View Fig ) and the shape of the maxilla, the five pairs of lateral processes on the thorax and the presence of only two pairs of thoracopods, i.e., second and third ones ( Monod 1928; Huys 2001). According to Huys (2001), four other species belong to this genus: B. microcephala (type species), B. risbeci , B. disphaerocephala and an unnamed Briarella sp. (see also Monod 1928). Briarella risbeci has a very elongate body with four pairs of short lateral processes (“lobes” according to Monod 1928), while B. doliaris shows a stocky body with an enlarged thorax and a slender abdomen, and five pairs of longer lateral processes. Furthermore, B. risbeci possesses three setae on the maxillule ( Huys 2001), whereas B. doliaris has only two spines at the apex of the maxillule. Monod labelled a mandibular palp for B. risbeci ( Monod 1928) . Huys re-examined B. risbeci and B. disphaerocephala . In his drawings he reproduced a structure similar to the mandibular palp of Monod, but did not mention it in the text ( Huys 2001). Nevertheless the presence of a mandibular palp can be confirmed in this study ( Fig. 1E View Fig ). In the specimens examined herein the antennule is indistinctly 4-segmented, while in B. risbeci it shows 5-6 segments ( Monod 1928). Further differences concern the thoracopods. In B. doliaris both pairs of thoracopods are biramous, with a 2-segmented exopodite bearing 5 strong spines, whereas in B. risbeci the thoracopods are uniramous, with the second thoracopod bearing 5 spines and the third thoracopod bearing none ( Monod 1928). In contrast to B. risbeci , which has egg sacs longer than the whole body, B. doliaris has short egg sacs. Briarella thus far was exclusively found in dorid nudibranchs ( Huys 2001), what also applies for B. doliaris , which infests Ceratosoma trilobatum . The latter is already known as host for B. microcephala (see Monod 1928).

Monod (1928) described B. microcephala with five pairs of lateral lobes, but with a very vermiform body shape; this stands in clear contrast to the stocky body of B. doliaris . Briarella disphaerocephala is considered to be similar to B. risbeci (see Monod 1928; Monod & Dollfus 1932; Huys 2001). In B. disphaerocephala the maxillule possesses three setae like in B. risbeci (see Huys 2001) and B. disphaerocephala possesses two more pairs of lateral lobes. One pair is situated on the sides of the head and one pair is located in the pregenital area (Monod & Dollfus 1932). Thus B. disphaerocephala is also different to B. doliaris .

Bergh’ s unnamed Briarella sp. (see illustration in Monod & Dollfus 1932: fig. 17E) externally is very similar to B. microcephala (see Bergh 1876) and to B. risbeci (see Monod 1928), and thus differs from the stocky body shape of B. doliaris . The egg sacs of Briarella sp. are only half as long as the whole body, and thus more similar to those of B. doliaris . Bergh (1876) also describes the antennule of Briarella sp. as 5-segmented, while in B. doliaris it is indistinctly 4-segmented. Briarella sp. is only known from the Philippines, where it infests Chromodoris elisabethina and A. cespitosus as hosts ( Monod 1928).

Our material examined thus differs from all known congeners, and the new species B. doliaris is established.