Floresorchestia kongsemae sp. n. a new species (Crustacea: Amphipoda: Talitridae) from Kasetsart University, Bangkok, Thailand

Abstract Background The genus Floresorchestia Bousfield, 1984 is widely distributed in terrestrial and marine coastal habitats. It has been found from coastal South Africa through to the Indo-Pacific region and the Caribbean Sea in Central America. Two species of Floresorchestia have been reported in Thailand, Floresorchestia boonyanusithii Wongkamhaeng et al. 2016 and Floresorchestia buraphana Wongkamhaeng et al. 2016. This work reports on a new species of Floresorchestia found at Kasetsart University in a man-made pond and neighbouring areas. New information Classification of the new species was achieved by considering the left mandible 5-dentate; gnathopod 2 posterior margin merus carpus and propodus of gnathopod 2 covered in palmate setae, palm reaching about 33% along posterior margin; uropod 3 peduncle with three robust setae; telson dorsal mid-line half the length of its breadth and four robust setae per lobe.


Introduction
Floresorchestia, a member of talitrid amphipods, has been reported in the Indo-Pacific Region. This genus contains members of 25 coastal (16) and terrestrial (9) species Springthorpe 2015, Lowry andSpringthorpe 2019) which inhabit a variety of habitats, including supralittoral, mountain and moist areas near freshwater streams. Many reports have found that amphipods survive in man-made habitats, suggesting that they have good adaptation and high migration abilities (Friend and Richardson 1986, Lowry and Springthorpe 2015, Wongkamhaeng et al. 2016).
This paper reviews the genus Floresorchestia in Thailand and describes a new species from a man-made habitat at Kasetsart University, Bangkok. The dichotomous key in this region are provided.

Materials and methods
This study is based on material collected in February 2020 from the leaf litter of a manmade swamp in front of Chakrabandhu Pensiri Hall, Kasetsart University, central Thailand. Samples were collected using a hand-net and carefully transferred into a plastic container for fixation in 10% buffered formalin. In the laboratory, amphipod specimens were sorted and stored in 70% alcohol. The animals were then examined under a stereomicroscope and later selected for dissection. The dissected specimens' appendages were examined and figures were produced using a camera lucida attached to an Olympus CH30 light microscope. Pencil drawings were scanned and digitally inked using a WACOM Bamboo CTH-970 graphics board following the method described by Coleman (2003). Setal and mouthpart classifications were made following Zimmer et al. (2009).
The palm measurement length was made following Lowry and Springthorpe (2015) as a percentage of the length of the propodus of male gnathopod 2. The percentage is calculated using the formula 100(1 -a/b)% (Fig. 1) where 'a' is the length of the posterior margin measured from the seta at the corner of the palm to the base of the propodus and 'b' is the length of the propodus measured from the base of the dactylus to the base of the propodus.

Description
Based on holotype male, 5.5 mm, THNHM-Iv-18766 Head. (Fig. 2) Eye large (greater than 1/3 head length). Antenna 1 short, exceeding article 4 of antenna 2 peduncle. Antenna 2 less than half body length, peduncular article slender; article 2 and 3 shortest; article 5 longer than article 4; flagellum of 13 articles and subequal to peduncle, final article of flagellum with an apical cluster of setae.
Pereopod 3 (Fig. 4) coxa longer than broad, with posterior process; merus longer than carpus and propodus, slightly expanded; posterior margin lined with group of robust setae; carpus shortest, posterior margin with group of robust setae; propodus slender and longer than carpus; dactylus without notch on posterior margin.
Pereopod 4 (Fig. 4) slightly shorter than pereopod 3; coxa longer than broad, without posterior process; merus and carpus shorter than those of pereopod 3; merus distally expanded, longer than carpus or propodus; carpus shorter than propodus posterior margin with group of robust setae; propodus slender with group of robust setae in posterior side; dactylus slender and longer than dactylus 3, with a notch in posterior margin. Pereopod 5 (Fig. 4) coxa bilobed, anterior lobe more distinct than posterior lobe; basis posterior margin serrate and small setae; merus and carpus distally expanded, propodus distinctly slender, longer than merus or carpus.
length to outer ramus, with two marginal robust setae; outer ramus with two marginal robust setae. Uropod 3 uniramus, peduncle with three robust setae; ramus subequal to peduncle, with one marginal robust setae and four apical robust setae.
Telson (Fig. 5) longer than broad, apically cleft, dorsal mid-line half of the telson, with four marginal and apical robust setae per lobe.
Pereon. (Fig. 6) Gnathopod 1 coxa anterior margin straight, ventral margin with robust setae; merus subtriangular, posterior margin without lobe; carpus anterior margin with one robust setae, posterior margin with three robust setae covering the lobe; propodus anterior margin with two groups of robust setae; dactylus posterior margin with three robust setae.

Remarks: Floresorchestia kongsemae sp. nov. is the third member in the genus
Floresorchestia that have been reported in Thailand. Floresorchestia kongsemae sp. n. differs from F. boonyanusithii in the following ways: 1) the left mandible lacinia mobilis has 5-dentate (vs. 4-dentate); 2) uropod 1 peduncle with eight robust setae and three robust marginal setae in inner ramus (vs. four robust setae in the peduncle, four robust marginal setae in inner ramus); 3) uropod 2 peduncle with four robust marginal setae, outer ramus with two robust marginal setae (vs. peduncle with three robust setae, outer ramus with two robust marginal setae); 4) uropod 3 peduncle with three robust setae, apical four robust setae (vs. peduncle with two robust setae, apical three robust setae) (

Etymology
The species is named in honour of Dr. Mesayamas Kongsema of Kasetsart University, Thailand, who contributed to the study of the life history of this new species.

Ecology
Floresorchestia kongsemae sp. n. is found in man-made ponds, similar to other terrestrial species found in moist areas or areas covered by organic materials. The amphipods generally live on the surface (1-2 inches under the surface) during the rainy season or optimal weather days (25-30°C). During sunny days or during periods of high temperature (> 30°C), they burrow deeper looking for more humid conditions.

Biology
Floresorchestia kongsemae sp. n. has two breeding periods per year (late summer/ early rainy season and the end of the rainy season). peduncle with two robust setae, ramus with a marginal robust seta; telson with five robust setae per lobe.

Discussion
The new species identified in this study can confidently be assigned to the genus Floresorchestia, based on the combination of characters mentioned by Lowry and Springthorpe (2015) and Lowry and Springthorpe (2019): 1) vertical slits on the ventral margins of the epimera; 2) posterior margin of merus, carpus and propodus of gnathopod 1, each with lobe covered in palmate setae. Floresorchestia, as a speciose and widespread genus, is also diversified in terms of ecology, including 16 coastal and 9 terrestrial species (Lowry and Springthorpe 2019). In Thailand, Floresorchestia kongsemae sp. n. is the third known member in this genus. Other species are Floresorchestia boonyanusithii, a field-hopper found in north-eastern Thailand and Floresorchestia buraphana, a beachhopper found in supralittoral man-made ponds located in eastern Thailand (Wongkamhaeng et al. 2016). In this study, samples of Floresorchestia kongsemae sp. n. were collected from a man-made pond in front of Chakrabandhu Pensiri Hall, Kasetsart University. Floresorchestia kongsemae is classified as a field-hopper and is present in coastal vegetation, meadows, pastures, grasslands and urban gardens, as well as amongst litter bands under stones and logs (Lowry and Myers 2019).